2026-10-09 APP 2.0.0-beta48 has been released !
This is mainly a bug fix release for the reported bugs in beta47. In addition it has a significant User Interface performance improvement noticable when you need to process 1000s of images in APP.
2026-10-03 APP 2.0.0-beta47 has been released !
This is a very big release... many code optimizations/rewrites, many parts of APP are much faster and more precise, especially star analysis and registration are much faster ! Big mosaics will go much faster 🙂
And we introduce a new preview filter, which includes the new Adaptive Deep Sky Stretch and a General Levels Stretch, this has been long over due. The old preview filter (the panel on the right side to stretch and preview your data) has not been updated for a couple of years and it is a critical part of any APP session.
Adaptive Deep Sky Stretch or ADSS is a much more intuitive stretch algorithm. It is also color preserving (which is a great new addition in itself ! ) which means that the highlights are no longer bleached, color is maintained from the linear data while stretching. You can simply stretch your data using the sky background level and signal width sliders which work much easier and more intuitive. You no longer need to fiddle with the old complicated sliders with zoom buttons. All the zoom buttons for the sliders are made redundant. And you can enter slider values in the slider value fields yourself. I will make a youtube video in the coming days to explain and fully introduce ADSS. Once the video is ready, it will be highlighted on the forum.
RGB Combine upgrade !. The RGB Combine Tool has been rewritten mostly. The tool is faster and easier to use and most importantly, the Luminance slider to inject a luminance channel or channels into the RGB composite is now working correctly. It no longer bleaches the RGB colors. Combined with the new ADSS preview, you will get much better and easier great composites with great color! I will also explain this in a new youtube video.
The Crescent Nebula only in the light emitted by Hydrogen Alpha (red) and Oxygen III (green and blue). I took 48 subs of 600 sec each with a ZWO Ha filter and 127 subs of 180 sec each with a Baader OIII filter using a SkyWatcher Esprit 80ED and an ASI1600MM-C Pro. Processing, colour combination and background calibration done in AstroPixelProcessor, final touches in PixInsight.
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Cheers, Wouter
Good work,
Beautiful image !
Which ratio did you use ? 1/1/1 ?
@patrick Thanks!
@franck_chile I set Ha to 50% R and OIII to 50% R, 100% G and 100% B. That way I could tame the high intensity of Ha better. And I used the linear images for this but I just saw this comment
https://www.astropixelprocessor.com/community/tutorials-workflows/hubble-palette-tutoriel/#post-7964
where combining Ha and OIII are recommended to do after stretching so I will give that a try as well.
Hi Wouter,
Very nice work! You mentioned:
"I took 48 subs of 600 sec each with a ZWO Ha filter and 127 subs of 180 sec each with a Baader OIII filter"
I am wondering how you decided on those exposures? Are the filters dissimilar bandwidth?
Thanks.
Thank you! The Ha filter has a bandwidth of 6 nm and the OIII 8 nm. The sky in my backyard (where I shot Ha) suffers from much more light pollution than the sky at the observing location in southern France (where I shot OIII). Plus I am very new to small band imaging and I am still trying out things.
I noticed that some of the very red stars in the picture (for instance to the lower right of the Crescent and also to the far right of the image) have a red halo and a white core. This means that their cores are saturated in the Ha image so I should take subs of less than 600 seconds in Ha. I don't see any blue/green halos around white cores so the OIII exposure time of 180 seconds was correct (or at least better than 600 seconds) and I will use that next time I shoot Ha.
Hi Wouter,
Thanks for your reply. It is very interesting that you should notice star halos. I too have seen them, and also in one of Sara Wager's image that I am working on now. In her shot it is an OIII halo around a white core (Ha+OIII = white).
As an aside, when I do LRGB imaging I use different exposures for RGB that I predetermine by photometrically measuring the light from a G2V star, the purpose of which is to compensate for the differences in my sensor's QE curve. The objective is to balance the SNR.
I know for a fact that my sensor is least sensitive to red and most sensitive in green, so my red exposures are longer. For narrowband at the present moment I have been following Sara's lead by using the same exposure for Ha and OIII. I don't know what her QE curve looks like but I should look into it. The fact that she has OIII halos indicates to me that her sensor is more sensitive to that wavelength.
My gut tells me that I should lower the OIII exposure but for now I am following Sara's lead. There may be other factors that I haven't considered.
Thanks.
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