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Cartwheel galaxy with OSC from bright sky: ASI183mc EdgeHD11 f/7

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#1 freestar8n

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Posted 19 January 2020 - 02:40 AM

I have a backlog of images I'm going through.  I did several experiments with OSC from a bright location and this is one:

 

cartwheelb_irg_xgradcs.jpg

 

full res at astrobin:

 

get.jpg?insecure

 

Text from astrobin:

 

This is the famous Cartwheel galaxy in Sculptor - imaged from fairly bright suburban Melbourne skies with SQM 18.6 mag/arcsec^2 with an OSC camera, ASI183MC. EdgeHD11 f/7. 64x5m exposures over a few nights.

 

This is a very interesting galaxy structure that isn't imaged very much, but can be captured with a backyard setup and OSC camera with no special filters. Details in the galaxies are visible - along with several faint background galaxies.

 

Raw pixel scale is 0.25" per pixel, resampled x2 to 0.5" per pixel for the final version. Bayer drizzled with custom code using nearest neighbor interpolation and gradient removal - then linear scaled and imported to Photoshop for application of levels to stretch. Finally a x2 reduction in size to 0.5" per pixel. No denoising or other color alteration.

 

===========

 

This shows you can use OSC from bright locations and still capture color.  It also shows you can image at 0.25" per pixel and do ok as long as you resample for the final version.  And although this is an OSC image, there was no DeBayer performed.  It was Bayer drizzled using custom code - and that is no different from what happens when imaging with mono filters.  The only difference is that 3 filters are being exposed at once, and one of them (G) is doubled.  Which may be a good thing.

 

Frank


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#2 james7ca

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Posted 19 January 2020 - 04:57 AM

I'm not sure I've ever seen an amateur image of this galaxy before. It must be a fairly small object given your 0.5 arc second per pixel image scale (SkySafari says it has a visual magnitude of 19.3 and a size of about one arc minute). I wonder how it would look using a mono sensor at f/10.

 

Thanks for posting.



#3 Janco

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Posted 19 January 2020 - 10:27 AM

Carefull Frank, you might spark another OSC vs Mono debate .

Excellent image. Thanks for sharing this rarely captured galaxy.

Sent from my SM-G975F using Tapatalk

#4 freestar8n

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Posted 19 January 2020 - 04:03 PM

Thanks, James and Janco.  Yes, this thing is very small at just over one arc-minute.  I see people asking about a scope to use for galaxies - and when they are this small you need large aperture and long focal length.  The raw pixel size was 0.25" per pixel and this was resampled to 0.5".  The small pixels are needed to get detail in this interesting and complex structure.

 

Somehow I thought it was much smaller and only visible with HST or something - but the first exposure was a pleasant surprise.  Small, but still visible in detail.

 

I have other OSC images in the backlog that I will be posting.  OSC does work from bright areas - but I think it is slower than mono for rich color, but I'm not sure why.

 

Frank



#5 sunnyday

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Posted 20 January 2020 - 07:08 PM

wow nice 



#6 astrovienna

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Posted 20 January 2020 - 10:34 PM

All this with OSC and bright skies.  Great work, Frank.

 

Kevin



#7 bortle2

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Posted 20 January 2020 - 11:37 PM

I'm not sure I've ever seen an amateur image of this galaxy before. It must be a fairly small object given your 0.5 arc second per pixel image scale (SkySafari says it has a visual magnitude of 19.3 and a size of about one arc minute). I wonder how it would look using a mono sensor at f/10.

Look at this thread at CN, which should have some of your questions answered: Cartwheel galaxy with 10" f/9.1 RCOS and mono SBIG 11000M. Along with comparison to the HST image.

 

Both (Frank's and Terry's) images are very impressive.


Edited by bortle2, 20 January 2020 - 11:38 PM.


#8 bortle2

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Posted 21 January 2020 - 10:03 PM

This shows you can use OSC from bright locations and still capture color.

What was Bortle / SQM for that location?



#9 freestar8n

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Posted 21 January 2020 - 10:23 PM

Sqm reads about 18.6 with no moon.

Transparency varies - can be good or very bad.

Bright streetlight about 10m away but shielded from shining directly.

I have other osc images on the way.

Frank

#10 pixlimit

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Posted 23 January 2020 - 02:38 AM


That is a very nice image, Frank. Well done!

Clear skies
Peter

#11 namh

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Posted 23 January 2020 - 08:32 AM

Everything was working really well to capture this image. Great job Frank.

 

JB



#12 freestar8n

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Posted 23 January 2020 - 05:00 PM

Thanks Peter and JB!

More coming as I work on color stretches.

Frank


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