The original plan for the night was to image infrequently or never imaged globular clusters that hover low near the southern horizon. Near the zenith 30 to 60s exposures are used where I do imaging. With skyglow from surrounding towns near the horizon limited exposures to about 15s. Unexpected intrusions from trees to the south left some planned targets for another time. NGC7293 was not part of this night's plan but made for a fun and revealing experiment with the GraXpert app. Usual setup: Celestron 8/AVX, Starizona Night Owl 0.4X Focal Reducer, ZWO ASI294MC Pro. Exposures: 30x15s subframes. Post processing: stack averaging with Autostakkert!4. Stretching and gradient reduction with GraXpert 3.02, Final processing: Paintshop Pro 2021.
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| Messier 19 |
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| Messier 22 |
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| Messier 28 |
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| Messier 54 |
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| NGC 6712 |
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| NGC 7293 Helix Nebula |
A Bit on GraXpert A.I.
The GraXpert app uses sophisticated gradient removal algorithms including Kriging, Splines, RBF and a recently introduced A.I. algorithm. The non-A.I. routines require an editable sampling matrix be applied to the image. For the A.I algorithm you need only load the image, set the stretch value then run it. However, there is a smoothing parameter that can be set to value between 0.0 and 1.0. It's affect on an image can be dramatic and unlike the non-A.I. algorithms there's no sampling matrix or settings to play with to try to improve your image. The above images were all processed with RBF I most frequently use in linear mode. Where needed I tweak the sampling matrix. Below are three images processed with GraXpert A.I. mode using 0.0, 0.5 and 1.0 smoothing settings. I'll stick with RBF or Kriging.
