Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_comet_46p.thumb.jpg.9baae12eeb853c863abc6d2cf3df5968.jpg

Recommended Posts

Here is my second attempt at imaging.

1096052676_M81and82.thumb.jpg.0fbeabb11577e5e31f28b591c2f3aad0.jpg

The image is stacked in Pixinsight and after the stacking i had these strange red and blue streaks/ribbons on the image. I use a SW 150pds and a canon 450d. I used Dark, flat and bias frames for stacking. I also tried to stack the image in DSS. If i use DSS the red and blue streaks/ribbons disappeared. Any one know why this is present in Pixinsight and not DSS.

Also i could not get rid of the white hue on the middle right part and the left edge of the image

Comments and input is highly appreciated.

 

Regards Bjarni

  • Like 2

Share this post


Link to post
Share on other sites

Streaks are hot pixels that are moving between the frames and when stacked - turn into streaks.

In DSS you are most likely using sigma clip stacking - this sort of stacking removes anomalous values (like hot pixels at a particular place - if not present in other frames - because it moved for example).

I'm sure PI also has this method of stacking - look it up, it should be called sigma reject, or sigma clip or something like that.

As for white hue thing - I believe it is due to mismatching darks - with DSLR you simply can't work around that because there is no temperature control.

What you might try to solve it is - dark frame optimization in DSS (look it up under settings) - you need both bias and darks to try to make it work (in some cooled astro CMOS cameras it simply does not work because of bias not behaving properly, but it might work in DSLR). PI should also have similar option. This option tries to match darks to temperature, and sometimes it actually does the good job.

Last remark is that you are trying to push your data too much and this is why all the states is so obvious. Try what I suggested (or other members when they suggest possible workaround for your problems) and then try to be a bit gentler in your processing. Although gentler processing won't show as much it will be more pleasing to the eye.

  • Like 1

Share this post


Link to post
Share on other sites

Some great advice from vlaiv there.

Despite the issues you state I think there's some lovely dust lane/spiral arm detail captured :)

Share this post


Link to post
Share on other sites

Good advice already given.

How many subs of what length are you using? I am guessing it is quite a short integration time and would benefit from more data.

Also, I think your field is not flat - stars in part of the image (particularly top right) are egg-shaped.

But, that said, it is a lot better than my second image was. Well done.

Share this post


Link to post
Share on other sites
9 hours ago, bjarnit said:

Here is my second attempt at imaging.

1096052676_M81and82.thumb.jpg.0fbeabb11577e5e31f28b591c2f3aad0.jpg

The image is stacked in Pixinsight and after the stacking i had these strange red and blue streaks/ribbons on the image. I use a SW 150pds and a canon 450d. I used Dark, flat and bias frames for stacking. I also tried to stack the image in DSS. If i use DSS the red and blue streaks/ribbons disappeared. Any one know why this is present in Pixinsight and not DSS.

Also i could not get rid of the white hue on the middle right part and the left edge of the image

Comments and input is highly appreciated.

 

Regards Bjarni

If I'm not wrong lots of the pros don't use pixinsight for stacking as it's quite complicated but use other programs like DSS for stacking and then do the final process in pixinsight. 

You must be thrilled with your result at this early stage of imaging. Well done 

Kind regards 

Gerry

Share this post


Link to post
Share on other sites

In PixInsight, once you've calibrated, cosmetically corrected (the process that would remove any hot or cold pixels not removed during dark calibration) and star aligned your images, your ImageIntergration process should look something like this:

image.thumb.png.5f7ba07ca2742efc28b734b1dfe5cb7f.png

The rejection algorithm under Pixel Rejection (1) should be Linear Fit Clipping for larger stacks of images. When you mouse over the drop down a handy popup will appear and recommend the right algorithm for different size stacks. I find the default values in Pixel Rejection (2) to be fine. I amend the buffer size and stack size as I have a powerful PC with lots of RAM so I increase these to 65 and 10000 respectively, so more of the stacking is done in memory (at least it seems to work faster).

Share this post


Link to post
Share on other sites

As @Filroden suggests, use cosmetic correction in pixinsight. Also, experiment with not using dark frames when calibrating lights. Play around with cosmetic correction settings, and high pixel value rejection during stacking. This should solve the issue.

Finally, use 12 pixels or more dithering when shooting with a dslr.

Share this post


Link to post
Share on other sites

Thank you for your comment and suggestions I will try what you suggest.

 

Regards Bjarni

Share this post


Link to post
Share on other sites

Just a note i have had the same problem this week ,on M82 ribbons and blue lines with Startravel ST120 , Canon EOS 450 D modded J

I noticed in DSS that there was an option ticked for hot pixels , not sure what the exact description was but will look again

Thanks as well for the answers

Nice pic by the way

i have relatives in Norway are u near Bergen or Askoy ?

 

 

 

 

 

 

 

M82_MM.jpg

Edited by mikemabel

Share this post


Link to post
Share on other sites
1 hour ago, mikemabel said:

Just a note i have had the same problem this week ,on M82 ribbons and blue lines with Startravel ST120 , Canon EOS 450 D modded J

I noticed in DSS that there was an option ticked for hot pixels , not sure what the exact description was but will look again

Thanks as well for the answers

 

 

M82_MM.jpg

Playing a bit with bright pixel rejection in Cosmetic Correction and image integration should solve that problem.

In DSS there is an option to add cc to the calibration workflow. In PixInsight it's a process you'd use after image calibration, and before image registration.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.