NGC246 and NGC 255
Planetary Nebula and Barred Spiral Galaxy in Cetus

Click here for higher-resolution versions: 1564x1041 (40%)  2541x1691 (65%)   3909x2601 (Full Resolution)


NGC246, the bright blue/purple object on the right side of the image, is a moderate-sized (3.8 arcminutes in diameter), bright (magnitude 8 according to most sources) planetary nebula, the type of nebula which it is generally thought our Sun will produce as nuclear fusion slows and then dies in its core, and it expels its outer layers of gas. NGC246 is estimated to be about 1600 light years from us, which would make it about 2.5 light years across.

NGC255 (the little spiral galaxy on the left side of the image) is estimated to be about 70 million light years away from us, and 63,000 light years in diameter (compared to our Milky Way's 100,000 light year diameter). It's too far away to get much detail, but I thought it complemented the little planetary nebula nicely, and gives a powerful illustration of perspective--The galaxy is something like 25,000 times as large (in terms of diameter) as the little nebula, but is so far away that it looks to be a bit smaller.

I always love how almost any view of the heavens will show so many background galaxies, and this is no exception. If you examine the highest-resolution version, you can see many tiny galaxies mixed in among the stars (they're the ones that are either quite oblong or faint and blurry, so generally a galaxy). Of course, these are huge things, tens of thousands of light years across, with billions upon billions of stars in each one, but they're so far away they barely show at all.


Technical Information:

LRGB: 400:120:140:400 (Luminance layer consists of twenty 20-minute images through the blue filter, unbinned; R, G and B consist of 20-minute images, all unbinned).

Equipment: RC Optical Systems 14.5 inch Ritchey–Chrétien carbon fiber truss telescope, with ion-milled optics, at about f/9, and an SBIG STL-11000M with internal filter wheel ( Astrodon type II filter set), guided by a MOAG/AO-L combination, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP, working in concert with TheSky v6.

Processing: All images calibrated (darks and dawn flats), aligned, and combined in Pixinsight. Color combine in Pixinsight. Finish work (curves and levels, adjustment of contrast, High Pass Filter and Smart Sharpen of the luminance layer, and Neat Image noise reduction) was done in Photoshop CS5.

Location: Data acquired remotely from Fair Dinkum Skies, Moorook, South Australia.

Date: Images taken on many nights in December 2015 and January 2016. Image posted January 27, 2016.

CCD Chip temperature: -5C

Copyright 2015-2016 Mark de Regt

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