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Date: 19 Sep 2006 18:17:25
From:
Subject: Orion ST 120 f/5 or 80 ED
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First let me start by saying I own a C5 and a C8.
The C8 is bulky and needs long cool down times so I rarley use it. I
don't really care for dobsonians.
I use the C5 on a camera tripod with slowmotion controls and it is
great for grabbing quick views of planets.
But now I am contemplating a completly different beast.
I just bought a really nice DSV-1 'Steady View' Alt-Azimuth Mount from
Desert Sky Astro. It has no slow motion controls, but it is silky
smooth and is comfortable to use up to about 50 power, for me.
I was thinking I would get a stellarvue nighthawk or even an orion or
celestron 80ED to put on it at LOW power. I would get a 2" 35mm or
40mm eye piece along with a 2" diagonal and just use it like a kind of
one eyed binocular. At low powers I would be getting a 7mm pupil
diamiter and it would be great for scanning the milky way.
So here is my question; If I'm only using it at low powers, is the
80ED really going to be better than a ST120 that is going to be almost
twice as bright? As far as that goes, would the 80ED really be all
that better than a stellarvue nighthawk at low power.
I figure with the ST 120's 600mm focal length, I would achieve a 7mm
pupil at 17 power with a 35mm eyepeice. I would almost never use it
for anything higher as I would probably have either my C5 or C8 set up
next to it. It would be capable of seeing things my C5 can't and I
could use it to find objects that would be hard to find in the C8.
Well your not having fun unless you have at least three scopes set up
at the same time in your backyard, right?
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Date: 19 Sep 2006 23:39:35
From: Stephen Paul
Subject: Re: Orion ST 120 f/5 or 80 ED
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larrymiracle@amicomm.net wrote:
> So here is my question; If I'm only using it at low powers, is the
> 80ED really going to be better than a ST120 that is going to be almost
> twice as bright?
I'd say not.
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Date: 19 Sep 2006 20:20:08
From: Howard Lester
Subject: Re: Orion ST 120 f/5 or 80 ED
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<larrymiracle@amicomm.net > wrote
> So here is my question; If I'm only using it at low powers, is the
> 80ED really going to be better than a ST120 that is going to be almost
> twice as bright? As far as that goes, would the 80ED really be all
> that better than a stellarvue nighthawk at low power.
The Orion 80ED can be used at HIGH power, not just low. (I have one, along
with the infamous ST80 achromat.) Is the 80ED better than a Nighthawk? If
the latter is a basic 80mm achromat (I think f/6), then yes, the Orion is a
lot better even at low power. The Nighthawk may be like looking at the sky
through dirty eyeglasses by comparison. I love my 80ED.
Now, if I was only interested in low power wide field views and had to
choose between an ST120 and an 80ED, I'd most likely pick the 120 for its
ability to go much deeper. However, not having looked through a 120, it is
possible I'd still prefer the 80ED, because what it CAN show will be much
more pleasing to look at due to its near lack of any false color and its
tight stellar images.
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Date: 19 Sep 2006 23:56:47
From: Stephen Paul
Subject: Re: Orion ST 120 f/5 or 80 ED
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Howard Lester wrote:
> <larrymiracle@amicomm.net> wrote
>
> > So here is my question; If I'm only using it at low powers, is the
>> 80ED really going to be better than a ST120 that is going to be almost
>> twice as bright? As far as that goes, would the 80ED really be all
>> that better than a stellarvue nighthawk at low power.
>
> The Orion 80ED can be used at HIGH power, not just low. (I have one, along
> with the infamous ST80 achromat.) Is the 80ED better than a Nighthawk? If
> the latter is a basic 80mm achromat (I think f/6), then yes, the Orion is a
> lot better even at low power. The Nighthawk may be like looking at the sky
> through dirty eyeglasses by comparison. I love my 80ED.
>
> Now, if I was only interested in low power wide field views and had to
> choose between an ST120 and an 80ED, I'd most likely pick the 120 for its
> ability to go much deeper. However, not having looked through a 120, it is
> possible I'd still prefer the 80ED, because what it CAN show will be much
> more pleasing to look at due to its near lack of any false color and its
> tight stellar images.
