Hi guys
I've taken the plunge into astrophotography and I'm aware of the need of guiding the main imaging scope with a guidescope - so I have almost all the equipment to now do so, and while I'm awaiting the delivery of my autoguider, I'm trying to figure out the best way to mount my guidescope. This is not an SBS vs other types of mounting question, but just a "what am I doing wrong" type of thing.
I have an ED 80 as my imaging scope with the tube rings that came supplied, and a ProStar short tube refractor as a guidescope. The guidescope was purchase from myastropshop 2nd hand and they kindly made up some guide rings (modified skywatcher rings) with custom adjustment screws for alignment (which you can see in one of the images below). However, it's mounting these rings on top of each other that's presenting the issue!! I've tried looking through the forums for ideas, I've looked at other people's setups but I can't figure what to do - It seems everyone has their guidescope mounted on a dovetail bar which bolted onto the holes of the main imaging scope if I'm not mistaken?
So, I thought "yeah, the holes at the top of the of the ED 80's rings will be the same size/thread of the holes of the bottom of the guide's rings (as they're the same style of rings)" so I measured the small bolts that came with the guide's rings and it came out to be an M6 size, and accordingly I went out and bought appropriately sized bolts of a longer length so they could go through the top of the ED80's rings, through the bottom of the dovetail and then into the guide rings... well it was then I found out that the top of the ED80's rings (the piggy back thread) is not really the same fit as the bottom of the tube rings. This seemed really odd to me, and so I measured the thread size and then noticed that the top whole has a wider thread spacing that that of the bottom of the rings.
So I had effectively bought long bolts that couldn't fit through the top of the ED80's ring holes to make it through the dovetail and the rings. And it appeared that the piggy back screw that comes with the ED80's rings is too big to fit through the corresponding hole at the bottom of the rings. So as a frustrated/quick fix, I drilled out the threading of the bottom of the guide rings, took a spare piggy back screw from one of my other scopes and threaded it through the two ED80 top piggy back holes. However, these screws are too short to make it through a dovetail plate and then into the guide rings. So right now, I've got the guide rings sitting right on top of the imaging scope rings with a bolt on each end holding things in place (see photo). This, to me, seems like a stupid idea as I'm sure this is going to introduce all types of flexure issues.
So how the heck does everyone do it?? Am I missing a key component to my setup here?! Is it just a matter of getting some extra long screws of the same size/thread that fit through the top of skywatcher tube rings (seems to be camera thread sized)??
The first image simply shows a close up of the top ring above the ED80 ring with a nut holding it in place. The second image is showing how the 4 rings are currently setup. The third image is of the two screws (both supplied as piggy back screws from my ED80 and my other skywatcher) on the front and back ring. And the fourth is just how the ED80 sits on the dovetail, which is how I thought everything would fit together for the top rings... but hence the reason for this huge post!!
So any info/ideas you guys have would be really appreciated - and go easy on me... I gave a pre-emptive warning of newbie questions in my introductory post
I'm also very sorry for the super long post, but I've literally written everything that popped into my head, and I'm sure I'll add more later!!
Thanks guys!!
I'm not into flexure lol.
