NGC 3184 Galaxy with very good seeing (8" f/4 astrograph)

[Dan_Paris]

  Hi,

Monday night the sky was hazy but the seeing conditions were really good. On the stacked luminance the median FWHM is 1.76". The best luminance frames have an median FWHM of 2,1 pix, namely 1.4" or 5µm. I think I never had such results before in broadband.

NGC 3184 is a beautiful face-on spiral galaxy in Ursa Major, about 40 millions l.y. from us. It is not very contrasty so difficult to bring out of the sky background, especially in these conditions (Bortle 7/8, haze, quarter moon) so I pushed the integration time to six hours for the luminance.

Here's a slightly cropped FOV, with also the little NGC 3179 galaxy and many more in the background  (right-click for full resolution):

And a tighter crop on the galaxy:

 

Finally the annotated luminance, with many PGC galaxies and quasar labelled by their redshift (up to z=3.33 !).

 

Clear skies,

 

Dan

 

 

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), very good seeing (1.76" FWHM), quarter moon, low transparency
Processing with Pixinsight

Edited February 15, 2023 by Dan_Paris

[tomato]

Super sharp, well done!👍

[gorann]

Outstanding detail Dan! Clearly seeing is more important than transparency when it comes to small details in galaxies. This inverse relationship between seeing and transparency is often reported and I assume it has a good meteorological explanation.

[ONIKKINEN]

There is a real sense of scale and distance here with the bright foreground star and its diffraction spikes covering more area than an entire galaxy made up of billions of stars just like it. Great image!

Also have noticed the best seeing always occurring with high cloud and low transparency. If i recall the meteorological explanation it was something about stable skies being helpful for cloud formation, so good seeing always has clouds just around the corner. @gorannif your skies are as baltic (unpredictable) as mine these good seeing nights are often forecasted as fully or partly cloudy, even during that sort of clear spell so its difficult to prepare.

[MartinB]

Great image Dan.  I imagine living in Paris you don't have the best of skies.  

[Justin richens]

looks great!

[Dan_Paris]

On 15/02/2023 at 09:45, tomato said:

Super sharp, well done!👍

Thanks !

 

On 15/02/2023 at 11:00, gorann said:

Outstanding detail Dan! Clearly seeing is more important than transparency when it comes to small details in galaxies.

 

Thanks Gorann !I completely agree with you  although unfortunately some low-surface brightness galaxies need both transparency and good seeing... (you'll see with my next one 😉)

 

On 16/02/2023 at 11:06, MartinB said:

Great image Dan.  I imagine living in Paris you don't have the best of skies.  

 

Thanks Martin! The light pollution is rather horrendous but seeing is not that bad.

 

On 16/02/2023 at 11:12, Justin richens said:

looks great!

 

Thanks a lot Justin!

 

On 15/02/2023 at 18:14, ONIKKINEN said:

There is a real sense of scale and distance here with the bright foreground star and its diffraction spikes covering more area than an entire galaxy made up of billions of stars just like it. Great image!

Also have noticed the best seeing always occurring with high cloud and low transparency

Thanks ! The only exception to this general rule, at least for me, is the end of summer when there are some nights with good transparency and seeing conditions. Unfortunately the nights are not yet very long...

 

 

Clear skies,

 

Dan

Edited February 18, 2023 by Dan_Paris

[KY Cygni]

I cant like image 2 enough, superb