>
Indeed. I've had my 80ED longer than any other scope I've owned. It has
a lot going for it in terms of portability and capability for an 80mm
refractor.
That said, my 6" F5 reflector is fast becoming a favorite scope. On a
stable tripod with altazimuth head (like the UA Unistar), the eyepiece
range from horizon to zenith is easy to deal with while standing, and it
excels at both wide field and deep sky (compared to the 80ED). The
compromise of a little longer focal length and 1.25" focuser, is
outweighed by its 6" aperture and operates well beyond the capabilities
of an 80ED or an ST120 on any DSO or solar system object. (It yields 2
degrees of field with the 24mm Panoptic, and easily hits 166x (barlowed
9mm) for planets.)
It _is_ larger than either of the refractors suggested, but not
imposingly so. The mount is more work to man-handle than the scope
itself, but that's true of most scopes on a tripod mount.
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Date: 20 Sep 2006 06:13:23
From: Howard Lester
Subject: Re: Orion ST 120 f/5 or 80 ED
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"Stephen Paul" wrote
> Indeed. I've had my 80ED longer than any other scope I've owned. It has a
> lot going for it in terms of portability and capability for an 80mm
> refractor.
>
> That said, my 6" F5 reflector is fast becoming a favorite scope.
But he was asking about an ST120 for comparison, not a 6" f/5. I have one
similar, a homemade 6" f/5.5 with 2" JMI focuser and 1.5" E&W secondary. I'm
sure if I ever got a Paracorr and a 35mm Panoptic it'd be an amazing,
compact scope for at least wide field viewing. I'm curious as to just which
Unistar mount components you have, but that's off topic here.
Howard Lester
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Date: 20 Sep 2006 00:43:56
From: AM
Subject: Re: Orion ST 120 f/5 or 80 ED
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Stephen Paul wrote:
> That said, my 6" F5 reflector is fast becoming a favorite scope.
It does seem to be about the right size. Which
makes me wonder why JMI's little 6" on a split
EQ mount just never made it.........
--
AM
http://sctuser.home.comcast.net
CentOS 4.3 KDE 3.3
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Date: 20 Sep 2006 13:21:16
From: Willie R. Meghar
Subject: Re: Orion ST 120 f/5 or 80 ED
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larrymiracle@amicomm.net wrote:
>So here is my question; If I'm only using it at low powers, is the
>80ED really going to be better than a ST120 that is going to be almost
>twice as bright? As far as that goes, would the 80ED really be all
>that better than a stellarvue nighthawk at low power.
For low power, wide field visual astronomy the greater aperture of the
ST120 would be, in almost all cases, *clearly superior* to the 80ED.
Exceptions would be when an even wider true field was needed (not too
likely) and when greater portability was needed.
An alternative that might be worth considering is a pair of 25x100
binoculars. You get to use both eyes at the same time! Under a dark
sky these binoculars are quite awesome. Of course, you would need a
suitable mount.
>I figure with the ST 120's 600mm focal length, I would achieve a 7mm
>pupil at 17 power with a 35mm eyepeice. I would almost never use it
>for anything higher as I would probably have either my C5 or C8 set up
>next to it. It would be capable of seeing things my C5 can't and I
>could use it to find objects that would be hard to find in the C8.
I would advise against a 7mm exit pupil. In my opinion and experience
a 5mm exit pupil is a better compromise between image contrast
(important for deep sky observing), image scale, and wide field of
view.
My preferred binoculars for deep sky observing are 20x80s and 25x100s.
Both have 4mm exit pupils. I prefer the performance of 8x42
binoculars (smaller exit pupils) over 7x50s (larger exit pupils) for
casual astronomical use.
Back in the days of visual comet hunting (not that those days have
completely ended), a 5mm exit pupil was looked upon as the ideal for
comet seekers of around 8 inches of aperture and smaller. Only when
apertures got in the neighborhood of 10 inches and larger were larger
exit pupils recommended (necessary to achieve a wide enough true field
to remain competitive).
