Technique for removing unwanted artifacts from stars with PixInsight

Discuss how you are able to get those fantastic images!!!
Post Reply
User avatar
STEVE333 United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3466
Joined: Sat May 11, 2019 5:01 pm
4
Location: Santa Cruz, Ca, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Technique for removing unwanted artifacts from stars with PixInsight

#1

Post by STEVE333 »


I recently learned a new technique for inserting RGB stars into narrowband images (thanks to "starfield"). For some reason the large and bright stars had halos around them. This technique has allowed me to remove those halos. The two pictures below show the before (left) and after (right) results for one of the bright stars that I repaired.

Comparison.jpg

This technique can be applied to more than one star at a time. However, for this explanation only one star will be corrected. It typically takes me about 5 minutes to correct a star. The explanation below is a little long to make it clear, but, each step actually doesn't take much time. The approach does use the GAME script to create a mask.

Here is the technique:
  • 1) Select the image and expand it so that the pixels in the star are clearly visible. Place the cursor on the left edge of the actual star (not the artifact) as shown in the image below and note the x-position in the readout window as X1.
X1.jpg
  • 2) Repeat step(1) but with the cursor on the right edge of the actual star and note the x-position as X2.
  • 3) Calculate the radius of the star as R=(X2-X1)/2. If the answer isn't an integer round the answer up to the next integer value.
  • 4) Calculate the x-center of the star as x=(X1+X2)/2. Round the answer to the nearest integer.
  • 5) Repeat steps (1) and (2) but with the cursor on the top and then the bottom of the star and note the y-positions as Y1 and Y2.
  • 6) Calculate the y-center of the star as y=(Y1+Y2)/2. Round the answer to the nearest integer.
  • 7) Open the GAME script and expand the image about the star being repaired. Select the Ellipses tab and then click the +Add button. Enter the calculated x and y values and then enter R into the a and b boxes. Select the Binary Mask option and deselect the Gradient Mask option. Click on OK button at the bottom to create the mask. Rename the mask as "Mask".
  • 8) Open the Convolution process and use the settings shown in the picture below. Apply the process to Mask. This is approximately how the finished star will appear as shown in the second picture below. You can adjust the StdDev parameter to your liking. Increasing StdDev will result in a fuzzier final star. The mask is now complete.
Convolution.jpg
Mask_3.jpg
  • 9) Make a clone of the image and name it CS. Expand the image until the desired star with artifact is present as shown below.
Non_CS.jpg
  • 10) Use the CloneStamp tool to cover the star and repair the artifact as shown below.
CS.jpg
  • 11) Open PixelMath and use the setting shown below. Use the name of your image in place of "Image_w_Artifact". Drag the blue triangle icon onto your image and the star will be repaired as shown in the second picture below.
PixelMath.jpg
Final.jpg

Hope this is helpful for you.

Steve
Steve King: Light Pollution (Bortle 5)
Telescope + Mount + Guiding: W.O. Star71-ii + iOptron CEM40 EC + Orion Magnificent Mini AutoGuider
Camera: ASI 1600MM Pro + EFW Filter Wheel + Chroma 3nm Siii, Ha, Oiii + ZWO LRGB Filters
Software: PHD2; APT; PixInsight ***** My AP website: www.steveking.pictures
Image
Image
User avatar
Juno16 United States of America
Universal Ambassador
Articles: 0
Offline
Posts: 8195
Joined: Sun May 12, 2019 3:13 pm
4
Location: Mississippi Gulf Coast
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#2

Post by Juno16 »


Really interesting technique Steve!

I assume that this technique can be used for star halos too.
I’m imaging IC63 spurred by Steve’s (@Mac fine image posted recently and I can see in the subs that the star Navi (visual mag 2.2) is going to be a problem. Probably going to have a significant halo.
Would you think that the method that you posted would help in this situation?

I appreciate the post. Kind of reminds me of a star halo remediation technique that you mentioned to me awhile back when I had a bad halo with Alnitak.
At the time, I had some success reducing the halo, but I couldn’t get it quite right and eventually gave up.

