Sunday, May 13, 2012

A Night To Remember!

Last night was the Springtime Star-B-Que for the Tucson Amateur Astronomy Association (TAAA) at the Kitt Peak picnic area.  These are usually a lot of fun - meet in the late afternoon for some socializing over a potluck and grill, then some primetime observing with our own telescopes in some of the darkest skies available.  The picnic area is a great venue - about 6500 elevation, with a pavilion, picnic tables enjoying a multitude of viewpoints, and flush toilets!  The weather had been great all week, though the night before had a blustery wind.  Fortunately, Saturday was pretty near perfect.  We had a great cookout and the sunset revealed not a cloud in the sky.  The picture at left revealed a bit of a hazy horizon, but a couple TAAA members enjoying the sunset.

I had practiced imaging the sun w/the scope I'm hoping to use at the Canyon next weekend, and after that set up the Celestron 14" for observing when it got dark.  I also had a couple camera setups - one watching the top of the mountain for a time lapse, the other on a driven mount for some tracked exposures when it got dark.  During the rapidly changing light levels of twilight, I had to monitor my time-lapse camera and adjust exposures accordingly.  When it finally got pretty dark, I returned to the starparty and switched between the scope and taking photos.  At left is the early evening Zodiacal Light - sunlight is reflecting off meteoritic dust in the plane of the solar system.  Brightest near the sun, here the conical glow reaches from Venus down in the trees at right, extending up past mars at upper left center.  All photos taken w/the Canon XSi, this one used a Nikon 8mm fisheye, F/2.8, ISO 1600, 2m exposure.  Yes, Nikon lenses work with Canon bodies with the appropriate adaptor ring...

I used the same setup with the exposures upped to 2.5 minutes for imaging the much fainter Zodiacal Band across the entire sky.  Here, a dozen exposures were combined (about 30 minutes of total exposure) were added and stretched to show the band which reaches from Mars and Regulus at upper right, through Saturn and Spica at center towards Antares, Scorpius and the rising milky Way at lower left.  Just visible in Libra, just to the right of Scorpius is a brightening known as the Gegenshein - the counter-sun brightening of the same meteoritic particles in the solar system plane.  The glow along the left side of the frame is partly rising Milky Way at bottom, merging into some of the light glow of Tucson at upper left.

I overheard some complaining how bright  the sky appeared - yet the sky brightness meter (TAAA arranged a group buy a few months ago) revealed 21.73 magnitudes per square arcsecond, the lowest I've routinely gotten, and almost .1 fainter than my best Kitt Peak results from a couple months ago.  So it was pretty dark!  An object I've always wanted to image was the  dark lane Barnard 228 that is barely observable naked eye to the west of Scorpius in Lupus, the wolf.  This one is a sum of 25 minutes of exposure with a Canon 80-200 zoom lens at F/3.2 set to about 100mm.  Like many dark nebulae, deep exposures reveal the're illuminated by diffuse starlight, so glow faintly.  This object is right on the border of the Milky Way, so has a gradient of illumination across the image.  This frame is significantly cropped from the full field.

In my opinion, one of the coolest views in a dark sky is of the rising Milky Way.  It seems even brighter with the dark silhouette of trees in the foreground.  I'm not sure this is an optical illusion, but the view of our galaxy rising framed by the picnic area trees was just jaw-droppingly amazing last night.  Because the camera is tracking the stars, the trees are blurred slightly in the 2.5 minute exposure - this is  single exposure, this time with a Nikon 16mm fisheye working at F/4.  The red lights are from the flashlights of TAAA members.

Finally the last frame is from one of my favorite imaging spots in the sky.  The yellow star is Antares - the brightest star of Scorpius, with the big globular cluster Messier 4 just to its right.  The area is virtually packed with clusters and combinations of clouds of dark and bright nebulosity.  The field is visible just above center of the wide field above.  The 30 minutes of exposure were taken with the 80-200 zoom again at ISO 1600 at F/3.2 and a focal length of 140mm.  I do love this field!

Friend Donna and I left for Tucson at 1:20am, and there was still one serious observer with one or more fields to check out before quitting.  When we hit the main road we spotted the moon just clearing the horizon - perfect timing for our departure, and the end to a great night of observing.

1 comment:

David A. Harvey said...

Great shots Dean! I too love that Rho Oph field! Here's to the upcoming eclipse. I hope you have good weather and get some great shots.