Guest post: David DeLano’s ultimate Galileoscope quest, Part 4 – The GS F11 SCT GS to end all GSMarch 9, 2014
The moment you’ve all been waiting for–I would be shocked if anyone, anywhere, ever, has put this much time, thought, experimentation, and additional gear into their GS. But having used it in the field, I can tell you that David’s monster GS is both a potent observing tool and a real pleasure to use. To see how David got from the stock GS to this, see the previous posts in this series.
There is actually one other way to solve the Galileoscope focal length issue. When the Learning Encounters site (http://www.leosciencelab.com/ [not linked here because there is nowhere to go–MW]) was functional, they carried a diagonal kit, with which you could construct your own diagonal to go with your Gallileoscope. Part of the kit was a new, F11, objective. With this longer focal length objective, a diagonal will work in the GS without shortening it. This is the ideal solution, but it is likely very difficult to find one at this point. I had modified my daughter’s GS with this kit, and it worked perfectly well with a Stellarvue diagonal w/helical focuser. I also had a spare kit, originally bought for my son, but he lost interest. So, I decided to use it for myself.
Somewhere along the way in this project I also bought a used SCT focuser off of Cloudy Nights. The SCT focuser ended up to be a lot larger than I had thought it would be. It was far to long to use the original F10 objective, but since I had the F11 objective I decided to give it a try.
I had a 2″ adapter with SCT threads from my previous experimenting. I had to buy a M-M ring to mate it to the focuser, and the first one I tried didn’t quite work. I found a second one that had a lower outer profile, and it actually nestles inside the focuser barrel so that the 2″ adapter and focuser are mated with no additional length. I tested this out, and it was almost short enough to focus, but not quite. The SCT focuser has a 2″ EP holder on it, and I used the shortest 2″ to 1.25″ adapter I could find, but was still in need of a couple mm in length. I also found that the tube was butting up against the inside of the 2″ barrel, so I shortened that a bit (and at this point it barely touches, which is the best length to have), but I was still not satisfied. I found a prism diagonal with a lower profile EP holder, but was still not quite satisfied. I found a 2″ to 1.25″ adapter at ScopeStuff that was almost zero clearance. It would be zero clearance with an EP but since I was attaching a diagonal, it added 1-2mm. ScopeStuff, however, removed the lip on the adapter for a small fee, and this gave me the focal length I desired – I can focus with my glasses on or off! The adapter attaches to the diagonal barrel with a couple of inset hex screws, which works perfectly.
I added a more than necessary red dot finder that I had bought cheap somewhere along the way. It looks like overkill, but actually helps with the balance. This scope is really too much for a finder, though I did use it while observing at the Salton Sea with Matt. It will likely end up as my lightest grab and go as the mount it is attached to in the picture rides on a photo tripod, and both the scope and tripod fit into a bag together. All that is needed is an EP or two. As a finder, I had been permanently using a 32mm Plossl, but as a viewing scope I’d likely take along a couple of other EPs to use.
Side by side with Matt’s modded GS you can see that it is about 50mm longer, which is what the F11 objective gives you. The SCT focuser makes it look even more massive, but it still is a GS at heart.
And also to give some comparison, here are, top to bottom, the SCT set, Matt’s set, and the ABS part, so you can see how much focal length each adds.
I think I’ve covered everything. If you are still reading this, I hope you enjoyed the ride. If you have a Galileoscope kit, I hope that I have inspired you to turn it into a usable scope or finder. If you have questions, please post them to the blog comments, and I’ll try to clarify.