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Askar FMA 230 backfocus


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Does anyone use Askar FMA230 scope? According to the manual, the backfocus distance is 55mm, and I also confirmed with the manufacturer the distance is measured from point 2 (thread start), not 1. 

fma230-backfocus.jpg.e5892c63948bb4337b46d6e2336a289d.jpg

but I achieved the best results with a full-frame camera at 52-53mm distance, so the focuser ring at 16.5 point. Can you share your backfocus distances? At 55mm APSC frame was okay, but full-frame corners were significantly distorted. Here is how FF corners look like at 52mm (no calibration frames, so vignetting visible):

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And the first light - 10x30s stack (not calibrated) of comet next to Aldebaran:

2023-02-16-comet_hyades.thumb.jpg.4c329ac2cb81d7208791c6d93c5f5565.jpg

Sony A7II, SW Adventurer.

 

Edited by drjolo
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  • 4 months later...

Hi,

Thanks for that. I just ordered the FMA230.

It may be useful because I thought I can use my ZWO OAG and ZWO filter drawer, but if it happens and the back focus is also shorter than the 55mm in my case, then I have to consider removing the OAG and using some spacers and another guider instead. It's not nice to play with the components, as they are well aligned now.

Edit.

I just realized that it may be OK for the APS-C., so let's see. 

Edited by Vroobel
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