I need some help with these star trail Images

[cbobchin]

Hi all,

I shot a couple of star trails this past weekend and have started processing them in PI using the startrails script that pas posted a couple of years back. However when I go to export it as a TIF file the results are far less impressive than what I see on the screen in PI. I'm still fairly new to PI and

What am I doing wrong?

I've posted a zip file with the fits files (Master dark, Master flat, the two calibrated raw images and the final combined image) to my public dropbox folder. https://www.dropbox.com/sh/grlvcfopgepspt1/AADhrvlGaE5vEmZuu0l8Ey3aa

I've also got some other wide field images I'm trying to stack and align. (They're 1 min subs non tracking and as such have some trailing). I just want to see what I can get out of them. I can post those later.

Any help is appreciated.

[TobiasLindemann]

Hi,
IMO your integrated image looks good. I think the problem is just to display it. Try to save as a 16bit, or 8bit TIFF.
Other improvements:
IMO your image looks better with no DBE, just with ColorCalibration. I think it looks better, if you see the color-gradient of the horizon on those images.
Furthermore you should not use a pause between your exposures, so there is no gab between the trails.
It looks like you use different exposures in the two images. Before integration you may lift up the lower one, so that the trails are of the same brightness.

Greetings
Tobias

[cbobchin]

Hi Tobias,

The issue I have is when I save it to Tiff format (16 bit) I lose a lot of the detail and fainter stars that I see in PI. I'll try your suggestion of no DBE and just color calibration and see how it works.

I did not change the exposures between shots, but it did get darker between the two shots. How can I fix that?

As for the pause, I gave it a minute so teh chip would cool down a bit. I'm using a Canon20d that has a lot of noise compared to today's cameras.

[TobiasLindemann]

The issue I have is when I save it to Tiff format (16 bit) I lose a lot of the detail and fainter stars that I see in PI.

If you want to see fainter stars, you can do another HistogramTransformation, or CurvesTrasformation, or what ever. Do you want to do another post-processing with another programme?  In any case, I think 16 bits are enough to do a fine adjustment.

I'll try your suggestion of no DBE and just color calibration and see how it works.

Sorry, I had looked at the wrong image. I think your final image is good balanced.

As for the pause, I gave it a minute so teh chip would cool down a bit. I'm using a Canon20d that has a lot of noise compared to today's cameras.

Hm, IMHO the gap would bother me more than a little bit more noise. I think the sensor heats up very fast, so the little pause is no much difference in s/n.

I did not change the exposures between shots, but it did get darker between the two shots. How can I fix that?

Your images are of the same exposure, but differ in ISO. So the stars are of different brightness. You can fix it easily with the "LinearFit" process.

Greetings
Tobias