Synta or Guan Sheng dobsonian?

I think I've decided on a 6" f/8 dobsonain as my first real scope. 6"
is enough aperture to start to do deep-sky, and the long f/ratio
should make it less likely I'll get one with bad optics. I'm still
considering an 8" f/6, but I think I'll go with the 6" due to its
lower cool-down time.

Now...it seems my choice is between a Synta or Guan Sheng built dob. I
read in a couple of places that Guan Sheng is generally slightly
better optically. WHich brands are Guan Sheng? The only one I know of
is Sky Mentor from Khan Scope Center.

"Patrick" wrote in message
om...
I think I've decided on a 6" f/8 dobsonain as my first real scope. 6"
is enough aperture to start to do deep-sky, and the long f/ratio
should make it less likely I'll get one with bad optics. I'm still
considering an 8" f/6, but I think I'll go with the 6" due to its
lower cool-down time.

Now...it seems my choice is between a Synta or Guan Sheng built dob. I
read in a couple of places that Guan Sheng is generally slightly
better optically. WHich brands are Guan Sheng? The only one I know of
is Sky Mentor from Khan Scope Center.

Patrick,

I wouldn't worry about the difference in cool down times between a 6" and 8"
dob. The extra 2 inches will more than compensate for the added cool down
time. The 8" is bigger than the 6". I'll throw out the standard blurb that
I hear (and agree with): Buy as much aperture as you can afford, transport
and use every night it's clear.

Synta = Orion Telescope XT line
Guen Sheng = all the rest (Khan, OPT, Hardin, Hands on Optics)

If you don't ever plan to use or be curious about DSC's, then I'd get the
cheapest of those GS dobs. I have an XT10 and love it.

Clear skies,

Tom

Hi,

Hands On Optics has Guan Sheng reflectors, but I think they only have
the 10" and 8" ones.

http://www.handsonoptics.com/index.html

Thier 8" with accessories is $449 shipped. You can also skip the
accessories to lessen the price.

Sol Robbins

Pat

I agree with Tom if you can swing the extra dollars go with the 8" F6
you get brighter images and more resolution. The cool down is not
significantly longer from an 6" mirror to and 8" mirror.

Rich


On 16 Oct 2003 15:29:04 -0700, (Patrick) wrote:

I think I've decided on a 6" f/8 dobsonain as my first real scope. 6"
is enough aperture to start to do deep-sky, and the long f/ratio
should make it less likely I'll get one with bad optics. I'm still
considering an 8" f/6, but I think I'll go with the 6" due to its
lower cool-down time.

Now...it seems my choice is between a Synta or Guan Sheng built dob. I
read in a couple of places that Guan Sheng is generally slightly
better optically. WHich brands are Guan Sheng? The only one I know of
is Sky Mentor from Khan Scope Center.

"Sol Robbins" wrote in message
m...
Hi,

Hands On Optics has Guan Sheng reflectors, but I think they only have
the 10" and 8" ones.

http://www.handsonoptics.com/index.html

Thier 8" with accessories is $449 shipped. You can also skip the
accessories to lessen the price.

And to even further confuse you...Hardin (GS) just got in a new batch of
8"'s:
http://hardinoptical.com/dsh8.html which are $349 plus shipping. My 10"
should arrive tomorrow. Woot!

How do I know it will be in tomorrow (besides UPS tracking)? Rain is
threatening the local club's Skywatch tomorrow night so I'm sure I will not
be able to even use it. : (

-riff

On 16 Oct 2003 15:29:04 -0700, (Patrick) ...reflected:

I think I've decided on a 6" f/8 dobsonain as my first real scope. 6"
is enough aperture to start to do deep-sky, and the long f/ratio
should make it less likely I'll get one with bad optics. I'm still
considering an 8" f/6, but I think I'll go with the 6" due to its
lower cool-down time.

Oh, phooey on the cool-down time; treat yourself to the 8",
as it collects 73% more light than the 6", according to my Orion
Telescope catalog.

You'll be glad you did.

Now...it seems my choice is between a Synta or Guan Sheng built dob. I
read in a couple of places that Guan Sheng is generally slightly
better optically. WHich brands are Guan Sheng? The only one I know of
is Sky Mentor from Khan Scope Center.

Syntas are made in mainland China, whilst Guan Shengs are
made in Taiwan. "Oceanside Photo and Telescope, Hardin Optical,
Hands On Optics, Murnaghan Instruments and others" reportedly
carry the Guan Sheng Dobsonians.

Orion used to be, but are Syntas now.

Alan

Thanks guys. I can get a Sky-Watcher (which I think is Synta) 6 or 8"
dob for a good price at a local store. But they don't sell any Guan
Sheng dobs. So if I want a Guan Sheng, I'll have to pay for shipping,
so it'll cost me more.

