Celestron OAG qhy5l-ii

[rodrigol]

1 minute ago, michael8554 said:

That's better, Reducer and guidecam spacing now look correct. 

Moon's out, an easy target to fine-tuned on! 

Michael 

That's exactly what I did! Many thanks for your advice and patience! 

[michael8554]

That's what we're here for, next time you'll be helping us. 

Michael 

[rodrigol]

I was wondering if you could let me know about the placement of the 0.5 focal reducer? 

Many thanks be forehand  !

 

[rodrigol]

I've posted my first image of M27 taken with the rig as described above (https://stargazerslounge.com/topic/340204-m27-dumbbell-first-oag/). 

I'm very happy with the results and looking forwards to more clear skies (but work has taken me away from y scope 😞 ). If anyone is using a 0.5 FR with their guidecam and OAG, can you let me know about how this one is placed in the guidecam imaging train? I suspect it is in front of the camera but when I tried I was not able to get focus at all. 

Much appreciated!

R:)

 

[GraemeH]

@rodrigol - apologies for missing your question about using the 0.5 FR with the guidecam and OAG.  I have attached a picture of my current setup - it's obviously different from yours because I'm using my OAG with a DSLR and the C8 Edge (which has a shorter backfocus distance from the SCT thread).  I have my 0.5 FR screwed to the 1.25" thread at the front of the guide camera, which is then inserted into the helical focuser of the OAG.  By using the FR, I had to shorten the distance from the prism to the guide camera sensor (without moving the DSLR) to compensate for the reducer - I think it's probably moved in by around 15mm, but I'm not sure of the precise distance.  Main point is, the guide camera will need to move closer to the prism to achieve focus with the reducer.

Forgive me if this is teaching granny to suck eggs, but the precise amount of reduction depends on the distance between the reducer and the sensor - I took an image with the guide camera and platesolved it to check on the exact reduction.  This told me that the effective FL to the guide camera is now 1141mm (my DSLR images report a FL of 2142mm with the C8 Edge - I know this is a bit more than the nominal FL, and I'm not sure why), so the reduction isn't exactly 0.5 but it's pretty close.

Hope this helps.

Graeme

[rodrigol]

@Graeme, many thanks for the picture and apologies as well for the time it took to respond. I've been out of action due to kidney stones, which I'm not going to go into here. I don't remember where now, but I did find info on where the FR was supposed to go in the first place. In front of the camera, as you say, and further away if one want a different FR ratio. I've been having tracking issues, which I've tracked down to a loose RA axis and which resulted in horrible backlash. Rather than attempting to compensate  for that I decided to adjust the worm gears. I now have a very smoothly balanced and backlash-less mount. I also changed the saddle for the ATM one, which is very forgiving when balancing and has human friendly knobs. The original celestron cgem saddle is not designed for people with long hands and fingers, like me, and is in fact a bit dangerous. My next challenge is to fit a 2"filter to the OT.

Many thanks for your support!!! 

R:)