Carina Dwarf Galaxy

sjastro · #1 10-04-2009, 06:11 PM

Not your run of the mill object to image.

The extremely faint Carina Dwarf Galaxy.
The surface brightness of the galaxy at 16.0 Vmag/sqdeg is much fainter than the natural sky glow at the darkest sights (13.0 Vmag/sqdeg.)

Since I don't use a GOTO mount finding and framing the object was somewhat challenging. I downloaded the DSS image which of course only showed the star field but not the object. Only some recognizable star patterns allowed me to locate the object.

20 hr luminance exposure, BRC-250 and ST-10XME.

http://users.westconnect.com.au/~sjastro/carinadwf.html

Clear skies

Steven

Kevnool (Kev) · #2 10-04-2009, 06:44 PM

Yep can notice it in the mix.
To right its faint.
Cheers Kev.

TrevorW · #3 10-04-2009, 07:18 PM

Is it the fussy bit in the middle

strongmanmike (Michael) · #4 10-04-2009, 07:19 PM

Nice work Steven, there is certainly a galaxy in that image so your budget Where's Wally approach to finding it and framing it looks to have been successful

.

Did you use accurate flats on this image? I ask only because the apparent glow of the galaxy also looks decidedly like vignetting so it would be nice to confirm that you are indeed picking up the actual glow from the galaxy, all images I could find, including very deep amplified UK Schmidt shots, show no uniform circular glow like that in your image...?

Very interesting image mate, thanks for shooting something a bit different

Mike

Bassnut (Fred) · #5 10-04-2009, 07:41 PM

I pushed it hard to see if I could find it, but im not sure, could you put an arrow on the image?.

sjastro · #6 10-04-2009, 08:41 PM

Thanks for the comments.

The best way of seeing it is:

(a) Calibrate your monitor against a stepped grey scale.
There is one on my web page http://users.westconnect.com.au/~sjastro/small/

(b) Look at it in a darkened room.
(c) Reduce the size by 50% on your monitor.

What you should hopefully see is a circular glow slightly off centre to the right which takes up about 30% of the FOV.

Regards

Steven

Bassnut (Fred) · #7 10-04-2009, 08:47 PM

Ahh, I get it, so the circular glow that looks like no-flats-used is the galaxy, cool, thanks.

sjastro · #8 10-04-2009, 08:50 PM

Quote:

Originally Posted by strongmanmike

Nice work Steven, there is certainly a galaxy in that image so your budget Where's Wally approach to finding it and framing it looks to have been successful

.

Did you use accurate flats on this image? I ask only because the apparent glow of the galaxy also looks decidedly like vignetting so it would be nice to confirm that you are indeed picking up the actual glow from the galaxy, all images I could find, including very deep amplified UK Schmidt shots, show no uniform circular glow like that in your image...?

Very interesting image mate, thanks for shooting something a bit different

Mike

Thanks Mike,

I had to redo the flats as the galaxy was subtracted out of the image.
Vignetting is definitely not an issue with a BRC-250 and ST-X10ME chip.

Perhaps it is an auto contrast scaling issue in Photoshop.

Then again it might be the real thing.

Regards

Steven

Chippy (Nick) · #9 10-04-2009, 09:24 PM

I never would have guessed it if I didn't read the posts.

Peter Ward · #10 10-04-2009, 11:35 PM

Well executed and seriously deep sky.

atalas · #11 11-04-2009, 01:28 PM

Wow,20 hrs?how faint is this galaxy Steven?

sjastro · #12 11-04-2009, 02:56 PM

Quote:

Originally Posted by atalas

Wow,20 hrs?how faint is this galaxy Steven?

Thanks Louie.

The integrated magnitude is 10.7. The size is 20 X 15 arcmin making the surface brightness very faint.

Regards

Steven

strongmanmike (Michael) · #13 11-04-2009, 11:42 PM

I think this one might have benifited from a larger FOV?....yes Fred et al there are reasons for having larger FOV's than a postange stamp

It is hard to appreciate the galaxy when it just looks like vignetting

Shame as you spent a bit of time on this one.

Mike

glenc (Glen) · #14 12-04-2009, 09:06 AM

I haven't seen that before, thanks Steven.

It was found in 1977 and has B mag 11.3. It seems to be half as old as the Milky Way galaxy.

Garyh · #15 12-04-2009, 01:24 PM

Now that`s something different! Great work Steven!

sjastro · #16 12-04-2009, 10:51 PM

Thanks for the kind comments.

It might look like vignetting but the Carina Dwarf is a dwarf spheroid!!

Kind regards

Steven

gregbradley · #17 13-04-2009, 06:22 PM

Wow, what an effort!

You must have placed a lot of confidence that you were imaging in the right spot as it could have been really easy to miss.

Well done.

Greg.