Located in Ursa Major, Messier 81 is a beautiful spiral galaxy. This 60 minuute luminance image is a
composite of 12 five minute exposures. Within the spiral arms you'll note clumps of star formation known
as Hydrogen II (HII) regions. Dark dust lanes appear wrapping around the galaxy's core. At a relatively
close distant of 4.5 million light years, M81 is an easy telescopic target and under dark skies readily
visible to binocular observers.
Photographing galaxies "near by" or "extremely far" require long image exposures. The long exposures increase the precision guidance requirements. Unfortunately the motor drive of my LX200 telescope is imprecise (being polite about it). As a result I am constantly challenging its precision limits with new devices/techniques. In this image I was trying my new SBIG AO-7 Adaptive Optics add-on to the ST-7XE CCD camera. The AO-7 has an electronically controlled mirror which inserts into the light path at a 45 degree angle ahead of the SBIG ST-7XE CCD imaging chip. To make a long story short, the electronics borrow images from the ST-7XE's auto guiding chip. The AO-7 electronics sample the guide star position and "tip-tilt" the mirror to correct guidance errors while simultaneously overriding mount correction commands from the ST-7XE auto guider. The AO-7 will attempt to keep the guide star centered instead of issuing regular corrections to the LX200 motor drive. When the mirror tip-tilt exceeds specified thresholds (e.g., 10 percent of the initial 45 degrees) the AO-7 electronics issue commands to the LX200 motor drive to "catch-up". I will spend more explanation of this process under the "AO-7 on Deck" section of this site. But first I need to learn how to use it.
I captured this 25 minute luminance image (first image using 5 images each 5 minutes) of the Whirlpool Galaxy, Messier 51 (M51). I cut the evening short as it was a work night. Two years earlier I assembled the second image. At that time I was restricted to 10 second images. Here there are 20 such images digitally combined. After satisfying myself that the AO-7 did indeed improve the LX200 guidance and image quality, I filed away the image and went to bed. Little did I know that something fantastic was stirring in the outer spiral arms of M51.
Later in mid-July, I received a note from a member of the Cedar Rapids Amateur Astronomers group (CAA)
asking if I had been imaging recently. He noted that he had taken video imagery of the supernovae in M51!
A supernovae is a spectacular ending of supergiant stars. They literally explode into their surroundings expelling material at ultra-high temperatures
and and therefore brightness. During the explosion the star's luminosity can outshine all other objects in its parent galaxy.
On July 20, 2005 under a bright, nearly full, moon I returned to imaging M51. The image at the right is actually the May 3 imaged reprocessed to emphasize the stars rather than the spiral arm structure. If you click on the image (500KB Dialup Users Warning!) it will launch an animation of 3 overlayed images. The first being the May 3 image. The second the July 20th image. And the third showing the July 20th image with cross hairs identifying the supernovae. Unfortunately I missed the peak brightness of this event. My understanding is the supernovae grew in brightness rivaling (if not exceeding) the brightess stars recorded on the image at right. You will notice the images have different appearances as they cycle. This is due to the bright sky background from the near full moon in the second and third images. Also the first image was much better quality seeing conditions and exposure length.
Stellar events are often discussed in hundreds of thousands to millions to billions of years. In a few short weeks this supernovae grew from invisibility to a prominant beacon across 15 million light years of distance. Imagine that!