Hi Joe and Chuck, This thread is getting pretty long so I'll try to address all of your posts at once. On 09 Dec 2008, at 10:34 , Joe Bauman wrote:
Patrick, would a focal reducer help by enlarging your field of view? -- I intend to try this the next time I'm out with the telescope. -- Joe
Good point. I should have mentioned that. Before I got into lightcurve work I used a focal reducer. That does yield a wider field and could increase your chances of discovery. Just be sure and make really good master flats to remove the vignetting focal reducers tend to cause. The reason I no longer use one is because for minor planet light curves the targets have an irritating habit of passing very close to a background star. Longer focal lengths tend to minimize the bad effects of such encounters. I could switch back and forth depending on what I'm shooting but that would mean shooting new flats (and possibly darks) every time and that's not worth the effort. That's also the main reason I almost never remove or even move the camera. On 09 Dec 2008, at 10:22 , Joe Bauman wrote:
How does binning help? Thanks, Joe
In one way binning is like film grain. As you probably remember the faster the film the coarser the grain. Same with CCDs. If I bin 1x1 I get very fine grain but much slower speed. 3x3 is coarser but also records the really faint targets more quickly. So for "pretty pictures" I might use 1x1, for lightcurve work 2x2 and anything requiring maximum useable sensitivity (like trying to find new minor planets) 3x3. On 09 Dec 2008, at 12:16 , Chuck Hards wrote:
I'm sure Patrick can answer more specifically, but binning is primarily a noise-reduction technique.
I'll need to defer to Jerry or Tyler on that. I'd don't _think_ binning changes noise but I don't know for sure.
I think that his "finds" are almost indistinguishable from image artifacts, being merely tiny blips- thus the multiple images of the same field for comparison.
You've got that right on. If I remember, when I get home I'll post a shot of my most recent find. It's so hard to see I never would have known it was there had CCDSoft not pointed it out to me.
Patrick is probably imaging on the edge of detectability, thus more noise in the raw images. Am I near the mark, Patrick?
VERY near. Of course one could go with longer exposures (I use 4 minutes) but then I'd have to start guiding and guiding on multiple fields would be a real pain. Plus one has to remember the minor planets are moving so if the exposure is too long all one will have is a very faint streak that's even harder to see and harder still to measure. It's very different for the MPs I do lightcurve work on. They are typically very bright and practically jump off the screen. On 09 Dec 2008, at 12:27 , Chuck Hards wrote:
I seem to remember that binning is also a tool to match the effective pixel size to the resolution of the telesope. Patrick?
Yes. And thanks to Jerry for educating me on this one. patrick