I would like to return my SG-2/Aluma filter wheel to the factory for troubleshooting

The spacing of the reducer to the CCD chip is pretty critical, I don't know how much this would affect getting a star on the guide chip but it might be something to consider.

 

Hi William:
Yes, I could work with the smaller sensor size of the ST9XE. The problem seems to be that I cannot get the pick-off prism far enough into the fov working with the f/6.3 reducer. I have not seen the shadow of the prism and it is fully extended.
I like your idea about creating a special subframe size in TheSkyX! Also, I suppose I could add a guidescope and small camera, but my Aluma/FW8 and SC2 are only a year old and I'd like to get them to work properly. But I'm getting close to calling it quits. I'm not there yet though, so I'll keep on trying. I really loke the Aluma and the FW8.

John G.

 

Hi John,

Having looked at the SC2 published archive material this afternoon I can now understand the problem better!

As I'm from an engineering background my solution would have been to have a pair of 5mm thick offset adaptor plates machined to fit between the SC2 and the filter wheel on one side of the SC2 and the OTA coupling on the other, to physically offset the SC2 relative to the filter wheel by around 10mm and bring the pickup mirror/prism closer to the optical axis.
But that does presume that the reducer/flattener can be moved another 10mm towards the camera to make up for the extra adaptors.

Unfortunately with labour and materials costs being what they are a bespoke solution like that would be prohibitively expensive as a one-off and trying to find time in a busy workshop to schedule something like that could see another six months pass before the plates were ready.

Colins idea of moving the reducer closer to the SC2 might just work, it all depends how much tolerance there is on the flattener back-focus distance and if that is critical you would then need to add the equivalent spacer(s) between the FW and the Aluma that you moved the flattener towards the SC2 to maintain the BFD.

I'm still mulling over the problem and will post back if I have any "lightbulb" moments but right now I have nothing better to suggest.

William.

 

Thank you William and Colin for your suggestions. I have looked around through all of my junk boxes in my observatory and ours at school and I have nothing that will allow me to decrease the distance between the reduce ad the SC2. Nor am I able to insert the 5mm spacers. I can only increase the distance between the reducer and SC2--not any help, I know. I am still experimenting with things here and I will post again when I make some progress. Again, thanks to you both for taking so much time to help.

John G.