NGC1187 Spiral Galaxy

[gregbradley]

This was actually the first light for the Trius 694 camera. Taken on my CDK17 scope and PME mount.

10 minute subs may be a tad too long for this camera and 15 minutes for an LRGB image is for sure. Perhaps I will do 5 minute exposures next time. Its all part of the learning curve with new gear.

This image also shows that oversampling (too many pixels per arc sec compared to local seeing in arc secs) whilst it may reduce sensitivity as the same amount of flux is being shared by more pixels does give you much better deconvolution ability. These images were able to take more deconvolution than 9 micron pixel camera images can. So this tends to offset the sensitivity to seeing somewhat and is an unexpected bonus.

I was very pleased with this result because this is a quite small and dim galaxy and so you tend not to see images of it as a result. Its magnitude 11.4 and 5.3 x 3.6 arcmins in size. As opposed to the Sculptor Galaxy which is 29.0 x 6.8 arc mins and magnitude 7.3.

We have some very nice spiral galaxies in the southern skies but a lot are quite small and dim.

7 hours total using 10 minute sub exposures, colour binned 2x2.
Flats, darks, bias. Darks show some uneven illumination which appears to be amp glow and flats show mild vignetting (not much). Thermal noise is minimal at -20C. Software used was CCDSoft, The Sky X, CCDstack, Photoshop, Startools.

http://upload.pbase.com/gregbradley/image/153248961/large regular size

http://upload.pbase.com/gregbradley/image/153248961/original large size

Greg.

[renormalised]

Nice shot there, Greg. Was there much oversampling at 10 mins for this camera? Might need to leave the longer subs for those nights when your seeing is top notch.

[gregbradley]

Its .35 arc secs/pixel at that focal length. There are different views about what a good sample is but .66 arc sec is one (3X sampling assuming around 2 arc sec seeing), 1 arc sec is what Roland Christen recommends (3 arc sec seeing which is probably pretty common).

So either nearly twice as much or nearly 3X as much as needed. Its about twice as much sampling as my Proline 16803 at 9 micron pixels does.

The issue is not the sampling though its the small wells of the camera causing some haloing on bright stars. They are only 18,000-20,000 electron wells which is even smaller than the KAF8300 which is around 25,500 and it can sometimes halo bright stars depending on your setup.

Greg.

[Stevec35]

Haven't seen that one before Greg - looks pretty good. The link to the large version doesn't work for me. This sometimes happens with your images - no idea why.

Cheers

Steve

[RickS]

Looks good, Greg!

[gregbradley]

Thanks Steve.

You can click on original under the image and it should take you to the large version.



Cheers Rick.

Greg.

[The Mekon]

Wonderful image Greg, I am constantly amazed at how amateurs today can produce better results than the pros of 40 years ago. But surely the dimensions of this galaxy are 5.3 arc minutes x 3.6 arc minutes not seconds?

[gregbradley]

Thanks! Yes you must be right about the size. The Sky 6 did not specify the units.

Greg.

[Elio]

Great image but... are you sure about colours? I see to much red there, but my lcd isn't perfect... congrats anyway, your setup is lovable!

[E_ri_k]

Looks good Greg, glad the new gear is working for you.
Erik

[gregbradley]

Thanks Elio. I just checked some professional images of it and you are right its more blue and less red. I thought perhaps we were looking through a Milky Way dust area and hence the reddish look.

Corrected now.

Greg.

[renormalised]

As small as it appears, at its distance from our galaxy (60 million ly), it's nearly 94,000 light years across.

[Elio]

Thank you for share :thumbsup:

[gregbradley]

Amazing isn't it. I am continually amazed at the distances and quantities of our Physical Universe.



Thanks for your feedback Elio. Sometimes we miss the obvious when processing an image and feedback helps spot it.

Greg.