Kevin UnderOak Observatory Celestron Hyperstar C8 SCT Celestron Classic (1972) Orange C8 SCT Vixen VC200L Losmandy G-11 Gemini Losmandy GM-8 Televue 76/SolarMax 40 Televue NP101 ST-402ME/Nikon D70 DSLR SBIG DSS-7 Spectrograph SBIG ST8-XME & CFW9 filter wheel Starlight Xpress SXVF-8MC Pyxis LE Camera Field Rotator
Quote:The problem with significant undersampling is that the tiny star images may not fully illuminate a pixel and could even fall between pixels. I observe this first hand with my all-sky camera. I once considered using it to watch bright varuabkes like Algol. But nope, the star brightness vary greatly as the flow from one pixel to the next or flow between pixels. The fix? Combine enough images to blur the stars out a bit. It is not nearly good enough for photometry, but it lets me get fairly good images from a simpe camera.
Quote:'We've' (lol) seen WFPC2 errors on single shots >20mmag as an e.g.So for precision just defocus until get to a sweetspot.
Quote:Quote:'We've' (lol) seen WFPC2 errors on single shots >20mmag as an e.g.So for precision just defocus until get to a sweetspot.I would expect anything in the charge shifting to look like readout noise and not be dependent on where the photons strike or wavelength. Likewise, I can't see where variations in the silicon would cause variations base on photon location or wavelength...the charge shifts across the chip for readout. I can see the variations arising from variations in the phosphor coatings or cosmic ray hits, etc...but maybe it's from something else?I'm curious to know how universal this effect may be across cameras. I don't think I can measure it on my current equipment.