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Date: 04 Sep 2007 08:36:34
From: Margo Schulter
Subject: Starhopping, star-strolling, and star-drifting?
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Hi, everyone, and recently I've been considering some
possible strategies for observing with a Dobsonian
telescope in light-polluted urban skies, which, of
course, might also apply to other types of scopes
(especially those which are usually guided visually
in a "hands-on" fashion) or observing venues.
The classical strategy, of course, is starhopping,
and maybe the other two I'm going to sketch out here
are simply variations on that; in fact, I've seen
one form of the second ("star-drifing") mentioned
as an approach for finding objects.
As someone new at this, I suspect that I may be
reinventing the wheel given the range of approaches
that experienced observers have doubtless tried, but
maybe my remarks may invite some interesting anecdotes
or suggestions from people with more experience.
In what I might call classic starhopping, there might
typically be lots of guidestars easily visible to the
naked eye, or at any rate in a finder scope.
Also, from the descriptions I've read so far and a
bit of experience (more confident with binoculars
than with my 20cm f/6 Dob), I'd take it that classic
starhopping often implies moving from one object of
interest to another over distances considerably
greater than the field of view (FOV) of the eyepiece
in use, with the destination as the main interest.
The term "star-strolling" occurs to me as a possible
observing strategy where one uses an eyepieces with a
very detailed star atlas to "stroll" slowly from field
to field, taking an interest in what each field shows.
Possibly one might ultimately be moving between specific
Messier or NGC objects as planned in advance, but one
looks at the intervening fields between such objects
as interesting _in their own right_.
To use a metaphor, if starhopping is like using a
city bus or subway system to get from one point to
another, star-strolling is more like walking through
the neighborhoods along the way, taking an interest
in each block -- or each square degree of a star
atlas.
"Star-drifting" means letting the Earth's rotation
do the driving of the scope, or at least most of it.
Possibly one would manually move the scope a bit from
time to time along the way to catch some nearby object
of interest, whether known in advance or spotted at
"on the fly" on an atlas page -- but mostly it's
"drifting along the river of space," with the atlas
as a guide to the sights that pass by. I almost
picture a cosmic version of the childhood story
of "The Owl and the Pussycat," who went "to see
what they could see."
From one perspective, this might be creative
opportunism: "If you can't be in the field you
love -- or maybe are simply not in a rush to get
there -- then love the field you're in."
From another, it might be an urban observing
strategy that focuses on a more relaxed approach
to compensate for the complications of light
pollution and trespass and canopies, etc., and
ultimately might encourage getting to know the
sky _really_ well, which could also help with
more conventional or "athletic" starhops.
The more cues I'm familiar with in a given area
of sky, the less likely I am to get lost, and
the more likely to move efficiently from "Point
A to Point B" when efficient motion is indeed
the goal.
There's also the factor that I enjoy looking
at starfields as a recreation and contemplative
experience in itself, even if I have little
idea of where I am. ("Well, M25 is now outside
my viewable area, so I must be somewhere to the
East of that.")
Perhaps star-strolling and star-drifting are
the other side of a continuum also featuring
Messier Marathons, where the object is to get
lots of places rather quickly.
Two helpful things for these more relaxed
styles of DSO observing are a nice wide
field of view (which a rich field telescope
like a typical medium to large Dob and a
lower-power, wide-angle eyepiece can provide),
and a set of really detailed charts that
match closely the view through the eyepiece.
Possibly I'm influenced in this kind of
direction both by light pollution problems
and by my apartment observatory situation
where the available area of the sky is quite
constrained, so that it is attractive to
make the most of every eyepiece field.
Have people noticed a tendency for urban
DSO observing sometimes to lean toward
these lines of strategy -- or maybe even
dark sky observing?
At this point the idea of leisurely
drifting through space from Capricorn
to Sculptor, say, and relishing every
minute of RA along the way while following
everything in an atlas with discreetly
applied red LED flashlight is a delicious
thought-experient -- and yes, there would
be no rule against now and then pausing
for some hands-on tracking of a diverting
object along the way.
If a Messier Marathon suggests an athletic
contest, this is more like a raft on the
river of space with a good guidebook.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 05 Sep 2007 02:21:57
From:
Subject: Re: Starhopping, star-strolling, and star-drifting?
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On Sep 4, 10:14 am, "Steve Paul" <smarshallp...@gmail.com > wrote:
>
> IIRC, it was Sketcher who once defined his favorite method as PAL (Point and
> Look).
You recall correctly! I'm (pleasantly) surprised that anyone
remembered! The PAL method works best in conjunction with a dark sky
and a 1x finder such as any red-dot finder. One basically commits to
short-term memory the location of M1 (or any other object) relative to
the naked eye stars in a magnitude 6.5 (near enough to my typical
naked-eye limit) atlas. One then finds the same star pattern in the
sky (some familiarity with the constellations is presumed) and plant
the red dot exactly on M1's memorized position. For the final step
one simply looks into the primary telescope's low-power, wide-angle
eyepiece and viola! There's M1 staring right back at you! (With hand-
held binoculars one can do this without the aid of a finder).
