Monday, March 9, 2015

A Couple Hours of Darkness...

Since the full moon last week, I've been waiting patiently for clear skies, and enough dark time between twilight and moonrise to get in some exposures of a few objects. Sunday seemed to be a perfect afternoon - there were some clouds well east of Tucson, and with moonrise scheduled for about 9:15, I had almost 2 hours of dark time. I loaded up the van with a couple cameras, tracking mounts, and a case of lenses towards Kitt Peak. I set up along the mountain road just past milepost 8 at about 5,500 feet elevation. Some scattered high cirrus appeared right at sunset, but it was a lot calmer than the gale from last time!

My first target of the night, shortly after it got dark, was the continuing planetary grouping in the west. As mentioned in my last post from town, Venus and Mars in the west are currently serving as guideposts to locate Uranus in binoculars between them. I was setting up a 135mm lens for my first primary object, so used it to barely fit the scene in that telephoto. I stopped the lens down to F/5.6 to give a nice diffraction pattern around Venus, and even Mars shows one at the bottom. Uranus is between them, and even if you don't know which of the points of light it is, the greenish tint guides you to it in the image. I provide the labeled version at right. In a few more days it will drop below Mars (Mars is moving away from the sun faster than Uranus), so do check it out soon!

As it moved towards darkness, I was able to align the Polarie tracker on Polaris and line up on my first target.  Discovered barely 3 weeks ago, Comet SOHO C/2015 D1 is/was a sungrazing comet.  SOHO, a spacecraft designed to observe the near-sun environment has also discovered 2,875 comets, including C/2015 D1.  After passing 2.6 million miles from the blistering Sun's surface, astronomers started watching for it in the night-time sky, but evidently the nucleus disintegrated - all that is visible is a remnant tail!

Never having seen a "ghost comet" before, I was hoping it would last long enough that I could try capturing it, so that was the first object on my list. Fortunately, a couple websites like that last link provided a map of where to look, so started exposing with the Canon XSi and my ole' reliable Nikon 135 lens set to F/4. I wasn't expecting to see it on the screen - I suspected that the power of stacking images would be needed to be able to see something like this. Sure enough, nothing detected, but when my lucky 13 exposures were stacked at home later (22 minutes total exposure), out popped a little Cheshire Cat mustache! Shown at left is the full frame of the 135mm field and APS sensor, the remnants of Comet SOHO is bottom center. Unfortunately, the comet was on the northern edge of the Zodiacal Light, so there is a nice gradient across the field that I'm not really interested in removing as it is real...

Doing a little cropping reduced the effect of the gradient and lets the comet stand out a bit more. Shown at left is the cropped view of the comet among the stars of Pisces. And I've done the work for you in identifying nearby stars, and even a galaxy in the field of the telephoto lens in the labeled version at right. I had the camera oriented square to the horizon, so north is towards the 2 o'clock position in these views. I've not quite recorded anything like this before, and I think it is quite amazing! If there is another chance of getting out in the next 10 days or so, I'd definitely go after it again!

To round out the night, another bright comet is still around - old reliable Lovejoy C/2014 Q2. I've posted a few times, my favorite was when I shot it passing the Pleiades when I was fresh out of the hospital with bronchitis in January. Now on the opposite side of the sky when it first moved above our southern horizon, it is up in Cassiopeia, back in the Milky Way again. It was competing a little with the skyglow with Phoenix from my location, but it is a shadow of its former self. While obvious in binoculars, try as I might I just couldn't quite make it out naked eye. But is it in a beautiful field with lots of open star clusters and even scattered dark nebula. The bright star to the comets right is Delta Cass, Arabic name Ruchbah. The image at left is only 12 minutes of stacked exposures, and stretched enough that I can almost imagine the tail stretching to the top of the frame.

Cropping the frame again allows more detail, showing ultimately how sharp the film-era Nikon lens is, and how well the Polarie tracks for the 2 minute long exposures. The exposure at left is shown at full camera resolution (no downsizing for the blog). Comet Lovejoy is passing a pair of star clusters here, the bigger one being a popular visual target. With the pair of bright stars involved in the edge for eyes, it is sometimes called the Owl Cluster. Don't see it? Excuse my photoshop drawing of an owl, but may jog your brain into seeing a bird - though my sketch looks more like a bat. Definitely needed more exposure, but moonrise was imminent, and I promised Melinda I'd be home shortly after 10pm - it was a school night, after all! But by recording these two comets, I was a happy camper!

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