Grus Quartet…errr…doublet?

[Dennis]

Hi

Well, now that the Tak reducer/flattener had arrived, and the Adapter to fit the ST7E CCD camera, there was no excuse for not going outside (Sat 29 Sept 2007) to put them through their paces. Except for a full moon and very heavy dew that is. Anyhow, here are 2 galaxies NGC7599 (11m5) & NGC7590 (11m3) from the Grus Quartet.

Tak Mewlon 180 (1800 F12 DK) on Tak EM200 mount.
Tak x0.8 RC (F9.6), SBIG ST7E (parallel) CCD camera.
First light for home built LED flat field box.

5 mins exposures self guided with ST7E. Total 45 mins.
9 sub frames dark subtracted, flat fielded and combined in MIRA AP6.
Finishing in Photoshop CS3.

The almost full moon, too few frames, not quite enough exposure and suburban light pollution has made the results a little washed out and grainy, but things bode well for the future. Now if only I had an ST8.

Cheers

Dennis

PS – here is a link to Paul’s recent post (http://www.iceinspace.com.au/forum/showthread.php?t=23820)and wide field shot (http://www.iceinspace.com.au/forum/attachment.php?attachmentid=31770&d=1189319051)for an interesting comparison.

[middy]

Nice shot Dennis :thumbsup:

You've been very quiet lately. I was beginning to think you had sold off all your gear and moved on to a different hobby!!

[jase]

Nice work Dennis. As you acknowledge a few things were against you. Things out of your control aside, imaging at F/9.6 will require considerably long sub exposures to bring out the faint spiral structures of the galaxies - even with the high QE of the ST7. If you're operating an ABG then I'd go for 10min subs as a minimum. An NABG would probably be around 5-7min exposures at this focal length (1728mm) before blooming will occur. A 1.07 arcsec/pixel is cutting it fine assuming the conditions are prime. The data looks like it could be stretched a little more. I note the file name indicates you used a sigma clip for the combine function. You may wish to alter the Sigma Factor to ensure you don't discard too many outlier pixels. It actually looks like the value is too high as the background is really smooth, almost mono tone when further brightened using curves. A colour rendition on the cards perhaps? Look forward to seeing more.

[Dennis]

Hi Andrew

Good to hear from you and thanks!

I’ve been having a break from late nights at the ‘scope as my wife has been on long service leave and our time and energies have dwelled recently more on terrestrial events. Other than that, haven’t really had too much to write about or say, so I’ve remained quiet rather than take up bandwidth with babble.:lol::lol:

Cheers

Dennis

[Dennis]

Thanks Jase for the analysis and commentary, which are spot on based upon what I was observing with the ST7 last night. I think I was collecting around 45,000 in the wells at 5 min subs.

This is a definite project for a dark site and as you suggest, with added colour from the CFW8A. I’m rapidly and inexorably approaching the event horizon of multi-session single images, as opposed to my previous approach of going for 10 in one night!

Cheers

Dennis

[Dennis]

Another night, an extra galaxy, a different ‘scope and worse transparency! There was a heavy smell of burn off which was probably the cause of the milky appearance of the skies, especially when illuminated by the gibbous moon.

For this image of 3 of the quartet, I used the Vixen 102mm f9 ‘scope (918mm fl) with the ST7E parallel SBIG CCD Camera.

Exposures were 12 x 10 mins. Darks, Flats and Combine performed in MIRA AP. Curves and sharpen performed in CS3. Not there yet, but a useful session in terms of experience.

Cheers

Dennis

[jase]

The 2.02 arcsec/pixel combination yields a much pleasing result. Certainly would have help if the seeing was as you explained. A fine effort.