Saturday, January 3, 2009

Kitt Peak Wrap Up

It seems like a good day to follow up on those activities that really need more than one post to cover! Last Sunday I made a trip up to Kitt Peak to visit friend David Harvey, who had observing time on the 90" Bok Telescope. My first posting is here.

Dave presented an opportunity to use the 90" for some imaging with my camera and I eagerly accepted - but what to shoot? Realize that the 90" (2.3 meters diameter) at F/9 (focal length is 9X the diameter) has a focal length of 21,000mm - that is quite the telephoto lens! The problem is that the field of view with my little Canon XSi is something like 4 arcminutes - about a 15th of a degree or an eighth of the Moon's diameter. Another issue is that there was no autoguider available, so an object would have to be bright enough for relatively short exposures so that there wouldn't be any trailing of the image with ordinary tracking without correction. Dave took some exposures later in the evening with a shorter focal length scope mounted on the side, as illustrated here as he was setting up - it is a BIG telescope!

I chose 2 objects - the first was a small planetary nebula - NGC 7662 that has a pretty high surface brightness and was high in the sky. My first exposures of it were astounding at only 30 seconds long! Many of these planetaries show multiple ring structure, and this one has a very bright inner ring inside of a fainter spherical shell. The progenitor star is still in the center - now a white dwarf after spewing a good percentage of it's mass into the shells of gas seen here. Even with the short exposures (most were about 90 seconds long) there was some bloating of the star images - the reason for Dave's engineering run was to improve the collimation, and while focusing, the stars were not exactly point sources... An alternate name of this object is the Blue Snowball, because it is one of the few sky objects that shows color. Most faint objects are not bright enough to trigger the color sensors of the eye.

The other object chosen was a companion galaxy to M31, the Andromeda Galaxy. NGC 205 appears in a spectacular image of Andromeda a few months ago by David Harvey. It appears above center in this image from his blog. The companion galaxy overflows the field of view of the 90", but what was of interest to me are the dust clouds that are sometimes visible in this galaxy when imaging with a small telescope. Normally visible as little specs seen against the multitude of stars in the galaxy, but with this extended focal length the extent of the dust clouds can be seen. The granular appearance of the galaxy's glow perhaps indicates partial resolution of the stars 2+ million light years away.

Later in the evening, I took a series of exposures that I used to make a little animation of the telescope tracking Orion across the sky. There are only 9 frames in the sequence, so is all to short, and I've not figured how to load it directly into the Blog, so go here to see the GIF file. It is only about .75MB, so should load up reasonably fast even with a dial up connection. If you choose not to load it, here are one of the frames.Ninety Inch telescope KPNO

It was a great night - thanks again to David for the chance to join him up at the observatory and play astronomer!