Omega Centauri DSI III Deep & Colourful

[gerry aarts]

Hi All,

The weather turned good last night but too late to set up at our WSAAG club observing site at Linden in the Blue Mountains.
So I set up at home at Cranebrook and stayed up until 4 am this morning.
The Omega Centauri Cluster did not rise above the tops of the surrounding trees until 2.00 am.

This was my second opportunity to use the Celestron GPS11 with f1.8 Hyperstar and the new DSI III camera.
The DSI III Envisage software previously kept crashing but after re-installing and using a powered USB hub, all worked well
It does consume a lot of memory and slows down the laptop, but at least it worked.

This is a combination of 40 x 15 seconds exposures. (8 minutes at f1.8 is the equivalent of around 120 minutes at f10)
I was set up` in altazimuth mode so was limited to 15 – 30 seconds exposures. Not a perfect picture but a pleasing one.
I notice most images of the Alpha Centauri cluster do not show nice colour, and the DSI III seems to do so very well.

Hope you like it.
Gerry Aarts
WSAAG http://wsaag.org

[peter_4059]

Gerry,

That's a nice image. I was already impressed with my DSI II pro but now thinking I need a DSI III.

Peter

[dcalleja]

Gerry
Nice Omega - Every time you post a new image with your III I keep feeling the urge to upgrade. What sort of laptop are you using? How much RAM - I'm curious about your comments re slowness.

[Ric]

A good capture Gerry, you have brought out some great detail in the core.

Cheers

[Peter Ward]

Sorry, but this is simply not correct.

With point sources an 11 inch F10 scope is identical to a F1.8

Only aperture counts with point sources (eg stars).

You might also want to have a look at Greg Bradley's recent effort....

http://upload.pbase.com/gregbradley/image/92706659/original

[quote=gerry aarts;295898] (8 minutes at f1.8 is the equivalent of around 120 minutes at f10)
/quote]

[gerry aarts]

Hi Peter,

The image you steered me to is certainly vastly superior to my feeble efffort.

What do you mean by point sources?

Please find attached the Starizona site refering to the Hyperstar specs. I am not am expert in these matters but assume a credible Astronomy dealer must use actual facts in their promotions.
http://starizona.com/acb/hyperstar/whatis.aspx

What do you think?

Regards
Gerry

[Satchmo]

I guess the issue then is do globular clusters behave photographically as collections of stellar ( point) sources or nebulae. Certainly the main disc is an amorpghous blob of unresolved stars with some resolved ones across the face and the outerliers would be individual stellar objects and not respond so well to faster f ratio as to more aperture.

I don't know the answer but I find it intriguing.

[Peter Ward]

Gerry,

For extended objects, a faster F-Ratio does mean more (extended) flux in a smaller area.

But an 11 inch scope should be easily able to resolve Omgea's core stars
into "points"...hence the aperture (only) rule should apply..

Mark may have a point with regard to any diffuse glow that may be unresolved being brighter in a faster system.... Omega is however pretty easy to resolve.

...don't feel bad....the only reason I pointed you to the other image was to show what a much smaller and slower system (F7.4) could do.

There is a fair bit of hype regarding "Fast" systems, the details of which which unfortunately many manufacturer's choose to gloss over....

[sjastro]

Peter,

Remember the flare up on the SBIG forum a few years ago regarding F-Ratio and CCDs for extended objects.
http://www.stanmooreastro.com/f_ratio_myth.htm

I don't agree with Stan's assertions but this report is hard to refute on the evidence presented.

Regards

Steven
http://users.westconnect.com.aa/~sjastro/small

PS

Don't tell Stan about it!

[Peter Ward]

Yes, I recall the debate well!

For extended sources I suspect the truth lies somewhere in between the two....in any event Stan's analysis certainly confirms aperture only rules with stars.

Steve Crouch's image of Omega using a F2.8 episilon showed some very faint nebulosity near the cluster that very few had seen before... I suspect the fast F-ratio was a factor.

[gerry aarts]

Hi all,
Thanks for the infromation.

You know the saying less is best.
Here is a classic example.Reprocessed Omega Centauri, applied very little levels, curves and sharpening.

I believe I fell in the trap of over processing the first time.

What do you think???

Gerry

[EzyStyles]

hi gerry, this image is much better than the first. i would love to give the DSI III a go!