Help re: Zwo EAF Step size for autofocus Quattro 200

[SB (Chris)]

Hi Everyone
Would be grateful if you could share your settings for ZWO EAF Autofocus for this Newtonian. Tried a Quattro 200 out last night for the first time and couldn’t get the FWHM below 7 with the EAF autofocus.

The stars were also a little egg shaped and in the morning I found the collimation to be out quite a lot. Now readjusted.

Presently I have the EAF step size for autofocus set to 30. Gives a fairly shallow V curve. I’m using a Sharpstar 1x MPCC, IR/UV CUT filter, back focus is 57mm (2mm extra for the filter).

Many thanks

Chris.

[AstroViking (Steve)]

You don't say what software you're using to drive everything.

If it helps, I have my step size set to 50, and a backlash amount of 35. Software in play is Ekos.

Cheers,
V

[SB (Chris)]

Originally Posted by AstroViking

You don't say what software you're using to drive everything.

If it helps, I have my step size set to 50, and a backlash amount of 35. Software in play is Ekos.

Cheers,
V

Hi V,
Thanks for pointing that out. I’m using ASIAIR PRO to drive everything. My guiding is good at 0.35 using an OAG.

Chris

[Drac0 (Mark)]

I don't use a newt or the ASIAir, but with my setup using APT I use steps of 100 for the autofocus routine. I found that smaller settings were giving me almost flat results but 100 is giving me a nice curve.

[Camelopardalis (Dunk)]

It’s kind of a “suck it and see” experiment…at f/4 the critical focus zone is quite slim, and on a decent night your Quattro should give you quite tight stars (when collimated!)

[SB (Chris)]

Originally Posted by Camelopardalis

It’s kind of a “suck it and see” experiment…at f/4 the critical focus zone is quite slim, and on a decent night your Quattro should give you quite tight stars (when collimated!)

Thanks Everyone,
Here is last nights second effort with the new Quattro on NGC 1532. The stars are a little better but are elongated by some red CA. I still can't get the focus below 5.3 FWHM. Perhaps I need to try adjusting the back focus slightly? Other options (apart from fine tuning the collimation again) are to change the filter wheel to a filter drawer to reduce weight on the focuser ( it's a low profile R&P focuser).

Chris

[Camelopardalis (Dunk)]

Not bad. Looks like your collimation is still needs work.

The FWHM can be misleading if you’re using a small pixel camera, and average/poor seeing will bloat the stars too.