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Helix Galaxy (NGC 2685 / Arp 336)


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The Helix Galaxy in Ursa Major, about 42 millions l.y. from us, is one of the few known lenticular galaxy with a polar ring. It is a rather difficult target to image from a suburban backyard, as it is both small and rather faint. Monday night the seeing was vary good (1.8" after stacking) but six hours of luminance was not enough, so I shot six more hours of luminance on Tuesday night. Unfortunately the seeing worsened around midnight.

For the final version I retained eleven hours of luminance, with a median FWHM of 2" on the stack and limiting magnitude m=21.2 according to ASTAP.


Here's first a slightly cropped version (right-click for full resolution):




And a tighter  crop on the galaxy:




There are many very distant galaxies in the background, including my most distant quasar to date (redshift z=3.827) and a galaxy cluster about 2.7 billion light-years away from us.


Thanks for looking and clear skies,




Technical details

200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube
AP900 CP4 mount on Losmandy HD tripod

ASI183mm (0.66"/pix)
TS 2.5" Riccardi-Wynne corrector
ZWO LRGB filters
Guiding : ZWO OAG + ASI120mm mini + AsiairV1
Luminance : 360 *60sec
Chrominance : 30*60sec for each R, V and B filter
Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), variable seeing, low transparency
Processing with Pixinsight




Edited by Dan_Paris
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On 18/02/2023 at 01:32, Sunshine said:

Great capture!

Thanks for your message !


On 18/02/2023 at 13:42, Zummerzet_Leveller said:

Lovely, such an interesting object.  Great result.


Thanks Jody !


clear skies,



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