Thursday, July 15, 2010

Hyperstar Snapshots

I've mentioned using the Hyperstar before with my Celestron 14". Click on the "Hyperstar images" label on the right middle to see earlier posts. The lens set replaces the normal secondary of the mirror, allowing the short focus of the telescope primary to reach the camera focal plane directly with the camera on the front of the telescope. It converts the optical system to an equivalent 670mm focal length lens at the astounding F-ratio of 1.9, with nearly a 2 degree field of view! The lens set, developed and built by Starizona here in Tucson, is a marvel of telescope optics. The fast f-ratio permits very short exposures, normally less than a couple minutes at the darkest sites at ISO 800. When shooting bright Messier Objects in the Milky Way, even shorter exposures must be used to keep the image from saturating.

While out observing the weekend of the 4th, just as a demonstration, I shot a number of summertime Messier objects with 45 second exposures on the Canon 20Da. I was shooting automatic darks, so after the exposure, it took a 45 second dark to subtract from the image. During this time, I moved to a new field, restarting as soon as it was ready. No guide stars, just the G-11 mount tracking as normal... So the enclosed 5 exposures were taken in under 10 minutes!

Four of the objects are clouds of mostly hydrogen gas appearing near the brightest part of the summer Milky Way. These clouds of gas are star formation regions and often have star clusters associated with them, where they've formed. The reddish glow is caused by the young hot stars causing the hydrogen to fluoresce, much like the bluish glow of a mercury light. Generally there are dust clouds that show up in dark silhouette against the glowing gas.

From the top is the Triffid Nebula, Messier 20, with star cluster M21 to the upper left. The image to it's right is the Lagoon Nebula, Messier 8. Both of these gas clouds have dark lanes caused by dust. Continuing at left, the next image is M17, the Omega, or Swan Nebula (visualized shapes, if you use your imagination!). The last nebula image is M16, the Eagle Nebula - clicking on the image loads a larger view, allowing the "Pillars of Creation" to be more easily seen. This object was made famous by the Hubble Space Telescope image, showing how dust and gas condensed to form stars and planetary systems. The lowermost image is Messier 11, a galactic star cluster, sometimes called the "Wild Duck Cluster", from a V-shaped wedge of stars visible in a small telescope.

While these snapshots show slight trailing and other faults upon close examination, they show how swiftly an image can be built up in a fast optical system. Normally, I would guide carefully and stack many exposures to bring out the subtleties of a faint object, but sometimes, it is nice to take some nice snapshots of bright objects!


Anthony Vodraska and Anita Gilbert said...

Nice post as I have been curious about the particulars of your optical/photographic system. Pretty amazing.

David A. Harvey said...

Great to see your setup Dean! Wonderful oics as usual!