New Feature : Satellite Trail Removal

All the latest news about new features and improvements to SharpCap
User avatar
admin
Site Admin
Posts: 12984
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

New Feature : Satellite Trail Removal

#1

Post by admin »

Hi folks,

SharpCap 4.0.8709 introduces a new feature to allow automatic satellite trail removal from deep sky images. Given the massive increase in the number of satellite trail problems recently, this feature should be very useful, particularly when live stacking.

How does it work?


There are three modes for satellite trail removal :

* Off - no satellite trail detection or removal
* Test - SharpCap will attempt to detect satellite trails in the image and if found will highlight them - this can be used to help adjust the trail detection settings, but *DO NOT* use this mode when capturing or live stacking.
* Remove - SharpCap will detect satellite trails, and if detected will replace the trail in the image with pixel values taken from nearby in a non-affected part of the image. This is rather similar to the way that scratch marks are removed from old photo images. Note that Trail Removal is a SharpCap Pro feature
Capture.JPG
Capture.JPG (22.53 KiB) Viewed 5917 times

Satellite Trail Settings

There are three additional controls that let you adjust the detection of satellite trails:

* Trail detection sensitivity - this behaves as you would expect - higher values will help detect fainter trails, lower values can be used if the test mode reveals that false trails are being picked up
* Minimum Trail Length - this is sets (approximately) the minimum length of line that will be picked up as a satellite trail, in pixels. It's not a perfect switch from not detecting below the limit to always detecting lines longer than the limit - the chance of detection goes up from close to zero at or below the limit to reach full detection at about 1.5 times the limiting length
* Trail Width - This affects both the detection (set larger values to detect wider satellite trails) and the width of the region that will be replaced when wiping out the satellite trail in remove mode (or highlighting it in test mode).

How to get started

Ideally, find some previously captured frame images that have satellite trails in them to allow you to test and configure the detection settings. You can load these images into 'Test Camera 1 (Deep Sky)' using the Image browse control. (Note: Test Camera 1 will now automatically set the colour space based on the file you choose - for instance RAW16 if you select a 16 bit RAW FITS file).

Here's a frame that was sent to me to help develop this feature:
Capture2.JPG
Capture2.JPG (182.39 KiB) Viewed 5917 times
Note that this view is *strongly* stretch - in the original frame, without a stretch, only the two bright stars top-right and bottom-left are visible.

Once you have selected a frame with a satellite trail in, turn the 'Remove Satellite Trails' control to 'Test' mode. This will draw bright lines onto the image over the satellite trails that have been detected, like this
Capture3.JPG
Capture3.JPG (30.34 KiB) Viewed 5917 times
Remember that those bright highlights of the detected trails will go into saved images/videos and live stack images. DO NOT use 'Test' mode when capturing or live stacking.

If your satellite trails in the image are not detected, try turning up the sensitivity, or reducing the minimum length.
If other parts of the image are wrongly detected as satellite trails, try turning down the sensitivity or turning up the minimum length.
If the highlighted area does not seem to cover the entire width of the trail, try turning up the 'Trail Width' setting.

If you cannot find a balance where your satellite trails are detected without detecting other non-trail parts of the image, please share the problem images with me for further testing :)

Turning Trail Removal On

Now that you have the trail removal settings largely correct, you can turn on 'Remove' mode - at that point you should see the trail removed from the image, like this:
Capture4.JPG
Capture4.JPG (28.81 KiB) Viewed 5917 times
If the trail removal doesn't seem to be complete, try turning up the 'trail width' setting a bit. If you have other satellite trail images available for testing it's worth trying them before moving back to your real camera to put this feature into use.

In the example above, the background brightness of the image is about 210 ADU (out of 65000). The satellite trail is about 600-700 ADU (so about 1% of maximum image brightness). After removal, the area is about 225 ADU, so about 97% of the brightness of the trail has been removed.

