Hello. I have some problems focusing with astrdodon 5nm ha and sii filter. With esprit 80, moonlite focuser automation and ASI183.
I’am using robofire acquire star focusing method. My OIII filter focuses nicely to around 1.8-2.2 HFD, but HA and SII filters end up in 3-3.8HFD.
HA stars were at first 4+ HFD, but tweaking some setting I managed to lower the avarage HFD with about 0.5.
I do think it is related to my setting, as I got it better with tweaking them. But I must admit that I do not fully understand the settings and need help. Seems like Voyager wants to over saturate the HA and SII stars for some reason, what setting I need to change for this?
Below are my settings and one example of over saturated focus:
Ha star(what looks like soft focus):
Saturated or not the focus star doesn’t affect focus … focus is done out of focus and Voyager use HFD method, if star at HFD parameters used from Voyager have peak satured this is a problem.Final HFD value is not a reference value itself but if you use robostar method a relative reference in a series of image of the same star. Also more is small pixel and more is bigger HFD.
Difference in filter depends on filters, telescope correction, star type,seeing, region of sky, altitude, air glow … a lot of environment.
Your HFD parameters is probably in not linear parts of focus this can affect final result. DEfault is Near 10, Start 20 and Vcurve limit 40. Really important that your near value is out of non linear focus zone. Be sure you dont have backlash and if you have … setting it in Voyager.
All the best
If you use LocalField the HFD parameter are not used , forget.
I use one star focus, as it is better for me.
When I lowered the HFD values, I was able to get smaller HFD when focusing. I knew it must be in the linear part, so I placed near focus at 5.5HFD. But maby 7 would be better.
How about the min and max star flux settings? Should I change them?
I do not understand what I should do to get better HA and SII focus. As I get OIII focus perfectly, I dont know what there could be wrong in HA and SII =))…
From the VCurve in image you cannot go under 8/7.5
If you get better HFD (if you are able to repeat this all the times during more moons) this mean you have optical problem on your telescope/train.
Min and max are a range … if you dont have error its ok.
How to get better focus i cant help you, focus process doesn’t depend on filter.
From my experience you cannot think that all filters give you the same HFD.
I think you entered in a wrong loop.
All the best
After all, I did not have problem as I thought I had. The Ha and SII stars comes little different from my system then oiii. But the focus was spot on, checked with bahtinov mask multiple iterations.
HFD is little higher with sii and ha, but I cant get better focus. So planing for new scope before next season.