Postcard from the Reef – Velvet Star
Shooting Film Again
Photography was not always a process of pixels, megabytes, SD cards and Photoshop. Once it was chemicals, paper, darkrooms and something called film. I learned to shoot in another age, when every shot counted, there were only 24 or 36 frames available. When it was a week or at least a few days before you knew if the shot worked.
Snow on the Mountain
Winter might just be starting in Hawai’i. A fall storm dropped the season’s first snow on the summit of Mauna Kea this afternoon. Not much, just enough to turn the summit white. I had to scrape the frozen snow from the windshield to free the wipers before I could drive down.
We got 1.2″ of rain at the house, quite a bit when you consider we get 10″ a year in the shadow of the mountain. I am headed back to the summit tomorrow morning, wondering what we will find, this storm is just starting.
Postcard from the Summit – Crimping Tools
AO Cables
Warped
Warping is not much fun. Warping is now on my list of responsibilities. At least I know I am accomplishing something critical to the operation of the telescope.
Exchanging segments does require some interesting procedures to realign each new segment, each must be warped and the edge sensors tuned. The first few hours of the night after a SegEx is used to evaluate the performance of the newly replaced segments. Using a special alignment camera system the optical figure of each segment can be evaluated and a set of corrections generated to be applied the next day… Warping.
To apply the correct pressure there are small knobs and screws at specific points in the whiffle tree. Each adjustment point also contains a strain gauge, allowing the applied pressure to be measured precisely. A computer and analog interface allows all of the points to be read out and checked against the calculated values.
After setup, it takes about an hour to do each segment, an hour of painstaking frustration. the mirror cell is just the right height, too high to sit down and reach the knobs, too low to stand up fully. Working in a jungle gym of frigid steel just makes it worse. A day in the mirror cell is a nice recipe for a tired and sore body.
How careful was I? Did I get all of the points set correctly? The computer is displaying all of the correct numbers. I will not know until the next day, when the night’s performance data is reduced, when we can see the figure of the primary mirror and check the errors.
My first warp is a success, most of the segments show less than 20nm rms error. Next SegEx there are only two segments being exchanged, but Sergey is threatening to have two others re-warped to address some lingering issues. Four? Better than six. Only 360 adjustments to make, more or less.
Mercury at Maximum Elongation
Today Mercury reaches maximum elongation, the furthest point it will reach from the Sun in our sky and the highest it will be above the sunset for this evening apparition. The planet is easily visible as a bright, starlike object about 25° above the setting Sun as twilight begins. Over the next couple weeks Mercury will slide back into the sunset, heading for inferior conjunction on November 1st.
Typewriter
A Second Try for the EOS-M
My readers may remember that I purchased an EOS-M last fall. For a number of reasons I ended up returning the camera, a failed experiment.
In the interim a new revision of the camera firmware has addressed some of the major complaints about the camera, including the sluggish focusing. Low price, improved focusing, why not give it a try? I still like the idea of a camera with near DLSR capability, that is small enough to be carried at all times. Fine, I will order it again.
In Alaska I had four cameras with me… A Canon 60D, the EOS-M, a GoPro Hero 2 HD, and a Canon G12. It was the EOS-M that I used for all of the walkabout shooting on and off the boat.
The only real drawback to the EOS-M is speed, it simply does not shoot fast. As a result I kept the full DLSR ready with the long lens, the 70-200mm L series telephoto. When wildlife appeared I was ready to shoot fast. Whales bubble net feeding, a gizzly on shore, for these it was the Canon 60D I grabbed. For everything else it was the EOS-M in my hand.
I have come to appreciate the EOS-M for the reason I originally wanted the camera. It is a great carry camera, small enough to keep with you at all times, ready to get the shot. It isn’t fast, but it does take beautiful photos, providing better quality than a compact and capable of shooting in a wider range of conditions.
Typewriter
