Wednesday, March 30, 2016

March '16 ARGOS Run

Regular readers know that I love recording things in the sky. While the Large Binocular Telescope (LBT) and the ARGOS system are not a natural phenomenon, since I worked on the fabrication of the mirrors of the huge telescope, I feel a natural bond to it atop Mount Graham. I've posted about it many times before - most recently in October, I was in position at a new observing spot about 20 miles south, but a stubborn cloud cap remaining from a clearing storm prevented their opening while I waited below. However, that post resulted in my finally putting together a nice time-lapse nearly 2 years earlier from November '13. A more general post describing the instrument and the other telescopes atop Graham is from that earlier date. This time (a couple weeks ago on 12 March) the weather was great, though a little chilly with a bone-chilling breeze. I was set up about a mile south of a small development, and about 16 miles south of the brilliant lights of Fort Grant, a State Prison, visible at the left side of the above image. From 20 miles, the laser was barely visible to the naked eye, but with binoculars could be spotted nearly to Polaris about 30 degrees high! In this image, I'm lit up by a several-day-old moon in the west, that was to set about 11pm.

Once the scope and telephoto lens was set up, you realize how difficult it is to align and focus in pitch black conditions! I ended up focusing on the rising stars of the Big Dipper's handle, but alignment on the LBT (before the laser started up) was tough requiring many short exposures as trial. It would have been much easier to get there an hour or so earlier, but time seems a rarity lately!

Finally success, as shown at left is the view of Graham with LBT and ARGOS with the 70-200 zoom set to 70mm. You can spot some of the local lights and how much the lights of the prison illuminate the southern flanks of Graham. At right in this wide image is Heliograph Peak, and while it looks to be the tallest peak, because of perspective (it is a little closer to my position) it isn't... At right is a shot of the mountaintop through the TEC 140 with its nearly 1,000mm of focal length, and the scopes atop the peak labeled. You can even spot the illumination from Fort Grant on the side of the LBT enclosure! Amazing what a minute will show in the exposure, since the laser was barely imagined to the naked eye.

All was going swimmingly - I ended up shooting over 2 hours of images with the TEC 140, potentially for a time-lapse (see below!). But when I took a first-look at the images later, I found a surprise! Shown at left is an image taken less than an hour into my shooting. While LBT had moved on to its second object of the night, there appeared to be a second "laser" appearing to emanate from the Sub-Millimeter radio telescope. But there were 2 clues about it's real source. First, clicking to load the full-size image, you can see wiggles in it as the source was affected by atmospheric disturbances, like the distant stars themselves... Also the telephoto caught part of the trail as it was disappearing behind the mountain. It was likely a distant sun-illuminated satellite disappearing over the horizon... Unfortunately, using Heavens-Above, I couldn't locate any possible candidates...

And yes, I did put together the time-lapse sequence, after editing the 140 images taken that evening with the TEC 140, and uploaded it to Youtube for your convenience! Note that the change in lighting over the time-lapse is due to the moon setting towards the end.

In conversations with the LBT director, he ended up using the shot of mine of the satellite disappearing over Graham in the LBT blog, which also includes highlights of the ARGOS run. Evidently ARGOS, which projects laser spots 10km up for partial correction of atmospheric turbulence, improved the seeing over a moderate field of view to .2 arcseconds. See the blog entry for more info.

Addendum: When I published this post late last night, I totally spaced that I got more shots of this run from a different perspective a few days later! Joe Bergeron, visiting from out of town, and I went up to San Pedro Vista on the Mount Lemmon Highway and spent an hour or so shooting towards Graham. Four days later and the moon was a lot brighter, and we were over twice as far away as above at nearly 50 miles. As a result, it was sort of murky and bright, but managed a few frames. Three images were stacked together to make the image at left. You can see a moderately bright star, heavily reddened by the the low elevation rising past the telescope and ARGOS laser. There is also enough ambient light that you can see snow on some of the higher slopes of Graham.

Another thing I've found in the last 24 hours is that when you play the above time-lapse, one of the clips it will auto-play is one made by the ARGOS team from adjacent to the LBT! It is a spectacular clip, showing what is possible with the short exposures and wide angle lens as a result of being 40 yards away, as opposed to shooting from 20+ miles with a meter-long focal length! Impressive stuff - copied here for your convenience - enjoy!

1 comment:

lbusoni said...

Fantastic pictures and description!
I linked this page to our project's page
Thank you