Thursday, May 30, 2013

Another PanSTARRS Session

I just can't seem to get enough of the latest Comet PanSTARRS performance.  The Earth crossed the orbital plane of the comet early in the week, and instead of a anemic comet with a small tail, the comet appears to have a HUGE anti-tail many degrees long!  It isn't very bright, but still visible in hand-held binoculars, including a couple degrees of anti-tail.  But it is still easy to photograph, with exposures of a fraction of a minute showing it and its new tail appendage.

Tuesday night, I again headed North up the Mount Lemmon Highway in search of dark northern skies.  Instead of stopping at Geology Vista, I went up another 3 miles and perhaps 500 feet higher to San Pedro Vista.  Those few extra miles distance to the Tucson metropolitan area makes a big difference.  I set up at the pullout and set up 2 cameras.  The first was with my tripod-mounted Canon XSi and a 50mm lens (a Nikon F/1.4 stopped to F/3.5).  With the comet so close to the celestial pole, it doesn't trail very much - I took a series (15 in total) of 1 minute exposures, then used the program "Nebulosity" to take out the rotation around Polaris, and reduce the noise from individual exposures.  The lens' field of view is wide enough to show all of the Little Dipper, as well as a pretty good view of the comet, anti-tail, and it also caught the passing of an Iridium Flare during one of the exposures!  It is shown at left, and an annotated version is shown at right.

At left is shown a cropped version of the single 60 second frame where the Iridium Flare occurs - shows up much better here since it is not diluted by averaging with 14 other frames.  I've talked about these Flares before - the antenna of the communications satellite reflects sunlight down on a narrow path on the Earth's surface.  These appearances can be predicted accurately (Heavens-Above).  A fainter satellite also appears - many were in the above stacked frame, but only the Iridium Flare was bright enough to show in the sum (appeared to be about magnitude -2).

The other camera I used was Melinda's T1i on my Vixen tracking platform with the 70-200mm zoom set to 100mm at F/3.2.  It doesn't show a lot more than the above frame, but has a little better image scale.  There was a blustery wind blowing and critical analysis of the star images show some movement, but at these resampled images isn't too objectionable.  It is a stack of six - 100 second frames, so 10 minutes total exposure.

While wrapping up the imaging, before heading back down the hill, I took a few exposures of Mount Graham, visible to the east outlined by a dim glow of Safford, AZ about 50 miles away.  I've been up to the LBT telescope there and was amazed by the amount of light atop the mountain from the state prison at Fort Grant on the southern base of Graham.  Sure enough a full-resolution crop of a stack of five minute-long frames shows not only the LBT enclosure, but shadows in the canyons cast by the lights of Fort Grant!  Click the image to load the full-sized version.

After packing up, I dawdled at Windy Point Vista, a "scenic viewpoint" which is a favorite at night to see nearly the entirety of the Tucson valley.  Of course the city lights are spectacular if you are into that sort of thing.  This is a five-frame panorama with the same 50mm Nikon lens used above.  Unfortunately, our blog provider only allows a maximum picture width of 1600 pixels, so you can't enjoy the 16MB file that is 16,000 pixels wide.  What you see here is the maximum allowed...

Another great night of comet observing.  The tail will tilt-offline from the main tail and get faint again, but the visibility of this anti-tail will be burned in my memory as quite spectacular!  The Grand Canyon Star Party starts in 8 days, and I'm hoping we'll be able to show some good telescopic views to the public there...

1 comment:

Andrew Cooper said...

Thanks fot the updates on C/2011 L4 ovre the last week. I made it the first real target of the new astrophoto setup.