StarTools

Good day Ivo,

I have been taking in the last few days different sets of light frames of comet Lovejoy.
All sets are of about 10 -15 frames each at ISO 1600.
I have 60 sec, 120 sec sets and a few frames at 240 sec
All frames taken with modded EOS1100D trough my Meade LS6" reduced at about f7 and guided on the comet

I can manage (with lots of tribulations) to stack each separate set in DSS .
Opening the autosave file I can get an "acceptable" image of the comet, and of the star field .
What I cannot manage is to bring out the tail of the comet, no matter what I do, no tail

do you have any suggestions / method to bring out the tail?

Here is the link to a DSS stack of 11 x 120sec ISO1600, taken on the 8th of January the moon was was not so bad. somewhere there should be a tail.....
https://drive.google.com/file/d/0B6oGP3 ... sp=sharing

Thanks for the advice!

Have a nice weekend

Hi Marco,

I too was unable to find a tail in there... What settings did you use to stack? Also, are you sure you stacked RAWs?
You could maybe try averaging instead of median or similar.

The best advice I can give you is using AutoDev and a region of Interest to bring out faint regions of interest...

Looking at your info, it may be that with an F7 system and moon up that you're going to be pushing you're luck. And any LP would make it alot harder. Here's what I did with F5.75, 5@120s, iso800, Canon 60Da, no moon and Sierra skies about the same time. It's also possible that the higher iso is clipping your data . More info on AstroBin. Darks, flats and bias used, natch! And you might find it useful to output the DSS file in 32 bit .fits, more dynamic range. This is rather an extreme dynamic object right now.

Hi Ivo,
Yes I stacked the raw
I have tried different DSS settings, the one posted was a median, in superpixel modus.
I am still trying all the other combinations, but for the moment no joy

It could be as Starry Eyes suggest that I'm pushing my luck at f7 with the moon, and local LP (I'm in red zone) most probably more frames are needed.

Regarding the clipping possibility at 120sec the lights are not clipped. The red channel is a bit on the right side, but not against the border, let's say 90% (it is a modded camera) blue and green are about in the center.

I'm trying now an other stack averaging, let's hope it will be better.....

Marco;

Here's a procedure I've worked out for comets with aditional comments on STools on the bottom.



Ok if I share what works for me?
1) Take timed sequenced lights with your acquisition software. Must be equally time for exposure and interval. (I use BYEos)
2) The name of the lights need to be alphabetically arranged sequentially according to time.

DSS

3) Open DSS. Place all the sequenced lights in the Main Group. Place your bias, darks, and flats there too. Check all.

4) Register all. Do not stack yet. Check numbers. No N/C's? Good. Past go!

5) Show first light on screen. zoom way in on the nucleus. Pick comet icon on screen to set. Use the shift key to disable the often useless snap function.

6) Ditto for the last light in Sequence. Look out not done yet!

7) DSS has selected the light with the highest score and made it the reference frame. Mark the comet in that one too! (Note; If your sequence is not precisely timed you'll have to mark all your lights. What a pain!)

8) Now in the Stacking Command use the recommended settings. Then in the Stacking Parameters you should see the comet tab. If you don't, check your work. Within the comet tab pick fixed stars trailed comet, or fixed comet, trailed stars, or fixed comet and stars.

9) Stack. Note that the fixed comet and stars option will take a long time and often display a DSS message that it has stopped working. Don't believe it! Be patient.

10) Save in .fits format.

11) Now pick your poison to process!

See Here for results Then see with the same data fixed comet trailed stars on my AstroBin page.

Ongoing issues: The fixed star and comet function is leaving artifacts around the brighter stars. What to do?

Now in StarTools I binned 25%, autodev, crop, reauto dev, wipe with Dark anal filter @~7 pixel and defaults, manual dev, hdr,sharp color and so on.

Comments?

Hi Starry eyes,
Thanks for taking the time to write the info, much appreciated!
But the procedure you describe is the one I use as well, to be sure I mark the comet in each frame

I will just try again with more frames.....