The PAL method fails when there's a multitude of faint galaxies (etc.)
within a *small* area of sky. In such crowded situations I often
resort to a detailed atlas (such as the Millennium Star Atlas) and use
a low-powered, wide-field eyepiece with a known true FOV (information
that any halfway serious observer ought to have measured and
recorded). With these tools in hand it's easy to use the primary
telescope (or for really large telescopes -- the magnifying finder) to
match the star patterns in the atlas with those seen through the
telescope -- with due regard to "correct" image orientation in the
finder and primary telescope. (A 90-degree, erect-image diagonal
works well with refractors. Many of the 45 degree, erect-image
diagonals tend to be too poor in the quality department). I've
navigated in this manner with refractors as well as with reflectors.
Of course, computer generated charts can be substituted for
commercially printed atlas charts.
I've experimented a bit with scanning regions of sky one square degree
at a time using an eyepiece that has a one-square-degree field (thanks
to a homemade, square fieldstop), the Millennium Atlas (with lines of
constant declination plotted for every degree of declination) and an
equatorial mount (allowing the scope to smoothly move along the lines
of constant declination. Of course, one adjusts the eyepiece so that
one pair of sides of the square field stop run parallel to the lines
of constant declination. Such an arrangement works very nicely if one
is interested in scanning the night sky via telescope one atlas page
at a time.
Then there are methods of pointing a telescope (or mounted binoculars)
at a star, comet or planet in the daytime sky utilizing a simple, non-
computerized, alt-az mount (It *can* be done. I've done it for stars,
planets and even for one daytime comet).
There are numerous methods that can be used by the creative amateur.
In the end, it's a situation of "whatever works for you".
Bill Greer
To sketch is to see.
http://cejour.blogspot.com
http://www.rangeweb.net/~sketcher
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Date: 06 Sep 2007 04:00:43
From: Margo Schulter
Subject: Re: Starhopping, star-strolling, and star-drifting?
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AstroSketcher@gmail.com wrote:
> On Sep 4, 10:14 am, "Steve Paul" <smarshallp...@gmail.com> wrote:
>>
> You recall correctly! I'm (pleasantly) surprised that anyone
> remembered! The PAL method works best in conjunction with a dark sky
> and a 1x finder such as any red-dot finder. One basically commits to
> short-term memory the location of M1 (or any other object) relative to
> the naked eye stars in a magnitude 6.5 (near enough to my typical
> naked-eye limit) atlas. One then finds the same star pattern in the
> sky (some familiarity with the constellations is presumed) and plant
> the red dot exactly on M1's memorized position. For the final step
> one simply looks into the primary telescope's low-power, wide-angle
> eyepiece and viola! There's M1 staring right back at you! (With hand-
> held binoculars one can do this without the aid of a finder).
Hi, Bill, and Steve's mention of PAL got me very curious! Maybe the
closest I've come to this was with finding M4 when I finally got to
a dark site after well learning the position through many "dry runs"
in light-polluted skies. (The triangle M4 forms with Antares and
another star at the base of what I call the "Rho Ophiuchi Pentagon"
was easy to visualize from star charts even though I never had
positively seen M4 itself in urban skies.) Of course, with a 7-degree
field, this might be more like just finding Antares and doing an
almost instantenous "hop" from there.
But I get the idea of a kind of "mental Telrad circle" effect: you
know the offset from that pattern as if looking at a Telrad chart.
> I've experimented a bit with scanning regions of sky one square degree
> at a time using an eyepiece that has a one-square-degree field (thanks
> to a homemade, square fieldstop), the Millennium Atlas (with lines of
> constant declination plotted for every degree of declination) and an
> equatorial mount (allowing the scope to smoothly move along the lines
> of constant declination. Of course, one adjusts the eyepiece so that
> one pair of sides of the square field stop run parallel to the lines
> of constant declination. Such an arrangement works very nicely if one
> is interested in scanning the night sky via telescope one atlas page
> at a time.
Observing visually with a Dob, an equivalent scenario is very much on
my agenda. I'm figuring that for this kind of visual survey, comparing
my 1-degree or 2-degree field of view with the square degrees of the
atlas should keep me oriented, and this kind of "visual sky survey"
should be lots of fun; but, of course, your imaging will show much
more. Thanks, by the way, for the opportunity to Google "square field
stop" and learn a bit more about the imaging side of things.
[...]
> There are numerous methods that can be used by the creative amateur.
> In the end, it's a situation of "whatever works for you".
As someone just starting out, and trying mainly to keep from getting
lost too easily <grin >, please let me thank you for the initiation
into PAL, an interesting test of real familiarity with the sky as I
grow in this art.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 04 Sep 2007 21:57:34
From: Marty
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Bill Greer was saying
>In such crowded situations I often resort
> to a detailed atlas (such as the
> Millennium Star Atlas) and use a
> low-powered, wide-field eyepiece with a
> known true FOV (information that any
> halfway serious observer ought to have
> measured and recorded).
I (and I'd suppose many others,) made little circles on acetate plastic
the size of my finder scope fov, for each of my star atlases. In the
case of the Uranometria 2000, I made one for my low power eyepiece too.
That makes it particularly easy to plan out a star hop before I even get
out into the dark.
The finder scope circle also works with my 11x80 binocs.
For dimmish stuff, I'd be lost without those little plastic
circles.
