Focus Assist Problem

A place to report problems and bugs in SharpCap
Forum rules


If you have a problem or question, please check the FAQ to see if it already has an answer : https://www.sharpcap.co.uk/sharpcap-faqs

Please also read about Troubleshooting USB Issues before posting.

*** Please do not post license keys - please report any problems with licensing to 'admin' by private message ***

Please include the following details in any bug report:

* Version of SharpCap
* Camera and other hardware being user
* Operating system version
* Contents of the SharpCap log after the problem has occurred.
[If SharpCap crashes, please send the bug report when prompted instead of including the log]
Post Reply
Luling_Skies
Posts: 10
Joined: Thu Feb 23, 2017 10:40 pm

Focus Assist Problem

#1

Post by Luling_Skies »

I'm running the new 3.1.4944 beta version on my HP Omen laptop with my ZWO ASI071MC-Pro camera. I previously used Sharpcap version 3.0.4008.0 and in particular its focus assist with the Bahtinov mask tool. I find on the new beta version the program fails to find the star spikes, see attached screen shot. Any changes in the Bahtinov mask coding?

Tim
focus capture.JPG
focus capture.JPG (156.28 KiB) Viewed 2410 times
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Focus Assist Problem

#2

Post by admin »

Hi,

I think that you've been bitten by a bug in 4944 where the selection area rectangle is not being drawn - this is fixed in 3.1.4949. I expect that the (invisible) selection rectangle wasn't around your star. Sorry about that!

cheers,

Robin
Luling_Skies
Posts: 10
Joined: Thu Feb 23, 2017 10:40 pm

Re: Focus Assist Problem

#3

Post by Luling_Skies »

Thanks for the prompt replay. I have installed version 4949 and will try it out probably tonight and let you know if the issue is resolved.

Regards,

Tim
Luling_Skies
Posts: 10
Joined: Thu Feb 23, 2017 10:40 pm

Re: Focus Assist Problem

#4

Post by Luling_Skies »

Robin,
I tried the focus assist again last night with the 3.1.4949 version and it reported it found the diffraction lines from the Bahtinov mask. Here was my view without the tool engaged. The spikes are centered well so I should be close to optimum focus.
visual focus.JPG
visual focus.JPG (105.22 KiB) Viewed 2375 times
Then I engage the focus assist and it gave the report below. What gives me pause about the numerical calculation of focus is that the projected lines by the program do not align well with the diffraction spikes from the mask.
sharpcap focus.JPG
sharpcap focus.JPG (157.77 KiB) Viewed 2375 times
Any ideas on why the lines don't align? Are the calculated focus results valid?

Regards,

Tim
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Focus Assist Problem

#5

Post by admin »

Hi Tim,

so I tried loading your image above into the deep sky test camera and turned on the Bahtinov function. I can make it detect correctly subject to a couple of changes

1) Turn up the black level - you see the area excluded from the calculation because it is below the black level as it is shaded in red. You want this to be a loose fit around the bright area as shown below.

2) Brighten the image (by setting a 2s exposure with the test camera - you would need to increase gain or exposure).
Capture.PNG
Capture.PNG (276.23 KiB) Viewed 2370 times
Perhaps having a digital gain in here might help in a future version, but hopefully the ideas above will get you going.

Robin
Luling_Skies
Posts: 10
Joined: Thu Feb 23, 2017 10:40 pm

Re: Focus Assist Problem

#6

Post by Luling_Skies »

Thanks Robin. I'll give it a go next observing session.

Regards,

Tim
Post Reply