posted on Feb, 1 2011 @ 01:23 PM
Originally posted by Chadwickus
What kind of magnitudes are we looking at with the nanosail?
Is it a constant? or will it be like Iridium flares?
Great questions. The answer to the first isn't easy to come by. On the one hand, Ted Molczan, one of the world's most experienced satellite
trackers, failed to find it with the aid of a pair of very large binocs on the first night he went looking for it. He thought it had be below
magnitude 7 or 8. On the other hand we have a "satellite trail" picture of it from an observer in Finland which shows a strong signal, but the
photographer couldn't give an estimate of the brightness except to say it must have been "fairly bright." Based on the other stars visible in his
picture I'd put a rough guess at around magnitude 4-5 at least. No one can seem to get a consistent answer and I think the real answer is this; it
depends. It was supposed to tumble at first which would average out the brightness, but then its attitude was supposed to become stabilized by the
orbital drag. If you're viewing "edge-on" for a pass, it will be nearly invisible by eye. If you're viewing it "face-on" it should be pretty bright,
but unfortunately there's no way to know for sure what its attitude is until you observe it.
That brings me to your second question, and the answer is that it will not be constant at all, and depending on the angle of the sun you may indeed
catch a very bright flare off the sail. The team estimates it could appear as much as ten times the brightness of Venus during momentary flares as
its altitude decreases. The rest of the time I'm guessing that magnitude 4~5 is a good estimate, though heavens-above.com has a more optimistic
estimate of around magnitude 2.
I'm intentionally low-balling my estimates though to be on the safe side; I'm going to try to practice on magnitude 4-5 satellites in the coming weeks
to make sure my viewfinder camera can detect satellites that dim and to determine the exposure setting needed on the main camera (if needed I can
adjust on the fly, but if I under-expose then I'd have no way of even knowing if the satellite is in the main view or not). If the viewfinder cam
doesn't cut it then I'll have to reduce my main camera's magnification so that I don't need to rely on the viewfinder at all. That would prevent me
from resolving the sail as more than a point-like light source though, and that's my ultimate goal. Not that a video showing a stationary dot
whizzing by the stars isn't cool, but it would be cooler to actually resolve it, if only barely.
edit on 1-2-2011 by ngchunter because: (no