Langrenus and Petavius

Dear Friends,

With the moon starting to ride fairly high on the ecliptic, I sat down very early this morning to pursue some high-resolution imaging. Two samples are the following:

www.perseus.gr/Astro-Lunar-Crater-Petavius.htm
www.perseus.gr/Astro-Lunar-Crater-Langrenus.htm

I managed to get very good detail but there is an annoying vertical gradient which is quite frustrating. Any ideas?

Anthony.

Those are absolutely stunning!

Im very impressed

Anthony - very nice detail on both images given the number of frames. I think you achieved your high resolution objective!

Did you sharpen them up? They look a tad oversharp on my monitor. Or its probably the high contrast with them being on the terminator.

I don't see any sign of a gradient on Lagrenus but you can see the stacking lines to the upper right.

Patavius shows a pretty gruesome looking gradient. And it looks like a colour gradient - brown to the left 1/3rd, grey, then a reddish looking thin portion to the right. I'm not sure why you would get this. Maybe try to reduce the image to greyscale then using levels and see if it is a light gradient (rather than just colour).

What you might be able to do then is tweak the image using the PS gradient tool. Alternatively, on the SBIG boards a while back, there was a GradientBuster utility (for sale ) that might help.

But it seems odd that the gradient is very pronounced in Petavius but I really can't see a hint of a gradient in Langrenus...

I bet you've got a dodgy Starfire

Cheers!

Dave

Martin, thanks for the kind words. I am happy that you approve.

Dave, I looked at the individual channels and the red has a very slight trace of a gradient. It is very visible in the green channel and very intense in the blue channel.

All of this brought back memories from a similar experience about a year ago with a different telescope (my Celestron 14" SCT). Please look at the individual channels at www.perseus.gr/Astro-Planet-Sat-20041107b.htm ....

It must be the webcam that is somehow causing the problem. I looked a the individual frames and the problem still persists (on a frame by frame level) which rules out the processing software.

I will take some images and then turn the camera slightly to still if the problematic gradient also rotates.

Any idea if the camera can be adjusted in any way to correct for this problem? I went back to my images and fixed the problem but I would prefer the fix to be at source (obviously).

Anthony.

Hmmm. I'd be out of my depth talking about webcams but if Dave Grennen or Dave Gradwell are watching this topic, I'm they would be able to offer more guidance.

Are the RGB differences the same for each image - ie Petavius *and* Langrenus? The final images look very different as I said above...

I think you can certainly safely rule out the Starfire, especially as the C14 seems to have given you the same results. Tilting the webcam will certainly help identify that as a possible root cause.

But it might be worthwhile to try a number of strategies. If you have distant objects (eg mountains) you could even do it during the day. Try eliminating the barlow and the IR filter as well as turning the webcam, to ensure that they are factored out.

Other than that, I'm afraid that's as far as my expertise would go. Let us know how you get on.

Cheers

Dave

Nice images Anthony. Very high resolution.

I'm afraid I dont have any technical comments to make on the images, as I got distracted by a cat in your image of langrenus!



Best Wishes