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Twisted Lip

Disappointing evening with Lovejoy. No antiques.

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Hi all

This is more of a cry for help than a showcase but I seem to have produced a situation where a single sub is giving me a better result than a DSS stacked image!

The long and short of it is last night (16/01/2015) was the first clear night for ages so I spent some time outside trying to get as much data as possible in varying formats (ISO800, 1600 and 800 with Powermate). The examples below are ones taken at native FL at ISO1600 with a non-modded Canon 1100D with Astronomik LP filter through the WO GTF81. Subs are 120 seconds, 24 of them (a few more lost to star trails probably caused by the wind).

At first I saw the subs coming through looking reasonably good, albeit bluish thanks to the LP filter. I could see a bit of a tail and was encouraged that I might get a good result after stacking with DSS. An example of one of the subs (in JPG format, the CR2's are even better but of course I can't upload them here to view) is below:

C/2014 Q2 (Lovejoy) Single Shot

After all subs were taken I took another 25 bias. Started to take darks but then had snow so had to bring everything in - I used darks from the library so not ideal. Flats also from the library. Stacked them in DSS using the 'stars and comets' option (option 3 for those who know DSS) but the result that came out the other side has sadly given me very little. I've stretched it beyond reason in PS CS5 and there simply isn't much there (see PNG output below):

C/2014 Q2 (Lovejoy) Stacked

If you fancy a stab at the data feel free to grab the 16-bit TIF here or the 32-bit TIF here.

So the question is, any ideas? What am I doing wrong or is there anything else I can get out of this? Or is the equipment simply not good enough to get the detail, especially with the LP filter?

As always I value everyone's opinion so don't hesitate to throw anything at me!

Cheers all

Will

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Cannot see the LP filter stopping you getting a decent image.

I got it ok with a clip filter in my 60Da.

I would suggest may be longer subs.

Get your exposure in the histogram up near 40%, second line of the histogram.

Here is what I got, with a hazy sky and 10 x 300secs at f4.5.....105mm lens.

Not the best but chuffed to get some tail.

lovejoytest.jpg

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I think they look ok, even without a tail. Better to have something than nothing at all. Hopefully you can return to the processing and get a better result next time.

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Thanks Mike, you definitely got a better result than me by a long way. Did you stack in DSS?

Yes.

I did some longer subs but I just could'nt get the tail out of the crud.

Although the sky looks clear there is something like haze, may be polution, I don't know, but

it messes with the images.

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Thanks guys.

Starman - perhaps you're right and I'm just being over critical of the images. Wouldn't be the first time although I guess I was just frustrated at the results :/

Mike - I was hoping tonight was going to be a clear so I could try some 300s subs and follow your example. Sadly its clouded over but if it clears again in the next few days I'll definitely give it a crack.

Cheers

Will

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Mike - I finally managed to get another chance to image and followed your lead a bit. Tried with 300s subs instead of 120s but kept with ISO1600 and the images I think came up much better.

First image is a single sub of 300s @ ISO1600 (balanced in PS CC)...

C 2014 Q2 (Lovejoy) Single Sub

...and the second is a DSS stack of 8 subs (from 25 taken) with darks, bias and flats. 

C 2014 Q2 (Lovejoy)

Overall i think I'm much happier than I was but I still think I can do a little better.

Cheers

Will

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