Marty
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Date: 05 Sep 2007 16:59:27
From: Jan Owen
Subject: Re: Starhopping, star-strolling, and star-drifting?
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"Marty" <movac5@webtv.net > wrote in message
news:5295-46DE1B1E-53@storefull-3333.bay.webtv.net...
> Bill Greer was saying
>>In such crowded situations I often resort
>> to a detailed atlas (such as the
>> Millennium Star Atlas) and use a
>> low-powered, wide-field eyepiece with a
>> known true FOV (information that any
>> halfway serious observer ought to have
>> measured and recorded).
>
> I (and I'd suppose many others,) made little circles on acetate plastic
> the size of my finder scope fov, for each of my star atlases. In the
> case of the Uranometria 2000, I made one for my low power eyepiece too.
> That makes it particularly easy to plan out a star hop before I even get
> out into the dark.
> The finder scope circle also works with my 11x80 binocs.
> For dimmish stuff, I'd be lost without those little plastic
> circles.
> Marty
>
Actually, I made a set of circles made from vacuum tubing like you might
find connecting the aerator to an aquarium pump... That's what I had LOTS
of at the time, so that's what I used...
And I made one with the AFOV for all the eyepieces I was likely to use (at
the time), so I could overlay them on my beloved Wil Tirion Sky Atlas 2000
charts... They were meant to show what I would see with each of my
eyepieces in the scope, and NOT the finder field... Didn't need much help
with finder fields at the time... I already knew the sky pretty well by
then... They worked like a charm...
--
Jan Owen
To reach me directly, remove the Z, if one appears in my e-mail address...
Latitude: 33.6
Longitude: -112.3
http://community.webshots.com/user/janowen21
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Date: 04 Sep 2007 17:59:54
From:
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Dennis Woos wrote:
> In fact, there is no Nebuluim but rather known elements
> in unusual states, though it took many years to figure
> this out. I take it that this is why we use OIII filters?
That's right: so-called nebulium was later found to be
doubly-ionized oxygen (aka O-III). It was unexpected
because at ordinary densities and pressures, O-III is too
active to survive. It is only in the rarefied nebulae that
it forms faster than it combines.
--
Brian Tung <brian@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 04 Sep 2007 17:19:15
From: Marty
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Hi Margo,
I think that all of the methods you mention qualify as starhopping.
Starhopping can be as large and sweeping as finding the North Star from
the Big Dipper, (no, the Big Dipper wasn't killed in a plane crash with
Ritchie Valens,) or finding the Pleiades by shooting up from Orion's
Belt, or as small and fine as finding the little globular cluster ngc
6453 at the end of the little zig-zag line of stars on the north edge of
M7.
Whether one allows one's self to enjoy the view along the way
depends on whether a person is able to enjoy the various visual delights
as he moves along, or if he's a knuckle dragging troglodyte. Or (like
me,) you might forget where you're at and where you're going.
The "star drifting" technique is a good one when two objects have
about the same declination, and it's been around for quite some time. I
can remember reading instructions for finding various things in
observing books along the line of "put such and such a star in the
middle of the field and wait 12 minutes and 20 seconds for "x" to
appear. If the scope is roughly polar aligned though, and you know the
size of your FOV and the distance to your target, you can just sort of
"scoot over." Star drifting may be a valuable technique given your
situation of observing through your window through light pollution.
I'd expect maybe "star drifting" was more popular in times past,
when writers such as Garrett Serviss could advise people to sit outside
and watch the stars drift in order to learn the apparent motions of the
sky. In this day and age, most writers would advise readers to look at
the stars and then look again an hour later. Fine points, but
significant.
Marty
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Date: 06 Sep 2007 02:52:54
From: Margo Schulter
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Marty <movac5@webtv.net > wrote:
> Hi Margo,
> I think that all of the methods you mention qualify as starhopping.
> Starhopping can be as large and sweeping as finding the North Star from
> the Big Dipper, (no, the Big Dipper wasn't killed in a plane crash with
> Ritchie Valens,) or finding the Pleiades by shooting up from Orion's
> Belt, or as small and fine as finding the little globular cluster ngc
> 6453 at the end of the little zig-zag line of stars on the north edge of
> M7.
Hi, Marty, and thanks for your helpful observations.
It's curious that for many years, with binoculars, Orion and the Pleiades
were my main DSO attractions (M42 and M45). Next session I want to check
out that M7-NGC 6453 hop.
> Whether one allows one's self to enjoy the view along the way
> depends on whether a person is able to enjoy the various visual delights
> as he moves along, or if he's a knuckle dragging troglodyte. Or (like
> me,) you might forget where you're at and where you're going.
Last night, a jaunt through Capricorn was a bit like this for me, although
following the sidereal time with Taki's 8.5 Magnitude Star Atlas gave me
some semblance of orientation. I was trying for M30, but also enjoying
the star fields for their own sake. However, at other times I have had
fun with little idea of what constellation I might be in -- a sign
of enthusiasm, if not indisputably of the most perfected technique <grin >.
