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First attempt at Lovejoy

Dave 2112

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Thought I'd share this before I call it a night. I might have taken around 300 images of this tonight and will have a go at stacking and processing tomorrow.

Its 60s, 1600 ISO, unguided, unmodded 100D in a 200p on EQ5. The wind didn't help much but the moon hadn't risen and for once everything seems to work. Also the first time I've used APT, what a great piece of software that is.


And one day I'll figure out how to make images in my posts look a little bigger.
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Thats nice, the tail is just showing.

What I do with images.

Resize the final processed image to one of these widths.

640.....800......or the max on here 1024.

Then when saving as a jpeg set the compression to somewhere like 70 to 80%.

Juggle the compression for a clean image, no artifacts and as small a file size as possible.

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Excellent job with a sail of a scope in that wind! I was using my 72mm frac, as I wasn't prepared to even attempt it with my 200P, and I've still got mostly duff subs because of the wind. It was really strong. Well done!


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Hi Alex,

Stacking comets seems a real test of patience, almost makes me glad they are rare events.

I couldn't get the comet stacking option to work in DSS. The reticule would lock on to every star but wouldn't lock on to the comet and all stacks ended up as large blobs. In the end I used the edit star button to remove every star in one sub as an attempt to make it lock on the comet but it still wouldn't. I stacked it anyway, 10 subs, with darks, didn't compute offsets, stacked using the kappa sigma option and left everything else to default. The end result was very washed out, but I saved it with no changes and even my total beginner PS skills got the colour back. It ended up like this...


Star might be a little egg ish, at the edges particularly, but its brought a bit more tail out and reduced the noise. I might have another go with more subs when my patience levels build up a bit.

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Thanks Dave. There are two Sigma-Kappa settings in DSS if I remember rightly. One's Median. I chose that one as Median sounded like 'Middling' to me! That's as technical as I get with this! :grin:  Interestingly, the colour was OK if I just stacked the comet and left the stars to trail. It's when I stack both stars and comet that I lose the colour. I'll ask on the DSS Yahoo group when they accept my registration.

I'm afraid I can't see your image at work as it's blocked. :embarassed:

EDIT:  I've just had a look at the DSS page and it states:

  • With the RGB Channels Calibration the three red, green and blue channels of each light frame are normalized to the same background value which is the minimum of the three medians values (one for each channel) computed from the reference frame. On top on creating compatible images (stacking wise) this option is also creating a neutral gray background. A side effect is that the overall saturation of the stacked image is quite low (grayscale look).

It is important to check one of these options when using Kappa-Sigma Clipping or Kappa-Sigma Clipping Median methods to ensure that the pictures being stacked have all the same background value.

I don't know if I might have got something wrong here.

Edited by Astrosurf
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Excellent, thanks! I see you did the sensible thing and read the manual, I just did the usual...steamed in and pressed buttons.

When I get back home I'll double check the settings for Kappa and RGB and let you know. Also I was using DSS 3.3.2 although I have just updated to 3.3.4 not sure it makes any diffence to the final image though.

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After much experimentation this evening the options that seem to work best for me are definitely Kappa Sigma (not median), per channel background calibration, everything else default. Used DSS 3.3.4 and images taken with a 100D.

Marking the comet doesn't seem to make any difference I can see, adding darks keeps the noise down. I had the star detection as high as I could get it on 10 x 30s at 1600 ISO, and adding more data just increases noise around the comet without adding detail to the tail. A very purple image came out, fiddling with the levels, upping the saturation to 20% and a curve like this seems to bring it back. I keep reading you should do the colour stuff in PS, but my PS knowledge pretty much stops right after "click here to install".

DSS comet

Might be able to tweak it further and end up much better, might even read the help files. :smiley:

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