Milky Way, 12 years, 1250 hours of exposures and 125 x 22 degrees of sky
source link: https://astroanarchy.blogspot.com/2021/03/gigapixel-mosaic-of-milky-way-1250.html
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Tuesday, March 16, 2021
Milky Way, 12 years, 1250 hours of exposures and 125 x 22 degrees of sky
It took nearly twelve years to collect enough data for this high resolution gigapixel class mosaic image of the Milky Way. Total exposure time used is around 1250 hours between 2009 and 2021.
The final photo is about 100 000 pixels wide, it has 234 individual mosaic panels stitched together and 1,7 gigapixels. (Click for a large image)
The California Nebula, NGC 1499, can be seen at bottom left of the large mosaic image.
There are about 20 million individual stars visible in the whole mosaic image.
Click for a large image
Image spans 125 x 22 degrees of the Milky About 20 million individual stars are visible in my photo!
My processing workflow is very constant so very little tweaking was needed between the mosaic frames. Total exposure time is over 1250 hours. Some of the frames has more exposure time, than others. There are some extremely dim objects clearly visible in this composition, like a extremely dim supernova remnant W63, the Cygnus Shell. It lays about six degrees up from North America nebula and it can be seen as a pale blue ring. I spent about 100 hours for this SNR alone. An other large and faint supernova remnant in Cygnus can be seen at near right edge of the image. G65.5+5.7 is as large as more famous Veil nebula. There are over 60 exposure hours for this SNR alone. (Veil SNR is just outside of the mosaic area for compositional reasons but can be seen in "Detail" image above.)
I took my current toolset as a base tool since it has a relatively high resolution combined to a very large field of view. Also it collects photons very quickly since it's undersampled and I can have very dim background nebulosity visible in very short time (many times 30 min frame is enough)
I do all my mosaic work under the PhotoShop, Matching the separate panels by using stars as an indicator is kind of straight forward work. My processing has become so constant, that very little tweaking is needed between separate frames, just some minor levels, curves and color balance.
I have used lots of longer focal length sub-frames in my mosaic to boost details. (See the mosaic map at top of the page) To match them with shorter focal length shots I developed a new method.
Firstly I upscale the short focal length frames about 25% to have more room for high resolution images.Then I match the high res photo to a mosaic by using the stars as an indicator. After that I remove all the tiny stars from the high res image. Next I separate stars from low res photo and merge the starless high res data to a starless low res frame. And finally I place the removed low res stars back at top of everything with zero data lost. Usually there are some optical distortions and it's seen especially in a star field. Now all my stars are coming from a same optical setup and I don't have any problems with distortions. (I'm using the same star removal technique as in my Tone Mapping Workflow)
Click for a large image
Click for a large image,
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