WBPP frame weighting B2 vs B6 skies

Dieter Lubbe

I live in a B6 zone but have a cabin in a B2 zone, so at times try and process same target from both zones if circumstances allow. I recently had 2 good nights in B6 (around 130 x 5 min subs) and 1 night with 70 x 5min in the B2 location (all subs in 4 day window, moon <20%). EDGE8 at 2032mm without reducer, 2600MC. No filter at B2 location, Antlia RGBUltra at B6. Because of clearly better SNR, stars, etc, WBPP will reject almost all my B6 location subs when processing B2 and B6 subs together. The calibrated subs from my B6 location have been aggressively trimmed via subframe selector, but I still have to set frame rejection minimum weighting at 0.00 to allow inclusion. But then the B6 subs still almost have no contribution because of very low weighting. Why do I need B2 subs you may ask as clearly B2 alone may be sufficient and superior? Well, I obtained a really good Ha signal with the Antlia RGBUltra in B6, and very poor signal without filter at B2 (don't understand why). See attached WBPP calibrated output with STF only of B2 processed alone and B6 processed alone, you can see difference in Ha clearly. I also included screenshot of WBPP weighting of all subs together from running log script, massive difference in most parameters as expected (first 2/3 of frames are B6). I have combined the individual 2 sites in Photoshop successfully to benefit from B2 SNR signal and B6 Ha signal, but wonder if there is a way in WBPP to force equal weighting to preserve Ha signal, or other techniques to overcome this. I have watched all your recent weighting videos but have not seen this specific issue come up. I have tried PSF signal weight vs PSF scale SNR without effect. Would appreciate thoughts. Thanks. Dieter

BlockHead

HI Dieter,

I am trying to follow... I think you are explaining you are mixing narrowband and broadband images. Due to the transmission of NB filters... (and the effect of double filtering) I would expect the NB to be given very little weight. This is normal and it is not quite normal to mathematically combine this kind of information. You can certainly blend two kinds of images together... but stacking them I think is problematic if you want the kind of contribution to the integrated result you are expecting .

This is actually a very complex kind of thing to do. So I do not have anything specific on this other than I believe it to be a non-standard approach to stacking.

-the Blockhead

Dieter Lubbe

Thanks Adam, I guess I was approaching it as blending two different sets of OSC RGB data, but as you point out, the RGB ultra really is NB and not jus "light pollution" filtering, that's what's causing the issues. Thanks.