Focus Assistance Tool

[StarzSkies]

I have a question regarding the Bhatinov mask feature in Focus Assistance.
I have been using a mask and visually have been doing well with focusing.
After seeing the tool in Sharpcap, I gave it a try. What I find is I get a few yellow bricks, a few green bricks or a combination of both, then suddenly get large red bricks up or down. I'm wondering if perhaps something has crossed the field of view.
I experience this with any filter and when using a bright, or not so bright star.
Any adjustments to focus at this point are very slight.
I am also using a selected ROI and frame the defraction spikes accordingly.
I have not changed any default settings.
Using a WO Spacecat 51 V3 (same as redcat 51 V3, just color scheme difference)
I have also changed the stock built in mask with a better mask and the refraction spikes look great to the eye when focusing without the tool.
Any suggestions would be helpful.
Frank

[admin]

Hi,

setting up the Bahtinov tool in SharpCap can be tricky - there is first the challenge of getting the camera settings right to show the spikes nicely but not give a massively bloated core, then adjusting the focus tool black level and line width options to make sure that the spikes are being detected cleanly. There is some guidance in the user manual

https://docs.sharpcap.co.uk/4.1/#Using% ... nov%20Mask
https://docs.sharpcap.co.uk/4.1/#Bahtinov%20Mask

You need to be confident that the overlay lines that SharpCap draws when it detects the spikes are really following the spikes, and are not jumping around from frame to frame.

It's probably worth giving 'SkyCal' a go - that's what I use when I use a tri-bahtinov mask to collimate, and I find it is pretty good. https://www.cloudynights.com/forums/top ... 0-release/

cheers,

Robin

[StarzSkies]

Robin,
Thanks for the quick reply.
I’ll check the tool out.
Visually, the diffraction spikes look good but I’m sure can be better.
Frank