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Final 8mm Fisheye Lens Sky Tests;
NGC660 Polar-Ring Galaxy

Posted: 9 January 2013

The sky clouded up after my 5 January session in the observatory, but was clear on Tuesday, 8 January 2013. The observatory was opened at 1806 MST, 58°F. At 1811 MST, viewed Jupiter, 77X. Three moons were visible. Switched to 222X, but seeing had not quite steadied down from the daytime atmospheric heating.

I began setting for all-sky photography using the D7000 DSLR with 8mm 180° fisheye lens. The camera was mounted on a LXD55 tripod. My goal was make a final determination of the best f/ ratio and ISO setting for capturing meteor shower activity. I had previously determined that airplane trails would make great stand-ins for meteors for testing purposes. And from my last tests, I knew that f/5.6 gave sharp star images. This night's tests would be done at f/4.5, f/5, and f/5.6, 2 minutes, using ISO settings of 5000 and 6400. The LXD55 tripod would provide tracking. Once twilight had ended, I began imaging at 1856 MST. Every time I saw an airplane I would take an exposure. Many satellites were seen this night, and some were even captured. This cropped image shows three polar orbiting satellites (arrowed), taken at f/5.6, ISO 5000:


South is at the left and North at the right. Jupiter is the bright object left of center, between the Hyades cluster (Taurus) and the Pleiades.

During the times when no planes were flying over, I observed Jupiter at the telescope, 222X. At 1832 MST, I picked up the moon Io making its transit of the planet's disk. At times, it was difficult to see, but at other times, especially when seen against the background of a darker region of the North Equatorial Belt, it was much easier to see. At 1842 MST, the Zodiacal Light became visible in the western sky.

From my tests this night I have decided that f/5, ISO 5000, should be the best for capturing meteors. This image (f/5, 2 minutes, ISO 5000), East at the top and South at the left, shows an airplane trail (top), the Milky Way running vertically, Jupiter near the top, and the Zodiacal Light at the lower left, making an inverted "V" with the Milky Way:


I completed sky imaging tests at 2000 MST. I returned to the 8" LX200-ACF and slewed to a "polar-ring" galaxy, NGC660. I could just see this galaxy with a 2" 9mm eyepiece (222X). It was much easier to see with a 1.25" 26mm eyepiece (77X), although the "ring" was not visible. I began setting up for prime focus + Off-Axis Guider imaging of the galaxy. After doing a focus test image with the Bahtinov Mask on a star, I did a framing test exposure of the galaxy. I found a very faint guide star, but since the framing was good, I decided to try it. Unfortunately, the star was too faint to maintain sight, resulting in poor manual guiding corrections during the 5 minute exposure. I began a search for a brighter guide star and did some more framing test exposures. I finally located an excellent guide star and acquired this guided, 5 minute, ISO 6400, (cropped) image:


The main NGC660 galaxy is easily seen, with its "polar ring" just visible (oriented horizontally in the image). I plan to do additional imaging to better capture the "ring".

I ended imaging at 2056 MST. I did some brief observing of M42 in Orion, 222X and 77X.

The observatory was closed at 2107 MST, 43°F.

Comments are welcome; use the Comments section below, or you can Email Me. Thanks.

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