Jupiter - My first shadow transit (1/5/07)

[middy]

After trying to collimate my scope the other night I took it outside to test it on Jupiter. I noticed that there was a shadow transit in progress and the GRS was also visible. I quickly grabbed the Toucam and laptop and set them up for a quick run.

The seeing was very bad so the results ain't pretty

The shadow looks a bit smeared. I'm not sure if that was just the seeing or if the shadow had moved that much from start to end.

What is the longest time you can image before the shadow starts to streak when the images are stacked?

[iceman (Mike)]

Hey Andrew
That's not a bad image for the conditions (and the fact that it's an undriven dob!)

How long was your total capture time, and what moon is it?

I think it's a bit hard to tell if the shadow is smudged, given the image scale and the conditions.

If the moon was Io, which moves the fastest, try and keep your total capture time (for a colour camera) under 90 seconds. For other moons you could go up to 2 or 2.5 minutes, especially at that image scale.

[middy]

The capture time would have been less than 30 secs given the rate it drifts through the FOV.

Maybe I should try some MAP processing to sharpen the moon a little.

I think it was Io from memory. I know it seemed to have moved a lot from the time I first spotted it to when I had got the Toucam set up ready to go.

[iceman (Mike)]

I took your image into photoshop and looked at teh individual colour channels - the blue channel is very overexposed in the SEB/SEZ area making the colour balance way off and impossible to correct (I tried!). What were your capture settings and what did the histogram look like?

What capture program did you use? How did it look on screen?

[middy]

I can't remember all the settings off the top of my head and I am at work now. I will have a look when I get home. I used k3ccdtools v1.

I do remember the first few avi's were overexposed so I thought I'd try the exposure at 1/100 and crank the gain up a bit to compensate for the dim image. I also remember the saturation being maxed out.

I didn't set everything up properly because it was late, the scope wasn't cooled, the seeing was bad and it was cold

[middy]

Here are the individual RGB images as they came out of Registax (slight wavelets applied to each image).

First image: Red
Second image: Green
Third image: Blue

Processing procedure:

VirtualDub - save frames to BMP
Ninox - centre Jupiter in image
RGBSplit - separate each BMP into R,G,B channels
Registax - Process each set of R,G,B images
Photoshop - Merge R,G,B channels into composite image

[iceman (Mike)]

I'm not sure what your merging process is, but the individual colour channels aren't overexposed so you might need to take some more care in combining and post-processing.

Here's my effort at combining your individual R,G,B bitmaps in AstraImage, taking it to photoshop and aligning the channels, adjusting with some curves, colour balance and saturation.

Your original is on the right. I thikn the elongated shadow is simply due to the conditions and the fact that you were using an undriven dob.

[middy]

Thanks Mike. I think I need to practice with Photoshop more.