Wednesday, May 31, 2017

Out And About!

After a month in the Midwest and a brief taste of dark skies on the CAC bus trip the weekend before, the draw of dark skies on the long Memorial Day holiday was enough to get me out to look at the stars! On Friday, after feeding the kitties, I headed out towards Kitt Peak and set up on a favorite pullout along the access road. Unfortunately it had been a windy day and the winds failed to drop like they were supposed to. I was way underdressed for the gale winds and cool temps at elevation - fortunately the snow mobile suit I keep in the van was still there and made the night's observing possible! The wind also limited the scopes I could use - I stayed with the 500mm Canon lens and the 70-200 zoom for some wider-field imaging.

The highlight of this time of year is always the rising Summer Milky Way! How can I avoid shooting my favorite area of the sky yet again - the area around the orange supergiant star Antares in Scorpius? At left is a spectacular 2-frame mosaic with the 500mm lens. Antares is the orange star very near the center - its light scattering off the dust cloud through the center of the frame. Right of Antares is the huge globular star cluster Messier 4, while between them and a little above is another globular - NGC 6144, located more than 4X the 7,200 light years of Messier 4. I love this field of view because of the complicated mix of dark, reflection and emission nebulae.

But I knew there would be another visitor as well! I recently saw a finder map for comet 71P/Clark. It is not particularly bright, but visible as a small greenish smudge not far from the left edge. The right image shows it a little better, complete with a little tail trailing off to the upper right! Comets that display any color usually show some green - caused by the sunlight breaking up carbon molecules that will glow green in the vacuum of space.

Another target on Friday was an emission nebula in Scorpius. I was shooting with 2 cameras - a recently-obtained T5i that has been modified for increasing red wavelengths to better record the red nebulosity of ionized hydrogen clouds. My other "new" camera (now over a year old) is the full 35mm format Canon 6D which also seems to excel at recording red nebulosity. I headed for what is called the "Cat's Paw Nebula", NGC 6334. At left is a wide field with the Canon T5i and 70-200 lens working at 175mm focal length. The two bright stars at lower left are the "stinger" stars of Scorpius, so this field is quite low in the sky. But right in the center is the "Cat's Paw" - looking like a red-ink print of the paw of a cat. The red coloration, of course, is caused by the ionization of hydrogen by ultraviolet light from hot stars in the cloud of gas. At right is the view with the 500mm and 6D, and again, has good red sensitivity for these hydrogen clouds. Both are relatively short exposures - the wide field at left is 12 minutes total exposure, the right is only 10 minutes! I've still got some exposures from Friday to look at, but these are gonna be my favorites!

On Saturday, I decided to head out to the Chiricahua Astronomy Complex (CAC) of the Tucson Amateur Astronomy Association (TAAA). Even though I had just been out the weekend before, with the 40" scope as a potential viewing instrument, and the dark skies there is a powerful draw making up for the 2 hour drive... I got there just before sunset and set up my mount and the same setup as the night before on Kitt Peak. However, this time there was no wind and it was much more pleasant! At left Carter Smith is at right with his trainee John Meade, getting the 40" telescope ready for the evening. While it looks like a shot taken about sunset, it was considerably darker, but thanks to the "magic" high speed of the 6D, 1/3 second at ISO 8000 makes it no problem! Returning to the pads where my gear was set up, the same shot reveals the hubbub of observers preparing for the night...

My main goal for the night was a "bright" comet - C/2015 V2 Johnson! When it comes to comets, most anything visible in a small telescope or binoculars is considered bright, and unfortunately, this one will not quite be visible to the naked eye. Some of you know that Melinda's maiden name was Johnson, and as far as I know, the discoverer of Comet Johnson is not a relative! He is Jess Johnson, and works for the Catalina Sky Survey right here in Tucson. This comet was discovered as a faint smudge in November of 2015, and is just now at its closest point to the sun and the earth. We'll be able to show it as part of the Grand Canyon Star Party this June, after which, it will slowly be leaving the solar system - its hyperbolic orbit means it will not return to our part of the solar system again. With the 500mm lens, I got 10 frames of 2 minutes each and used the "Nebulosity" program to stack the images on the slowly-moving comet image. The result is at left. The bright star at right is Epsilon Bootes, and the comet is slowly moving almost due south.
What is interesting about the comet is that when zooming in, a sun-ward pointing spike appears!  This usually indicates that the earth is passing through the orbital plane of the comet.  At right is a cropped, stretched version perhaps showing it more clearly.  These sunward spikes are illusions and are actually well beyond the comet.  The solar wind pushes released gas and dust away from the sun to make the tail, and as we pass the plane of its motion, long-ago releases material can appear to point towards the sun.
That was the highlight of my Saturday at CAC. I tried some similar low Milky Way objects, but ran into some of the light dome off of Douglas 20 miles south of the observing site. Best to stay higher in the sky! I'm spoiled by the black high-elevation skies of Kitt Peak... Oh, and I did get a glimpse thru the 40"! While my camera was shooting comet Johnson, I ambled up and was just in time to view the huge globular cluster Omega Centauri. With it so low, no stepstool was needed, so extremely comfortable to observe. The cluster looked for all the world like a swarm of fireflies as the long path thru the atmosphere made the stars dance wildly! It was a sight not easily forgotten!

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