Focusing with Sharpcap

[dimkavall]

Hello everyone!

This my first post here , I am relative new to AP and very new to imaging with an Astro camera. My setup is :

SA star tracker 2i pro
Redcat51
ZWO ASI533 MC pro
ZWO mini scope with 120mm mini guide camera

I am doing everything with Sharpcap pro ,including PA,plate solving,guiding,dither,focusing and image acquisition (not live stacking) and this piece of software is great!

My issue is the focusing part , I am focusing with FWHM tool with mediocre results…I read that because my scope is and pretzval APO ,it is difficult to proper focus it manually because of the moving parts.What do you recommend to do with Sharpcap tools do I use the bahtinov mask?I didn’t have this issue with my Nikon dslr….

Edit : Please check a light frame of mine https://drive.google.com/file/d/1AdGKdp ... sp=sharing
Also, is it true that even with the bahtinov mask, ideal focus cannot be achieved with a pretzval APO and an astro camera?

Thank you

[admin]

Hi,

I'm not familiar with any particular problems with that type of quadruplet. In general, problems occur most with achromatic doublets, where small adjustments may taken you from 'red in focus, blue horrible' to 'blue in focus, red horrible'.

Not sure if you were using the single star or multi star FWHM, but normally the multi star is recommended.

cheers,

Robin

[dimkavall]

Thanks Robin!

Using the bahtinov mask is an equivalently efficient method, right?

[admin]

Hi,

as long as the lines are clear and crisp then yes.

cheers,

Robin