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Contains:  M 31, Great Nebula in Andromeda, NGC 224, M 32, NGC 221, M 110, NGC 205, The star 32And
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M31, the Andromeda Galaxy, 


            Wei-Hao Wang
M31, the Andromeda Galaxy

M31, the Andromeda Galaxy

Technical card

Imaging telescope or lens:Takahashi TOA 150

Imaging camera:Pentax 645z Mod

Mount:Takahashi EM-400 Temma2

Guiding telescope or lens:SharpStar 50 ED

Guiding cameras:ZWO ASI290MM MiniFishcamp Starfish

Focal reducer:Takahashi TOA 67 Flattener

Software:PixInsightAuriga Imaging RegiStarPhotoshop CC

Filter:H alpha

Resolution: 10962x6027

Dates:Nov. 5, 2016Jan. 3, 2017July 19, 2018Sept. 3, 2018

338x480" ISO800
40x60" ISO800
H alpha: 40x300" ISO12800
H alpha: 23x720" ISO800

Integration: 53.7 hours

Avg. Moon age: 9.95 days

Avg. Moon phase: 36.40%

Bortle Dark-Sky Scale: 2.00 job: 2275710

RA center: 10.680 degrees

DEC center: 41.268 degrees

Pixel scale: 1.348 arcsec/pixel

Orientation: 270.183 degrees

Field radius: 2.342 degrees

Locations: Mt. Shiao-Shuei (Taiwan), Taichung, Taiwan; Mt. Ho-Huan (Taiwan), Taichung, Taiwan

Data source: Traveller


This is a three-frame mosaic. The mosaic panels have large overlaps. The exposures were taken over 16 different nights over three years (July 2016 to Sep 2018). Most of them were taken under good seeing. Those taken under poor seeing were discarded or given low weights in the mosaic.

The exposures were Bayer-drizzed plus 2x-drizzle stacked in PixInsight. As a result, the final mosaic has a dimension of 31320 x 17220 (539 mega pixels). The version uploaded here is reduced by 0.35x (equivalent to 0.7x the camera's native pixel size) to avoid overloading some browsers. To see a pan/zoomable higher-resolution version (0.6x reduction), you can visit this page:

Rev A (final) is the regular RGB image.

Rev C is the exposure time distribution, in unit of minute, for Ha+RGB. The deepest area (red) contains 30 hours of exposure. The median exposure time is about 20 hours.

Rev D is a version with slightly brighter background, to adopt to somewhat older monitors whose display brightness ranges are smaller. You may feel more comfortable viewing this one if you feel the original version has a background that is too dark.

Rev E is a starless version, just for fun. Obviously the many background galaxies, and star clusters and compact HII regions in M31 are also removed.

Rev F is an inverted black and white image with strong stretch, to show the faint outer halo and stellar streams around M31.



Wei-Hao Wang
License: None (All rights reserved)


  • Final
    M31, the Andromeda Galaxy, 


            Wei-Hao Wang
  • M31, the Andromeda Galaxy, 


            Wei-Hao Wang
  • M31, the Andromeda Galaxy, 


            Wei-Hao Wang
  • M31, the Andromeda Galaxy, 


            Wei-Hao Wang
  • M31, the Andromeda Galaxy, 


            Wei-Hao Wang

Sky plot

Sky plot


M31, the Andromeda Galaxy, 


            Wei-Hao Wang