I will save this information and try it out soon!

Thanks a bunch Steve!
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
User avatar
STEVE333 United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3466
Joined: Sat May 11, 2019 5:01 pm
4
Location: Santa Cruz, Ca, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#3

Post by STEVE333 »


Juno16 wrote: Wed Oct 19, 2022 6:58 pm Really interesting technique Steve!

I assume that this technique can be used for star halos too.
I’m imaging IC63 spurred by Steve’s (@Mac fine image posted recently and I can see in the subs that the star Navi (visual mag 2.2) is going to be a problem. Probably going to have a significant halo.
Would you think that the method that you posted would help in this situation?

I appreciate the post. Kind of reminds me of a star halo remediation technique that you mentioned to me awhile back when I had a bad halo with Alnitak.
At the time, I had some success reducing the halo, but I couldn’t get it quite right and eventually gave up.

I will save this information and try it out soon!

Thanks a bunch Steve!

You're welcome Jim. Yes it will work for halos. In the Clone Stamped image just make sure to remove the star and all of the halo. Then proceed with the rest of the technique as shown in the tutorial.

Steve
Steve King: Light Pollution (Bortle 5)
Telescope + Mount + Guiding: W.O. Star71-ii + iOptron CEM40 EC + Orion Magnificent Mini AutoGuider
Camera: ASI 1600MM Pro + EFW Filter Wheel + Chroma 3nm Siii, Ha, Oiii + ZWO LRGB Filters
Software: PHD2; APT; PixInsight ***** My AP website: www.steveking.pictures
Image
Image
User avatar
Juno16 United States of America
Universal Ambassador
Articles: 0
Offline
Posts: 8195
Joined: Sun May 12, 2019 3:13 pm
4
Location: Mississippi Gulf Coast
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#4

Post by Juno16 »


STEVE333 wrote: Wed Oct 19, 2022 7:58 pm
Juno16 wrote: Wed Oct 19, 2022 6:58 pm Really interesting technique Steve!

I assume that this technique can be used for star halos too.
I’m imaging IC63 spurred by Steve’s (@Mac fine image posted recently and I can see in the subs that the star Navi (visual mag 2.2) is going to be a problem. Probably going to have a significant halo.
Would you think that the method that you posted would help in this situation?

I appreciate the post. Kind of reminds me of a star halo remediation technique that you mentioned to me awhile back when I had a bad halo with Alnitak.
At the time, I had some success reducing the halo, but I couldn’t get it quite right and eventually gave up.

I will save this information and try it out soon!

Thanks a bunch Steve!

You're welcome Jim. Yes it will work for halos. In the Clone Stamped image just make sure to remove the star and all of the halo. Then proceed with the rest of the technique as shown in the tutorial.

Steve

Can't wait to try it Steve!

I hope to get another shot at collecting data on this target.

I really never noticed it before (Skysafari is my usual sky atlas tool). IC63 is really nice looking especially if I can bring out the same effect as Steve did by making the nebula look like the star Navi is shining a spotlight on the nebula. I'm hoping that the L-eNhance will allow me to collect decent data on this dim Mag 10 target.

I really appreciate that you shared this here. I hope that more folks save your technique too, because all of us have to deal with star halos at one time or another.

Thanks!
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
User avatar
Juno16 United States of America
Universal Ambassador
Articles: 0
Offline
Posts: 8195
Joined: Sun May 12, 2019 3:13 pm
4
Location: Mississippi Gulf Coast
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#5

Post by Juno16 »


Hi Steve, @STEVE333

I kept this thread bookmarked just in case!
The target that I was imaging when I responded above was the Ghost of Cassiopeia and the halo was remediated by working with the star only image.

I imaged the Jellyfish Nebula recently and both Mu Geminorum and Propus both produced massive obnoxious halos that star reduction methods didn't touch. In fact, even StarXTerminator pulled one star out, but not the other. Both halos were left behind in the starless version.

