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Date: 06 Aug 2006 18:21:09
From: Martin R. Howell
Subject: Observing Plato's craterlets with smallish scopes
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A few nights ago, with the 9 day old moon only 20 or so degrees above the
s.s.w. horizon, I attempted to observe any of the craterlets (or a hint of
them) on Plato’s wonderfully smooth floor. It had been a hot day and, just
after sundown, it was still pretty toasty. The atmosphere was slightly
hazy/dirty and turbulence was present. There was also an expansive and
wispy cloud right in front of the moon. Obviously, this was not a great
night for attempting my goal, but I was off work the next day and which
gave me a whacky, “why the heck not?,” attitude.
Using my 114mm reflector — my second smallest scope — I slipped in a 24mm
eyepiece and found the image to be surprisingly good (but what isn’t with a
1″ focal length EP?). Next I inserted a 12.5mm EP and the image still held
up fairly well. Plato was now big enough to reveal its crisp, serrated rim
but no craterlets. Finally, using a 7.5mm EP, atmospheric issues became a
limiting factor. I could still get a halfway decent glimpse of the crater
in moments of better seeing, yet no craterlets were apparent. Had
conditions been better, it didn’t seem impossible that my 6mm or 3.8mm
eyepieces may have produced the illusive craterlets.
So I put it to you, what is the smallest aperture scope which you have used
to successfully yield Plato’s craterlets?
--
Martin R. Howell
"The Astro Post"
www.theastropost.com
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 06 Aug 2006 23:04:01
From: Davoud
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell wrote:
> A few nights ago, with the 9 day old moon only 20 or so degrees above the
> s.s.w. horizon, I attempted to observe any of the craterlets (or a hint of
> them) on Platos wonderfully smooth floor...
> Using my 114mm reflector my second smallest scope I slipped in a 24mm
> eyepiece and found the image to be surprisingly good (but what isnt with a
> 1? focal length EP?). Next I inserted a 12.5mm EP and the image still held
> up fairly well. Plato was now big enough to reveal its crisp, serrated rim
> but no craterlets. Finally, using a 7.5mm EP, atmospheric issues became a
> limiting factor. I could still get a halfway decent glimpse of the crater
> in moments of better seeing, yet no craterlets were apparent. Had
> conditions been better, it didnt seem impossible that my 6mm or 3.8mm
> eyepieces may have produced the illusive craterlets.
> So I put it to you, what is the smallest aperture scope which you have used
> to successfully yield Platos craterlets?
89mm, f13 Maksutov-Cassegrain with a 12mm eyepiece. Near the equator,
still, humid air, remarkably dust-free, at an elevation of about 3,000
ft.
I've had the privilege of observing from some very good sites around
the world, but I have never been able to use a 6mm or smaller eyepiece
for anything more than a quick glance that let me say "Yes, I'm pretty
sure I saw it, fuzzy as it was." I wonder how many people can take
advantage of such an ocular to get a good, sharp look at a lunar or
planetary feature?
I have had no view of the moon that matches Alan Friedman's remarkable
photo <http://tinyurl.com/p8n32 >!
Davoud
--
usenet *at* davidillig dawt com
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Date: 07 Aug 2006 18:10:03
From: Chris L Peterson
Subject: Re: Observing Plato's craterlets with smallish scopes
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On Sun, 06 Aug 2006 23:04:01 -0400, Davoud <star@sky.net > wrote:
>I've had the privilege of observing from some very good sites around
>the world, but I have never been able to use a 6mm or smaller eyepiece
>for anything more than a quick glance that let me say "Yes, I'm pretty
>sure I saw it, fuzzy as it was." I wonder how many people can take
>advantage of such an ocular to get a good, sharp look at a lunar or
>planetary feature?
What does the focal length of the EP have to do with its clarity? Surely
that is a matter of magnification; a 6mm EP on a 500mm refractor will
give similar results to a 24mm EP on your SCT (ignoring other specifics
of the optics, of course). Your comment and question suggests to me that
most of your viewing experience has been with longer focal length
instruments.
In any case, a 6mm EP on your 89mm aperture f/13 Mak puts your
magnification right about at the maximum you could normally use, and the
12mm EP is probably about optimum for typical conditions.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 07 Aug 2006 13:27:03
From: Fred Scharmann
Subject: Re: Observing Plato's craterlets with smallish scopes
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Wow !!!! What a photo.
