Another Jupiter, a bit smoother

[Jusher]

Hi everyone. Looking at my other image of Sept 20 I do think it was sharpened a bit too much, so I've tried a different processing routine with a different set of AVIs from that evening. Here's the result - I think it looks a bit more natural, but still has plenty of detail.

Equipment used: Skywatcher 12" Auto Tracking Dobsonian, Shorty Plus, Orion Flip Mirror, Orion RGB filters, DMK21 USB camera. 30 frames/second; stacked approx. 800 frames per channel in Registax. Final image upsampled to 130 percent.

Jonathan

[iceman]

Nice work Jonathan.

Though I had a quick look in Photoshop, and your RGB channels were a little misaligned. I think some of it is due to the field rotation from your alt-az mount.

How long do you capture each channel for?

Unfortunately the EQ area is a little burnt out (at least on this screen).

I re-aligned the channels and I also adjusted the levels to make the background black, and a slight colour balance tweak.

[Jusher]

Thanks for the comments and re-processing - looks nice!

Yes I've noticed there can be some field rotation - a limitation of my existing setup and my methodology. I take about 50 seconds per channel, with 3 channels total. However I only have a manual filter wheel so we can add some time to the total based on that (and sometimes when moving the filters I knock the image off screen so I have to slew back to Jupiter - sadly it does happen because the scope's mount has a fair bit of free play in it).

If I did just R and B channels and synthesized G from those that should help. And if I moved to 60fps that would also help BUT then I always run into the "onion ring" fringing problem that seems to plague the DMK21 when using 60fps rather than 30fps. So a move to a SkyNyx would help too.

Even better would be to also get an EQ mount and some rings that would fit the Dob's tube - I'm looking into that now (eg the EQ6 Pro mount). I worry though that the load would be too much for the mount. If anyone has experience with using a 12" Dob tube on the EQ6 Pro, I'd be interested to hear it.

One other thing about moving to the EQ mount - it would remove much of the convenience from my setup. Currently I just pick up the entire Dob, mount and all, carry it a few feet outside, point the tube level North, turn it on, haul the tube manually over to Jupiter, and it tracks from there. It doesn't get much easier than that!

Jonathan

[Quark]

Hi Jonathan,

Looking good, a much smoother result. I am sure Mike will be able to advise you regarding the 12" on the eq, I seem to think that is what he is using.

Jonathan, 50 seconds with your manual filter wheel is probably to long. I also use a manual filter wheel and have found that 40 sec captures really are optimal to produce the best results possible ( that is with my particular setup), allowing 10 sec's to rotate the filter wheel, that means that I have captured my 3 channels in 140 sec's.

The onion ring fringing you mention is not a fault with the DMK 21, it relates to gamma setting that you use. You should use the default gamma setting for the DMK 21 which is a setting of 100. With your gamma at this setting you will not get onion ring fringing.

Regards
Trevor

[Jusher]

Hi and thanks for the suggestion - I'll try backing off the time to 40 seconds per channel. Additionally I can try manually rotating the channels to compensate for field rotation, and then align on planetary features. And hopefully the EQ6 would work OK with this big tube :)

Regarding the fringing I've been experiencing at 60fps, I'm not the only one to find this a problem -and I keep my gamma at 100 and the histogram properly exposed. I get almost no fringing at 30 fps. Here's a link where someone else is discussing the issue with a support engineer at the Imaging Source forums: http://www.theimagingsourceforums.com/showthread.php?t=322135. Note the comment at the end of the thread from the engineer ("I think these ghost images are a side effect of this high frame rate. I do not think, it can be avoided, since we do not know, how these ghost images are created in the CCD.")

Jonathan

[Quark]

Thanks for the link Jonathan.

The only time I have experienced this onion fringing was due to having the gamma setting to high.

I have never felt the need to capture at more that 30 fps, I have a 16" f4.5 Newt so have absolutely no problem filling my histogram and recording enough frames in a short enough period

Some of the best planetary images ever recorded have been achieved on the DMK 21.

Cheers
Trevor