Rev 247, Oct 27 - Nov 6 / 2016 Options

[Ian R]

Blast my impulsive nature! This morning I decided—against my better judgement—to tackle this seven-footprint RGB monster of a mosaic. It's still not finished, but should still give a good idea of what the final product will look like:

[jasedm]

Very beautiful - stunning work as ever!

Just one question, where Saturn's shadow bisects the rings is it really that black? Is there not saturnshine or ring shine bouncing light around a bit? (I know it's work-in-progress)

[Ian R]

Thanks Jase!

Good question about the non-visibility of the rings draped by Saturn's shadow. Any infill light from reflected ringshine on the night side of the planet must indeed have *some* effect, but these compressed JPEGs effectively snuff out any such marginal signal, I reckon.

Just to check, I stacked the four available raw frames for this footprint and got nada:

[JRehling]

Are the ISS images 8 bits in depth? If so, you'd need a ratio of considerably less than ~256 between the sunlit surfaces and the shadows to have any chance of seeing detail in the shade.

Taking my own images of deep sky objects, I'm getting quite used to the hassle of trying to get details in the beautiful fuzzy areas without overexposing something else. Solar system objects give you a ratio of "surface" brightness on a par with the biggest differences in albedo (a range usually no wider than ~0.1 to ~0.7 plus or minus phase angle effects). With a ratio of 10 or so, you don't need many bits to capture the detail. With a ratio of >1000, you're out of luck with 8 bit images. I've begun wrestling with 12 bit images in my own astrophotography. There are a lot of signal-to-noise issues to deal with once you make that adjustment, too.

[Ian R]

Getting there .....

http://s21.postimg.org/u091ixct1/Glutton_Mosaic_WIP.jpg

[jasedm]

Thanks for the answers re: shadow. I think I spot Atlas, Prometheus and Pandora in there as well, even at this range.

[Ian R]

I've finished the mosaic (Hurrah!):

https://www.amazon.co.uk/clouddrive/share/o...share_link_copy

Only three moons are visible, as far as I'm able to ascertain: Epimetheus (just above the right ansa, near Saturn); and Atlas and Prometheus (at the tip of the right ansa). Pan is too faint to be detectable, and Janus must be just out of frame.

[Lewis007]

Good news: there's a new interface on the site https://saturn.jpl.nasa.gov/galleries/images/ which makes it easier to browse the raw images. This way, my computer won't crash like it did with the previous version.

I was told that the "old" website http://saturn-archive.jpl.nasa.gov/photos/raw/?start=1 which was maintained in the interim (and went down last week) will disappear in the future (users will be redirected to the new site).

[ngunn]

Excellent! Thanks for pointing this out. I had almost given up, but now I'll be back to following the raws day by day.

[xflare]

Excellent! Thanks for pointing this out. I had almost given up, but now I'll be back to following the raws day by day.

Ahhh thank goodness we have a new raw browser page. I had given up looking at them, that old page pretty much tried to kill my PC!!