For such a specialized scope as you've outlined above, I would not
want to settle for any ol' eyepiece. I would want a quality 2 inch OD
eyepiece with good edge of field performance. A 27mm Panoptic comes
to mind. (I used to use a 27mm Panoptic with a 13cm f/6 apo for comet
hunting.) This eyepiece should provide you with a true field of view
of approximately 3 degrees, comfortable eye relief, good edge of field
performance, and a pleasant apparent field of view as well.
My big, heavy, Meade 40mm Super Wide Angle eyepiece (with its larger
exit pupil) is one of my least used eyepieces. It's used *only* when
I *need* a wider true field of view; but even then, the poor edge of
field performance of that eyepiece is a bit of a 'turn off'.
Of course, you could start with one eyepiece and later enlarge your
collection by one or two more.
Willie R. Meghar
http://meghar.blogspot.com/
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Date: 20 Sep 2006 21:25:47
From:
Subject: Re: Orion ST 120 f/5 or 80 ED
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On Wed, 20 Sep 2006 13:21:16 -0600, Willie R. Meghar
<NoMail@thisaddress.net > wrote:
>larrymiracle@amicomm.net wrote:
>
>>So here is my question; If I'm only using it at low powers, is the
>>80ED really going to be better than a ST120 that is going to be almost
>>twice as bright? As far as that goes, would the 80ED really be all
>>that better than a stellarvue nighthawk at low power.
>
>For low power, wide field visual astronomy the greater aperture of the
>ST120 would be, in almost all cases, *clearly superior* to the 80ED.
>Exceptions would be when an even wider true field was needed (not too
>likely) and when greater portability was needed.
>
>An alternative that might be worth considering is a pair of 25x100
>binoculars. You get to use both eyes at the same time! Under a dark
>sky these binoculars are quite awesome. Of course, you would need a
>suitable mount.
>
>>I figure with the ST 120's 600mm focal length, I would achieve a 7mm
>>pupil at 17 power with a 35mm eyepeice. I would almost never use it
>>for anything higher as I would probably have either my C5 or C8 set up
>>next to it. It would be capable of seeing things my C5 can't and I
>>could use it to find objects that would be hard to find in the C8.
>
>I would advise against a 7mm exit pupil. In my opinion and experience
>a 5mm exit pupil is a better compromise between image contrast
>(important for deep sky observing), image scale, and wide field of
>view.
>
>My preferred binoculars for deep sky observing are 20x80s and 25x100s.
>Both have 4mm exit pupils. I prefer the performance of 8x42
>binoculars (smaller exit pupils) over 7x50s (larger exit pupils) for
>casual astronomical use.
>
>Back in the days of visual comet hunting (not that those days have
>completely ended), a 5mm exit pupil was looked upon as the ideal for
>comet seekers of around 8 inches of aperture and smaller. Only when
>apertures got in the neighborhood of 10 inches and larger were larger
>exit pupils recommended (necessary to achieve a wide enough true field
>to remain competitive).
>
>For such a specialized scope as you've outlined above, I would not
>want to settle for any ol' eyepiece. I would want a quality 2 inch OD
>eyepiece with good edge of field performance. A 27mm Panoptic comes
>to mind. (I used to use a 27mm Panoptic with a 13cm f/6 apo for comet
>hunting.) This eyepiece should provide you with a true field of view
>of approximately 3 degrees, comfortable eye relief, good edge of field
>performance, and a pleasant apparent field of view as well.
>
>My big, heavy, Meade 40mm Super Wide Angle eyepiece (with its larger
>exit pupil) is one of my least used eyepieces. It's used *only* when
>I *need* a wider true field of view; but even then, the poor edge of
>field performance of that eyepiece is a bit of a 'turn off'.
>
>Of course, you could start with one eyepiece and later enlarge your
>collection by one or two more.
>
>Willie R. Meghar
>http://meghar.blogspot.com/
Thanks for the good advice and insight Willie.
Larry
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