Welcome to William L.T. Ng's Astronomy Page
Latest Updated : March 08, 2019
M42 Project
Since 2008, I have taken this object every year in Hong Kong with DSLRs and a variety of telescopes. However, no decent image can be obtained due to the severe light pollution and low air transparency (usually from October to May every year) in Hong Kong. At the beginning of 2019, I had a thought. What the result will come out if all of the M42 images ever taken were stacked?
For the core and bright part, it is not a problem, we can get quite good data still in Hong Kong even the air conditions are not so good. But I am curious if the faint nebula can become a bit obvious after so much exposure is integrated, even it is seemed quite meaningless to stack all sets of subs taken with different telescopes, exposure time, cameras and iso settings. So as to get the telescope resolution as close as possible, I selected those images taken with 4" refractor and 6" Newtonian.
Firstly, each set of subs (if no. of subs > 2) were stacked in PI (PixInsight) or in DSS (if no. of subs = 2), but some sets were stacked without darks, bias or flats (or good flats) calibrated. Then the stacked images were "pre-processed" with DBE and PCC tools in PI. After that, they were "post-processed " in PS with Level and Curve adjustment so that the overall brightness of each one looked similar on monitor. Then, they were registered in PI, and the registered images were stacked in DSS. Finally, the final image was re-touched with PS.
However, due to image orientation issue, after star alignment, some could not overlap well and needed to be rejected from this project. So, only 5 out of 10 individual images were used for this project finally. They are image 1, 2, 4, 9 and 10, giving the total integration of exposure time = 276 min (4 hr 36 min)
| Below is the result from this project. (Total exposure = 4h36min) |
| (Click HERE for a HDR version and HERE for one of the RAWs of each set of subs) |
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HDR version
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| Image | RAW | Processed from this set of subs |
| 1 |
 6" F5 Newtonian + 350Da, 2 x 360s @iso 800 |
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| 2 |
 DED108SS + 350Da, 9 x 360s @iso 400 ¡@ |
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| 3 |
 6" F5 Newtonian + 350Da, 8 x 360s @iso 400 ¡@ |
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| 4 |
 DED108SS + 300Da, 26 x 180s @iso 400 ¡@ |
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| 5 |
 6" F5 newtonian + 300Da, 4 x 240s @iso 400 |
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| 6 |
 ED103S + 300Da, 7 x 300s @iso 400 |
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| 7 |
 AX103S + 300Da, 2 x 300s @iso 800 |
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| 8 |
 AX103S + 300Da, 17 x 240s @iso 1600 |
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| 9 |
 ED70S + 300Da, 25 x 240s @iso 800 |
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| 10 |
 AX103S + 0.7x reducer + 100Da, 9 x 480s @iso 800 |
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