Carina Dwarf Galaxy: 30 hr exposure

[sjastro]

The imaging of this object started two years ago.

After a total of 30 hr luminance, the law of diminishing returns suggests that further imaging will not add much to this extremely faint object.

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

As a comparison here is an image of the dwarf taken by combined exposures from the 2.2 meter MPG/ESO and the Victor M. Blanco 4-meter telescopes in Chile.

http://blogs.discovermagazine.com/ba...-dwarf-galaxy/

Regards

Steven

[astroron (Ron)]

Very impressive Steven
Thanks for shareing
Cheers

[Stevec35 (Steve)]

Nice catch Steven. Your skies must be pretty dark to do so well on such a faint object.

Cheers

Steve

[RickS (Rick)]

Congratulations on your perseverance. Great catch!

[strongmanmike (Michael)]

Not bad Steve, 30hrs huh, certainly got something there I'd recon ..but hmmm?..I am not sure what is the galaxy and what is vignetting , the outer areas of the image do look very black like they are severely clipped and/or vignetting is playing havoc..? Leaving the entral area very bright.

Great project though

Mike

[gregbradley]

A fabulous effort and a great catch. There is something wrong with the way you processed the background. Its like you've done a subtract layer and its taken away the background where there are no stars. There are ways of processing out the background gradients without clipping it or removing actual background data.

Greg.

[sjastro]

Originally Posted by astroron

Very impressive Steven
Thanks for shareing
Cheers

Thanks Ron.

Originally Posted by Stevec35

Nice catch Steven. Your skies must be pretty dark to do so well on such a faint object.

Cheers

Steve

Hi Steve. Actually my skies are not very dark. I reckon a visual limiting magnitude of 5.5-6.0.

Originally Posted by RickS

Congratulations on your perseverance. Great catch!

Thanks for your comments Rick.

Originally Posted by strongmanmike

Not bad Steve, 30hrs huh, certainly got something there I'd recon ..but hmmm?..I am not sure what is the galaxy and what is vignetting , the outer areas of the image do look very black like they are severely clipped and/or vignetting is playing havoc..? Leaving the entral area very bright.

Great project though

Mike

Hello Mike,

Vignetting on a teeny ST-10XME chip?
It's the real thing. It's not called a dwarf spheroid for nothing.
Here is the AAO image, so stretched it makes the dwarf look like a globular.
http://spider.seds.org/spider/LG/car_dw.html

Originally Posted by gregbradley

A fabulous effort and a great catch. There is something wrong with the way you processed the background. Its like you've done a subtract layer and its taken away the background where there are no stars. There are ways of processing out the background gradients without clipping it or removing actual background data.

Greg.

Hi Greg.

The surface brightness of the galaxy is much fainter than the natural sky glow from the darkest sites on Earth. The only reason it can be imaged is due to the additive effects of surface brightness and sky glow.
The object is for all intents and purposes a variation of the sky background. To make it visible I had to subtract the sky glow from my site including any existing noise in the stacked image.
This allowed me to aggressively stretch the image and not lose it in the background.

I can make the background more natural looking by adding some noise to the background but I am satisfied with the way it turned out.

Regards

Steven

[Ross G]

An amazing capture of an amazing object Steve.

Looks great and thank you for showing me something I have not seen before.

Ross.

[sjastro]

Originally Posted by Ross G

An amazing capture of an amazing object Steve.

Looks great and thank you for showing me something I have not seen before.

Ross.

Much appreciated Ross.

I think these objects are much more interesting as they are a real challenge to image and are off the beaten path.

It shows they can be imaged by amateurs under less than ideal conditions, provided one can extract the data out of the noise.

Regards

Steven

[Ric]

A nice capture Steven, that's a galaxy I have not seen before.

[Alchemy (Clive)]

I saw the title, and thought 30 hours ???? Where did he get the time to do that.... Then I read the thread ( last 2 years) Yep that's about all the clear sky we've had in the last 2 years, or so it seems.

I think I've seen you refer to this previously, or a target of a similar nature, so I get the whole background thing. Quite a challenge.

[gregbradley]

Great shot Steven. I got it about the background. An interesting technique then to be able to bring up an object dimmer than th ebackground.

I admire your tenacity.

Greg.

[sjastro]

Originally Posted by Ric

A nice capture Steven, that's a galaxy I have not seen before.

Thanks very much Ric.

Originally Posted by Alchemy

I saw the title, and thought 30 hours ???? Where did he get the time to do that.... Then I read the thread ( last 2 years) Yep that's about all the clear sky we've had in the last 2 years, or so it seems.

I think I've seen you refer to this previously, or a target of a similar nature, so I get the whole background thing. Quite a challenge.

Not only have we been hard hit by bad weather Clive, when the clouds have disappeared the seeing conditions have been terrible.

Originally Posted by gregbradley

Great shot Steven. I got it about the background. An interesting technique then to be able to bring up an object dimmer than th ebackground.

I admire your tenacity.

Greg.

Thanks Greg.

I have posted a comparison between the skyglow subtracted image and a normal processed image.

Regards

Steven

[sjastro]

For a normally processed image it was impossible to extract the Carina Dwarf.

Regards

Steven

[Moon (James)]

The headline 30 hours got my attention straight away too - but this galaxy is special and deserves it. Very well done indeed and thanks for presenting it to us!
James

[gregbradley]

An interesting comparison. That technique really works well.

In my case because the CDK17 vignettes quite a bit I would be concerned that what I was seeing was a bad flat result. So you'd have to have confidence in your processing technique and what you normally get when subtracting the background.

How did you subtract it anyway? Apply image/subtract?

Gre.

[sjastro]

Originally Posted by gregbradley

An interesting comparison. That technique really works well.

In my case because the CDK17 vignettes quite a bit I would be concerned that what I was seeing was a bad flat result. So you'd have to have confidence in your processing technique and what you normally get when subtracting the background.

How did you subtract it anyway? Apply image/subtract?

Greg.

Here is the procedure Greg.
http://users.westconnect.com.au/~sja...ackground.html

Originally Posted by Moon

The headline 30 hours got my attention straight away too - but this galaxy is special and deserves it. Very well done indeed and thanks for presenting it to us!
James

Thanks James.


Regards

Steven

[CraigS]

Awesome image Steven.

I'm left wondering how many other similar galaxies might be out there that we don't know about because they're so faint ?

With this procedure, and a bit of luck, we might be seeing lots more unusual objects in the future (??)

Very innovative .. congratulations ...

Cheers

[sjastro]

Originally Posted by CraigS

Awesome image Steven.

I'm left wondering how many other similar galaxies might be out there that we don't know about because they're so faint ?

With this procedure, and a bit of luck, we might be seeing lots more unusual objects in the future (??)

Very innovative .. congratulations ...

Cheers

Thanks Craig.

I might try it out on even more challenging targets. The Phoenix Dwarf and SN 1006 come to mind.

Regards

Steven

[glenc (Glen)]

I am very impressed Steven!