Which Is the Better Deep-Sky Telescope?

I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Dave Mitsky

On 26 Aug 2004 08:00:10 -0700, (Dave Mitsky) wrote:

I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

For deep-sky, there is a very significant difference between a 5" and a 10"
aperture. If you are speaking only in terms of the optics, I don't see how you
could ever find the smaller scope a better choice for DSOs.

Of course, there may be other factors to consider. Certainly, the ease with
which the smaller scope can be used on an equatorial mount could be strongly in
its favor.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Opinion on whether a 127mm mak is better than a 10" dob, for deep sky?

I have a 127mm f/12.
There is no comparison between it and my larger dobsonians for deep sky.
Aperture on a stable mount wins.
____________________________

For the light weight, quick, no hassle deep sky equation, I choose the 150mm
f/5 newtonian/alt-az solution over the 127mm f/12. Orion, Celestron and others
have these also.

The 150mm f/5 is capable of far lower power ( and larger field ) observing. At
50x the 150mm is brighter than the 127mm. Not dramatically so, but it is
certainly noticeable.
However it will _not_ do high power like the 127mm f/12.


john

The 10" naturally. I agree with Jon that higher mags and better planetary
views might be possible with the 127, but a quality 10" will usually put it
to shame.

"Dave Mitsky" wrote in message
om...
I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Dave Mitsky




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I've had both the (GS) XT10 and the Starmax 127.

The comparison is utterly ridiculous. There is nothing that the 10" Dob
can't do better optically.

The only advantages to the Starmax, is the ability to pack it away into
small pieces for a trip. Well, that, and the ability of the EQ3 to track
with the optional motor drive.

Stephen Paul

"Dave Mitsky" wrote in message
om...
I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Dave Mitsky

I have an 10 inch DOB, had a ETX-125, have a C-5 (among others..)

It only took one trip to a dark sky location with the 125mm MAK to decide to
sell it. With the 1.25 inch eyepieces, the maximum exit pupil is not much more
than 2mm, the field of view is less than 1 degree. Sweeping a dark sky was
very underwhelming as were the DSOs.

Compared to a 10 inch F5 Asian DOB, there is no contest, 2 degree FOVs, bright
targets, galaxies.....

Personally I think the most under-rated DSO scope is the Orion SpaceProbe
130ST, the 130mm F5 Newtonian with a good quality Parabolic mirror. Its about
6 lbs and 24 inches long, its compact and yet provides some nice views, both
widefield and high power. I have taken mine way past the 50X per inch on double
stars, waste magnification to be sure, but round airy disks at 1300X are pretty
neat anyway.

The mirror is small so cooldown is not much of an issue.

I consider this scope to be the half pint brother to the XT-10. The one I have
has a 2 inch focuser, (not standard) and that really opens up the sky for a 5
inch scope. Its Central Obstruction is a bit large at 29% but still smaller
than that of a Mak or SCT.

This scope will do 3+ Degree FOV (with the 2 inch focuser, 2.5 Degree
Otherwise) at 20x with 6.4mm exit pupil.

Pretty hard to be that for doing the Milky Way.

-------------

Don't know why you are asking this question, but for what its worth, there is
not doubt in my mind that a 10 inch DOB will do everything better except fit in
a small car and of course track. But the small exit pupil and small aperture
limit the usefulness of tracking when viewing DSOs.

jon

I would say the 10" Dob is better on two fronts.

1. More aperature = brighter views at the eyepiece, better limiting
magnitude, and greater resolution.

2. Wider field. The Dob is at f/4.5 or f/5, for a focal length of 45"
or 50". The Mak is focal length f/15 which is 75" of focal length. The
wider field will make looking for galaxies and fitting large open
clusters in the FOV alot easier.

Just my $.02

(Dave Mitsky) wrote in message . com...

I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Gosh, how good can your reason be ...

Seems simple enough to me. For deep-sky observing, a bigger scope
always shows more than a smaller one, with three exceptions:

1. The bigger scope has very poor optics (inherent or due to
poor collimation, thermal problems, etc.)
2. The object being examined doesn't fit in the FOV of the
larger scope but does in the smaller scope.
3. The object in question has extremely low contrast, and the
bigger scope does significantly worse in this arena.

I've viewed through a couple of Orion 10" Dobs, which had perfectly
fine optical quality, and I've had extremely reliable sources vouch
for the quality of the Hardin 10". So #1 is out.

Because of its very low f/ratio and its 1.25-inch focuser, the Orion
Mak-Cas actually has a *smaller* maximum FOV than most 10-inch Dobs.
So much for #2.

Case #3 is quite rare, and decent Dobs have pretty good contrast,
and the contrast of the Mak-Cas is inevitably limited by its CO.
So there can't be many cases, if any, where the Mak-Cas wins in
this department.

That means that the only way the Mak-Cas can conceivably be called
a better deep-sky scope is if you end up using it more because of
its portability. That, obviously, is going to depend on the user
and the details of his/her situation.

- Tony Flanders

10 inch -- but then you have to haul it (my 10" Dob tends to languish as
a result .. and my smaller scopes are used more)

Phil

Dave Mitsky wrote:
I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Dave Mitsky

Sorry, I'm laughing.. I hope you'll tell us why you're asking.
The 10" by far. Only possible reasons to choose the 127mm are
portability or ability to put it on an equatorial mount.
Bill Kocken

I'd like to hear your opinions on whether a 127mm Orion
Maksutov-Cassegrain is a better deep-sky telescope than a 10" Orion or
Hardin Dob that is now on sale for about the same price. Don't laugh I
have a very good reason for collecting this information.

Dave Mitsky