Is automatic aperture 1.5 times FWHM applied for each star in the sequence? Why different stars on small previews (Color Photometry page) have equal apertures and annulus?
All stars in a single image require the same aperture. VPhot calculates the average FWHM of the stars in the image and applies this average aperture (1.5xFWHM) to all measured stars.
Ken
It’s not the best news. I beleived, each star automatically get optimal aperture 
Well, what to do now? Use maximal circles or short sequences?
Mikhail:
For clarification, I assume you are referring to ‘Single Image Photometry’ and NOT ‘Time Series Photometry’?
Ken
Yes, yes. Two color transform.
For untransformed images I choose recommended aperture, but in this case I blindy hoped on automation…
It will be better to use manual set.
I wonder if the confusion here is wanting to measure faint stars with a smaller aperture than a bright star. If image-quality is reasonably uniform across an image, however, it turns out the full-widith-at-half-maximum is the same for all the stars. I agree it is very difficult to gets one’s eye/mind around that, but that’s how it works out. So the VPHOT scheme of using a uniform aperture is correct.
\Brian
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Mikhail:
Actually, what you have shown is normal and correct. The aperture is not too small! What you see visually is a result of the screen stretch of the thumbnails. I suspect you think the aperture of a ‘brighter’ star is not big enough. That is incorrect.
Watch the attached video from my VPhot course. Look at the ‘Measurement Details - Star Profiles’ for some faint to bright stars to prove this fact to yourself. You will find that the aperture where the star profile returns to background is the ‘same’ for both fainter and brighter stars!
Ken
PS: I shared a google drive link with you by email. I also shared to others below.
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Ken is correct. It does look too small for the bright stars, but the aperture is taking in the same fraction of the light profile for all the stars. There is very little information beyond about 2.5-sigma in an assumed Gaussian profile. One could quibble a bit (from your image) and make the gap between the ‘star’ aperture and ‘sky’ annulus a bit larger, just to get the sky measurement out farther from the wings of the profile, but that should make very little difference.
\Brian
Thank you, Ken and Brian, for the explanations! I thought, thin gap between star and circle is needed for avoiding of exposed pixels cutting. Of course I believe to VPhot, but these previews…
Mikhail:
Yes, you do want a reasonable ‘gap’ to make sure your sky annulus avoids most of the target wings as Brian mentioned. The gap you set in “Tools” is a radius not a width so if you make this setting too small it is possible that poor seeing (large FWHM) may cause the auto-adjusted measurement aperture to get quite large and approach the gap outer radius. Obviously not wanted but usually not a problem.
With a little judgement and typical seeing, this should not present a problem but you do need to readjust the gap setting if it causes such a problem. Just check a few times and adjust the gap radius and you should avoid any problem. I rarely need to adjust my settings.
Ken