> The "star drifting" technique is a good one when two objects have
> about the same declination, and it's been around for quite some time. I
> can remember reading instructions for finding various things in
> observing books along the line of "put such and such a star in the
> middle of the field and wait 12 minutes and 20 seconds for "x" to
> appear. If the scope is roughly polar aligned though, and you know the
> size of your FOV and the distance to your target, you can just sort of
> "scoot over." Star drifting may be a valuable technique given your
> situation of observing through your window through light pollution.
This ties in with the question how using an alt-az scope like a Dob
might contrast with a polar mount. Ah, now I realize: if two objects
are on the same declination, and I'm viewing the one to the west,
then drift will provide a perfect RA drive! Near the meridian, I could
try to sweep manually and hope that azimuth was close to RA -- but
letting the Earth do the driving is ideally accurate.
> I'd expect maybe "star drifting" was more popular in times past,
> when writers such as Garrett Serviss could advise people to sit outside
> and watch the stars drift in order to learn the apparent motions of the
> sky. In this day and age, most writers would advise readers to look at
> the stars and then look again an hour later. Fine points, but
> significant.
Maybe that does go to the "observing lifestyle" aspects that I was trying
to explore with my article. Of course, detailed charts can make the
drifting more fun. Last night, although I was only sporadically oriented,
I saw various galaxies on those atlas charts and wondered if, as a beginner,
I might be seeing galaxies and simply taking them as stellar. Also, of
course, drifting might be especially fun in a place like Sagittarius
or Virgo with lots of DSO attractions.
> Marty
>
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 04 Sep 2007 18:20:15
From: Howard Lester
Subject: Re: Starhopping, star-strolling, and star-drifting?
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"Marty" wrote
> Hi Margo,
> I think that all of the methods you mention qualify as starhopping.
> Starhopping can be as large and sweeping as finding the North Star from
> the Big Dipper, (no, the Big Dipper wasn't killed in a plane crash with
> Ritchie Valens,)
You KNOW what I LIKE!
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Date: 04 Sep 2007 16:44:50
From: David Knisely
Subject: Re: Starhopping, star-strolling, and star-drifting?
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One technique I use with an equatorial mount is the "right-angle sweep".
I have a low-power eyepiece which gives me about a full degree of
field. To find an object, I find a star within a few degrees of the
target on an atlas and the mark off how many 1-degree "fields" in right
ascension and in declination it takes to get from the star to the
object. I then go to the telescope, find the "take-off" star, and use
the fainter stars I see in the eyepiece to step off that many fields
first in R.A. and then in Declination. It is still a sort of "star
hop", but it ends up using a *lot* of stars to do the hopping. A good
set of setting circles would work for this as well, but my 10 inch isn't
driven and only has a crude home-made equatorial mount to work with.
Still, I can often get to some objects as fast or faster than I can with
my NexStar 9.25 inch Go-to scope, depending on how long it takes to mark
off the fields and find the take-off star. Clear skies to you.
--
David W. Knisely KA0CZC@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/
**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************
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Date: 06 Sep 2007 02:30:54
From: Margo Schulter
Subject: Re: Starhopping, star-strolling, and star-drifting?
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David Knisely <KA0CZC@navix.net > wrote:
> One technique I use with an equatorial mount is the "right-angle sweep".
> I have a low-power eyepiece which gives me about a full degree of
> field. To find an object, I find a star within a few degrees of the
> target on an atlas and the mark off how many 1-degree "fields" in right
> ascension and in declination it takes to get from the star to the
> object. I then go to the telescope, find the "take-off" star, and use
> the fainter stars I see in the eyepiece to step off that many fields
> first in R.A. and then in Declination. It is still a sort of "star
> hop", but it ends up using a *lot* of stars to do the hopping.
Hi, David, and thanks for this explanation, as well as your fine articles
about filters and their comparison for different objects. By the way, I'm
hoping to try mine soon, and need mainly to have confidence that I'm not
likely to scratch or otherwise harm them before I figure out the mechanics.
Anyway, with my Dob I sometimes try a kind of crude approximation of a
right-angle sweep, since my observatory's viewing window is close to the
meridian and not too far for the most part below the celestial equator.
Sometimes I try to get "trigonometrically sophisticated" and follow
the hypotenuse of a triangle with RA and Dec as the sides at right angles;
but "one dimension at a time" might be wiser and more accurate. My success
story so far is getting between M25 and M24, where it's pretty much an
RA sweep. The next time I try a sweep with significant motion in both
dimensions, I'll remember: "Take one dimension at a time."
Since the right-angle sweep method very much appeals to me, it should be
fun to see how well I can pull it (or an approximation) off with a Dob.
> A good
> set of setting circles would work for this as well, but my 10 inch isn't
> driven and only has a crude home-made equatorial mount to work with.
> Still, I can often get to some objects as fast or faster than I can with
> my NexStar 9.25 inch Go-to scope, depending on how long it takes to mark
> off the fields and find the take-off star. Clear skies to you.
One thing I'm wondering: might alt-az setting circles for my Dob serve any
useful purpose? I saw some in a review by Terence Dickinson of an earlier
version of this scope, a Sky-Watcher 20cm f/6 Dob -- or what he calls
"numbered disks," and himself says "have little practical application."
As I mentioned in another post, maybe simply knowing the sidereal time
and the location of the meridian might be a reasonable substitute if the
idea is simply to find my bearings in a star atlas and starhop or sweep
from there.
