First Impressions of GSO 12" R/C Truss

[Paul Haese]

Originally Posted by loc46south

Hi - here is a link that may explain the problem from another perspective and the solutions used. http://stargazerslounge.com/topic/18...-rc-dissambly/

Cheers
Geof Wingham

Geof, that thread is full of misconceptions. I have read through that many times and the assumptions are not correct. Yes putting in an 18 point cell would give better support but if you look through my images with the same scope I don't get that problem at all. You have pitched optics and nothing more than that. You need to check the edge clips and the central baffle tightness and ensure the secondary is not warped by too much pressure from the collimation screws. The weight you have on the back of the scope will not cause that problem. It is not possible mechanically from this system to cause pitched optics with the weight of the camera on the back.

[loc46south (Geoffrey)]

I Hope you are right, the scope is up at the observatory and I will give it another run once we get clear skies again - you may be right - after reading that thread and a couple of others I backed off the secondary screws a full turn and did the same to the primary screws - then I did a collimation with a Tak Collimating scope. The screws were tight and by tight I mean tight - you would think that they had been put in with an impact wrench. I had to use a fair bit of force to get them started with a T-Bar hex key. Depending on what the outcome is I may crack the back and check the clips. Just to confuse the issue I will attach a 10 sec Bin 1 x 1 image take further outside focus - the triangular shap is still evident even though the interior of the donut is round.

[Paul Haese]

The primary collimation screws have to be tight. The secondary is just finger tight only. You will need to back off the mirror clips to remedy this problem, that means taking the back of the scope. The rear screws will not affect the pinching. I recommend you get Suiters book on Star Testing Telescopes. It will help you identify what the problem is here.

[loc46south (Geoffrey)]

Done

[torana68 (Roger)]

Originally Posted by loc46south

Done

as in fixed?

[Paul Haese]

If you google images of pinched optics, you will see lots of images like yours both at focus and out of focus too. It will be comforting to know that you at least know what the problem is and how to fix it.

[loc46south (Geoffrey)]

Originally Posted by torana68

as in fixed?

Nope as in ordered book

[torana68 (Roger)]

LOL , its a good read that book, heavy reading but good

[loc46south (Geoffrey)]

Originally Posted by Paul Haese

If you google images of pinched optics, you will see lots of images like yours both at focus and out of focus too. It will be comforting to know that you at least know what the problem is and how to fix it.

If you go back to my first post you will see that I quoted the problem as pinched optics - as to its cause and cure I still have no real answer - was it bad QC from GSO or is there some other force at work here.

This link that may provide some real clues http://www.loptics.com/articles/star...starshape.html -

Cheers
Geof Wingham

[Paul Haese]

Originally Posted by loc46south

If you go back to my first post you will see that I quoted the problem as pinched optics - as to its cause and cure I still have no real answer - was it bad QC from GSO or is there some other force at work here.

This link that may provide some real clues http://www.loptics.com/articles/star...starshape.html -

Cheers
Geof Wingham

Sorry Geof yes you did say that but pinched optics are not caused by any other method than exerted force being placed on actual optics. The force being applied by the mirror clips for instance but not by the anything hanging out the back of the scope.

[loc46south (Geoffrey)]

Paul - I think the focus of this thread had drifted a little - over the last few days I have recieved numerous PM's detailing instructions of fixes or band-aids for the problem - this was not my intent. My intent was to understand the possible causes - any fixes for those causes remain the responsibility of the manufacturer. The number of threads encountered on the internet detailing this or similar encounters points to an obvious problem with the mirror cell on the GSO 12" R/C telescopes that causes mechanical astigmatism. The matter is now in the hands of GSO - their response will decide my future actions.

Whether it is a case of bad Quality Control, bad design or a combination of both matters not, what matters is until it is rectified it is a matter of buyer beware.

Cheers
Geof Wingham

[clive milne]

Hi Geoff,
Did you buy it from Bintel or Andrews'?

[loc46south (Geoffrey)]

I bought it from neither - it was purchased from a retailer in New Zealand. But in saying that I must add that this is not the retailers fault and I believe he is doing everything in his power to clear the situation up. The fault lies with the maufacturer.

[Paul Haese]

Originally Posted by loc46south

Paul - I think the focus of this thread had drifted a little - ........The number of threads encountered on the internet detailing this or similar encounters points to an obvious problem with the mirror cell on the GSO 12" R/C telescopes that causes mechanical astigmatism.

