10 replies to this topic

[slammel]

Hi all,

This is a first for me, usually my scope is pointing at the Moon but who could resist this spectacular target!

Turning the wavelets up to eleven has brought out some structure in the coma, the image is a composite of 2 versions of the same image. The gross over-processing was the only way I could tease out this detail, I will try some other less aggressive techniques and post here if it works out, any suggestions welcome...

http://www.pbase.com...113343/original
http://www.pbase.com...113321/original

Both images stack of 440 exposures 3-6 sec, green & no filter, Infinity 2-1M & 10in f4.8 Newt. 29-Oct-07 22:30UT.

Regards,
Stefan

mild wavelets processing...

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[slammel]

Jet structure revealed by heavy wavelet processing, resampled 150%...

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[Dave Mitsky]

I've seen a couple of shots showing the comet's jets today but this is far the best. Congratulations!

Dave Mitsky

[PeteLawrence]

Hi Stefan,

Comet imagers usually use something like the Larson Sekanina filter to enhance shell and jet features. In the image below, I've taken a Registax wavelet enhanced image and applies a custom rotational filter similar to the Pellet method that would be used to enhance solar coronal detail during a total solar eclipse. The detail that is visible in the enhanced version is, as far as I can tell, all real in that it can be traced back to the original wavelet.

http://www.digitalsk...500_to_1000.jpg

[slammel]

Thanks very much Dave!

Pete - thanks very much for pointing me in the direction of the Larson-Sekanina filter, boy does that work a treat!

I discovered the demo version of Astroart has this filter and this is a screen shot of the result with the default settings, what an amazing filter! I wonder if it is available elsewhere or maybe I will have to fork out for the full version if I get into this...

Your homegrown filter works very well without the weird effects of the L-S. Creating your own filters shows real dedication, well done!

Regards,
Stefan


the squiggles at top right are from a couple of hot pixels - must learn to use darks...

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[PeteLawrence]

Hi Stefan,

Larson-Sekanina is very good but it's a strong filter and can produce a number of side effects that look like cometary structures but aren't. I'm not convinced that the structures that I've seen around many L-S filtered images are real. The two biggest problems with the filter are that the two variables that control it can produce wildly varying results with just a small tweak and the filter does produce convincing looking artifacts. For example, I would be very suspicious of the effects in the lower left of your L-S coma (that's not a criticism of you, just an observation ). It would be useful to try L-S on a standard calibrated 'coma' created with PhotoShop and see what it makes of it.

[slammel]

Pete,

I can see there is a significant difference between the L-S filter and your rotational filter. Its fascinating that such a different impression of reality can be brought out by different processing. The curving of the jet in the lower left of the L-S version seems quite convincing but as it doesn't show in your image it has to be doubtful. This is really fascinating stuff!

Now its on with tonights show, looks like it should be good!

Regards,
Stefan

[chrysalis]

Great work!

[slammel]

Thanks Mark!

more from 30th...
http://www.pbase.com...235868/original

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[slammel]

and 31st, here you can also see that it appears to have slightly expanded...
http://www.pbase.com...235873/original

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[slammel]

... as you can see I still have problems with the hot pixels despite using a dark frame in Registax. It looks like it doesn't apply it to all the frames or maybe I'm doing something wrong?

Stefan