Pls help me decide, GSO or Ostahowski 16" mirror?

[mbaddah]

I've just ordered a 16" SDM with a GSO mirror (YAY!), however I am having 2nd thoughts about the GSO and thinking of the Ostahowski...

I am receiving mixed opinions about whether to stick with the GSO or not. If anyone can provide me with relevant information, personal experiences with both mirrors etc... It would be greatly appreciated, cheers :)

[pgc hunter]

If you can afford the Ostahowski mirror, then definately go for it. He's a well known manufacturer of premium mirrors who's optics are highly regarded and used to figure mirrors for Discovery Telescopes.

[AG Hybrid]

I wonder what the sterhl of a GSO mirror is anyway? If its about 0.90, do you think you will see the difference between 0.90 and 0.95+ ?

Id get a Zambuto though. Peter does supply them with his dobs if you want. Infact I will get a dob with Zambuto Optics one day!

I may never own a Astro-Physics refractor but Ill have a Zambuto mirror which in itself has alot of mystique about it, like a AP.

[pgc hunter]

You also have to keep in mind things like surface roughness. A hand figured mirror is almost certainly guaranteed to be smoother than a mass produced one, which translates to higher contrast at the eyepiece.

[Waxing_Gibbous]

Are you extra-super keen on the absolute best views ever or will a very, very good view suffice? At this size, prices become a major factor, the difference being many hundreds if not thousands of 'star coupons'.
As Adrian noted, do you think that extra .05 of a "Strehl" is worth it.
For general observing, I'd say probably not. Only if I was to catalouging objects or doing long-term observations of a piece of sky, would I be that worried.
Having said that, I'd want the best GSO mirror I could get though!

[norm]

Hi Adrian,

I'll be biased here and say Ostahowski.

If your budget is tight, the GSO serves its purpose, the option is that you can always upgrade in the years to come. IMO, if your going to spend the bucks on an SDM why not go the whole distance and go with the premium optics.


Each to there own, but this is one vote for a T.O mirror.

I have no issues with mine.

Cheers Norm:)

PS: have you tried contacting Mark Sutching for a price - superb mirrors from an Australian.

[norm]

Hi Adrian,

You wouldn't believe it, but SDM038 16" GSO mirror practically new for sale for $4000 - bargain.

Check out the trade section.:thumbsup:

This is unbelievable :eyepop:

Cheers Norm.

[gb_astro]

Agree.
Drop everything mbaddah and get that #38
gb.

p.s. I was going to point out that a GSO mirror might affect the scope's resale value....

[mbaddah]

Thanks everyone for your input :) I'm nearly tempted to switch over to the Ostahowski!

I had liased with Stephen selling the SDM#038 a few days ago. Unfortunately there were a few things it doesn't have which I want, such as:

- 10k encoders for Argo Navis
- Dew heathers for secondary, eyepiece and telrad including controllers.
- New block solid for truss poles.

Not sure if I've missed anything else? hmmm it is tempting though to get it straight away instead of waiting for a while :)

[Phoenix]

Did you happen to discuss with Stephen his thoughts on the optical quality of his GSO mirror with Galaxy secondary, etc. in the SDM setup? - re: your decision on which mirror to purchase. Despite the image scale, its a nice Jupiter avi that Stephen has captured with the SDM#38 - see SDM web page.

Nix

[norm]

Hi Adrian,

If your planning to travel with your scope, go for the UTA hardcase.
I've got the padded soft fabric for the truss poles, it does the job well.

There is also the optional soft covers for the Rocker box/mirror cell from Astrosystems.
Don't forget a cover for the scope itself when fully assembled and not in use (home or at an Astrocamp).

These add up to the final price, but you can't really go without any of them, especially if you want to protect your investment:thumbsup:

Cheers Norm

PS: I recently made a box to fit the argo stalk/argonavis and telrad when transporting it around. See if Peter has a contact to make one up.

I tried to keep the cost down when making my box, but ended costing me around $180 (spray paint, handles, latches etc add to cost). Don't even get me started on the foam!! Honestly - get one made up - works out cheaper and will probably look better too!;)

[AG Hybrid]

Hi Norm,

Why are you always directing all your posts at me ? i'm not the one buying the dob :lol::lol::lol: :rofl::rofl:

Fyi I am thinking off getting a 12.5 inch obsession as my first premium observing tool. Either that or get a Skywatcher 12 inch truss dob with tracking and then spend the saved money on a plethora of 82 & 100 degree Explore Scientific eyepieces. And then do the ATM thing with a feather touch focus and rigel viewfinder etc.

I do wonder though, would I get much improvement out of the skywatcher mirror if I got Sachmo to refigure it? Once again whats the strehl and P/V of these GSO and skywatcher mirrors, has no one tested them?

[ngcles]

Hi Mbaddah,



I agree with every word Norm has posted here. I have two main 'scopes: my 31cm (12") with a Deep Sky Optics (DSO) (Mark Suchting) mirror that is an outstanding performer. Highly recommended.

I have two friends who also have DSO mirrors in their 'scopes. One is a 41cm (16") f/4.5 that started life as mirror from another well-known manufacturer (not one of the ones mentioned here) that had a good 1/2 wave of spherical aberration. Mark re-figured it and it is now superb. Another friend has a 50cm (20") f/5 from Mark -- also an outstanding performer.

My 46cm (18") is a "Discovery" mirror that was made by Terry Ostahowski. Superb optic. Can't fault it. Highly recommended.

