Back to forums

Williams 71 gt with rotator back focus

William Optics Gran Turismo 71 / GT71 ZWO EAF Rotator Flattener
5 replies•336 views
Dan Kearl avatar
Dan Kearl avatar
I have my Williams 71 gt scope set up perfectly with back focus of 64mm..
I bought a Rotator because Williams is too cheap to have one and when I put it on it messed up all the focus,
I cannot even polar align now.
Has anyone had this problem? I took to off after screwing around for an hour and it works fine again.
What do I set the Flattener at with the added rotator to get the Scope in focus again.
I have an EAF attached.
Mark Germani avatar
Mark Germani avatar
Where is the rotator attached - between the OTA & flattener, or between the flattener and camera? AFAIK, it should be between the OTA and the flattener, and then you don't need to touch the backspacing between the flattener and the camera.

If you're using an EAF, did you get it roughly in focus before starting your autofocus routine? If it can't identify any stars to use as a reference, the autofocus will fail.

Sorry if these are all things you've considered. CS!
Well Written Helpful Respectful Concise Supportive
Tarun Pulikanti avatar
Tarun Pulikanti avatar
I have a rotator attached to my GT71, it goes on to the scope before the Flattener and you dont have to touch the back focus !!
jjpoole741 avatar
jjpoole741 avatar
Dan Kearl:
I have my Williams 71 gt scope set up perfectly with back focus of 64mm..
I bought a Rotator because Williams is too cheap to have one and when I put it on it messed up all the focus,
I cannot even polar align now.
Has anyone had this problem? I took to off after screwing around for an hour and it works fine again.
What do I set the Flattener at with the added rotator to get the Scope in focus again.
I have an EAF attached.

I have nine set to ~9.5mm on the flattener and it works fine. I think the guide says 9.1mm.
Tarun Pulikanti avatar
Tarun Pulikanti avatar

 
Dan Kearl:
I have my Williams 71 gt scope set up perfectly with back focus of 64mm..
I bought a Rotator because Williams is too cheap to have one and when I put it on it messed up all the focus,
I cannot even polar align now.
Has anyone had this problem? I took to off after screwing around for an hour and it works fine again.
What do I set the Flattener at with the added rotator to get the Scope in focus again.
I have an EAF attached.

I have nine set to ~9.5mm on the flattener and it works fine. I think the guide says 9.1mm.

Yes I have a similar setup !! Below is a image of the same !!
Pariah avatar
Pariah avatar
If you have the 1.0x TS Flat it can cause issues if set up as rotator - flattener - backfocus- camera. The focuser extension is only 10mm with the TS flat so you wont get focus if you add a wo rotator

Which flattener are you using?