I did a project in college that required that I measure the size of star images on B&W film (I used a microscope designed for this) and to compare them with magnitude. I was looking for a correlation between brightness and dot size. There was one but the stars were hazy dots. Because a satellite moves the exposure would differ not only from brightness but from the speed of its movement across whatever part of the sky it's in. I image that makes accurately estimating satellite's brightness from a photograph quite problematic. Tom Iowa USA ----- Original Message ----- From: "npr61" <npr61@bellsouth.net> To: "Gerhard Groenewald" <bataleur@megaweb.co.za>; <SeeSat-L@satobs.org> Sent: Monday, September 14, 2009 6:01 PM Subject: Re: Bright Sat Photometry? > Mr. Groenewald: > > I'm wondering if I can use a DSLR to take raw images and do comparative > brightness (Sat vs. ref star). With only a 50mm lens & short exposures, > bright stars should remain point-like and thus amenable to measurement > with an aperture. The short sat trail, entirely within the frame, would > require a rectangle to encompass it. I imagine it will be tough to avoid > saturation, and may not give useful results at all. I basically wondering > if it is possible to "measure a streak". The goal is not research grade > work, just fun with a camera and software. > > Forgive my ignorance, but I figured this would be the place to ask about > measuring sat brightness. All of the AAVSO info I've read does not really > address sats. > > Neal Robichaux > 29.9884N > 92.1498W ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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