ZWO EAF Autofocus

[smr]

Hi,

I'm not really sure what I'm doing with regards the ZWO EAF I have. I bought the EAF in Spring this year but since then, mainly due to the weather and lack of astro darkness I haven't done any imaging. We've got a couple of clear nights forecast so I'm getting back into imaging.

I've installed the EAF and it seems to work fine, I can control it with APT although it took me a while to work out how to use it to focus. I'm just not sure if my routine is right.

Do I have to still manually focus with the bahtinov mask before each session and then run the autofocus tool in APT? How do I know for sure that the focus is completely accurate after the autofocus tool has run ? I don't want to focus with the bahitnov mask, run the autofocus tool and then start imaging without knowing that it's definitely focused properly but I'm not sure how to ascertain whether it is or not.

[scotty38]

Not sure how APT works but in NINA you'll see the resulting curve but having said that I still take a test image anyway to check. Can you do that?

Edited September 6, 2021 by scotty38

[bottletopburly]

First time you use it focus with the bahtinov so you know your in focus , then open  auto focus craft and focus aid  , press start in run and let autofocus aid do it’s magic , you may Need to tweak settings see how default works let it run once finished check with the bahtinov to see what the bahtinov spike looks like,  the new focus algorithm is very good . 

[smr]

Thanks guys, took me a couple of hours to get my head around how to focus manually, not easy after a few months not doing it and with the ZWO EAF for the first time.

(Let me know if any of this could be improved / better ) If anyone's interested I chose bin 4x4, 10 second exposures (because I've got the L-eNhance filter in the imaging train) and image preview 1:1. Slewed over to Deneb which was really nice to focus with.  I focused manually with my Bahitnov mask and recorded a focus position of 2680. 

I then slewed over to the Heart Nebula and took an image, chose a star at random really but with as low a HFD as I could and then clicked 'Run' on the Autofocus Aid.

Here are the results...

 

 

Does this look alright?

[bottletopburly]

Did you recheck with bahtinov after autofocus 

[bottletopburly]

Setting up auto focus https://aptforum.com/phpbb/viewtopic.php?f=28&t=4602

I need to study this and refine my settings 

[smr]

2 hours ago, bottletopburly said:

Did you recheck with bahtinov after autofocus 

No I just thought that 2694 wasn't that far away from 2680 but I will check tonight. 

When I recheck focus should I stay on a bright star ?

ie. last night I focused with the mask on Deneb, then slewed over to the Heart Nebula and chose a star in that star field for the auto focus routine, thing is I can't then recheck focus without slewing over to a bright star again so should I check manual focus with the bahitnov mask on Deneb, then choose a star there for autofocus, and then recheck focus on Deneb?

[smr]

When I focus on a bright star with the Bahitnov mask, should I then move to the target and run the autofocus tool or should I run the autofocus tool after removing the bahitnov mask (staying on the bright star) and then slew over to target to begin imaging?

[bottletopburly]

Run after autofocus but only the once your only checking for piece of mind not every imaging run 

[smr]

I'm going to start over tonight, now I've got a better idea (I think) of what I'm doing, but what I meant was, when focusing with the mask on a bright star, do I then remove the mask and slew over to the target I intend to image, and then run the autofocus aid, or do I stay on the bright star, and run the autofocus aid there, then slew over to the target to begin imaging ?

 

[Pompey Monkey]

There's  no harm in getting focus on a bright star and then slewing to your target.

However, you should ideally re-focus when on target in case anything in the optical train shifts slighty with the scope in a different attitude. Especially if you are using a reflector or catadioptric ota.