Again, thanks for your wisdom and encouragement.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 04 Sep 2007 13:19:27
From:
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Margo Schulter wrote:
> The term "star-strolling" occurs to me as a possible
> observing strategy where one uses an eyepieces with a
> very detailed star atlas to "stroll" slowly from field
> to field, taking an interest in what each field shows.
> Possibly one might ultimately be moving between specific
> Messier or NGC objects as planned in advance, but one
> looks at the intervening fields between such objects
> as interesting _in their own right_.
I'd say that both methods are commonly called
star-hopping, with the only difference being what you're
looking through (if anything) while you're hopping. So
what you call star-strolling is frequently called "through
the eyepiece star-hopping," and the others would be
"through the finder star-hopping," or "unaided-eye
star-hopping." Alan MacRobert has an enjoyable book
on star-hopping which is a mixture of through the finder
and through the eyepiece star-hopping, and its express
purpose is to smell the roses, so to speak, along the
way to your eventual target. (In fact, each step along
the way in MacRobert's hops has equal standing as
target; the last hop is just the last hop, nothing more.)
> "Star-drifting" means letting the Earth's rotation
> do the driving of the scope, or at least most of it.
> Possibly one would manually move the scope a bit from
> time to time along the way to catch some nearby object
> of interest, whether known in advance or spotted at
> "on the fly" on an atlas page -- but mostly it's
> "drifting along the river of space," with the atlas
> as a guide to the sights that pass by. I almost
> picture a cosmic version of the childhood story
> of "The Owl and the Pussycat," who went "to see
> what they could see."
Although you could observe this way, personally, I'd
find it a bit too slow for my taste. I like to take my
time on an object when actually observing it, but when
I'm moving from one object to the next, I prefer to take
more of an active role. So I let my motor drive keep
the object in the FOV while I'm looking at it, but I don't
stop it to move from one object to another. I might
recommend that for someone who's having a lot of
trouble finding something with an alt-az mount, but
otherwise, regular star-hopping is more effective and
I suspect allows you to learn the sky more fully, to
boot.
> Perhaps star-strolling and star-drifting are
> the other side of a continuum also featuring
> Messier Marathons, where the object is to get
> lots of places rather quickly.
Messier Marathons are generally hectic at just two
times: dusk and dawn. Other than that, there really
is a surprisingly long time for you to observe many
of the objects. It's an exercise in planning.
> Possibly I'm influenced in this kind of
> direction both by light pollution problems
> and by my apartment observatory situation
> where the available area of the sky is quite
> constrained, so that it is attractive to
> make the most of every eyepiece field.
In my experience, the best anodyne for bright skies
is driving. :) Barring that, though, a facility at
recognizing star fields in any orientation and scale,
plus the ability to move the telescope as though it
were an extension of your arm--these will stand you
in good stead.
> Have people noticed a tendency for urban
> DSO observing sometimes to lean toward
> these lines of strategy -- or maybe even
> dark sky observing?
The thing that I use the most is geometric figures
involving stars that are as far apart as maybe 40
or 50 degrees in the sky. This is more important
from light-polluted skies than it is from dark ones
because often, that's the best you can do. You
find that you can see dimmer stars than that, of
course, but you can't actually use the dimmer stars
to point your way as easily, because so much of
your effort is spent in just detecting them.
--
Brian Tung <br...@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 06 Sep 2007 01:55:24
From: Margo Schulter
Subject: Re: Starhopping, star-strolling, and star-drifting?
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brian@isi.edu wrote:
> Messier Marathons are generally hectic at just two
> times: dusk and dawn. Other than that, there really
> is a surprisingly long time for you to observe many
> of the objects. It's an exercise in planning.
Hi, Brian, and thanks for this clarification: I should
have said, "like dusk or dawn at a Messier Marathon."
Indeed, I recall that sometimes people have a couple
of hours maybe somewhere around the middle of the
night to get in a nap.
> In my experience, the best anodyne for bright skies
> is driving. :) Barring that, though, a facility at
> recognizing star fields in any orientation and scale,
> plus the ability to move the telescope as though it
> were an extension of your arm--these will stand you
> in good stead.
As to driving as the best remedy (or moving to a darker
location), of that there is no doubt <grin >. Trying
to find M4 in the city with my 7X50 binoculars, knowing
quite well where to look, and then trying it at a dark
sky site and finding it in one minute, convinced me of
that! The problem is finding some generous colleague
inclined to share a ride -- and also the complications
of getting the scope down and later up two flights of
stairs.
A humorous aside: I'm excited about an idea for one
strategy of getting oriented, when "lost in space"
or when starting a session without any obvious landmark
at hand. If I know the sidereal time, and can point my
Dob to the meridian, then I've found a known RA. While
it's a partial substitute for getting a ride to a dark
sky site, maybe we could call this the rapid transit
method.
> The thing that I use the most is geometric figures
> involving stars that are as far apart as maybe 40
> or 50 degrees in the sky. This is more important
> from light-polluted skies than it is from dark ones
> because often, that's the best you can do. You
> find that you can see dimmer stars than that, of
> course, but you can't actually use the dimmer stars
> to point your way as easily, because so much of
> your effort is spent in just detecting them.
