Cassiopeia Observatory

Imaging: Venus Spectrum, M13, Comet Garradd, Moon

Posted: 16 October 2011

The observatory was opened at 1719 MST, 99°F, about 30 minutes before sunset, to clear skies. At 1724 MST, Venus appeared as a nice disk at 77X. I tried for Mercury but the sky was too bright. I set up for some spectroscopy of Venus. I initially imaged the spectrum at prime focus of the 8" LX200-ACF using the Star Analyser on the D7000 DSLR. The sky was still very bright but a low contrast spectrum was captured. I waited for the sky to get darker and I added the focal reducer to make Venus more of a "point object". This is a processed 1/100sec, ISO 200, image taken at 1815 MST:

My next imaging target was Comet C/2009 P1 (Garradd). I removed the focal reducer and Star Analyser, and attached the camera to the Off-Axis Guider. Did a focus test on Altair using the Bahtinov Mask. Next, I centered the M13 globular cluster in the camera viewfinder and SYNCed the AutoStar. Since the camera was on M13, I decided to take a test exposure. This is 27 seconds, ISO 5000, unguided, taken at 1838 MST:

After I completed the M13 exposure, I replaced the Wireless AutoStar II batteries, which were starting to fail. I didn't want to begin comet imaging and have the AutoStar handcontroller stop working. I then slewed the telescope to Comet Garradd's RA/Dec; the comet was visible in the camera viewfinder. Did a short test exposure and then began waiting for the sky to darken some more. At 1908 MST, I begin comet imaging using 1, 2, 3, 4, and 5 minute, ISO 5000, exposures, all manually guided using a good guide star. This is the 5 minute exposure, slightly cropped:

At 1936 MST, I removed the camera so that I could do some visual observing of the comet, which I started at 1942 MST. With the 26mm (77X) eyepiece, the comet nucleus, coma, and faint tail were visible. I switched to the 15mm (133X) and then the 9.7mm (206X) eyepiece to track the comet's motion against the background stars. At 206X, movement was very noticeable in just a couple of minutes.

At 1958 MST, viewed Jupiter, low in the eastern sky, at 77X. It was too low for good viewing but 4 moons were visible. The eastern sky was beginning to brighten from the rising waning gibbous moon. At 2014 MST, I switched to the 15mm eyepiece, hoping for better seeing as Jupiter rose higher. At 2048 MST, the moon was rising over the hill. At 2101 MST, switched to the 9.7mm eyepiece and viewed Jupiter. Seeing had not improved much by this point. I decided to check out some filters while viewing Jupiter:

At 2127 MST, tried the 5.5mm (364X) eyepiece on Jupiter. Seeing was fair, but details in the cloud bands were better at 206X.

At 2130 MST, slewed to the moon, still low in the eastern sky. The view at 77X was pretty good. I began setting up for D7000 prime focus lunar imaging. Switched to the visual back; the lunar disk just filled the D7000 DSLR FOV, so there was no need for the focal reducer this night. I then began waiting for the moon to rise higher. I did take this iPhone 4 photograph of the 8" LX200-ACF, the "live" moon as seen by the D7000 camera, and the moon in the sky:

I then did some lengthy lunar observing with the 5.5mm, 9.7mm, and 15mm eyepieces. There were some outstanding views across the entire lunar disk, terminator, and limb. A lot of details were clearly visible.

At 2220 MST, Jupiter was now high in the sky. I viewed it at 133X; seeing was still not very good. I decided to close up after this over 5 hour session.