Things to Note

* The minimum length setting means that trails that only just show on the edge of the image may not be detected and removed.
* Like all other options in the 'Preprocessing' section, the changes to the image made by the satellite trail removal end up in the saved image, except in the case of saving RAW frames from live stacking, which are saved with no processing applied.
* The calculations needed to detect the satellite trails are quite extensive - approximately 1s to process a 15 megapixel frame on a high power PC. If you are using a high resolution camera with a low spec PC then the processing time may be many seconds.
* The extra settings (sensitivity, minimum length, trail width) only show when the satellite trail removal is turned to either 'Test' or 'Remove' - they are hidden when it is set to 'Off'. This is new with these settings, but I think it is a good idea to minimize clutter in the control list

Want to try it out

If you don't have any satellite trail images to test with, Test Camera 1 now has an option to add artificial ones to each frame - just turn the new 'Musk's Curse' setting to On...
Capture5.JPG
Capture5.JPG (20.6 KiB) Viewed 5917 times
Enjoy (and let me know how it works out)

Robin
Harmonious
Posts: 40
Joined: Tue Nov 28, 2017 11:20 pm

Re: New Feature : Satellite Trail Removal

#2

Post by Harmonious »

What a great feature! I tried it last night using the default settings with the scope pointed at a group of geo- something satellites, up to 6 short tracks per image. It worked very well.

No processing delay noticed.

Camera - ASI2600
PC - Ryzen 7 5700g CPU, 32GB PC4 3200 memory (CPU and memory slightly over clocked) and a 1TB PCIe 4.0 NVMe SSD
User avatar
admin
Site Admin
Posts: 12984
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: New Feature : Satellite Trail Removal

#3

Post by admin »

Hi,

thanks for the feedback - it didn't even occur to me that someone would go out and *deliberately* find satellites to check it out :D

cheers,

Robin
Xio1996
Posts: 41
Joined: Fri Feb 21, 2020 10:15 am
Location: Isle of Wight, UK

Re: New Feature : Satellite Trail Removal

#4

Post by Xio1996 »

Hi Robin,

Thank you for the new feature, satellites are getting very pesky! I found the sigma clipping in SharpCap very effective at removing satellite trails. Do you see these two functions working together or can I turn off sigma clipping and use this new feature instead?

Pete
User avatar
admin
Site Admin
Posts: 12984
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: New Feature : Satellite Trail Removal

#5

Post by admin »

Hi Pete,

the two features should be OK to use together - in fact they complement each other a bit. As noted above, the new satellite trail removal cannot always deal with a short section of trail if the satellite has either just entered or just left the field of view - sigma clipping should help with this. On the other hand, sigma clipping has a problem if one of the first 10 or so frames has a trail in it - satellite trail removal should help reduce the chances of this happening.

cheers,

Robin
Fabio
Posts: 2
Joined: Mon Feb 07, 2022 1:28 pm

Re: New Feature : Satellite Trail Removal

#6

Post by Fabio »

Hi!

Great feature!

Just a quick question: where can I find the option to activate it? I have the licence version.

Thanks!

Fabio
User avatar
admin
Site Admin
Posts: 12984
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: New Feature : Satellite Trail Removal

#7

Post by admin »

Hi Fabio,

you need the very latest SharpCap 4.0, from https://www.sharpcap.co.uk/sharpcap/downloads

If you have an older version then the feature is not there.

cheers,

Robin
Fabio
Posts: 2
Joined: Mon Feb 07, 2022 1:28 pm

Re: New Feature : Satellite Trail Removal

#8

Post by Fabio »

Hi Robin,

found it - it's in the preprocessing tab.

I kind of looked everywhere but there. I don't know why, because the placement of the feature within the UI seems very obvious. Now that I've found it, I don't know where my head was a few days ago!

Thanks!

Fabio
AndrewP
Posts: 4
Joined: Mon Jan 25, 2021 5:09 pm

Re: New Feature : Satellite Trail Removal

#9

Post by AndrewP »

Hi,

This is a great feature. Just one suggestion for future - maybe add an indicator to show when the processing has finished. It will just help speed up adjusting settings.

Cheers

Andrew
User avatar
admin
Site Admin
Posts: 12984
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: New Feature : Satellite Trail Removal

#10

Post by admin »

Hi Andrew,

thanks for the suggestion - do you find that the image update is taking quite a long time? Normally I have seen it at around a second or so, but if you have a large resolution camera and/or a slow PC then I guess it could take considerably longer.

cheers,

Robin
Post Reply