Sigma Clip stack help

[Paulkirk]

Hi - I am stacking some frames from a Mono camera using LRGB filters. One of the frames has a satellite/ plane track. I used Sigma Clip Average with sigma set to 3.5. In fact I tried with all the values of sigma, but the tracks remain in the stack. Have I missed something? Thanks for help.
Paul

[han.k]

Hello Paul,

The lower the value to more outliers like a satellite track are removed. The lowest value selectable is 2 but you can also type 1.5.

The sigma clip average algorithm works only well if the background is reasonable steady. In the image tab you can see a column "background". The background should be steady within maybe 10 or 20% variation. If it varies more, the algorithm will be less effective to remove the satellite tracks. If there are a few images with an abnormal high background value you could unselect them and try again.

Han

[Paulkirk]

Thank you Han, the background levels are all close to 1235, with the most difference being one sub at 1243, so all pretty stable. I tried a sigma value of 1.5 and that very nearly removed the track. Thank you for your help,
Paul