Images will not align using StarAlignment

[themongoose85]

Hi all. I am having some issues stacking in PI using my latest M51 data. When I run the same data through DSS it stacks fine but when using PI the resulting imaging is a blurry/smudgy mess. I believe StarAlignment is not actually aligning. When it runs it is finding roughly 7000-8000 stars which seems really excessive. None of my other data is remotely close to that. There is also no change between images as far as the delta in x and y.

Detecting stars: done
7901 stars found.
* Reference image: Limiting to 2000 brightest stars.
* Target image: Limiting to 2000 brightest stars.
Matching stars: done
1340 putative star pair matches.
Performing RANSAC: done
1211 star pair matches in 110 RANSAC iterations.
Summary of model properties:
Inliers     : 0.904
Overlapping : 1.000
Regularity  : 0.993
Quality     : 0.967
Root mean square error:
delta_RMS   :  0.061 px
RMS error deviation:
sigma_RMS   :  0.002 px
Peak errors:
delta_x_max :  1.716 px
delta_y_max :  0.429 px
Transformation matrix:
     +1.0000     -0.0000     -0.0029
     +0.0000     +1.0000     -0.0028
     +0.0000     +0.0000     +1.0000
scale       : 1.000
scale-X     : 1.000
scale-Y     : 1.000
rotation    :     +0.00 deg
dx          :     -0.00 px
dy          :     -0.00 px

Has anyone seen this before? This is the first data using my Nikon D5100. I've always used my Canon 450D with no issues in PI or DSS. This D5100 data however will not stack in PI. I've tried manually using the processes as well as using BPP. Thanks.

[themongoose85]

I think the problem is StarAlignment is matching on hot pixels which there seem to be a lot of them and I am not sure why. The hot pixels do not show im my regular daytime images I took back in April.

[pfile]

there's a star detection threshold in StarAlignment... i think the tab is closed by default so it's easy to miss. anyway, open the Star Detection pane and increase the sensitivity (larger numbers are less sensitive...) you can also increase "hot Pixel removal" and "Noise reduction" to try to get around this issue.

rob

[themongoose85]

Thanks Rob I did try fiddling with those but they didn't seem to help at all. I think I need to figure out where all of these specks are coming from there should not be this many. I was not using any darks and I am trying now with a few darks to see if they help. I did use some custom firmware on teh camera that wasn't being used the last time I took normal daytime photos so I am going to try reverting back to stock firmware and see if that helps.

For reference here is a master dark stacked from 7x5min frames. Obviously something isn't right:

[pfile]

yes to be honest there do seem to be a lot of hot pixels there but since they are also in your dark they should calibrate away. what was the sensor temperature? it's not necessarily unusual to have so many hot pixels in a hot sensor with a long dark/light...

rob

[themongoose85]

I am not sure what temp the sensor was. I don't know of a way to tell with Nikons. With my Canon 450D BackyardEOS displays it but BackyardNikon currently does not. I still am curious why DSS with no darks removed them and stacked fine but PI did not remove them and would not align/stack properly.


EDIT: PI failed to remove them and stack properly even using the master dark frame posted above.

EDIT2: I take that back. After using darks I was able to tweak the Star detection settings in StarAlignment and get a clean aligned/stacked image.

[themongoose85]

It seems after setting Hot Pixel Removal to 2 and Noise Reduction to 2 under Star Detection of StarAlignment that all the hot pixels were removed and the images were aligned and stacked properly even without using any Dark frames. Thanks for your help pfile. I thought I tried these settings before and it wasn't working but I guess I didn't try them both at the same time.

[pfile]

excellent... sounds good.

rob