Salvatore Iovene / Mostly astrophotography and code

NGC6946, aka the Fireworks Galaxy, owes its fancy name to being the galaxy in which the largest number of supernovae have been recorded. And that’s nine. Unfortunately my picture doesn’t show any, but the galaxy is framed with the nice and bright open cluster NGC6939.

The Fireworks Galaxy is quite near, at only ten million light-years, but lies behind clouds of dark nebulae in our Milky Way, since it’s pretty much on the galactic plane.

Curiously, I haven’t found a lot about NGC6939 online; I suppose it means that it’s a rather unremarkable open cluster.

This image is a crop because I had trouble with my flat frames (I accidentally shifted the focus knob) and therefore you can see defects and artifacts on the full frame. The night wasn’t particularly transparent, and 3.6 hours of exposure proved to be barely enough to show the galactic core.

And when there’s so little data to work with, stretching the histogram to the limit will show defects that are beyond the extreme care I can take in calibrating the frames, such as the non uniform sensitivity of the CMOS chip.

What you see above is an enhanced representation of what I had to routinely subtract from my DSRL astrophotography images through last season. It’s obviously not a defect in the optical train, nor a feature of the night sky. The only explanation I’ve been able to produce is that the image sort of maps areas of different sensitivity on the CMOS chip.

Naturally this kind of defect doesn’t affect daylight photography, but stretching the histogram to the limit while shooting extremely faint objects can show things like this on a camera that was not intended to be used for this purpose.

Great news! I got my first CCD camera: a Moravian Instruments G2-1600. It’s got a Kaf-1603ME sensor, so it’s a very sensitive NABG camera. I got narrow band filters too, so expect some images in the Hubble palette.

The image you see in this post was shot through a 12nm O-III filter.

It depicts what is usually put on the left in images of the North America nebula, NGC 7000.

Summer’s not over yet, but clear nights shall not be wasted. With the full moon and some degree of daylight in the atmosphere, just the core of this popular reflection nebula shows in the picture. It’s the stack of sixty 180-second sub-frames.

Was the summer long? Yes it was! But here I am again, taking advantage of the few dark (-ish) hours we have at night. The Astronomical Twilight hasn’t reached my latitude yet (it will on August 23rd), but at the zenith it looks like it’s dark enough for some imaging.

The image you see above is a crop to 100%, so please click through for the full sized version. It depicts NGC6871, a young and bright star cluster in Cygnus. The cluster should be bathing in a see of red hydrogen-alpha clouds, but my unmodded Canon 450D is pretty much blind to that. And what you see is the stack of mere 33 minutes! It’s the only time I had before the clouds rolled in, but the result is not too shallow.

Fifty-one times six minutes weren’t enough to capture a decent image of NGC2683, which might just be a target out of the scope of my equipment.

NGC 2683 is an unbarred spiral galaxy discovered by William Herschel on February 5, 1788. It was nicknamed the “UFO Galaxy” by the Astronaut Memorial Planetarium and Observatory. It is viewed nearly edge-on from Earth’s location in space and is located between 16 to 25 million light-years away. It is receding from Earth at 410 km/s (250 mi/s), and from the Galactic Center at 375 km/s (233 mi/s). The reddened light from the center of the galaxy appears yellowish due to the intervening gas and dust located within the outer arms of NGC 2683

(Wikipedia).

Back to the clusters with an evergreen: M45, aka the Beehive. This image is the sum of 25 six-minute exposures at ISO400.

The Beeive Cluster, also known as Praesepe (Latin for “manger”), M44, NG 2632, or Cr 189, is an open cluster in the constellation Cancer. It is one of the nearest open clusters to the Solar System, and it contains a larger star population than most other nearby clusters. Under dark skies the Beehive Cluster looks like a nebulous object to the naked eye; thus it has been known since ancient times. The classical astronomer Ptolemy called it “the nebulous mass in the breast of Cancer,” and it was among the first objects that Galileo studied with his telescope The cluster’s age and proper motion coincide with those of the Hyades open cluster, suggesting that both share a similar origin. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F, G, K, and M. Currently there is no consensus on the cluster’s distance, with recent sources suggesting 160 to 187 parsecs (520-610 light years). There is better agreement on its age, at about 600 million years. This is equivalent to the age of the Hyades (~625 million years). The bright central core of the cluster has a diameter of about 7 parsecs (22.8 light years)

(Wikipedia).

M101 is a beautiful face-on spiral galaxy. Unfortunately I could only take 11 ten-minute frames of this jewel, and I will certainly do more when I will be able too again. Summer is closing in, and nights are getting shorter and shorter.

The Pinwheel Galaxy, as it’s known, is 25 million light-years away and with a diameter of 170,000 light-years it is nearly twice the size of the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small bulge of about 3 billion solar masses. Another remarkable property of this galaxy is its huge and extremely bright H II regions, of which a total of about 3,000 can be seen on photographs. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars. On photographs M101 can be seen to be asymmetrical on one side. It is thought that in the recent past (speaking in galactic terms) M101 underwent a near collision with another galaxy and the associated gravitational tidal forces caused the asymmetry. In addition, this encounter also amplified the density waves in the spiral arms of M101. The amplification of these waves leads to the compression of the interstellar hydrogen gas, which then triggers strong star formation activity (Wikipedia).

Messier 109 is, to my equipment, an inconspicuous little galaxy in Ursa Major. I don’t have a lot of choice of subjects, this time of the year, and this galaxy, measuring only 7.6 x 4.7 minutes of arc in apparent size, proved to be a tough match.

M109 is the brightest galaxy in the M109 Group, a large group of galaxies located in the constellation Ursa Major that may contain over 50 galaxies. (Wikipedia).

This image is the sum of 35 seven-minute frames at ISO400.

Above is my take at the galaxy M108 and the planetary nebula M97. Unfortunately you cannot see any of the red outer layers of the nebula, because of the poor sensibility to the shorter wavelengths of my camera.

M97, also known as the Owl Nebula, is one of the faintest objects in the Messier catalog, and one of the four planetary nebulae there. A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life. M97 is thought to have formed 6000 years ago. (Wikipedia).

M108, instead, is an isolated member of the Ursa Major Cluster cluster of galaxies in the Virgo supercluster. It has a morphological classification of type SBbc in the de Vaucouleurs system, which means it is a barred spiral galaxy with somewhat loosely wound arms. This galaxy has an estimated mass of 125 billion times the mass of the Sun and includes about 290 ± 80 globular clusters (Wikipedia).