NGC253 Sculptor Galaxy

[Astrod00d]

My first decent galaxy.

NGC253, imaged in the early hours of Sunday July 6, just before the clouds closed in.

4 x 10-minute subs (Limited by clouds - I'll do more next time)
QHY8 Gain 1, 127mm APO prime focus.
Guided using a webcam and a short-tube 80 on and EQ6.

Stacked using Nebulosity, levels and curves in Photoshop.

The image is cropped to about 50%.

Cheers,

Rob

[AlexN]

nice shot Rob. detail/contrast seems really good, especially for 40mins data..

Hopefully tomorrow night yeilds better conditions.

[h0ughy]

wow - now thats something for me to attempt in a few weeks in qld. It will be the 127 except using my cooled 350D. Impressed me Astrodood!:thumbsup:

[Tandum]

My fist impulse was Yeeeeh .... it looks geat to me ....

[Geoff45]

Nice colour, detail and contrast, but fixing the trailed stars in Photoshop would make it much better..

[jjjnettie]

Terrific work.

When you look at this galaxy, you are looking at it from underneath aren't you?

[seeker372011]

nice shot Rob.I still havent managed first light with the 127 and looks like it wont be this weekend...violet halos around bright stars though are quite apparent..maybe use Noel Carboni's PS actions to get rid of them?

[peeb61]

Stunning...just stunning!

Paul

[renormalised]

Great shot, Rod...nice detail:)

[bluescope]

Good to start seeing some long exposures DSO's from the 127mm, nice image.

:thumbsup:

[Matty P]

Nice image Rob, good detail and contrast.

Well done.

[jase]

Good job on the Silver Coin. Some good details on display. Well done.

[Screwdriverone]

Beautiful Rob,

Stunning image, great details.

Well done!

Cheers

Chris

[Ric]

Great work Rob, a lovely detailed image.

Cheers

[gregbradley]

Nice one Rob.

I don't quite understand something though with this image. You have the larger stars round and the other smaller stars elongated from tracking errors. How come? Were there a few subexposures with tracking errors?

Here's a technique that can save some subexposures with tracking errors:

1. make a duplicate layer.
2. Set it to "darken".
3. Filters/others/offset
4. Set it to different amounts for vertical and horzontal to help correct the elongated stars.
5. Layers/flatten image.

You can also lassoo the area of the galaxy so only the stars get offset.
You'll save some images that way.

Also you can use the smudge tool to push elongated stars from different angles to make them rounder.

A couple of tricks for you mate.

Greg.

[Astrolabe]

Excellent Rob

George (astrolabe)

[Hagar]

Nice Galaxy Rob, Lots of detail in the galaxy wit very good focus. Definitely one for the pool room.

[Deeno]

Fantastic result....

[Astrod00d]

Thank you everyone for your great comments and suggestions! All very rewarding, encourages us to post more!


Hmm.. I've always thought it was viewed from 'above', but it could just as easily be seen as from 'underneath'. I really don't know. Confusing, since the viewing angle changes depending upon telescope design. Perhaps someone on this forum can help clear this up... underneath or above?


Yep, gotta get rid of those halos. The 127 has a nice flat field, but the colour correction is not perfect. Still excellent value though. I've had a look at Noel Carboni's PS actions, seems like good value and I'll probably make the investment.


Yep, trailed stars bug me. See my comments on trailed stars below..



Thank you for the offset trick! I've given offset a quick try with OK results, but I'll give it a bit more work before I post my results. As you suggest, I need to lassoo the galaxy (and the brightest stars) to optimise the result.
I've used the rubber stamp tool to clean up trails of hot pixels, this works nicely as well.

Trailed Stars:
I have an issue with guiding/flexure on this new set-up. Imaging with the 127mm f7.5 (953mm focal length) and guiding with a webcam through an 80mm f5.0. (400mm focal length) piggyback.
The system smears 1 to 1.5 pixels every 5 minutes. Measured by observing lines of hot pixels in stacked images.
The guider does not report errors, so this suggests flexure between the guidescope and the imaging scope.
Next time out, I want to use an ED80 (600mm focal length) as my guider, and fix the piggyback arrangement to improve rigidity.
Any suggestions as to piggyback mechanical arrangements will, of course, be most welcome! :)

Cheers,

Rob

[gregbradley]

Hi Rob,

Flexure - nasty.

I use a pair of Losmandy dovetail adapter plates that have Losmandy guide rings attached to them. I then attach this setup to a Losmandy dovetail plate. All up about $300.

This is quite rigid. I can still get minor flexure but it isn't very bad.

With the ED80 others can comment, but I think the focuser is a bit on the weak side and may well have flexure in it as well.

You may be best to use an extension tube and bypass the focuser or get a replacement focuser.

Greg.

[Astrod00d]

Thanks for the ideas Greg,

I've decided to attack flexure from a few angles.
Adjust and tighten the focusers on the ST80 and the 127ED.
Install a 12mm thick dovetail between the imaging and guide scope.
Change the EQ6 head to an ADM Losmandy-style dovetail foot.
Last but not least, rebuild the EQ6 and replace those crappy bearings. On inspection, the worm bearings have flat spots and would play havoc with tracking and guiding.

Cheers,

Rob