Are Guan Shengs better enough optically...or at least more consistent
optically...to warrant paying more?

I read that it's safe to store a scope outside in a dry shed. But
won't dew form on the mirrors...even if it's capped?

I think I've decided on a 6" f/8 dobsonain as my first real scope. 6"
is enough aperture to start to do deep-sky, and the long f/ratio
should make it less likely I'll get one with bad optics. I'm still
considering an 8" f/6, but I think I'll go with the 6" due to its
lower cool-down time.

Cool down is not a big issue compared to the advantages of the increased
aperture of the 8 inch scope.

There is a myth of sort that says one cannot use a scope that has not reached
thermal equilibrium. It is true that views will be sharper, especially at high
powers when the scope is cooled but there is plenty to see with a scope that
has just come out of the house or car, especially if you are wanting to view
DSOs. In any event, the difference in cool down between a 6 and 8 inch scope
should be minimal.

The advantage of the 8 inch scope are that it will have better resolution and
that it has about 78% greater mirror area. This is a big advantage for viewing
DSOs. If it is a GS scope it will probably come with a 2 inch focuser and an
8x50 finder, a real advantage in my view.

The disadvantages are that the OTA is somewhat heavier but physically the same
length and that the focal ratio is means collimation will be somewhat more
critical, not much but some. I find that the 22 lbs of my XT-8 OTA is easy to
deal with.

These days the mirrors on these scopes seem to be good, so I would avoid making
the choice based on that criteria.

In my view, the decision most often is not between the 6 and the 8 inch scope,
rather it is between the 8 and 10 inch scope. The 10 inch is significantly
bigger and while only slightly longer, it is more awkward to handle. The 10
inch does provide significantly better DSO performance than the 8 inch. But
the size as well as cost may be a factor, one really needs to see these in
person to make the decision.

I am lucky enough to own both the older XT-8 and the OPT Starhunter 10, both GS
scopes. Both perform well , most nights it is the 10 incher. For a quite trip
in the car or my back is bothering me, the 8 incher goes, otherwise it the 10
or something a tad bit larger.

So, IMHO, while the 6 inch DOBs are nice scopes and there is plenty to see and
enjoy using one, the advantage of the added inches of the 8 or even 10 inch
DOBs is worth the added cost.

In the 8 inch scopes, think the GS are the better deal over the Orion XT-8
because of the 2 inch focuser and the 8x50 finder.

Best wishes, hope all goes well.

jon isaacs

(Patrick) wrote in message . com...
Thanks guys. I can get a Sky-Watcher (which I think is Synta) 6 or 8"
dob for a good price at a local store. But they don't sell any Guan
Sheng dobs. So if I want a Guan Sheng, I'll have to pay for shipping,
so it'll cost me more.

Are Guan Shengs better enough optically...or at least more consistent
optically...to warrant paying more?

I read that it's safe to store a scope outside in a dry shed. But
won't dew form on the mirrors...even if it's capped?

I'll add my 2 cents for what it's worth. About a year ago I ordered a
6" f8 Dob from let's just say H. Optical as I don't want to start
anything, just giving my personal experience. It was a total piece of
crap, both mechanical & optical. I returned the scope & they even
returned my shipping costs! I then decided to order their 10" Dob in
hopes it would be better; well it wasn't. The mechanics were okay, but
the optics suffered severe astigmatism, so returned that one too. No
refund for shipping this time. I then ordered an Orion 6" f8 Dob &
this one was great right from the box. The mechanics are okay & it
needed a very slight collimation, but that's it. It easily splits the
double-double, gives good views of the ring at 150X, etc. & has a very
good no problem star test.

I'll add my 2 cents for what it's worth. About a year ago I ordered a
6" f8 Dob from let's just say H. Optical as I don't want to start
anything, just giving my personal experience. It was a total piece of
crap, both mechanical & optical. I returned the scope & they even
returned my shipping costs! I then decided to order their 10" Dob in
hopes it would be better; well it wasn't. The mechanics were okay, but
the optics suffered severe astigmatism, so returned that one too. No
refund for shipping this time. I then ordered an Orion 6" f8 Dob &
this one was great right from the box. The mechanics are okay & it
needed a very slight collimation, but that's it. It easily splits the
double-double, gives good views of the ring at 150X, etc. & has a very
good no problem star test.

That is one of the issues with the GS dobs. The secondary mirror is held
VERY tightly in its holder and this often casues mild to severe astigmatism
in the GS dobs. The Orion (Synta) dobs have a secodnary that is glued to a
stalk. The GS secondaries can be remedied fairly simply by removing the
secondary mirror and doing some sahving and sanding of the holder to relieve
the pressure. There is a lot of info in the Yahoo Skyquest group on how to
do this http://groups.yahoo.com/group/skyquest-telescopes/.

Clear skies,

Tom

XT10, highly modified