Starting Imaging with the ZWO EAF-5V

[reifermadness]

I am waiting for my ZWO EAF-5V to be delivered tomorrow.

I am currently using the Celestron Focus Motor (on my NexStar Evolution 9.25 SCT but can only use it manually (not auto-focus) to focus in BackYardEOS and ASTAP.

Due to the fact we have cloudy and smokey skies, I wanted to test it out the ZWO EAF-5V focusing on close objects (tops of trees, buildings, etc.).

My question is, can I use it to auto-focus on close objects or do I have to do it manually?

Thank you everyone,

Reif

Edited September 14, 2021 by reifermadness

[wimvb]

12 minutes ago, reifermadness said:

My question is, can I use it to auto-focus on close objects or do I have to do it manually?

Autofocus routines in astrophotography use the width of a point source (star) to set focus. They try to minimise this width. If you want to use autofocus during the day, you can perhaps do so on a reflection of the sun, or a very small light source at considerable distance away from the telescope. I've never heard of anyone trying this, though.

[reifermadness]

3 minutes ago, wimvb said:

Autofocus routines in astrophotography use the width of a point source (star) to set focus. They try to minimise this width. If you want to use autofocus during the day, you can perhaps do so on a reflection of the sun, or a very small light source at considerable distance away from the telescope. I've never heard of anyone trying this, though.

Thanks Wim!

That makes perfect sense. I was just now watching a YouTube video about mounting it to the scope and using the software that comes with it. I'll give your suggestion a try once I receive it.

[reifermadness]

9 minutes ago, wimvb said:

Autofocus routines in astrophotography use the width of a point source (star) to set focus. They try to minimise this width. If you want to use autofocus during the day, you can perhaps do so on a reflection of the sun, or a very small light source at considerable distance away from the telescope. I've never heard of anyone trying this, though.

What astronomy software do you use to close the loop when using auto-focus, image capture, and processing?

Thank you,

Reif

[Padraic M]

I use Nina for autofocus, and it works really well. I use a Primalucelab Sesto Senso on a 80mm refractor, and also a Celestron SCT focuser on a C8. The process is the same for both.

A couple of points to keep in mind.

As Wim said, it works by identifying stars in the imaging loop, and calculates their 'sharpness' (FWHM or HFD). This process won't really work with anything else, although you can buy test stars (small point light sources) that could work. 

Autofocus routines generally rely on the scope being close to focus to begin with, so you will still need to focus manually get into the rough focus zone. This can be done during the day (preferably, as it's easier to find a treetop than a star!) but I have good success finding a bright star at night (Vega at the moment) with a very-well-aligned finder scope, and getting it focused by eye. I sometimes use Sharpcap to help with this, but can do it in Nina either. Start looping in Sharpcap or Nina, and use the Celestron or ZWO focus manager until you see those out-of-focus star donuts.

The closer you get with this initial focus, the better autofocus will work. I know this sounds counter-intuitive, but once autofocus has found its focus point, it can repeat this process automatically until you do something to change the focus configuration like manually changing the focuser, or removing/replacing it.

Autofocus may need to be done routinely during the night as you change filters, or if the temperature changes. With experience of your own set-up, you will be able to decide when you need to rerun the autofocus routine.

In Nina, you can programme the refocusing into your imaging sequence so everything is done automatically during the night.

 

[wimvb]

I use the INDI platform (similar to ASCOM but for Linux) and Ekos/Kstars for image capture. PixInsight for stacking and processing.

Ekos/Kstars runs on a Raspberry Pi and is free software. It has routines for pointing (align module with plate solving), focus, image capture, and guiding (but can use PHD), as well as a scheduler for automatic observatory control.

https://www.indilib.org

 

[reifermadness]

Very good and thank you both for the explanations.

Reif