by jscotti » Thu Feb 03, 2005 2:52 am
Your trail is almost certainly a geosynchronous satellite. From mid norhtern latitudes, the parallax for a geostationary satellite puts them at around -5 or -6 degrees declination. If you tracked on the stars, they will drift in RA approximately the length of the exposure (i.e., a 5 minute, or 300 second exposure will trail roughly 5 minutes of RA - actually different by the sidereal/diurnal rate differences, or 1.0027 times faster than your wall clock). I'd say the trails in both images are very close to a minute of RA long. If they were taken approximately at the same time of night, the same satellite will be in roughly the same location (more correctly, if they are taken 1 sidereal day apart, they will appear at the same location). But there are many geosynch satellites to accidently shoot and they are as bright as around 9th magnitude as I recall. If you set your camera up without tracking, you can image them pretty easily with a good digital camera these days.
Jim.
Your trail is almost certainly a geosynchronous satellite. From mid norhtern latitudes, the parallax for a geostationary satellite puts them at around -5 or -6 degrees declination. If you tracked on the stars, they will drift in RA approximately the length of the exposure (i.e., a 5 minute, or 300 second exposure will trail roughly 5 minutes of RA - actually different by the sidereal/diurnal rate differences, or 1.0027 times faster than your wall clock). I'd say the trails in both images are very close to a minute of RA long. If they were taken approximately at the same time of night, the same satellite will be in roughly the same location (more correctly, if they are taken 1 sidereal day apart, they will appear at the same location). But there are many geosynch satellites to accidently shoot and they are as bright as around 9th magnitude as I recall. If you set your camera up without tracking, you can image them pretty easily with a good digital camera these days.
Jim.