Jump to content


Curved artifact help


Recommended Posts

In processing an SHO narrowband image, I seem to have acquired a large curved red artifact going from top right to bottom right, swinging almost a sixth of the way across my image. I have no idea how it got there. It appears as a dark band in Blue and a light band in Red, and completely absent in Green. Given this would be the Sii and Oiii, I checked the originals and can see just the faintest hint of it in the Sii data. 

Any view on what it could be and what are my options at this point? I have over stretched the image here to highlight the band.





Link to comment
Share on other sites

On ‎07‎/‎12‎/‎2016 at 15:12, MattJenko said:

Thanks Mark - TS60ED - Adaptor for - TS x0.79 reducer/.flattener - Baader Vari-spacer - SX filter wheel / Baader 1.25" filters - ZWO ASI1600 cooled.

There's nothing out of the ordinary in that arrangement.  The artefact is possibly some kind of reflection but tracking down the cause may not be easy.


Link to comment
Share on other sites

On 12/1/2016 at 09:30, MattJenko said:

Any view on what it could be and what are my options at this point?

Hi Matt

What you are seeing is scattered light that is probably caused by an out of field of view star that is reflecting off some surface of your system. I get this effect quite often. 

In terms of what to do about eliminating them from the image - if you use PS then I would advise following the method detailed by Adam Block in his cosmic canvas video tutorial.  I've found that this method gives excellent results and often gives close to 100% elimination of the problem. Unfortunately, the method is rather difficult to describe without seeing the video but I shall have a go....

1. Take a copy of the image and paste in layer above.

2. On the copied image make a selection of the scattered light area than you wish to eliminate - make this selection quite wide so that it includes non problem areas.

3. Fill the selected area with a content aware fill (right click in the selection area and choose fill content aware) - this will eliminate the scattered light but create false stars.

4. Using the spot healing brush eliminate all the content (eg false stars) within the selection area so you are just left with the back ground. At this point you have eliminated the scattered light but also the wanted content which you now need to put back.

5. Create a mask for the selection area.

6. Reselect the area. 

7. Set the opacity of the top layer to say 50% so that you can see the real stars in the selected area (the real stars are coming from the layer below).

8. Select the mask and using the paint brush poke holes in the mask at the points of the real stars. This restores the wanted content.

9. Put back the opacity to 100%.  



  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.