I have been using the Celestron autofocuser with no problem. Now, all I get is an error message when I try to do a single star focus using FWHM that says: NO PIXELS ARE ABOVE THE BLACK LEVEL - INCREASE EXPOSURE OR REDUCE THE BLACK LEVEL
I never had this problem.
Please help me
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Re: Please help me
Hi,
there are two things that you need to check
1) There will be a red box on the image - this is the selection area that is being used to mark out the star to be measured. If that box is over background dark sky rather than a star then you need to move it. If you can't see the red selection box at all, it may be very small - one trick to get it back is to double click on the image, which resets the selection box to about half the size of the current visible area of the image. Once you have done that you can adjust it back to the right size to cover the star of interest.
2) The 'Black Threshold %' setting on the left of the focus score area - pixels below this level are treated as part of the background and are ignored. If this is set to 10% and all the pixels in the selection area are below the 10% brightness level then you will get the message you are seeing. Note that if you are using the option to stretch the displayed image in SharpCap then that can make very faint stars (that are below the black threshold level) look bright enough to see - it's worth resetting the display stretch to check this.
Hope this helps,
Robin
there are two things that you need to check
1) There will be a red box on the image - this is the selection area that is being used to mark out the star to be measured. If that box is over background dark sky rather than a star then you need to move it. If you can't see the red selection box at all, it may be very small - one trick to get it back is to double click on the image, which resets the selection box to about half the size of the current visible area of the image. Once you have done that you can adjust it back to the right size to cover the star of interest.
2) The 'Black Threshold %' setting on the left of the focus score area - pixels below this level are treated as part of the background and are ignored. If this is set to 10% and all the pixels in the selection area are below the 10% brightness level then you will get the message you are seeing. Note that if you are using the option to stretch the displayed image in SharpCap then that can make very faint stars (that are below the black threshold level) look bright enough to see - it's worth resetting the display stretch to check this.
Hope this helps,
Robin