WBPP Pixel rejection seems a bit harsh?

[UlteriorModem]

Here is an image of some rejection maps generated by WBPP. It seems like it is rejecting some signal?

High rejection by Tom Whit, on Flickr

Dark rejection on the left, light rejection on the right.

Does this look right? If not how do I fix it?

Thanks

[ngc1535]

Tom,

That is a qualitative statement ("harsh"). I suspect some numbers would be helpful...
How many frames did you combine? Did you use the "default" setting for the thresholds or adjust them?
And most importantly, rejection is a mathematical operation in the sense that it is completely deterministic based on your data and the algorithm/parameters.
So if your frames (data) vary significantly from image to image in terms of signal- more rejection is certainly expected. Do your frames vary in quality (signal strength, resolution... etc)?

Unlike in the past, WBPP script will now "pick" an algorithm for rejection based on the number of frames and apply the default thresholds unless you change them. So which algorithm did it pick?
(Look in the FITs header of the integrated frame. Look for a HISTORY statement like "ImageIntegration.pixelRejection: Winsorized sigma clipping")

-adam

[UlteriorModem]

10 frames 180sec at 139/21.

I used the default for 'nebula' the object was M42 so there are some pretty bright regions.

The dark had to be 'optimized' due to it being a 300sec sub.

The frames look quite similar to one another in blink anyhow.

[Stu]

Hi UM/Tom (This is Stuart from the other forum)

You picked Nebula, but that's not rejection.  The nebula setting sets a weighting for stacking based upon your FWHM, eccentricity and SNR. It mimics the Subframe Selector script

What Adam is talking about is rejection, which you can find under the image integration submenu in the WBPP script.  The default is "Auto" which means that it will pick which rejection algorithm (eg: linear fit, windsorized sigma, etc) is the best.  You should be able to see what it used by looking at the process console or by looking at the history in the integrated frame as Adam said.  You can change the high and low rejection by fiddling with the sigma high and sigma low sliders. 

But if your final stack looks good, I wouldn't worry too much about it.

Stu