Well, I want to let you know that your method outlined here worked wonders!
Of course, it is not perfect. I am sure that I could have executed your method better, but it worked very well. Actually, it transformed an image with horrible star halos to a much tamer version.

When I first started the process, I was just following your instructions, then I realized your methodology and it all fell into place. The binary mask is genius! I had not worked with any other mask than the default Gradient Mask in the Game script.

As I said, I'm sure that I could have done a more precise job, but your method saved the image. Thanks a ton Steve!

Capture.PNG
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
User avatar
STEVE333 United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3466
Joined: Sat May 11, 2019 5:01 pm
4
Location: Santa Cruz, Ca, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#6

Post by STEVE333 »


Juno16 wrote: Thu Jan 19, 2023 12:19 pm Hi Steve, @STEVE333

I kept this thread bookmarked just in case!
The target that I was imaging when I responded above was the Ghost of Cassiopeia and the halo was remediated by working with the star only image.

I imaged the Jellyfish Nebula recently and both Mu Geminorum and Propus both produced massive obnoxious halos that star reduction methods didn't touch. In fact, even StarXTerminator pulled one star out, but not the other. Both halos were left behind in the starless version.

Well, I want to let you know that your method outlined here worked wonders!
Of course, it is not perfect. I am sure that I could have executed your method better, but it worked very well. Actually, it transformed an image with horrible star halos to a much tamer version.

When I first started the process, I was just following your instructions, then I realized your methodology and it all fell into place. The binary mask is genius! I had not worked with any other mask than the default Gradient Mask in the Game script.

As I said, I'm sure that I could have done a more precise job, but your method saved the image. Thanks a ton Steve!


Capture.PNG
Your welcome Jim. Nice job! Glad it helped "save" your image.

Steve
Steve King: Light Pollution (Bortle 5)
Telescope + Mount + Guiding: W.O. Star71-ii + iOptron CEM40 EC + Orion Magnificent Mini AutoGuider
Camera: ASI 1600MM Pro + EFW Filter Wheel + Chroma 3nm Siii, Ha, Oiii + ZWO LRGB Filters
Software: PHD2; APT; PixInsight ***** My AP website: www.steveking.pictures
Image
Image
User avatar
Juno16 United States of America
Universal Ambassador
Articles: 0
Offline
Posts: 8195
Joined: Sun May 12, 2019 3:13 pm
4
Location: Mississippi Gulf Coast
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Technique for removing unwanted artifacts from stars with PixInsight

#7

Post by Juno16 »


STEVE333 wrote: Thu Jan 19, 2023 4:02 pm
Juno16 wrote: Thu Jan 19, 2023 12:19 pm Hi Steve, @STEVE333

I kept this thread bookmarked just in case!
The target that I was imaging when I responded above was the Ghost of Cassiopeia and the halo was remediated by working with the star only image.

I imaged the Jellyfish Nebula recently and both Mu Geminorum and Propus both produced massive obnoxious halos that star reduction methods didn't touch. In fact, even StarXTerminator pulled one star out, but not the other. Both halos were left behind in the starless version.

Well, I want to let you know that your method outlined here worked wonders!
Of course, it is not perfect. I am sure that I could have executed your method better, but it worked very well. Actually, it transformed an image with horrible star halos to a much tamer version.

When I first started the process, I was just following your instructions, then I realized your methodology and it all fell into place. The binary mask is genius! I had not worked with any other mask than the default Gradient Mask in the Game script.

As I said, I'm sure that I could have done a more precise job, but your method saved the image. Thanks a ton Steve!


Capture.PNG
Your welcome Jim. Nice job! Glad it helped "save" your image.

Steve

I just posted the final image and you can see how well I applied the process. Not perfect, but much, much better. I have already thought of a few things that I would do differently next time, but removing the halo's (and they were really bad halo's) helped significantly.
Thanks again!
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

Return to “Image processing”