Friday, January 13, 2012

A "Working" Night on the Mountain

I've mentioned my work at Kitt Peak National Observatory...  The majority of my effort is with the Nightly Observing Program(NOP) where visitors enjoy a 4-5 hour early evening program that includes sunset viewing and Observatory orientation, then classroom and sky instructions of planispheres and binoculars before a session with a star guide at a 16" or 20" telescope.  It has been a lot of fun showing visitors the spectacular night sky objects, and entertaining for me as well to see how the sky changes from week to week for nearly a year now.

But besides the NOP, there is also an Advanced Observing Program - a more advanced observing session.  Here the visitors book a dorm room for the night, eat their meals in the dining hall, and have a one-on-one observing experience at one of the Visitor Center telescopes.  The program starts a few hours after sunset when the NOP finishes for the evening, and goes till twilight starts again in the morning.  There are several observing options for the AOP program, including advanced imaging with CCD cameras - still a bit beyond my skill set, but a lot of visitors want a visual program, where we also take short exposures with a digital SLR for images to bring home.  This I can do, and I just had one after Christmas a few weeks ago.

My guests for the night were on a cross-country road trip, the AOP program being one of their anticipated high points of their trip.  Booked several months in advance, Both of us looked forward to the evening under the stars.  The weather turned out great - a few wispy clouds early, the crescent moon setting before the end of the NOP, so no issues with any stray light.  While the NOP kept the telescopes busy, I took a few images of the twilight, including a sequence of pictures in the roll-off-roof where we would eventually be observing.  In the first picture above at left, the crescent moon and Venus hang over the WIYN Telescope at right and the WIYN 36" telescope at left.  The right image shows a fisheye view of the western sky from the Roll-Off-Roof 16" telescope.  Besides a view of the telescopes dotting the south side of the Observatory, the Moon and Venus are visible just over the roof, as well as the cone of the Zodiacal Light and part of the Summer Milky Way.  The telescope was in use for the NOP at the time of the 50 second exposure.

Finally the NOP finished and those visitors wound their way back down the mountain road and it was our turn for use of the telescopes.  First up we took a look at a few objects in the western part of the sky before earth's rotation made them inaccessible.  One of the early objects is a spectacular galaxy in Andromeda - NGC 891.  Visually it is rather dim and appears as an elongated streak in the sky.  With averted vision you can also detect a narrow dark lane down it's center.  With a moderate exposure (here 3 exposures of 3 minutes each were stacked) you can see that the galaxy is exactly edge on and the dust lane bisects the disk.  At a distance of about 27 million light years, it is dimmed somewhat by the dust in our own galaxy as it's location is near the Milky Way, accounting for the rich foreground of stars along the line of sight.  While visible in amateur sized telescopes, it's really spectacular nature becomes evident in images of it.

Another very spectacular object is visible in the early evening sky - the Pleiades star cluster, also known as Messier 45.  Visible to the naked eye as a cloudy spot to the casual observer, closer inspection shows 6 or 7 stars.  Also known as the Seven Sisters, it is well-known in many cultures.  In our binocular sessions in the NOP, many think the bright stars form a small dipper and ask if that is what it is called, but the Little Dipper is an asterism that is part of Ursa Minor.  Sometimes visible in a very dark sky through a telescope, an exposure reveals an intricate network of nebulosity.  Once thought to be leftovers of the gas clouds that formed the cluster, it is now known that the cluster is merely moving through a dusty part of our galaxy.  Only about 400 light years away, it is one of the nearest star clusters to us.

When we took a night lunch break, we set the telescope and camera on the Crab Nebula, Messier 1, and let the camera run while we were away.  It was a good way to make use of telescope time while taking a break from the cold.  The Crab is a supernova remnant with an unusual past - it was actually observed when it went off in the year 1054.  Chinese observers noted that it was visible in the daylight sky (!) for 4 months, and didn't fade from visibility for 2 years!  The  object is the first object in the Messier catalogue - a list produced by the comet-hunting astronomer of diffuse objects that were not comets.  The stacked exposures total about 50 minutes, and reveal the red wisps of nebulosity due to hydrogen gas emission.  The diffuse white glow is due to synchrotron radiation interacting with the gas of the nebula.

We also used the camera and fisheye lens to take a self portrait during the night.  While taking images of galaxies in the coma cluster, we took a shot with the winter Milky Way and Orion as backdrop.  I moved a little, so you can see stars through my head during the 60 second exposure. 

After viewing and imaging dozens of objects, we entered the springtime realm of the galaxies.  We imaged a few of the more striking of them.  As the night wore on some of the spectacular summer globular clusters rose as well. 

My visitor was interested in comets.  Unfortunately, there weren't a lot visible.  We tried to see Comet Gehrels2 earlier in the evening - we didn't see it, but were able to image it with it's little tail.  Just before twilight started we easily spotted Comet Garradd (C/2009 P1), even saw some of it's greenish glow, easily the brightest comet of the night, even visible in binoculars.  I've been watching it off and on the last few months, even rolling it out on the occasional NOP.  We took a few exposures to stack and I was surprised to see 2 tails!  Shown here, the dust tail broadly extends to the left, and the blue ion tail heads up in the 1 o'clock position.  It never got very close to the earth, and the heavier particles of the dust tail mostly trace out the path of the comet, while the lightweight particles of the ion tail are pushed straight back from the sun by solar wind.

One thing I hadn't pushed, but as we casually observed Venus, Jupiter and Uranus in the early evening, then Mars and Saturn as the night progressed, the chance existed to observe all 8 of the major planets.  Unfortunately, we had bypassed Neptune in the early evening, but as twilight broke, Mercury rose not far from the bright star Antares in Scorpius.  But seeing 7 of the planets was doing pretty well, and set a record for my guest that night.

So with the twilight, the observing drew to a close, and though we were tired, we were both exhilarated by the great night of observing.  After providing a copy of the raw data to my guest, we both headed down the hill - him to a road trip back east, me to my pillow and the rest of my Christmas holiday.  I've got another AOP scheduled in a few weeks - already looking forward to it!

Telescopic images courtesy Charles Parker/Dean Ketelsen/NOAO/AURA/NSF

2 comments:

Ross Dubois said...

awesome right up of an AOP. Great to see guides so enthused about their work! Keep it up Dean.

David A. Harvey said...

Great post Dean - and wonderful astro images!