I am starting this thread because of some issues that have popped up with my GSO 16" Truss dob. I know at least one other owner has had similiar issues and hopefully this will serve as a place where these things can be discussed and assistance provided.
First, I noticed today that Andrews Communications is advising on it's website that it in bringing in another shipment of the 16" dobs and the price has now dropped back to $1999 again.
Aperture $ value draws many people to the GSO 16 along with a pretty reasonable optics package for the $. Of course a budget price means that some other areas of the scope are probably either lacking in quality or in need to some owner work to improve the package performance.
It's a big heavy beast, obviously not as big or heavy as say a 20"+ dob but as a mass production unit it's near the edge in terms of ability to transport and manage. Despite breaking down into major components, transportation is exactly where my issues start:
I took my 16 up to Bretti last weekend, and carefully packed it vertically supported in my vehicle for the journey. Obviously collimation is a fact of life each time this scope travels, and on assembly at Bretti I found a problem that I had not encountered at home - lack of sufficient infocus on the shorter EPs. My 2" 30mm EP worked great as always, but I could not get anything below that to focus. You will be thinking the focal length is too long, and your right, when I moved the mirror up on its springs I managed to get focus again - but what changed from the home setup? Could the mirror have moved down during the trip - yes I may have left the locking knobs too loose.
I recollimated everything up at Bretti and the scope worked great from then on, but it was making some clunking noise towards the end of the last night which sounded like primary shifting to me. Yes, the GSO springs are probably in need of an upgrade. On the trip home the noise from the lower tube section got worse and it was obvious the mirror/carrier was moving around - while I did tighten up the spring bolts a couple of turns for the trip home it wasn't enough. When I checked at home I found that two of the three spring bolts had dropped out and the springs were in the bottom of the tube. There is no way of locking that heavy mirror from upward bump travel and it had worked the bolts loose on the bad road back from Bretti. Subsequent PM discussion with glenc revealed that he had an identical problem with his 16 on the way back home on a rough road from a weekend away. So it would seem that the 16 needs a primary locking system, and not just the locking support bolts because they only stop compression (they are not tapped into the carrier but only push against it) - its extension that's causing the problem. The answer may lie in through drilling and tapping a hole in the carrier to serve as an upward movement lock.
Regarding the infocus problem, here are my views. When the scope is packed by GSO the mirror seems to be to torqued down for shipment and thus way to the rear of optimal focal length position. Now as we all know, Andrews does not open the boxes or do any sort of setup on these scopes before they are warehouse shipped to the buyer. There is an obvious assumption that any 16 buyer knows dobs and how they should be setup, and that's ok as these are not usually something that a novice goes out to buy, but a sheet of paper reminding the purchaser to optimise the Focal length during collimation would be a good idea.
Related to this was a very loose secondary when I unpacked mine, ok again I know what to do about that, but it's potentially a big problem if not caught before assembly. This could be a shipping problem but it's something to watch out for when you open the top section box. Check it before you lift it from the box.
My 16 is now perfect again and giving me amazing views but it does require tuning work, don't expect to just open the box and put it together and find it's optimised. There is a learning curve but you will be better prepared for any future with this knowledge.
I know glenc has had his primary mirror (escape) issues when travelling but I would like to hear what other GSO 16 owners have to say as well.
I suppose this could be a GSO 16 user group thread, so let's hear from the other owners out there. I know there are a fair few because Andrews keeps selling these things by the container load. Maybe we can all get together one day at a dark site.
