State Of The Art!

A few weeks ago friends Stan and Ken came to Tucson and one of our side trips was up to Mount Graham and the Large Binocular Telescope. It is an amazing telescope, certainly considered state-of-the-art, and the guys were suitably impressed.  What I was most interested in was spending time in the telescope's enclosure, doing some time-lapse images. Seeing a telescope at work sort of brings it to life - I've done similar things to the dome exteriors, but interiors present a different set of problems. The biggest problem is that inside the domes, it is DARK!  Starlight is a little feeble, and astronomers are most averse to setting up lights to illuminate the dome's interior...

I've tried it before. Back in May of '08 (before I was married, so before this blog existed!) I was invited to go up with telescope scientist John Hill and spent a couple hours in the enclosure. I used my state-of-the-art Canon 20Da camera, only a couple years old at the time. With a maximum of ISO 1600 and a lens working at F/3.5 (the 10-22mm zoom, set to 10mm). the required exposure was 6 minutes! With time-lapse clips, you want frames to come in as fast as possible, but 10 frames per hour is slow in anyone's book! Adding to the problem, it was cold that night, near or below freezing, and my battery died about 2 hours in. The images confirmed that the noise level was pretty high - at left is shown one of the images taken back then, with a blowup of one of the sections at lower left. There is literally a blizzard of red, green and blue "hot pixels" from electronic noise. Even the cold temperatures (one of the tricks to reduce noise) had little effect on it. In-camera noise reduction, or observing and subtracting darks would have helped, but made life more complicated. In addition, at lower right in the image is a glowing blue cloud that might be amplifier glow...

Despite the problems, an interesting time lapse was produced.  Be sure to go to full-screen and up the playback to HD for best details. The astronomers were doing short exposures over the entire sky. From my position in the enclosure, the stars trail one direction if the scope is north of the zenith, the other direction if it is pointed south. Still, more frames were needed to make a reasonable clip. I figured I'd be better prepared next time...

Little did I know that the "next time" would be 7 years later! Cameras have improved over time - Canon has come out with more than 5 new models between my 20Da and Ken's 6D. The 6D has a larger sensor, in fact, it is the same size as the venerable 35mm film format - 24X36mm, considerably larger than the APS sensor of the 20Da. The data/noise handling was DIGIC II on the older camera, the newer is DIGIC 5+, allowing much higher ISOs and faster download times with less noise. In other words, there is a new state-of-the-art! This trip, in a similarly unlit enclosure, with the larger format I used a 16mm fisheye that worked a stop faster at F/2.8 compared to the earlier F/3.5. I also gained 2 stops of exposure by using the 6D at ISO 6400, so in all, we were shooting 3 stops faster, or 8X more sensitivity! Sure enough, 60 seconds made the dome interior look pretty brightly lit by starlight, and scattered light from Safford to the north. Check out the exposure here and compare it to that above - nary a single hot pixel in the whole image!

Unfortunately, this time the astronomers were doing long exposures - multi-object spectroscopy of star formation areas in distant galaxies. In the time lapse from the images taken, the scope only makes a small change between objects, making the clip a little boring, if not for the fact that we were doing short exposures in nearly pitch-black conditions!




The staff and astronomers treated us better than we expected. Hopefully we made some friends among them and will get invited up again. With a couple sessions under my belt, hopefully a future session will come up with something stunning! 

These little 30 second clips, made artificially longer by looping through a few times, is a little tedious - I'm hoping shortly to combine a few of them into a single longer sequence showing different aspects of the telescope...