Cassiopeia Observatory

More Stellar Spectra Imaging,
Comet C/2012 K5 (LINEAR)
Posted: 6 January 2013

I enjoy taking images of the moon that show mountain shadows at sunrise (and sunset) along the lunar terminator. The morning of Saturday, 5 January 2013, there was a similar effect at sunrise at Cassiopeia Observatory. Mountains to the southeast were casting nice shadows across the valley floor to the west of the observatory. This photograph (cropped), taken using the D7000 DSLR with a 8mm 180° fisheye lens, shows the mountain shadows. Also seen in the photograph are Kitt Peak (between the two trees on the left) and Cassiopeia Observatory (behind the second tree from the left).

The observatory was opened Saturday, 5 January, at 2107 MST, 43°F, to clear skies. Opening was delayed due to my watching the Packers win their NFL Wildcard game. At 2115 MST, I observed Comet C/2012 K5 (LINEAR) at 77X with the 8" LX200-ACF. The tail was visible. I had to wait before imaging the comet to allow it to clear the "zenith blind spot" of my POD. (I really must consider getting a "Zenith POD Table" one of these days!)

While waiting on the comet, I did some more spectra imaging using the Star Analyzer 100 and the "drift method". These are 5 second exposures at ISO 100:

Pollux - Spectral Type K0

Castor A & B - Spectral Type A1 & A2

Procyon - Spectral Type F5

Sirius - Spectral Type A0

I finished spectra imaging at 2158 MST and viewed M42. I then began trying to observe the Horsehead Nebula, which I have seen a few times in the past in the 8" telescope. It remained a difficult object, even with Orion high in the sky. I was able to see it intermittently at 77X, with and without a Hydrogen-Beta filter. The best view was with a 2" 30mm eyepiece (67X), but it was still difficult to see.

At 2238 MST, I slewed to Comet C/2012 K5 (LINEAR) (position as reported by SkySafari Pro on the iPhone) but it was not quite clear of the dome. I began preparing the D7000 DSLR for prime focus imaging. I knew that the comet was moving rapidly across the sky so I would have to keep exposures short. Therefore I did not use the Off-Axis Guider. At 2254 MST, I began observing the comet at 67X. Movement of the comet against the background stars was indeed very obvious. I switched to a 2" 9mm (222X) 100° eyepiece; the head was easily seen and movement was apparent in less than one minute.

At 2320 MST, I set up for prime focus imaging with the camera on the star diagonal. I did a focus test image on the star Aldebaran using the Bahtinov Mask, and then locked the focus. I did a framing test exposure of the comet, 1 minute, ISO 6400, unguided. I could see the comet, about Magnitude +9, in the camera viewfinder so I positioned it to capture the head and tail. I then took 10 exposures, each 1 minute, ISO 6400, unguided. This is one of the images of Comet C/2012 K5 (LINEAR):

Four of the 10 images showed some star trailing, but the other six were OK. I stacked the six images to yield this (cropped) image of Comet C/2012 K5 (LINEAR):

The same six images were combined to make this animated version (1.1 MB) showing the movement of Comet C/2012 K5 (LINEAR) over an 8 minute period:

Comet imaging was ended at 2353 MST. At 0002 MST, I took a quick look at Jupiter, 77X.

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