Tuesday, March 31, 2009

Astronomical Snapshots With The Hyperstar

While I have fun trying to image the night time sky, the effort of getting a "proper" image that is fully flat fielded, dark subtracted (correcting for electronic noise and non-uniformity in illumination in the telescope), as well as stacking dozens of images to bring up a faint signal, is just plain work! So on my usual partial night of observing, I usually only get one or two such objects. But sometimes I take "snapshots" to see how an object looks in the telescope field of view - then perhaps chase it down another night.

Case in point are these short exposures taken in the last month or two as test objects. The first was taken just this last Friday - I went out to shoot comet Lulin once more, and to work on a few potential objects for the observing list. This pair of galaxies was found from the East Valley Astronomy Club's edge-on galaxy list. The designations are NGC (New General Catalogue) 4631 (upper) and NGC 4656. Thought to be about 25 million light years away, this galaxy pair is sometimes referred to The Whale and The Hockey Stick, from their shapes. This image is cropped down slightly from the full frame of the Celestron C-14 plus Hyperstar imaging system with a Canon 20Da camera. It is a 60 second unguided exposure.

This next image is similarly another snapshot taken in January of the Rosette Nebula (NGC 2237) . A mostly hydrogen gas cloud, it acted as nursery for the star cluster that condensed from the gas. Shaped like a Christmas wreath, it is observable in the winter season. Similar to above, this is a 90 second exposure with the same hardware. These snapshots are easy with the Hyperstar setup (equivalent to a 660mm lens working at F/1.9) because of the wide field and short exposure. This image shows the light falloff at the upper part of the frame, which can be corrected in the flat fielding. Some day...

Lastly, this lunar shot was taken at the Messier marathon this last Saturday night. It is a .1 second exposure to show the "dark side" of the moon that is illuminated by the nearly full earth from it's perspective. It also shows the almost 2 X 1.3 degree field of view with the nearly half degree orb of the moon. Hardware is the same as above, and only simple levels adjustment was done to better display the images.

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