What I've found is that as long as I can survey the
sky without worrying about direct light trespass
(street or apartment lights glaring in my eyes),
then geometric figures are very helpful: the teapot
of Sagittarius and its different asterisms, or the
"Antares-Rho Ophiuchi Pentagon."
From my little experience, I can certainly agree that
an easily detected star is the most efficient pointer.
Antares and some of the brighter stars in Sagittarius
are favorites. Early the other morning, by the way,
I caught site of an old friend -- the belt of Orion.
What I have found, when using binoculars from below
the window level where light trespass isn't such an
issue, is that I might use the naked eye for initial
orientation, and from time to time, but do most of
my starhopping using binocular asterisms.
With the telescope and finder, it's mostly a question
of finding strategies that let me observe comfortably
and effectively from the refuge of that canopy, sort
of like being in a submarine <grin >.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 04 Sep 2007 13:04:59
From:
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Steve Paul wrote:
> I could be wrong, but I believe that drifting is a practice
> for a polar aligned mount. You look up the RA and Dec
> of the target, then set the Dec setting circle (which is
> fixed to wrt the mount) and sweep (drift) east or west.
> This allows you to look for the object in a single east/west
> motion, without having to fuss with your RA setting circle.
> Coincidentally, from my latitude, if your altazimuth
> mounted scope is aimed at M22 when it is east of the
> meridian, M8 is just a short sweep due west in a wide
> field eyepiece.
While a polar-aligned mount is required to sweep to the
second object, drifting can be performed by a telescope
on any kind of mount. In this case, if you can find M8
(an unaided-eye object from reasonably dark skies), you
can leave the scope on it, undriven, for about a half-hour
or so, and M22 will drift into the field of view. (It's about
a half-degree off, but that should be good enough with a
reasonably wide FOV.
--
Brian Tung <br...@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 04 Sep 2007 12:55:01
From:
Subject: Re: Starhopping, star-strolling, and star-drifting?
|
Dennis Woos wrote:
> I am currently in the process of moving the Cat's
> Eye to the "certain" category, as I like this object
> (including its historical significance) and want to
> be able to find it automatically in seconds.
I'm not sure which fact in particular about the Cat's
Eye you mean by its "historical significance," but in
case you aren't mentioning it already, NGC 6543 is
within a hair's breadth of the north ecliptic pole. For
those celestial mechanics nerds amongst you, that
means that its celestial coordinates (RA and Dec)
change almost not at all as the eons pass. It will
always be in the vicinity of 18h, 66.5d.
--
Brian Tung <brian@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 04 Sep 2007 16:50:44
From: Dennis Woos
Subject: Re: Starhopping, star-strolling, and star-drifting?
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> I'm not sure which fact in particular about the Cat's
> Eye you mean by its "historical significance," but in
> case you aren't mentioning it already, NGC 6543 is
> within a hair's breadth of the north ecliptic pole. For
> those celestial mechanics nerds amongst you, that
> means that its celestial coordinates (RA and Dec)
> change almost not at all as the eons pass. It will
> always be in the vicinity of 18h, 66.5d.
>
The historical significance I was referring to as described at SEDS:
The Cat Eye Nebula was the first planetary which was spectroscopically
investigated and displayed its typical (and peculiar) line spectrum, by the
English amatuer astronomer William Huggins, published originally in the
Philosophical Transactions of the Royal Society (London) in 1864 - in the
same volume where John Herschel published his General Catalog (GC) of 5079
entries for deep sky objects. (Huggins 1864).
And from the SEDS entry for Huggins:
He found his special discipline soon: Spectroscopy, where he was the
pioneer. He discovered dark-line spectra (Lines of some Fixed Stars, 1863),
and in 1864 he examined the spectrum of a planetary nebula, NGC 6543 in
Draco, and found that it had a bright line or emission line spectrum, namely
the two greenish lines which could not be identified as of any known element
at that time, and were then assigned to a new hypothetical element,
"Nebulium." He therefore concluded correctly that this nebula was not
composed of stars, which have a continuous spectrum, but of glowing gas.
In fact, there is no Nebuluim but rather known elements in unusual states,
though it took many years to figure this out. I take it that this is why we
use OIII filters?
Dennis
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Date: 04 Sep 2007 12:14:11
From: Dennis Woos
Subject: Re: Starhopping, star-strolling, and star-drifting?
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Star hopping is not a well-defined term, and I am sure different folks use
it in different ways. I don't use it to describe the case where you simply
point the scope at something which is visible to the naked eye. Let's take
M24 - there is no star hop, you just point the scope at it. This reminds me
of a post (SAA?) where someone asked how to find the Moon. Of course, what
is naked eye will vary, depending on how dark the sky is. The next level is
still a simple "point the scope", but the target is not visible to the naked
eye but is easily found, e.g. because of nearby star(s). M13 immediately
comes to mind - if I can see the keystone then I can point at M13 with
almost as much certainty as I can M24 (or the Moon). The next level for me
is where I can point in the general area, and a quick search with a low (or
even not-so-low) power eyepiece is all that is required. M81 and M82 are
like this for me. And then there is stuff like the Helix, where I have to
work a bit - sometimes I find it in seconds, and sometimes it takes a couple
of minutes. Even this I wouldn't call star hopping, as I am not moving from
star to star in a finder, measuring off distances, etc. Also, targets
regularly move from this hunt-a-bit to the point-with-certainty category as
I learn the neighborhood, though I have to admit that the Helix has resisted
becoming automatic. It is in a star-sparse area, is low in the South (where
I have some light pollution) and so not often a good target for us - like
the Silver Coin galaxy. I am currently in the process of moving the Cat's
Eye to the "certain" category, as I like this object (including its
historical significance) and want to be able to find it automatically in
seconds.
