Cassiopeia Observatory

D7000 DSLR Imaging: Asteroids Vesta & Ceres

Posted: 18 December 2012

The observatory was opened Monday, 17 December 2012, at 1806 MST, 54°F. The sky was clear, with a slight breeze blowing. At 1815 MST, viewed the crescent moon, 77X. I then switched to the Explore Scientific 2" 9mm 100° eyepiece (222X) that I purchased last month. The views of the moon with the wide angle eyepiece were great. I then viewed Jupiter, low in the east, 222X. It was too low for good seeing but four moons were visible.

I then began preparing to image the asteroids Vesta and Ceres, which were both near opposition this night. I wanted to image both before the weather turned bad (snow is forecast within the next 24 hours). I switched to the visual back and then used SkySafari 3 Pro on my iPhone to identify background stars in the 26mm eyepiece. At 1851 MST, I had a positive ID on Vesta. I then mounted the D7000 DSLR at prime focus + visual back on the 8" LX200-ACF. Did a focus test with the Bahtinov Mask on the star Aldebaran. Vesta was visible in the camera viewfinder so I centered it. At 1900 MST, I started imaging Vesta every 15 minutes for 10 seconds at ISO 3200. During post-processing, I used Photoshop Elements to align each of the five images (in separate layers, "screen" mode) and then saved the image as an animated GIF. (I had also used this technique with the images of the close approach of the asteroid 4179 Toutatis just one week earlier.) In just one hour, Vesta shows obvious movement in this full-frame image:

I then slewed to the asteroid Ceres, and beginning at 2005 MST, I repeated the 15 minute interval, 10 second, ISO 3200, imaging. This full-frame image shows the movement of Ceres over one hour:

It is pretty amazing to capture the movement of asteroids in such a short period of time. Of course, it helps to have the asteroids at opposition!

I ended asteroid imaging at 2105 MST. The humidity was high again this night (61%); the paper in my logbook was getting damp. I decided to end the session.

The observatory was closed at 2115 MST, 42°F.

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