Ngc253

[Shiraz]

sorry about this, but it is a beautiful galaxy.

Have been playing on and off for months with some old data and selected out 80 minutes of 20 second subs taken in pretty good seeing (better than 2 arcsec FWHM). Combined this with about 4 hours of colour data from an earlier image.

Full res may be toggled to from here: http://astrob.in/315472/C/

NGC253 is easy to overprocess and there are a few examples on the web of extreme extraction of "features" that don't appear to have much basis in reality. To try to keep the processing honest, I attempted to do no more than extract luminance features to match those of the Hubble image of the same region ( https://www.spacetelescope.org/images/heic0819b/ ) - nothing remotely like Hubble resolution of course, but hopefully there is nothing in the image that does not appear in the Hubble data at the same scale. Comparative Lum images attached for info.

Colour is saturated as the image has been kept relatively dark - deliberate to bring out the internal detail. I know it will not be to everyone's taste and would appreciate feedback.

thanks for looking. Cheers Ray

Oh - and don't spend time on the image below - the main one is at the Astrobin link.

[Peter Ward]

No apology required....it is a beautiful galaxy.

Ansel Adams returned to Yosemite so many times.

I could ruminate about Helmholtz, but the extra saturation is very well understood.

Expertly captured and processed. :thumbsup:

[RickS]

Beautiful image, Ray! It's often imaged but rarely as well as that...

[Atmos]

Exceptional Ray :) Very nice resolution!
I do keep wondering about the colour of this galaxy, every time I process it it seems a bit different and doing the PhotometricColourCalibration it comes out less blue.

[DJT]

Awesome Ray. Are you able to provide details of the original 4 hours of data? Maybe the processed image? Trying to gauge the contribution the asi made to the combined image, if that’s even possible?

It’s bloody good though :thumbsup: love the saturation.

[gregbradley]

Very nice Ray. I like saturated images too.

I am interested in how PixInsight presents the calibrated colour for this as well. I suspect it would be less blue but blue is probably the nicest colour in an astro image don't you think?

Greg.

[strongmanmike]

I remember the original version (http://www.astrobin.com/full/275078/0/) Ray, t'was very good. I like the saturation of the main body of the galaxy in the latest version but prefer the surrounds, including the cool galaxies, showcased in the original :)....of course it is a bit like deciding between supermodels :P

Mike

[Shiraz]

thanks very much Peter


Very generous comment - thanks Rick


I have trouble with this one and M83 - they never look right whatever I do. I used standard calibration in PI and got the attached colour image before the lum was overlaid and saturation boosted.


Thanks Dvaid. It was all ASI. the colour bit is attached.


This is the colour balance that the standard approach in PI yielded - with a lot of extra saturation due to the relatively light stretch on the luminance.
The colour component was as in the attachment.

thanks for the feedback. Cheers Ray

colour image prior to lum overlay is shown below - colour data was gathered in fairly ordinary seeing.

[Shiraz]

Thanks Mike. yeah, maybe it was a poorly conceived experiment at that.
cheers Ray

[strongmanmike]

Along with the streamers across the disc, I recon the asymmetric faint but extensive outer halo is the coolest thing about NGC 253, is it in your data?

Mike

[Shiraz]

I concentrated on the disk detail Mike - there is no halo worth looking at with 80 minutes of 20 second subs and limited stretching (not much of any background stuff actually). In the earlier version, a lot of poorer res data was included to get an image of the halo and the background galaxies. Maybe I should try for some more data.
This is the sort of thing I was trying to get part of the way to: https://apod.nasa.gov/apod/image/1105/NGC253-HST-Gendler3LL.jpg
cheers Ray

[Shiraz]

OK, agree with majority, it was a bit too saturated. have now wound back the saturation. thanks for all of the feedback - appreciated. cheers ray

[willik]

What is it
Martin

[Placidus]

Heart-achingly beautiful.

[Camelopardalis]

Love it Ray, another winner :cool:

[gregbradley]

The latest version looks good.

This galaxy's colour scheme has always seemed to vary a lot. Even the name "the Silver Dollar" implies its silverfish. Its a classic spiral galaxy so a yellow/dusty core and bluish outer arms makes the most sense.

I'd love to see what PI's new calibration tool shows as the colour.
Greg.

[Camelopardalis]

I don't have much data, but this is what PCC spat out, followed by Histogram Transformation to bring it in to the visible realm and a little boost to saturation using Curves Transformation. No individual channel controls were touched.

[Paul Haese]

I think somewhere in between the first and second version would look good. I like the blue in the first version but I think the reduction of the saturation is a little too much in the second.

Those 1600's have great sensitivity and can clearly collect a lot of data for short integration. I'll certainly be looking at a CMOS for my next camera, and it might be sooner than I think.

[gregbradley]

Well that's interesting. I suppose the colour balance looks very good but rather dull. But if you use that tool to get the colour balance right boosting the saturation to turn it into a pretty picture should be nicely on track.

Greg.

[multiweb]

The details are excellent Ray. Gotta be stoked with that one. :thumbsup:

[Camelopardalis]

Hope so...I was restrained with both the HT and saturation, given the paucity of data, I didn't want to noise to dominate the pic ;)