"Davoud" <star@sky.net > wrote in message
news:060820062304012241%star@sky.net...
> Martin R. Howell wrote:
>
>> A few nights ago, with the 9 day old moon only 20 or so degrees above the
>> s.s.w. horizon, I attempted to observe any of the craterlets (or a hint
>> of
>> them) on Platos wonderfully smooth floor...
>
>> Using my 114mm reflector < my second smallest scope < I slipped in a 24mm
>> eyepiece and found the image to be surprisingly good (but what isnt with
>> a
>> 1? focal length EP?). Next I inserted a 12.5mm EP and the image still
>> held
>> up fairly well. Plato was now big enough to reveal its crisp, serrated
>> rim
>> but no craterlets. Finally, using a 7.5mm EP, atmospheric issues became a
>> limiting factor. I could still get a halfway decent glimpse of the crater
>> in moments of better seeing, yet no craterlets were apparent. Had
>> conditions been better, it didnt seem impossible that my 6mm or 3.8mm
>> eyepieces may have produced the illusive craterlets.
>
>> So I put it to you, what is the smallest aperture scope which you have
>> used
>> to successfully yield Platos craterlets?
>
> 89mm, f13 Maksutov-Cassegrain with a 12mm eyepiece. Near the equator,
> still, humid air, remarkably dust-free, at an elevation of about 3,000
> ft.
>
> I've had the privilege of observing from some very good sites around
> the world, but I have never been able to use a 6mm or smaller eyepiece
> for anything more than a quick glance that let me say "Yes, I'm pretty
> sure I saw it, fuzzy as it was." I wonder how many people can take
> advantage of such an ocular to get a good, sharp look at a lunar or
> planetary feature?
>
> I have had no view of the moon that matches Alan Friedman's remarkable
> photo <http://tinyurl.com/p8n32>!
>
> Davoud
>
> --
> usenet *at* davidillig dawt com
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Date: 06 Aug 2006 22:06:06
From: dan&lisa
Subject: Re: Observing Plato's craterlets with smallish scopes
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Hi Martin,
I did spot two and a hint of a third with my 4" achromat during good seeing.
That's been a rarity, usually I only see the main central one.
Dan
"Martin R. Howell" <martinhowell@ilikestarsisp.com > wrote in message
news:15f76yvq7ri85.19izga10hr5m8$.dlg@40tude.net...
>
> A few nights ago, with the 9 day old moon only 20 or so degrees above the
> s.s.w. horizon, I attempted to observe any of the craterlets (or a hint of
> them) on Plato's wonderfully smooth floor. It had been a hot day and, just
> after sundown, it was still pretty toasty. The atmosphere was slightly
> hazy/dirty and turbulence was present. There was also an expansive and
> wispy cloud right in front of the moon. Obviously, this was not a great
> night for attempting my goal, but I was off work the next day and which
> gave me a whacky, "why the heck not?," attitude.
>
> Using my 114mm reflector - my second smallest scope - I slipped in a 24mm
> eyepiece and found the image to be surprisingly good (but what isn't with
> a
> 1? focal length EP?). Next I inserted a 12.5mm EP and the image still held
> up fairly well. Plato was now big enough to reveal its crisp, serrated rim
> but no craterlets. Finally, using a 7.5mm EP, atmospheric issues became a
> limiting factor. I could still get a halfway decent glimpse of the crater
> in moments of better seeing, yet no craterlets were apparent. Had
> conditions been better, it didn't seem impossible that my 6mm or 3.8mm
> eyepieces may have produced the illusive craterlets.
>
> So I put it to you, what is the smallest aperture scope which you have
> used
> to successfully yield Plato's craterlets?
>
>
> --
> Martin R. Howell
>
> "The Astro Post"
> www.theastropost.com
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>
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Date: 07 Aug 2006 04:59:19
From: RMOLLISE
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell wrote:
>
> So I put it to you, what is the smallest aperture scope which you have used
> to successfully yield Plato's craterlets?
>
Hi Martin:
It depends on your definition of "seeing." With a high Sun angle, I can
easily detect the main craterlet with a Short Tube 80 as a white spot
on Plato's floor.
As a genuine crater? I've _thought_ I could make one or two out with a
12-inch at about 700x under good seeing and with a good Sun angle.
OTOH, a webcam will easily show them up as craters with a C8.
Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
and
_The Urban Astronomer's Guide_
<http://skywatch.brainiac.com/astroland/index.htm >
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers:
<http://groups.yahoo.com/group/sct-user >
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Date: 08 Aug 2006 14:52:32
From: Brian Tung
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell wrote:
> So I put it to you, what is the smallest aperture scope which you have used
> to successfully yield Plato’s craterlets?
My experience is similar to David. I saw the central craterlet as such
in my 5-inch SCT under excellent seeing conditions, at a low solar
angle, and was able to detect, trivially, the Big Four with ordinary
seeing, at a high solar angle, with the same telescope.
--
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: 08 Aug 2006 16:24:58
From: Martin R. Howell
Subject: Re: Observing Plato's craterlets with smallish scopes
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On Tue, 8 Aug 2006 14:52:32 -0700 (PDT), Brian Tung wrote:
> My experience is similar to David. I saw the central craterlet as such
> in my 5-inch SCT under excellent seeing conditions, at a low solar
> angle, and was able to detect, trivially, the Big Four with ordinary
> seeing, at a high solar angle, with the same telescope.
I can see the "bowl" of the central craterlet, IIRC, under good seeing with
my 12.5 inch dob. This is much as Rod Mollise stated. I am not sure I see
much of them at all with a moon at, or just past, full. The 9 day old moon
seems to work best for me. Then again, I hardly qualify as much of a lunar
observer. I am just starting to turn my attention to it now as my dark
skies have been ruined by that "roundabout" thing I cited a few months
back.
--
Martin R. Howell
"The Astro Lines"
http://theastropost.wordpress.com
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 08 Aug 2006 15:54:10
From: David Knisely
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell posted:
> So I put it to you, what is the smallest aperture scope which you have used
> to successfully yield Plato’s craterlets?
Well, the central craterlet is visible as a tiny white "dot" in my 80mm
f/5 "short tube", but to see the craters *as* craterlets (i.e., a
bowl-shaped depression with a rim and hints of shadowing) requires
something larger. I have seen the largest four in a six inch under
really good conditions. I have seen probably 10 or so craterlets *as*
craterlets (and not just as white dots) on the floor of Plato with my 10
inch Newtonian. However, I rarely see that many, as it requires just
the right low sun angle and excellent seeing. 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 13th Annual NEBRASKA STAR PARTY *
* July 23-28, 2006, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************
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Date: 09 Aug 2006 22:42:41
From: Stephen Paul
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell wrote:
> So I put it to you, what is the smallest aperture scope which you have =
used
> to successfully yield Plato=E2=80=99s craterlets?=20
IIRC, I made the crescent in a Vixen 102mm F9 ED doublet refractor.
(That claim should be somewhere in the saa archives.)
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Date: 13 Aug 2006 03:17:16
From: Gerard M Foley
Subject: Re: Observing Plato's craterlets with smallish scopes
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"Stephen Paul" <smarshallpaul@gmail.com > wrote in message
news:d-OdnVkeAPWEAEfZnZ2dnUVZ_sydnZ2d@comcast.com...
Martin R. Howell wrote:
>> So I put it to you, what is the smallest aperture scope which you have
>> used
>> to successfully yield Plato’s craterlets?
> IIRC, I made the crescent in a Vixen 102mm F9 ED doublet refractor.
> (That claim should be somewhere in the saa archives.)
You can narrow down the date by seeing when Pluto was within about 50
million miles from the sun. It doesn't get that close very often.
Gerry
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Date: 12 Aug 2006 21:49:32
From: Martin R. Howell
Subject: Re: Observing Plato's craterlets with smallish scopes
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Gerard M Foley wrote:
> You can narrow down the date by seeing when Pluto was within about 50
> million miles from the sun. It doesn't get that close very often.
Am I missing something here? Let me read this again. I will now read
it upside down. Now sideways. Nope, I still don't get it.
--
Martin R. Howell
"The Astro Post"
www.theastropost.com
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Date: 13 Aug 2006 16:18:34
From: Stephen Paul
Subject: Re: Observing Plato's craterlets with smallish scopes
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Martin R. Howell wrote:
> Gerard M Foley wrote:
>
>
>> You can narrow down the date by seeing when Pluto was within about 50
>> million miles from the sun. It doesn't get that close very often.
>
>
>
> Am I missing something here? Let me read this again. I will now read
> it upside down. Now sideways. Nope, I still don't get it.
>
Me thinks, he thinks, I exaggerate.
(Pluto is _never_ that close to the sun, you understand.)
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