Sky Tracker

New Camera Mount

Over the years I've used my Nikon D40 DSLR camera to take pictures of constellations, conjunctions, and comets. Time exposures were limited to a maximum of 30 seconds for two reasons. First, 30 seconds is the longest available automatically timed exposure that can be done without unavoidable vibration caused by a finger physically depressing the shutter button. Second, 30 seconds is the maximum time before star images elongate due to Earth's rotation. I'm happy to say the 30 second barrier has been removed!

My new Ioptron Sky Tracker can follow Earth's rotation, so star images will remain round in long exposures. I also purchased a remote shutter control so I can manually control exposure time on the "bulb" setting without physically touching the shutter button. Check out my new sky photography setup below. The small cylindrical telescope tube to the right of the camera is the polar alignment scope. While gazing up through the polar alignment scope I adjust the black rectangular box in altitude and azimuth to bring the North Star, Polaris, to the proper position on an illuminated reticle. Once the mount is polar aligned, a battery powered motor inside the black rectangular box turns the camera at just the right speed to keep up with Earth's rotation.

The ball head camera attachment seen below allows variable camera pointing.

The whole camera mount is attached to a tripod.

I waited several weeks to try the new equipment. Weather was miserable - either too cold, too cloudy, or snowing. Finally, on March 7th the sky was clear and temperature was in the 40's. I carried the tripod into my back yard where I immediately cursed the many neighboring spotlights glaring at me from every direction. These lights made it hard to see Polaris through the alignment scope. I also learned alignment could easily be lost by the slightest nudge to the tripod. Camera position had to be changed very slowly and gently in order to maintain alignment.

With my lens set at 18mm I took 60- second and 120-second exposures of Orion, Taurus, and the Pleiades. The 120-second exposure is shown below. Tracking was excellent! Star images are round, though not in perfect focus. The winter Milky Way is visible to the left of Orion. The Hyades and Pleiades are to the upper right of Orion. Hints of pink hydrogen gas are present. This is a single image recorded in JPEG format with no fancy processing. I'm really pleased with the result and anxious to try again with better focus, image stacking, and dark subtraction.

Achieving exact focus continues to be a problem. All my attempts at magnified images were out of focus even though I thought they were in focus when I activated the shutter. It's so hard to judge focus on the camera's display screen. I make test exposures, magnify the results on the camera's image display, make small adjustments to the focus ring, and repeat until star images look sharp. But it's hard to see the display with so any blasted glaring lights all around, and it's hard to remain patient when my hands are freezing. I need to pay more attention to this in the future. I also need to get away from neighborhood lights.

The next image shows the effect of light pollution. This is a 120-second exposure of the constellation Cancer. The brightest object near center is Jupiter. Just above and to the right of Jupiter is the Beehive star cluster. I tried a more magnified image of Jupiter and the star cluster, but the result was out of focus. Notice how the sky is brighter in the lower left than in the upper right. The lower left was closer to the horizon and lit by neighborhood lights.

The zenith sky from my back yard was reasonably dark in 120-second exposures. When I tried 180-second exposures the background sky became light gray instead of black.

These first attempts are promising. I hope to try again soon.