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[QUOTE=rat156;485492]Although I don't have a GEM (yet, one on the way), I have observed that when they start to slew they start slowly then speed up. Is this the case for an EQ5? I don't know, perhaps someone with one can confirm this?
All mounts start off slowly and build up speed.
I am referring to what I have seen with my setup when the camera was say doing a focus exposure and I slewed it to some other spot. It leaves a straight line trail oir perhaps slightly curved. I'd have to do it again on purpose to tell but it wouldn't look like that it looks more like star trails and the whole line is the same intensity rather than a ball at one end and then trails off in brightness. All the stars in the image are lines or slightly curved lines.
9 secs is plenty long enough for that to occur but it would look different to that from what I have seen on my rig.
If it's slewing in both RA and Dec then the trails won't be parallel, as the scope may be moving at different speeds in each direction, That's what my RCX does, it slews each axis independently.
Yes it can be a bit curved rather than dead straight but even.
The bright spots don't fit a stellar profile, if you look at the intensities of the spots, the go from 0 to 128ish to 255 over three pixels, there are only 256 levels in an 8 bit image, so that's 0 to half full to full. That's pretty much what I'd expect from the conversion from RAW to Jpeg in camera for a colour CCD. The bright spot in the middle doesn't do this, it pretty much shows a gaussian profile until it gets saturated.
That's an assumption of what a star should look like. I have seen lots of stars that look like that in a very short exposure. At only 9 seconds they would be only barely exposed. My DSLRs never showed hot pixels that bright, that large and that many and certainly not with ICNR where there would be none. They are stars for sure. If his camera has that many hot pixels its time to take it back to the shop for a new one! Not saying for sure they aren't hot pixels but hot pixels on my cameras are way smaller and far less. In the CCD world a camera with that many "hot pixels" would be engineering grade or lower. DSLRs are different but the Niukon D70, Canon 20Ds and 40D I have used never showed anything like that many and that intense.
Perhaps, but that isn't a meteor, and why the bright spot in the middle?
Who knows what light comes off a buring meteorite or space junk can't answer that. I have never captured one just like that. Normally it is just an annoying streak of light in an image that disappears with median combine with other exposures that don't have it.
Have to disagree with you on this one Greg, never seen one, seen plenty of satellites, no meteors, though I may have, but I would have thought a meteor trail would be especially bright if it was visible to the naked eye. There's heaps of times I spend many hours out at night and don't see any meteors at all. That may have something to do with light pokkution though.
Never seen any metoerites? Do you image from an urban location which suppresses them. At my dark site which has virtually no light pollution on a no moon night if I stood and watched the sky I would be pretty guranteed to see 5 meteors per hour minimum of varying brightnesses. I see heaps of 10 minute exposures with meteorites. I mean really common. yes satellites as well but they are only closer to dawn and shortly after sunset when they are still in the sun at their high altitude not in the dead of the night. The occasional jet lights too.
Meteorites are very interesting to watch. Some are really unbelievably fast and scoot across a large amount of sky, some are really slow depending on whether they are moving, which direction into or away from earth (ie earth catches up with a slow moving one going away from us too slowly or one that is coming at us at a great speed.
I have seen some leave smoke trails (not often) a few that were quite bright, one that came down almost like a firecracker but none that were big fireballs (I have just missed out a couple of times).
But in short they are a really common thing out in a really dark sky but they lack contrast and only the really bright ones are visible in urban locations. Perhaps that is what has setoff this discussion your experience of hardly ever seeing any where you image and others who see them a lot in really dark skies as a fairly common event (several a night when you aren't even really looking out for them). I don't see many meteorites at home either. Only the very few that are really bright and most I see aren't that bright but are visible.
I remember once looking out the window of a jumbo jet at 36,000 feet near the equator and seeing many many meteorites. Must have been a shower at the time.
The best meteorite I have seen was after a night of imaging I was struck by the beautiful sight of a small crescent moon with Venus nearby as dawn was beginning and I was admiring the beautiful view and thought gee it'd be nice if a meteorite flashed nearby and one did right nearby and it set it off just perfectly.
Greg.
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