3 replies to this topic

[jonnybravo0311]

So I recently got the Pegasus FocusCube v2 and connected it to my GT81. I plugged it in, setup the software and ASCOM drivers. That night, I took the rig outside and played around. First, I used the manual controls and my GT81's built in Bahtinov mask along with NINA's focus assist to get a pretty bang-on focus. Next I started playing around with the auto focus in NINA and this is where my questions started to pop up.

 

I can set a step size as well as backlash compensation. When I first started playing with auto focus in NINA, it kept telling me my step size might be too small. So, I increased it. I also noticed that in the Pegasus software for the backlash compensation, it says the Pegasus should be set between 30 and 40. So, not having a clue if I even needed to compensate for backlash, I set it to 35.

 

My setup "seems" to auto-focus pretty well, but I really don't know if it's setup right, or how to diagnose what might need to change - if anything. For example, when the auto focus runs, it gives me a pretty decent parabola, although the bottom of it is a bit flat, rather than a nice curve down to the bottom of the V.

 

Any helpful setup tips or recommendations on what to look for?

 

Thanks in advance!

[jonnybravo0311]

I'm following up on my own post to add some more information from my own playing around and conflicting information I've found online (surprise, surprise) LOL.

 

Last night I spent an hour or so just playing around with the autofocus routine in NINA. I'm using the latest 1.11 nightly build. I'm still no closer to finding the "right" settings. However, at this point I'm mostly blaming my Lumix G9 and the ASCOM driver it uses. Basically, the only thing that works for me with that driver is using one of the image settings called "thumb". While it's fine for the plate solving, it's terrible for the autofocus (I think). Basically, that thumbnail is a low resolution image of 1440x1080 that also lies about the pixel size making it 12.01"/px so the plate solving works. The actual images on the camera are 5208x3904 and the sensor's pixel size is 3.32 microns.

 

The conflicting information I found is actually from Pegasus. In the focus control panel software, you can enable hardware backlash compensation. It suggests this should be set between 30 and 40 steps. However, also on the Pegasus site, in a document discussing how to setup the auto focus in SGP, it mentions that you should use a backlash compensation of at least 100 steps. Those are rather different settings. Watching Cuiv's videos on his ZWO EAF, he was horrified about how bad his backlash is at 93 steps. That leads me to question the 100 step recommendation in the Pegasus manual.

 

The next question is about WHERE I should set this. Is it recommended to set it in hardware via the Pegasus app? Or, is it better to let NINA control and set it? If I am using NINA to control it, should I use the Absolute or Overshoot method?

 

Thanks again for any assistance.

[evansg]

Backlash step count is from FocusCube motor gearbox's  + focuser mechanics. It is different for every setup varyiing from 30 steps to +100.

As these steps are microsteps the actual movement is very small.

It is always preferable to let the software handle the backlash compensasion so please set the backlash value to NINA and let NINA handle the compensation. 

Edited by evansg, 05 March 2021 - 08:16 AM.

[jonnybravo0311]

Thanks for the feedback! I'll turn off the hardware compensation and let NINA drive it. I'll play around again some more once I've got the new mono rig all setup.