September 4, 2021: First light of ASI294MM-Pro on Veil

[michael.h.f.wilkinson]

Finally got the new camera working. Got 2 hours of data on the Witch's Broom and Pickering's Triangle in H-alpha and O-III, and another 45 minutes on the Eastern Veil in H-alpha, using the APM 80mm, Tele-Vue TRF-2008 0.8x reducer, and the ZWO EFW2 filter wheel with Baader filter (LRGB, H-alpha, O-III and S-II). I have processed the first 4 hours of data quickly, and am quite pleased with the result. Stars in the corners aren't quite right, but I am getting there.

[david_taurus83]

Nice first light! Glad some people are getting a few clear hours!

If I had to be critical, I'd say your focus looks just a tad soft. If you got it nailed down perfect it should also improve the corners. 👍

[michael.h.f.wilkinson]

21 minutes ago, david_taurus83 said:

Nice first light! Glad some people are getting a few clear hours!

If I had to be critical, I'd say your focus looks just a tad soft. If you got it nailed down perfect it should also improve the corners. 👍

I think you are right. Will spend more time with the Bahtinov mask tonight 

[michael.h.f.wilkinson]

So here is the H-alpha-only version, with 45 minutes on the Eastern Veil added.

It is a bit soft, but I am mainly pleased to have got the camera working

[Rodd]

Looks good.  New equipment is awesome. I do agree that your focus might be a tad off. Still looks good though

[michael.h.f.wilkinson]

2 minutes ago, Rodd said:

Looks good.  New equipment is awesome. I do agree that your focus might be a tad off. Still looks good though

Cheers. I checked the Bahtinov images I shot and they look OK, but I have noticed that turning the locking screw of the focuser can shift focus slightly. There was also some high haze in the sky, which will not have helped either. I will try again for the Eastern Veil tonight

[Adam J]

Yes good test. I would say you need to remove some backfocus maybe 1-2mm to get a flatter field. I think this is the issue as opposed to just focus as other have suggested. 

[PadrePeace]

This shows how stars are impacted by too little or too much back focus. AdamJ is spot on with his diagnosis. 

Edited September 10, 2021 by PadrePeace

[michael.h.f.wilkinson]

3 hours ago, PadrePeace said:

This shows how stars are impacted by too little or too much back focus. AdamJ is spot on with his diagnosis. 

I am certainly going to remove some spacers. I think I forgot to include the filters in the computation of the back-focus distance. I will first shave off 0.5 mm, and see what happens. 

[PadrePeace]

Michael, filters in the optical path will always require additional BF to be added, usually 1/3 of the filter glass thickness. You do have a miscalculation here as there is obviously too much distance to the sensor at the moment. Would like to see a sub once you have it sorted.

Edited September 11, 2021 by PadrePeace