Telescopically imaging the ISS (plus some deep-sky)
Last week I have experimented with telescopic imaging of the International Space Station (ISS), using my Celestron C6 (15 cm F/10 Schmidt-Cassegrain). Above is the best image, shot 6 June 2014 at 22:07:13 UT as the ISS was zipping past beta Bootes. It is a single image from the series, taken at 1/4000th second at ISO 800.
I kept it simple: I did not actively track the ISS, but looked for points where it passed close to a reasonably bright star, and then pointed the telescope to that position. As the ISS passed that point, I did a rapid burst series of images, a few of them which then showed the ISS zipping through the field. I used 1/4000th second exposures.
That technique is actually enough to get some decent pictures. Later, I will probably experiment with active tracking using computer guidance of the mount, and see whether video might yield more that photography (one drawback of video is a lower resolution, so a need to work with Barlows).
Having the telescope out anyway, I made some deep-sky images too the last two nights, of some bright summer sky icons. Again, I kept it simple. As I work from a town center, and a location where I cannot see the Pole star due to obstruction by a building (which hampers telescope alignment), I kept exposure times short, to 10-15 seconds. Then I stacked large numbers of images.
The above image of M27, the Dumbbell nebula, a planetary nebula in Vulpecula, is my favourite. It is a stack of 57 images of 15 seconds exposure each at 2000 ISO. The faintest stars on this image are near mag. +16.8, which is not bad with short exposures from a town center.
Another iconic planetary nebula in the summer sky is M57, the Ring nebula in Lyra. The image is on the same scale as that of M27 above. This image is the result of stacking 60 images of 10 seconds exposure (the scope didn't track that well that night) at 1600 ISO.
The final image shows globular cluster M13 in Hercules. It is a stack of 57 images of 15 seconds exposure, taken at 2000 ISO.