- This topic has 2 replies, 2 voices, and was last updated 2 months, 1 week ago by
.
-
Posts
-
This is just a bit of light-hearted idiocy, so please don’t take it too seriously.
On Xitter today I saw that the Moon lies close to the Pleiades at the moment. My telescope doesn’t have absolute positioning but I can see the Moon through the finder and I can determine its position with MaximDL. Why not, I thought …
A quick snapshot (only 0.05s) through a Sloan i’ filter (to darken the sky as best I can) showed craters very nicely. Syncing the mount with the lunar position told the telescope where it was pointing to within 10 arcmin or so. I then slewed to Alcyone, and saw nothing. The field of view is only about 13 arcmin so it was not too surprising that no stars were visible.
Lots of slewing around pretty much at random produced a number of images which show stars. Unfortunately I have not yet been able to identify any of them but I am sure that they are members of Messier 45. Local solar time was between 13:30 and 14:00.
Encouraged by this success I may try to do a better job some time. It will require cleaner optics and a less hazy sky, presumably. The sky isn’t bad today but I have certainly seen it better. Another possibility might be to use the Moon, Jupiter or Venus (all of which are readily visible through the finder) for an initial position and then search for something as bright as Sirius or Rigel or Betelgeuse to refine the mount’s co-ordinates. A few half-hearted attempts at image processing also made the stellar images more readily visible.
If any more progress is made, I may try for other bright Messier objects by daylight. Only star clusters may be feasible, I guess. If anyone else would like to have a go, please report your success or lack thereof.
Stars with H alpha emission lines (of which there are several in the Pleiades) in a narrow band H alpha filter (where the solar spectrum has a deep absorption) might be interesting.
Robin: indeed an interesting proposal. I don’t have such a filter but others doubtless do. They are hereby challenged to try it!
I also thought of using a video camera, subtracting a constant level from each frame (the minimum value contained in the frame might work) and then co-adding a goodly number of frames. Again, a constant level would be removed from the final stack.
The sky, being a noisy constant, would be smoothed and reduced markedly but the (again noisy) signal from the stars would be increased relative to the background.
This, of course, is essentially what I do to image extragalactic GCs, TNOs, and satellites in the outer solar system, some of which are markedly fainter than the sky behind them, though rarely are more than a couple of hundred subs stacked.
- You must be logged in to reply to this topic.