Did I capture detail on Ganymede?

[Chrissyo (Chris)]

Hi everyone,

Last night the jetstream was very nice to me So I decided I may as well go out and get some Saturn and Jupiter AVIs. Anyway, I got up at about 4:00am to capture Jupiter. I decided "why not" and got a few seperate AVIs of Ganymede after seeing some of the fantastic shots around here recently of it. I didn't really think I'd get anything other than just a blob.

Anyway, I've processed them and there appears to be something that looks like it might be some sort of detail? I'm being skeptical about it at the moment so I thought I'd ask the opinions of others.

In the image attached below there are two white boxes. Each box represents a seperate AVI. The discs on the left are the proper size Ganymedes and the discs on the right are ones where I have zoomed in (I did this just in Microsoft Image View or whatever its called cause my photoshop is acting up at the moment and the resample thing on Registax didn't want to work with me tonight). Anyway I was most suprised because the 'markings' appear to be pretty much identical on both seperate AVI files. I whipped up a quick image in paint on what I thought this kinda looked like (the big ugly blob to the very right of the attached image

So what does everyone think? I had a quick search for albedo maps of Ganymede to see if I could make out any similar markings but I didn't find any suitable maps. I think I remember reading Mike somewhere saying some fellows he was incontact with had some way of determining which albedo features are where on Ganymede at any time. Does anyone have a program or map that I could use?

Thanks

[John K]

Awsome images! Well done! The best way to check is to use the JPL simulator here: http://space.jpl.nasa.gov/

Attached is what Ganymede looked like at 5.00am this morning

[Zac Pujic]

Hi Chrissyo

Although it is possible to detect Galileo Regio on Ganymede, a large dark central spot can also appear if too much unsharp masking is used. To find out if you have photographed surface detail, or simply have an unsharp mask artefect, you have to check the JPL simulator to see if Galileo Regio was visible when you photogaphed Ganymede. Another, more labour-intensive way, is to see if the detail changes shape over the course of several nights. The Galilean moons are rotationally locked to Jupiter, so the moon will appear to rotate slowly over several nights as it orbits Jupiter.

I have some notes here also,

http://astroimg.org/galilean.html

Zac Pujic
Brisbane, Australia
http://astroimg.org