NGC 5128 a quick comparison.

[kinetic (Steve)]

Hi,

This is a comparison animation showing my mono result from
May 26 2009 compared to a RCOS 12.5" image with SBIG AO-7.
I found the RCOS image on a similar comparison animation on
the ATS scope supplies page here...about halfway down:
http://www.atscope.com.au/rcos.html

Now firstly, this is in no way a definitive or laboratory comparison!.
Just a bit of fun.

Firstly, the RCOS image has been changed to a grayscale to match
my DSI II shot.
I have not altered anything on the RCOS shot apart from grayscale
and crop to match the animation.

My shot has been taken from the original here.
Mine has been resized down, and rotated 7 degrees to match the RCOS
shot.
So, if anything, mine has had some considerable loss of quality added.

I have done a histogram tweak on my image to suit the general size
of the RCOS halo.

Finally also, my shot is made of 365 frames x 5 sec with a Chinese
GSO-12" F5 and a mono DSI II chip (ICX 429).
I'm not sure what exposure was needed for the RCOS/ SBIG shot.

Comments/criticism welcome.

RCOS image courtesy of the ATS scope supplies page mentioned above.

Steve

[gbeal]

Nice comp mate, and I am sure this will start a discussion.
Gary

[strongmanmike (Michael)]

I like your sentiments Steve but the image size displayed is way too small to compare properly. Can you do a comparison with larger size images..? I also suggest you reprocess your shot and back off on the sharpening as the dark halos around your stars are pretty prominent and distracting in your image, anyone can apply strong sharpening to their image but to do it without being noticable is another skill all together.

Still fun to do though, like it

Mike

[Alchemy (Clive)]

the rcos has won the day, good detail in yours but that extra polish does come at a big price tag, so dont be disapointed.
i see you are using a GSO 12 inch newt, i just took my 12 inch off and went for a refractor, what are you running it on? Pic ?

[kinetic (Steve)]

Originally Posted by strongmanmike

..I also suggest you reprocess your shot and back off on the sharpening as the dark halos around your stars are pretty prominent and distracting in your image, anyone can apply strong sharpening to their image but to do it without being noticable is another skill all together.

Still fun to do though, like it

Mike,

Here's a repro that is probably the better one of half a dozen.
It's all 365 frames resized using Bspline algorithm and stacked as
per the original set. Seems to work even though being 150% bigger.
Halos not as noticeable either.

Originally Posted by Alchemy

i see you are using a GSO 12 inch newt, i just took my 12 inch off and went for a refractor, what are you running it on? Pic ?

Clive,
I use my 27 year old, 'work in progress', homemade GEM.
BTW Clive I haven't tried your processing tip yet! Must do that!

Steve

[Bassnut (Fred)]

Put the same SBIG cam on your scope, THAT would be interesting.

BTW, your pic is very good (well, apart from the over-sharpening, which works on the dust lanes, but not on the stars, selective layer processing would fix that). Im amazed at the detail given it was with a DSI, top work.

[Peter Ward]

Originally Posted by kinetic

Hi,

This is a comparison animation showing my mono result from
May 26 2009 compared to a RCOS 12.5" image with SBIG AO-7.

Steve....Sorry mate you have got a few things wrong here. I took both images, but both are now rather dated and used sub exposures that were not optimal for resolution.

The RCOS data did not have the advantage of AO.

It was the C-11 that an AO7 and this is clearly stated on the page.

I have not re-visited NGC5128 since taking this more recent image:

http://www.atscope.com.au/BRO/gallery5.html

[avandonk]

It is a waste of time comparing narrow field stacked images as used for planetary imaging to any optic that gives a high resolution flat wide field. Any decent optic is almost perfect (diffraction limited) at the optic axis. The real test is how wide a field can the optic produce with the same quality at the extremes of the field compared to the optic axis ie center.

A good example is the planetary blokes who image at f/40 and higher. The theoretical Airy disc at f/40 is about 60 micron. The reason they get high resolution is that they are only recording the tip of the central maximum of the Airy disk obove the noise as the contrast is very low and the dynamic range is also low. Their resolution is even better than the Dawes limit. The intensity of the Airy disk is not constant see image below.

At best an interesting observation.

Bert

[strongmanmike (Michael)]

Mike,

Here's a repro that is probably the better one of half a dozen.
It's all 365 frames resized using Bspline algorithm and stacked as
per the original set. Seems to work even though being 150% bigger.
Halos not as noticeable either.

Still looks a bit harsh and hard edged ie it's still obvious you have gone hard on the sharpening (not that that's a big thing). There's no doubt there is plenty of fine detail in there mate so top work .

Mike

[kinetic (Steve)]

Originally Posted by avandonk

It is a waste of time comparing narrow field stacked images as used for planetary imaging to any optic that gives a high resolution flat wide field....


At best an interesting observation.

Bert

In hindsight, it wasn't a very well thought out exercise Bert.
And thanks Peter for being such a gentleman about the use
of your image.

regards,
Steve

[Satchmo]

Originally Posted by Peter Ward

I took both images, but both are now rather dated and used sub exposures that were not optimal for resolution.

Peter , Could you clarify which two images you are talking about?

[Hagar (Doug)]

Nice comparison Steve. The DSI is proving to be no sloutch when paired up with your big scope.

Well done Mate.