I take your point here Geof but the perceived cause is not astigmatism via the mirror cell. It is via the mirror clips and possibly the secondary screws warping the secondary. The mirror clips should just barely touch the mirror if at all. The secondary screws need to be similarly tightened. Nothing should be hard up excepting the primary collimation screws.

Yes GSO are at fault here for producing the product with pinched optics. I don't defend that at all. The product should have come to you as such.

Something to bear in mind is that all things being equal had you received the scope in good condition; you would have had to clean the primary after 5 or so years. You would need to pull the scope apart to wash the mirror, re-install it into the cell and then re-collimate it.

It is a factor of these cheaper RC scopes that some tinkering is a necessity. I have had one of these scopes since they first starting coming into the country. Each scope I have bought I have had to fix issues which I have passed onto GSO and that has led to the improvements in each edition. I am sure I am not the only one doing this and nor will I be the last. In spite of all the minor dramas, these scopes still represent value for money. The optics are good and the new truss design is very strong and once the rear cell adaption is sorted these scopes will be even better value for money. With any reflector though, you need to manage pinching and collimation and sorting this out yourself will not void your warrantee. Though you could ask for a replacement as under section 51 and 52 of the Trade Practices Act, the product is not of merchantable quality and requires a replacement.

Yes Caveat emptor is at play here but the retailers and GSO are keen to see buyers happy. I know that Bintel are great at customer service in this regard, so if you bought it from them you will be satisfied in the fullness of time.

[noxidc]

Hey my GSO 12" had this same problem when i got it! Triangles, i just pulled the mirror cell out and loosened the clip holders so they BARELY touched the mirror surface and put the mirror cell back in, as Paul keeps describing. Problem was gone.

[loc46south (Geoffrey)]

Originally Posted by Paul Haese

It is a factor of these cheaper RC scopes that some tinkering is a necessity.

If you went out and bought your wife a new washing machine or yourself a new LED widescreen TV and then once you got it home you had to dismantle it, then repair/modify it to get it to work you would be quite happy - somehow I don't think so - and yet these items are far more complex and half the price of the telescope. You expect them to work perfectly, out of the box. every time. What makes a R/C Telescope different

What I have discovered over the last week or so is that there is a wealth of information out there about R/C design and optics from both telescope builders and opticians - all are in agreement that R/C's are sensitive to mirror issues and that for mirrors over 10" in diameter that 3 edge support systems are not recommended and they will cause astigmatism issues.

[Logieberra (Logan)]

Originally Posted by noxidc

Hey my GSO 12" had this same problem when i got it! Triangles. i just pulled the mirror cell out and loosened the clip holders so they BARELY touched the mirror surface and put the mirror cell back in, as Paul keeps describing. Problem was gone.

Question. These scopes travel such great distances from factory to overseas customers. Are the clips perhaps over-tightened, in factory, as a safety measure? The RCs do travel on their side to us, scope fully built, unlike the bigger GSO dobs (16" for example) which of course travel mirror down, as they require building.

Cheers.

[loc46south (Geoffrey)]

Don't know - suspect not. It was packed in a sealed double cardboard box - there was no documentation at all with the telescope apart from the packing slip from the retailer on the outside. No instruction manual - nothing

[gregbradley]

A common trend with many products these days (not just telescopes) is the early adopter customer tends to be the beta tester for the product.

It looks very promising and the cost for a 12 RC is unheard of anywhere else. Obviously some patience is required.

Greg.

[dpastern (Dave Pastern)]

Originally Posted by loc46south

If you went out and bought your wife a new washing machine or yourself a new LED widescreen TV and then once you got it home you had to dismantle it, then repair/modify it to get it to work you would be quite happy - somehow I don't think so - and yet these items are far more complex and half the price of the telescope. You expect them to work perfectly, out of the box. every time. What makes a R/C Telescope different

What I have discovered over the last week or so is that there is a wealth of information out there about R/C design and optics from both telescope builders and opticians - all are in agreement that R/C's are sensitive to mirror issues and that for mirrors over 10" in diameter that 3 edge support systems are not recommended and they will cause astigmatism issues.

I rarely post on IIS, and my thoughts are generally not well received, but I wholly agree with your post. I find it amusing that so many people are defending such poor quality.

Dave