For us (my sons and I, and our observing friends), most of the Messier
objects and many non-Messiers are in this category, which is why we don't
use charts, etc at public events - we can immediately find many more objects
(of all types) than we will have time to observe. Sometimes we spend all or
most of the night really star hopping, looking for some difficult/unfamiliar
target(s) by following detailed charts of star fields and stepping off
distances, etc. However, there are many (most) nights when we never star hop
and simply point the scope(s) and observe - the challenge isn't in finding
the target but rather in the observation.
Dennis
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Date: 04 Sep 2007 12:14:01
From: Steve Paul
Subject: Re: Starhopping, star-strolling, and star-drifting?
|
"Margo Schulter" <mschulter@web1.calweb.com > wrote in message
news:46dd1912$0$30973$d368eab@news.calweb.com...
> Hi, everyone, and recently I've been considering some
> possible strategies for observing with a Dobsonian
>
> The classical strategy, of course, is starhopping,
> and maybe the other two I'm going to sketch out here
> are simply variations on that; in fact, I've seen
> one form of the second ("star-drifing") mentioned
> as an approach for finding objects.
I could be wrong, but I believe that drifting is a practice for a polar
aligned mount. You look up the RA and Dec of the target, then set the Dec
setting circle (which is fixed to wrt the mount) and sweep (drift) east or
west. This allows you to look for the object in a single east/west motion,
without having to fuss with your RA setting circle. Coincidentally, from my
latitude, if your altazimuth mounted scope is aimed at M22 when it is east
of the meridian, M8 is just a short sweep due west in a wide field eyepiece.
> In what I might call classic starhopping, there might
> typically be lots of guidestars easily visible to the
> naked eye, or at any rate in a finder scope.
Not sure what you use for finding, but one of the best things you can do for
yourself in light polluted skies is to get a Telrad and a 9x50 Right Angle
Correct Image (RACI) finder. For areas of the sky that have enough bright
stars, the Telrad is all you need (and under dark skies). For areas that are
sparse in bright stars, the Telrad can be used as a simple unit power
"gunsight", and then the RACI can be used with the star atlas without any
mental or physical gymnastics.
>
> Also, from the descriptions I've read so far and a
> bit of experience (more confident with binoculars
> than with my 20cm f/6 Dob), I'd take it that classic
> starhopping often implies moving from one object of
> interest to another over distances considerably
> greater than the field of view (FOV) of the eyepiece
> in use, with the destination as the main interest.
Maybe defined a little differently (for better or worse), it is the process
of using one star as a jump point to get you to the next star, and hopefully
to a non-stellar object nearest the final star in the hop. It doesn't
require an eyepiece in the main scope at all. It can be done with just a
Telrad. However, some guidebooks will take you an a widefield eyepiece field
to field journey if you are so inclinde.
IIRC, it was Sketcher who once defined his favorite method as PAL (Point and
Look). :-) That process is mode more possible with a Telrad.
Enjoy!
-Steve
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 06 Sep 2007 03:29:33
From: Margo Schulter
Subject: Re: Starhopping, star-strolling, and star-drifting?
|
Steve Paul <smarshallpaul@gmail.com > wrote:
> Not sure what you use for finding, but one of the best things you can do for
> yourself in light polluted skies is to get a Telrad and a 9x50 Right Angle
> Correct Image (RACI) finder. For areas of the sky that have enough bright
> stars, the Telrad is all you need (and under dark skies). For areas that are
> sparse in bright stars, the Telrad can be used as a simple unit power
> "gunsight", and then the RACI can be used with the star atlas without any
> mental or physical gymnastics.
Hi, Steve, and I'm considering the RACI option; currently I have a 9X50 straight
finder which came with the scope, and am getting a bit more comfortable with
it (as with the main eyepiece on a Dob, turning the charts upside down can
sometimes help).
Actually one factor that might make RACI advantageous is the question of
light trespass. If I'm above the bottom of the open window I'm viewing through
with the scope, then those apartment and street lights outside give me
good reason to keep that Orion canopy nicely in place over my eyes. This
can be easier when looking through the main eyepiece -- or possibly a
RACI finder -- than when looking through a straight finder, with my
head turned in the direction of the light trespass. I'm learning how
to keep the canopy in place while draping it around the straight finder
to minimize any exposure to stray light, but it's a bit of a comic
posture.
If it wasn't for the direct glare, that makes me wonder how easy it would
be to look out through the Orion canopy and use a Telrad while keeping my
dark adaptation, I'd say that the Telrad could be very useful even with
the skyglow. Just place Antares at the right radius and angle with those
circles as shown in a Telrad chart: I could have M4 just about centered
in my eyepiece. for example. Even in Mag 3.5 skies, there are lots of
guidestars where I could use a Telrad: one of the Sagittarius Teacup stars,
as I recall, for M22; or Beta Sculptoris for approaching NGC 253.