That is not to necessarily "bag" the GSO mirror -- but it is a mass produced product and accordingly it is less expensive mainly because of the economies of scale and the cost of labour elsewhere.

Certainly some mass produced mirrors I've seen are also excellent. I've looked through maybe 10-15 GSO newtonian 'scopes (6-12"). Some were brief experiences while others I had a good opportunity to assess the optics. From those experiences, I can't personally say I've seen what I'd call a "dud". That is not to deny that they exist. I have heard from reliable sources of a couple of 'scopes that were not up to scratch.

For consistency, it's hard to beat a hand-figured "just-for-you" optic. You pay a premium, but you are assured of a premium product. If you ever have to re-sell it, you'll get the difference you paid in the first place back.

On the other hand, you might well get a very good or excellent GSO mirror that will be functionally comparable to a premium-priced one and have some dough left-over for a couple of nice eyepieces.

Up to you ...


Best,

Les D

[wavelandscott]

The Ostahowski mirrors are quite good. He made them for Discovery for a number of years but is now on his own (I think). If you can afford a premium mirror over the GSO I would encourage you to get one.

That is not saying that the GSO mirror is/will be a bad one but if you are spending the money on a quality SDM structure why would you not take full advantage of that quality by placing a great mirror in it?

Would you put cheap tyres on a sports car?

[astronut]

Moh,
How about a Suchting mirror?:)

[norm]

Hi Adrian,

NFI - sorry brains gone amiss somewhere during posting.:screwy::screwy:
Good Luck with the 12.5 Obsession btw!

Cheers, Norm

[mbaddah]

Thank you all for your informative posts.

I've decided to stick with the gso momentarily for now, I can always upgrade to a Suchting mirror once I wear out the gso and become a more proficient visual observer :)

For now, the "turbo" SDM fits right in between the "clunky" 16" LB and a 16" SDM with premium mirror, which is exactly what i was looking for. As many have iterated here and from my own experience having used gso dobs and a lightbridge for a while, optics is one thing, but the mount, scope and comfortability factor is just as important as well.

Looking forward to it :)

[Garyh]

Agree
Why not get in contact with Mark Suching for your mirror?
[/URL] [URL="http://www.iceinspace.com.au/forum/member.php?u=633"]Satchmo (http://www.iceinspace.com.au/forum/member.php?u=633) here on IIS.:thumbsup:

[erick]

Same for me, but financial constraints also came into play. I have had good reports on my GSO 12" from people that know more than I do, so I'll stick with that for now. Perhaps one day there will be good reason to upgrade to a premium 12" mirror?

[mbaddah]

Latest update on my SDM...

Peter received the 16" gso mirror not too long ago and conducted some tests, the results were shocking :eyepop: It was a total dud and in Peter's words, "I'd be kind in saying it had a Strehl ratio of about 0.5... in the star test instead of a point and a couple of aireys rings light was spewing out all over the F.O.V". Thankfully because Peter is such a nice guy (:thumbsup::thanx:) he has not charged me anything at all for the mirror (not even delivery charges in an attempt to receive a refund) and suggested I go for the Suchting mirror :)

I've been in contact with Mark and have placed an order on a 14.5" Quartz mirror :D I think it'll suit my "portability" needs more so than the 16" without compromising too much on the visual aspect. Mark isn't sure whether the Quartz has a visual advantage than the Pyrex ,but it'll make for an interesting test. Anyone here compared the two?

Lesson learnt though, above 12" mirrors for me in future no gso!

[Omaroo]

Congratulations Moh - you'll love the DSO mirror. A good compromise in relation to size too. Is the truss system going to be much shorter now - like the 7 or 8 inches I estimate?

[mbaddah]

Thanks Chris :thumbsup: Indeed it should be shorter by about 7/8 inches roughly, ~@63 inches. A nice height :D

[mbaddah]

Update: It's confirmed now the mirror is a 14.5" Quartz at f4.75 @69" , perfect for my height and no need for a parracorr :D

[pgc hunter]

wow that I think must be a rare exception, as GSO make very decent optics. But that's the risk with mass produced optics, the consistency of quality is not 100%. However, one is much more likely to receive a good mirror than a dud.

[Starkler]

Mines f4.8 and I wouldnt be without.

[pgc hunter]

Going on the advice of the guys here, I'm having my SDM built so it can be used both with and without a paracorr.

[wavelandscott]

While it may not be strictly needed, I seem to prefer using the Parracorr even at f5...on my f4.5 it rarely leaves the scope.

Sorry to hear about your mirror...but on occassion all mass produced goods throw out a lemon...glad it was caught before you got it out in the field!

[GrahamL]

Congradulations on the upcoming scope purchase :thumbsup:

I would like to replace my 12" gso mirror in time , works great but is
really quite slow to cool down in my scope. I'm not really familiar with quartz as a substrate ?..other than it used to be very expensive.

http://www.quartzmirrors.com/
For $350 .. I could probably live with pushing it under a bed someplace an waiting a while.

[Satchmo]

Not sure what you are looking at there . A 14.5" 1.4" thick Quartz blank including $150 curve generating is over $800 USD.

( Edit : you must be talking about an extra thin non generated 12" ? )

MS.

[mbaddah]

I found in my 10" LB at F5 there wasn't any coma (none that I could detect) and a parracorr was not needed. Although I have not used one in the scope so I can't be certain whether the before/after visual comparison would have been noticeable or not.



Indeed I'm glad it was caught as well :) I think it worked out for the best now though as the 14.5" is more portable and at f4.75 catered to my height :)