Some highlights from a rich observing session January 7, 2008Posted by dorigo in astronomy, personal, science, travel.
On the night of January 1st I spent four hours in one of the most deserted places of the eastern italian Alps, at minus 13 degrees Celsius, with nothing to drink but hot coffee (good, but something stronger would have gone a longer way, if you know what I mean). Here is a google earth view of the place:
The place, Casera Razzo, is located at lat. 46°28’45.39″ N, long. 12°36’35.36″E, and 1750 meters (about 6000 ft) above sea level, close to a pass called Sella di Ciampigotto. What is special about the place is that it is far from anything else – about as far as you can go from light pollution, if you are bound in the italian Dolomites. During clear moonless nights, the sky reaches close to Bortle 2 class, and visual magnitudes exceed +6.5. Not as good as Arizona or Mauna Kea, but just about as good as it gets in western Europe.
Being a die-hard visual amateur astronomer, I cherish the few chances I get of running away from everything else, driving 100 miles to reach Casera Razzo to chase faint fuzzies: galaxies (the fainter they are, and the farther from us, the more fascinating hunting them down), comets, planetary nebulae, other supernova remnants, dark nebulae. Last week I was not even alone in the darkness: I was in the company of Federico, another crazy astronomer, and we spent the time commenting our views and coordinating the hunt of the hardest objects.
The instruments at our disposal were my faithful Zen 16″ f/5 dobsonian telescope, his 10″ newtonian, and a dozen eyepieces, plus a few filters we made extensive use of: most notably, an O-III and a H-beta. The former allowed breathtaking views of the Veil nebula and the Rosetta nebula, while the latter caught the horsehead for us.
It was quite amusing to drive the last 10 miles in total solitude -no cars anywhere in sight- and enter the parking lot where we usually set our instruments merely seconds before my buddy arrived from the opposite direction. Quite a coincidence, since our meeting was scheduled at a very loose time, “between 6 and 7 PM”.
In fifteen minutes we set our instruments and I aligned the optics of mine. I had been careful enough to let the mirrors cool down in the cold evening air before leaving home, and even drove with no heating on to avoid spoiling the thermal equilibrium of the delicate surfaces: a difference of a few degrees between mirror surfaces and surrounding air is enough to create enough movement in the cooling mirror’s surface to worsen angular resolution from half arcsecond to two-three arcseconds or more. Stars from points of light become small disks of light, and one has to limit the magnification to below 100x-150x, preventing the observation of those fascinating details that only 400x-500x magnifications can reveal.
Before starting the observations, we spent some time looking at the sky with the best piece of our equipment: our bare eyes. The eye is a wonderful device, capable of a incredibly wide dynamical range. After dark-adaptation, we were able to see not just one, but two comets in the sky – and only 30 degrees apart! I estimated the limiting magnitude at about +6.4. We wasted no more time, and started our tour. Here is a short summary of some of the objects we saw.
NGC891 (see picture, right): a wonderful spiral galaxy, which is seen from a side and exhibits a perfect dark lane in the middle. A delicacy!
M42: a showpiece from every sky and every instrument, but on a dark site and with a large instrument it becomes unreal. At 400x magnification you fool yourself into believing you are walking in the middle of an explosion of gas and newborn stars, as you slowly move the telescope to examine different patches of this very extended nebula. The amount of detail, the delicate wisps of excited gas, the dark spots, make this arguably the most fascinating object to aim a telescope at, if you sit at northern latitudes.
M33 (see picture, right): this galaxy is often overlooked by amateurs, because it is considered faint and too large. However, if the sky is dark enough the amount of details you can see is astounding. The main spiral arms, the extended nebulosity around them, and at least ten different nodules on the arms and beyond them. Jaw-dropping!
Arp 28 (NGC7678, see picture on the right) in PEG, a nice face-on spiral of 12th magnitude, neatly framed by a trio of 11th magnitude stars. It possesses a heavy arm which we were not able to distinguish – we barely distinguished clockwise rotation in the shape.
Arp 1 (NGC2857) in UMA, another faint face-on spiral, of low surface brightness. It was seen in the same field of Arp 285 (NGC2854, NGC2856), another odd pair of 14th magnitude spirals.
Arp 6 (NGC2537, aka the Bearpaw): a very strange-looking spiral galaxy, which showed its irregularities at 400x magnification.
Arp 283 (NGC2798, NGC2799): a spectacular pair of faint interacting galaxies.
Arp 27 (NGC3631): another spiral with an odd arm, which we however could not discern.
Arp 299 (NGC3690, see picture on the right): a pair of very close galaxies, with additional very faint noduli of material away from them – I detected the brigthest (so to speak), which is of 16th magnitude – top right on the picture.
A truly wonderful observing session. I must say, also a very enduring one: screwing and unscrewing filters required removing gloves and caused extended pain (I twice dropped them on the ground, luckily covered with soft snow). After four hours at 260 kelvin, we could stand it no more, and we called it a night. I can’t wait for the next one!