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Old 15-09-2018, 12:24 PM
Placidus (Mike and Trish)
Narrowing the band

Placidus is offline
 
Join Date: Mar 2011
Location: Euchareena, NSW
Posts: 3,719
NGC 346, 371, 395: The Duck, the Rose, the Goldfish, and her Lover

NGC 346, the brightest piece of nebulosity in the Small Magellanic Cloud (but still faint at magnitude 10.3, surface brightness 14.3) is at bottom right. It is clearly the head of a duck (Daffy, most likely), facing to our right, and wearing a Centurion's helmet, as ducks in the SMC often do.

Exactly central is the much fainter NGC 371 (mag 12.5, SB 16.6), in the shape of a lilac rose bloom.

Both Centurion Daffy and the Rose are relatively strong in OIII due to young clusters within.

Balancing them, toward 9 o'clock is a goggle-eyed goldfish (NGC 395), suitably golden in colour, body twisted into an S-shape, and tail hooked around a piece of Magellanic seaweed. It is relatively richer in H-alpha than in OIII. The tail itself shows an interesting blistered texture.

Cropped off the thumb, but present in the full image here, in a gentle romantic touch and nothing to do with the movie, you will see neither cook nor thief, but her lover: a pair of red-gold H-alpha lips about half-way toward 12 o'clock.

This area is very typical of the Magellanic Clouds in that there is often very strong separation between OIII rich objects and H-alpha rich objects.

There are also several faint super-bubbles, great big gaseous shells, typical of areas with much past supernova activity. A large but vague one, as if made from drifting sea-weed, encloses the rose and goldfish. A smaller but more distinct superbubble can be seen toward top left of the goldfish. A tiny, presumably younger one is directly below the rose. It would be interesting to see if it was relatively strong in SII, but it would require a very long exposure.

Due to the 36 min arc field of view being a bit tight on the goldfish tail and the duck's bill, this is again a 3 panel strongly overlapping mosaic, just to give them a bit of swimming space. The full image is 50 min arc across, north up. The thumb is more the width of a single frame.

Red: H-alpha 14 hours; Blue: OIII 12 hrs; mostly in 1 hr subs.

The green channel is a mixture of the two. Feel free to suppress the green channel if you prefer to do so.

We did this one some years ago, using 2x2 binning because of its faintness. This time we've stayed unbinned, but used much longer exposure (total of 24 hours). We think that's done the trick.

Aspen CG16M on 20" PlaneWave.
Attached Thumbnails
Click for full-size image (Duck Rose Goldfish and her lover - NGC 346 LMC Ha 14hrs OIII 12hrs Thumb.jpg)
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Last edited by Placidus; 15-09-2018 at 05:54 PM.
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