M51 high dynamic range composition

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timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

M51 high dynamic range composition

#1

Post by timh »

Just to finally tie things up from my last post on using very short exposure autostacks to add sharpness to the bright centre of M51...

Herewith a final compilation image of M51 to bring it all together. The HDRC process in PI was used to first combine the Bortle 4 OSC frames that were blurry (FWHM 3.3) - but that nicely captured the fainter outer galaxy features - with a sharper (FWHM 2.2) OSC frame image from Bortle 6 that better detailed the core and middle regions of the galaxy. Then the luminance of this combined RGB image was further combined into another HDRC composition with an even sharper (FWHM 1.8) mono 796 x 3s image which provided the best resolution at the core. Finally this HDR luminance was added back into the combined HDR RGB image and the image tidied up using curves.

So overall ...the bright core of the image is sharpest (derived from FWHM 1.8), the middle also sharp (FWHM 2.2) and the outer fainter galaxy hood plus background galaxies the least sharp (FWHM 3.3) in the region where sharpness actually matters the least

Maybe this sort of process is overall a good way of imaging galaxies ? It means that you don't have to worry too much about sharpness when collecting those few and far dark sky frames -- it is enough to get them at all and to capture the fainter stuff.

Tim
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M51_HDRCdrizzle_integration167x40s_x1_DBE_ABE_PLUS Lyme_51x70s_40x40s_HDRCat0.025_strmsk2_SCNR_MLT_TRANS_plusLUM_HDRC0.0025_796x3s_plus_RGBlum_curves_MLT_affinity_16bit_miniPX.jpg
M51_HDRCdrizzle_integration167x40s_x1_DBE_ABE_PLUS Lyme_51x70s_40x40s_HDRCat0.025_strmsk2_SCNR_MLT_TRANS_plusLUM_HDRC0.0025_796x3s_plus_RGBlum_curves_MLT_affinity_16bit_miniPX.jpg (996.34 KiB) Viewed 1171 times
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