Barred Spiral NGC 5921

[furgle]

I'm not too sure if I'm happy with the colour balance on this one, but I've been playing with it for way too long


Higher resolution here (https://observatory.site/astrophotography/Barred_Spiral_Galaxy_NGC5921/)



Image:



63x 450s Red
16x 450s Red
16x 450s Green
18x 450s Blue

Total integration 14 hours 8 minutes.
Hardware:



Celestron 11" Edge HD
Skywatcher EQ8 Pro mount
QSI 683-ws8 Camera @ -15°C
Astronomik Typ2c Luminance, Deep Sky RGB filters
Starlight Xpress Active Optics
Starlight Xpress Lodestar X2 Autoguider
Innovations Foresight On Axis Guider
Starlight Instruments Focus Boss II

Location:



Orange zone in Brisbane, Australia. (Bortle 7)
Imaged over 6 nights, new moon.

Software:



Planning & camera alignment with Aladin 9
Captured with AstroArt 6
Guiding with PHD2 + PHD_Dither
FocusLock live focusing
CCDInspector: Image analysis & rejection
CCDStack 2+: Calibrate, align, stack.
PixInsight: Dynamic background extraction, noise reduction, deconvolution, combine LRGB, color calibration, background neutralization, HDR multiscale transform, curves, local historgram equalization, non-linear stretch

[Geoff45]

There’s good detail in that pic Adam, but as you mentioned the colour doesn’t seem quite right. Did you try the PhotometricColorCalibration in PI?
Geoff

[strongmanmike]

Apart from the colour, which looks a little purpley...wow, what a galaxy :eyepop: love it!...look at those arms, amazing :thumbsup: top shot Adam

Mike

[gregbradley]

A nicely detailed image. I wonder if the Milky Way looks like this.

Greg.

[Atmos]

Very nice galaxy shot, considering its size you've captured a lot of detail in the spiral arms. Bit purple in the galaxy (but not the stars) but the data looks great :)

[furgle]

Thanks, no matter what settings I tried, PCC could not find a star in the image. I've never had an issue with it before. Astrometry.net solved it, TheSkyX solved it, even PixInsight's ImageSolver script solved it. I have no idea why.




Originally I had manually tried to shift the arms towards blue, then I saw Adam Block's rendition (http://www.caelumobservatory.com/gallery/n5921.shtml). There's definitely some red in the arms, but I guess I didn't have the aperture to separate the blue & red properly.

[RickS]

I'm not a fan of the purple but it looks nice otherwise.



You can load the plate solve from an image solved with ImageSolver into PCC. Just use the button that says something like "Acquire from image".

Cheers,
Rick.

[furgle]

Thanks Rick, that worked.

Now to find some more time to re-edit.

One very interesting thing I just discovered that may be affecting my colour; every tutorial I've seen says to use linear fit on your R,G,B subs, but then when I use PCC, everything is red biased. If I don't linear fit, PCC gives me better colour.

[RickS]

Adam,

You don't need to match the colours with LinearFit if you're going to do some sort of colour calibration. It does help to do background neutralization before running PCC, either with DBE or the BackgroundNeutralization process.

Cheers,
Rick.

[furgle]

Thanks,


Much appreciated, as always.

[Stevec35]

Apart from the purple colour that's a really good image of a spectacular galaxy that I haven't seen before.

Cheers

Steve

[topheart]

Great target!!
Cheers,
Tim

[kosborn]

Is linear fit necessary? I've read that an unlinked screen transfer function works just as well. I'd be interested to know what the PI gurus think.


Kevin

[Slawomir]

Very nice detail Adam :thumbsup:

[Placidus]

The shape and form and depth in the spiral arms is delightful.