Different artifact
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Looks like a different blue artifact(?) than usual, sort of a diffraction pattern, mostly they are just square things. And a white spot next to it on a DECaLS object position. Are these more common in old SDSS images?
http://skyserver.sdss.org/dr9/en/tools/chart/chart.asp?ra=316.97883136&dec=-2.72501682http://legacysurvey.org/viewer?ra=316.9736&dec=-2.7215&zoom=16&layer=decals-dr3
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zoob1172
Field margin misalignment http://data.sdss3.org/fields/runCamcolField?run=7778&camcol=1&field=30
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Budgieye
moderator
IRAS F21053-0255 21h07m54.1s -02d43m27s IrS , no it isn't this
off the map in SDSS dr7
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Budgieye
moderator
It is parallel with the field lines, so the x shape must be an artifact of some sort. But what is the original blue object? Looks a pure blue, is it a cosmic ray hit?
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Yes indeed it seems aligned with the field lines. I would think cosmic ray hit too due to the single blue colour, but that pattern is what caught my eye, and I haven't seen this one before. Maybe a cosmic ray hit that was exactly perpendicular to the telescope line of sight / CCD chips plane?
I don't know what a 'field margin misalignment' is, but thanks for checking it out.
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c_cld
in response to Ghost_Sheep_SWR's comment.
Definitely #cosmic_ray hit!
If you look at fits files from https://dr12.sdss.org/fields/runCamcolField?run=8083&camcol=5&field=29, you'll find a single pixel in r wavelength with a value of 218.75 when all pixels of the galaxy range from -0.025 to 3.29. The stretching process and composition gives this neighboring coloring pattern in stacked unrotated raw frames.
I recommend easy fits viewer tools "fits liberator" and/or "QFitsView" before going to DS9 or similar
In this galaxy there is also another green #cosmic_ray hit just west of the blue located in spiral arm... 1237680191503663459 photometry r=21.66 , sky noise in other bands.
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Budgieye
moderator
Thank you c_cld, I feel better knowing that 😃
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