Not sure if I can reach focus

[E_ri_k (Erik)]

Hey guys. I'm not positive if I'm going to run into a problem or not, but I haven't got very high hopes. Been playing with adaptors and things trying to get the QHY9, filter wheel, and ONAG to co-operate. Of coarse nothing fits into anything else

Anyway, ended getting the tap set out and 2 adaptors are now screwed together.....

My Moonlite focuser is sitting right up to the RC with out any extension tubes, and it's almost racked all the way in. Then comes the ONAG. The QHY10 sits on top of the ONAG with a 15mm extension, and this reaches focus fine.

Problem is, with the QHY9 and filter wheel, the sensor is about 35mm further away, and I haven't got enough "in" focus to compensate for this. The weather hasn't been playing along, so I haven't actually tested this yet, but I'm pretty sure I'm right.

What do you do if you can't focus in any further......Other than trying to get some custom adaptors and reduce the length of the imaging train, but it's pretty short as it is......

Erik

[Lee]

Do you think you have 35mm of excess adaptor length in the imaging train??

With a newt you have to move the mirror.... with an RC?? Can the secondary in an RC be wound down closer to the primary?

[E_ri_k (Erik)]

Thanks Lee. Don't know about moving the mirrors?? Although after a bit of a headache and lots of measuring, it turns out the difference is 42mm, where I only have 6.5mm of inward travel in the focuser. I have looked at Preciseparts.com, and made up 3 adaptors to fit into the setup. The shortest I can go to make it work eliminates 39mm of this, and leaves me with 3.5mm of extra inward travel in the focuser to play with

The painful part is for the 3 parts it's going to cost me $422!!!

[E_ri_k (Erik)]

Actually, just managed to find one of the parts I need!!! Only need the two now, but still $350.......All ordered...a bit depressing though

Erik

[Lee]

Cripes.... I hope you can reach focus when you have it all assembled!

[E_ri_k (Erik)]

Originally Posted by Lee

Cripes.... I hope you can reach focus when you have it all assembled!

Haha, I hope so too!!! I'm pretty confident it will, otherwise I'll have some expensive pieces of metal sitting around

Gone over all the measurements/calcs half a dozen times! I'll let you know how I go when they arrive, probably be a couple of weeks or so.

Erik

[Chris85 (Chris)]

Hi Erik. Surely there's something wrong here. Just read that the focal plane of the Rc 10 is "235mm from the rear cell of the scope, without focuser, to the focal plane". I can't imagine the your image train shooting out past that?
Chris

[E_ri_k (Erik)]

Originally Posted by Chris85

Hi Erik. Surely there's something wrong here. Just read that the focal plane of the Rc 10 is "235mm from the rear cell of the scope, without focuser, to the focal plane". I can't imagine the your image train shooting out past that?
Chris

Hey Chris, Mine reaches focus at 228.5mm from the back of the scope. The ONAG fills in quite a bit of distance unfortunately. I have put some pics up with some measurements.

The QHY9 filter wheel is the main problem in the system. But I have eliminated all the bits marked with a green spot, the ONAG will now thread straight into the Moonlite draw tube, shaving off 24mm. The ONAG will connect to the filter wheel with a new adaptor, eliminating 7mm. And the final adaptor will allow the camera to connect to the filter wheel with a piece only 1mm thick, removing a further 14mm. There is still about 2mm to remove, but I have 6.5 mm of in travel in the moonlite. It will be a close fit but I'm sure it will work

[Paul Haese]

This unit seems an odd way of imaging. This will also cause all sorts of balance problems too. Surely a MMOAG would be better for this and give you all the back focus you need.

[E_ri_k (Erik)]

Originally Posted by Paul Haese

This unit seems an odd way of imaging. This will also cause all sorts of balance problems too. Surely a MMOAG would be better for this and give you all the back focus you need.

I admit it is a little bulky, and takes up a lot of space, but I haven't had any balancing problems with it attached. It actually guides really well, and being able to use the entire FOV of the scope makes finding a guide star possible in the matter of seconds. No rotating and fiddling with prisms.

I have seen quite a few people using the MMOAG, so it must be good! My only experience with an OAG wasn't very successful I spent 3 nights trying to get it to work, with no luck. In saying that it was a cheap Orion OAG, so that might have been why

The MMOAG does look very compact. I'm guessing you use the MMOAG with your RC, Paul? How do you find it to use?

Erik.

[Paul Haese]

Hi Erik, I use a MOAG not the MMOAG, only because I have an AOL on my STL11. The MMOAG is the recommended version if you are not using that type of AOL.

OAG are a little tricky to get right for sure, but mainly getting focus is the drama. Guiding is easy. I am sure that focusing the main camera would be easy and there would be plenty of back focus left. Another option would be to get a smaller focusor. I found that I had to buy another focusor (a FLI Atlas) so I could accommodate everything including rotator on the back of the RC12. I am not suggesting such an expensive buy but there are other options available. If you like the ONAG then focusor is your next option to change.

[E_ri_k (Erik)]

Hey Paul. Yes, focusing the imaging camera was easy. It was hard getting the guider to reach focus at the same point. Too many adaptors which wouldn't co-operate with each other

I never thought of getting a smaller focuser That Atlas would have been an expensive buy, but I bet you're happy with it!

I'm sure these adaptors will bring it all together, even if it just makes it! If they don't, then it'll have to be the focuser.

Thanks for suggesting that Probably the simplest solution, and I missed it
Erik

[E_ri_k (Erik)]

So the parts arrived, and guess what, it works! (Sigh of relief!) Reaches focus nicely, with about 8mm of inward travel left

Erik

[Paul Haese]

That is great Erik.

[E_ri_k (Erik)]

Thanks Paul, worked well. Had a few hours of clear sky last night. Got 4x15 minutes before the clouds appeared.

Erik