Help with imaging forthcoming Saturn/Moon grazing occultation.

[michaelmorris]

I'm presently scratching my head over how to image the forthcoming grazing (from my location) occultation of Saturn by the Moon. The difference in brightness between the Moon and Saturn precludes exposing a single AVI for both targets - trust me, I've tried it!.

I have four possible plans, all using webcams.

1) - If I can find someone nearby (Worcestershire) with a very similar focal length set up to help out. Each take 13 minute AVIs of the occultation, one exposing for the Moon, the other for Saturn. Then split up each AVI in to identical length bite-sized chunks, stack each chunk and make a composite of the Moon and Saturn exposed chunks. Finally, after processing, recombine the resulting bitmaps into a new AVI or animated GIF.

2) - as 1, but somehow combine the two actual original AVIs. (Heaven knows how!)

3) - If I can't get someone else to help out, take a 13 minute AVI of the occultation, one exposing for Saturn and two short AVIs exposed for the Moon immediately before and after the Saturn-exposed AVI. Then split up the long AVI into bite sized chunks, stack each one and combine the Moon and Saturn exposed sub AVIs. Finally, after processing, recombine the resulting bitmaps into a new AVI or animated GIF.

4) - Take a series of very rapidly alternating short AVIs, alternately exposing for the Moon and Saturn. This could be pretty exhaustive doing this for 13 minutes. Then continue as per 1. The problem would be lining up the Moon-exposed images with the over-exposed Moon on the Saturn-exposed images. At a focal length of 2000mm, the Moon is going to move relative to Saturn very noticeably from one 20 second exposure to the next. If I go for this option I could really do with some software to automate taking the rapidly alternating Moon-exposed and Saturn exposed AVIs. K3CCDtools will not do this.

Thoughts, comments and/or ideas please!

(P.S. - Remember this will probably all be futile anyway as you can pretty much guarantee there will be 100% cloud cover!)

[Kaptain Klevtsov]

Are you wanting to end up with a video of the thing, or just a still image?

For the still, I'd expose for Saturn and get that sorted out, then do the moon seperately. Then in Photoshop place the correctly exposed moon over the big white nasty blob. Obviously if you want an animation or video, this won't work.

To get both together sounds quite difficult, though I've never tried it. I did have a bash at Saturn crashing through a beehive last year and used the above method to tame it all.

Shame there isn't a lot of time to experiment on the day isn't it?

What you need, thinking about it, is a big neutral density filter on a stick fastened to the front of the 'scope so that it covers the moon but not Saturn

Captain Chaos

[michaelmorris]

What you need, thinking about it, is a big neutral density filter on a stick fastened to the front of the 'scope so that it covers the moon but not Saturn

No joking, but I've actually already considered this! In landscape photography it is not rare to use what is called a 'graduated filter' to darken the sky. The trouble is, no one (to my knowledge) makes one to screw in to the end of a 1.25" eyepiece.