Ngc 5128

[kinetic]

A set from last night.
Not my best result on this subject.
Focus a little soft, seeing was slightly better than average.
The most frames in a set ever of this galaxy by me, over an hour
of exposure.
Edit: a set of M83, no higher than 30-45 degrees up.

Steve

[kinetic]

2 repros:

1: best 480 frames of 719, resampled 1.6x then stacked.
Deconvolved then sharpened.

2. oversharpened to show detail in the arms.

[kinetic]

Wow, tough crowd ;):D.
I'd like to try and work out the arc sec size of features resolved in this
set.
This wasn't even great seeing, just slightly better than ok.
Just lots of frames means it survives aggressive sharpening that is normally
only limited by how good the seeing was.

Steve

[Shiraz]

some good detail there Steve - the start of a project?

Seeing was pretty ordinary over here at about 3 arcsec - only useful for colour. We need some more of the seeing that was around when you posted the lagoon in hi res. Regards Ray

[alpal]

I didn't know you could do a faint galaxy with such short exposures.
I would have expected the stars to be tiny.

[blink138]

heh steve the "tough crowd" have no info!
what telescope, focal length, camera, exposure and iso was used?
best of 480? was it a webcam?
pat

[Ross G]

Nice captures Steve.

What equipment did you use?

Ross.

[kinetic]

Thanks guys'
Scope is a slightly modified stock GSO 12 f5, camera a home cooled DSI II mono.
Exposures 719x 5sec, repro 480 of the sharpest frames.
Tracking thanks to homemade GEM and worm gear.

Steve

[ZeroID]

Ok, so now I'm impressed, it's an all DIY image. Nice images, well done indeed.

[SkyViking]

Nice resolution in the Cen A, and great experiment. Interestingly it does look almost identical to what I got with my 10" f/5 and QSI @ 0.87"/pixel. I think your image scale is pretty much the same?
I immediately recognised the features because I'm just now working on a repro of my own Cen A data and wanted to see how much resolution I could squeeze out. Seems I've got a bit more resolution than what ended up in the original process of the 120 hour image, so stay tuned :)

So, then perhaps there is no advantage in using 5 sec exposures since I used 5 mins. Maybe 5 secs is still too long so that you don't get the hi-res effect that can be achieved with really short exposures?. They probably have to be sub 1 sec I think, more like planetary imaging.

[kinetic]

Rolf,

with the DSI II, I have 8.3u x 8.6u pixels.
With the F.L. 1524mm (f5), I calculate that to be an 11.3 x 14.1 arc min field.

Nyquist formula tells me that is 1.16 arc sec/ pixel H and 1.12 arc sec/ pixel V.
For all intents I average that to about 1.14 arc sec / pixel.
Plate solves online in real time confirm a similar field and resolution.
That's why upsampling works so well. The seeing might be something like
2.00 to 2.50 on any given night so I can safely upsample my raw data
by a factor of anything from 1.5x to even 2.00x (or 4.0x on rare , exceptional nights (http://www.iceinspace.com.au/forum/showthread.php?t=107369)) and see a benefit after processing the data.

In the homemade worm thread I calculated the periodic error of the
entire circumference of the worm.
It has cyclic error wrapped all the way around the worm, but the worst
is about +/- 6 arc sec of PE. See here (http://www.iceinspace.com.au/forum/showpost.php?p=710292&postcount=134) and here (http://www.iceinspace.com.au/forum/showpost.php?p=684402&postcount=133).

As for exposures, I could go longer, 10 sec sets certainly make it go deeper. 15sec and 30 sec sets really make it pop out.
But there is always a trade off.
In an hour I can have 350 frames of 5 sec each.
On a good night I can nearly stack all of them.
On a bad night maybe I can stack only 150-200 that truly have
round stars and no major effetcs of seeing bloating the stars within that
5 sec exposure.
That's the trade off of going so narrow field. Wide field is a bit more forgiving.

You are correct, it is exactly planetary imaging principles at work.

[SkyViking]

Ah yes, without guiding you'd be limited to short exposures for sure, I missed that. I used to do all my imaging with sub 30 sec exposures when I used the ToUCam, which was very similar to your setup.
Some of the really bright deep sky objects can show great resolution with ultra short exposures. The Homunculus for example, which is extremely bright. I think I used something like 1/25th sec exposures for that one if I remember correctly. Planetary imaging indeed :)

[strongmanmike]

Hmmm?...well, we've seen quite a few close up short exposure B&W Cen A's from you Steve :whistle: :scared:...you da close up Cen A groupy :P It is a great galaxy to image...just ask Rolf...I used to be the chief Cen A -a- phile but Rolf took the title from me in a cheeky looooong exposure passing manoeuvre :sadeyes: :lol:

Mike