> Maybe defined a little differently (for better or worse), it is the process
> of using one star as a jump point to get you to the next star, and hopefully
> to a non-stellar object nearest the final star in the hop. It doesn't
> require an eyepiece in the main scope at all. It can be done with just a
> Telrad. However, some guidebooks will take you an a widefield eyepiece field
> to field journey if you are so inclinde.
That's a neat definition, which I certain accept as a helpful revision of what
I wrote.
> IIRC, it was Sketcher who once defined his favorite method as PAL (Point and
> Look). :-) That process is mode more possible with a Telrad.
Thanks for bringing up PAL, something that I hadn't heard of before,
and that looks very helpful from what I'm reading in this thread.
> Enjoy!
> -Steve
>
>
>
>
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 05 Sep 2007 03:34:36
From: Jan Owen
Subject: Re: Starhopping, star-strolling, and star-drifting?
|
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Date: 04 Sep 2007 19:52:38
From: Jan Owen
Subject: Re: Starhopping, star-strolling, and star-drifting?
|
"Steve Paul" <smarshallpaul@gmail.com > wrote in message
news:46dd7841$0$16915$88260bb3@free.teranews.com...
>
> "Margo Schulter" <mschulter@web1.calweb.com> wrote in message
> news:46dd1912$0$30973$d368eab@news.calweb.com...
>> Hi, everyone, and recently I've been considering some
>> possible strategies for observing with a Dobsonian
>>
>> The classical strategy, of course, is starhopping,
>> and maybe the other two I'm going to sketch out here
>> are simply variations on that; in fact, I've seen
>> one form of the second ("star-drifing") mentioned
>> as an approach for finding objects.
>
> I could be wrong, but I believe that drifting is a practice for a polar
> aligned mount. You look up the RA and Dec of the target, then set the Dec
> setting circle (which is fixed to wrt the mount) and sweep (drift) east or
> west. This allows you to look for the object in a single east/west motion,
> without having to fuss with your RA setting circle. Coincidentally, from
> my latitude, if your altazimuth mounted scope is aimed at M22 when it is
> east of the meridian, M8 is just a short sweep due west in a wide field
> eyepiece.
>
>> In what I might call classic starhopping, there might
>> typically be lots of guidestars easily visible to the
>> naked eye, or at any rate in a finder scope.
>
> Not sure what you use for finding, but one of the best things you can do
> for yourself in light polluted skies is to get a Telrad and a 9x50 Right
> Angle Correct Image (RACI) finder. For areas of the sky that have enough
> bright stars, the Telrad is all you need (and under dark skies). For areas
> that are sparse in bright stars, the Telrad can be used as a simple unit
> power "gunsight", and then the RACI can be used with the star atlas
> without any mental or physical gymnastics.
>
>>
>> Also, from the descriptions I've read so far and a
>> bit of experience (more confident with binoculars
>> than with my 20cm f/6 Dob), I'd take it that classic
>> starhopping often implies moving from one object of
>> interest to another over distances considerably
>> greater than the field of view (FOV) of the eyepiece
>> in use, with the destination as the main interest.
>
> Maybe defined a little differently (for better or worse), it is the
> process of using one star as a jump point to get you to the next star, and
> hopefully to a non-stellar object nearest the final star in the hop. It
> doesn't require an eyepiece in the main scope at all. It can be done with
> just a Telrad. However, some guidebooks will take you an a widefield
> eyepiece field to field journey if you are so inclinde.
>
> IIRC, it was Sketcher who once defined his favorite method as PAL (Point
> and Look). :-) That process is mode more possible with a Telrad.
>
> Enjoy!
> -Steve
>
I'll second that about PAL...
For many years (decades, actually), I was WELDED to optical finders. But
eventually, I bought a Rigel QuikFinder... While I thought I couldn't find
anything WITHOUT optical aid, I had learned my way around the sky decades
ago, so when I bought the Rigel to play with, I was astounded that I could
just swing the scope it was attached to around, circle the spot in the sky
where I expected a given object to be, and it was just THERE, in my low
power eyepiece field!!!
As Sketcher says, VOILA!!!
Since then, one by one, the optical finders have been in the process of
being replaced, or at least supplemented, by Rigel QuikFinders, on ALL my
scopes... Only two scopes without them, now, and both are candidates for
sale, so I really haven't made much of an effort to put QuikFinders on them
(they both have quite sufficient optical finders)...
But PAL works... Of course you DO have to learn your way around the sky.
But that's a FUN (and educational) thing to do... I spent the 1970's doing
that... And the 1980's and 1990's impressing friends with how FAST I could
find stuff all around the sky without charts... But in this new century,
the QuikFinder really brought this into it's own...
Of course, now, after all these decades of finding stuff with the good old
eyeballs and random-access memory, I'm beginning to play with GOTO (because
my random access memory is beginning to become somewhat more random with
age)... Heheheh!!!
--
Jan Owen
To reach me directly, remove the Z, if one appears in my e-mail address...
Latitude: 33.6
Longitude: -112.3
http://community.webshots.com/user/janowen21
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