Sunday, February 26, 2012

Under Dark Skies...

We're enjoying some warmer than normal temperatures, and the skies have remained clear the last few days.  With a skinny waxing crescent moon, we've been enjoying some nice dark skies.  Thursday was my normal night to work with the Nightly Observing Program (NOP) at Kitt Peak National Observatory.  Usually, we are so busy I don't have time to think about bringing a camera along to shoot anything, but with the moon and planetary alignment in the western sky I took the chance I'd have a minute or two.  Fortunately, Lucas, one of my compatriots took the sunset tour duties, and I was able to follow along with the tourists. 

It was a beautiful sunset - the above mosaic was assembled from 6 images.  There were just enough thin clouds to add some nice color.  Normally after the sunset, we walk up a little rise to show the folks the shadow of the earth rising into the sky.  Called the "Belt of Venus", it shows up as a bluish edge rising in the east.  I was going to catch Lucas (in yellow jacket) with the shadow in the background, but then I noticed the anticrepuscular rays over the group.  Caused by the cast shadows of mountains or clouds over the western horizon, perspective makes these "rays" appear to converge again in the anti-solar point.  They were pretty subtle visually, but they show up ok on photos, and another in the group imaged it as well once pointed out.

When returning to the western sky again to spot the planets aligned there in the fading glow, a shadow cast by a cloud over our horizon persisted in the sky like a dark searchlight.  I've never seen such a singular long shadow cast like that - particularly by something over the horizon by a sun that had set 15 minutes before!  The dome shown here is of the "SARA" telescope - the Southeast Association for Research in Astronomy, a consortium of  10 universities.  This is the location where we normally observe the sunset for the NOP.

Well the program started, and my group went into the adjacent 16 inch telescope for the observing program.  In quick succession we checked out Venus, the moon and right next to it, Uranus.  We took a break to go out and see Mercury with the naked eye, floating above the town of Sells to the west and below the crescent moon.  It was a beautiful sight, and the first-time view of Mercury for most.  I spent a couple minutes in an attempt to image all 4 planets in a line, but it was difficult.   Uranus is  binocular object, just under naked-eye visibility, but if you expose too long, you lose Mercury in the twilight glow.  The only way to get Uranus was with a telephoto lens, my 70-200 zoom set to 90mm with a 5 second exposure.  The wide view here shows the planets Mercury, brilliant Venus and Jupiter with the lil' lunar crescent, but no amount of stretching would show both Mercury and Uranus...  The closeup with the telephoto shows the slight greenish tint of Uranus readily...

It was a great program - the moon was too skinny to affect the sky and the folks had a great program.  Besides the above telescope views, we covered the basics of planispheres and navigation around the sky, some binocular viewing of the great objects up right now, then back to the telescope for Jupiter, Andromeda Galaxy, Orion Nebula, Hubble's Variable Nebula (one of my favorites), M82 (another galaxy), M47 (a star cluster with superimposed planetary nebula), and we closed out the night with a very nice view of the planet Mars.  So between naked eye views of Mercury and Saturn (just above the horizon as they left, they spotted all the current planets except Neptune which is behind the sun!

The next day I had experienced astronomical visitors from out of town, two that worked at major observatories and were used to visual observing with 60" to 80" telescopes.  I had asked for, and received permission to use the 20" telescope at the Visitor Center after the NOP ended, so we were up and rarin' to go at 9:45 as the program was winding down.  I was hoping to keep them occupied for a couple hours, but it turned into an extraordinary night.  The seeing was absolutely superb, and we routinely used 500X on many objects, including Mars, the Eskimo and Orion nebulas and Saturn as the evening finally wound down about 1:45!  Even the jaded observers agreed it was a memorable night.  As we got more dark adapted, we ended up turning down all the lights, even the plugstrips and computer power indicators so as to not affect our observing.  The view of NGC 2392 (Eskimo Nebula) was amazing - the high power view of it comparing favorably with the classic images of it taken with the 200" decades ago. 

I'd been wanting to set up a fisheye lens inside the dome during an observing session, but unfortunately with a full-house program, there just isn't room, a tripod would be a trip hazard.  But our little group of 7 was just perfect.  I set the camera for 50 second exposures at F/2.8, which has come to be my standard with wide angle shots that has pretty good depth for time-lapse shots.  Shown here is one of the still frames - The bright star Sirius and its Canis Major constellation can be seen out the dome slit.  Of course, I turned the exposures into a time-lapse video, after stretching all the frames a bit, and uploaded it to Youtube.  You can see that shortly after we got into the rythym of observing, we turned down the lights and only our red flashlights provided the ambient light.  Meanwhile, the stars slowly track across the sky, as does the telescope as we move between positions.  The brighter temporary flashes is the necessary light from the computer monitor as we change objects.  The video ends when I move the camera out to the catwalk for some frames of some of the Kitt Peak scopes and the Winter Milky Way setting overhead as I shut down the telescope.  For just about the first time I've ever recalled, I used absolutely every frame I took in the time lapse - no test shots, mistakes, or duds!

We ended up much later than I expected, but all were happy for the experience and chance for the memorable observing.  As always, the facilities and images are courtesy of the NOP/NOAO/AURA/NSF.

1 comment:

David A. Harvey said...

Very cool! All those planets!