Optics Ole'-Timers

Everybody's friend Bob Crawford died a week ago (7 April) on his 77th birthday. Well, I should say that if you had ever met him, he was a friend. One of the nicest folks I've ever known, he was on staff at the Optical Sciences Center's optics shop where I worked for a few years in the 1980s. He was a veteran Master Optician, and as a newcomer to optics after nearly a decade of astronomy in college and Kitt Peak National Observatory, he was quick to help and teach the newbie (me!) in any way he could in my new profession. Even though my duties were mostly in metrology and engineering, he answered my million-and-one questions about fabrication, and slowly I absorbed from the master...

One day I brought in my 4X5 view camera and took some pictures, including these of Bob beside what I recall was a spare mirror for the Multiple Mirror Telescope. I was called on it today by one of the old-timers from the period, but I wasn't around for the original six-mirror fabrication, so this had to be the spare, made out of the same surplus Air Force egg crate fused quartz substrates. In the other image, MMT engineer J.T. Williams was assisting Bob in measuring some of the physical parameters of what was likely a nearly-finished mirror in its handling ring. These negatives have never been printed, but this week I got them scanned and prints made for today's services.

The memorial today was absolutely amazing!  Everyone in the Tucson optics industry was there - a testament to Bob's outgoing personality and how he was loved wherever he went. Former OSC directors, secretaries and former co-workers and staffers of all levels came to pay their respects to Bob's memory, his wife of 52 years Joan, and adult children David and Jennifer. As is always the case (last time was the passing of another OSC optician Ed Strittmatter 2 years ago) it is a shame it takes the death of someone so loved to bring everyone together to catch up on our lives.

Melinda and I had just seen him a couple weeks before his passing while at the cancer center. Melinda was in getting blood tests, and Bob and Joan were on their way home after an oncologist appt. I'm sure he was feeling poorly, but we chatted for a good long while, waiting for Melinda to get out of the lab so they could talk to her and see how she was feeling too. But that was how Bob was - always wanting to be brought up to date, hear a story, a joke, bring out a smile. Thanks Bob - for everything!

Puerto Peñasco Mirage and Fata Morgana!

On our last trip to Puerto Peñasco at Christmas, we observed several mirage effects over the Sea of Cortez, and I was looking forward to our return to see if any more could be seen.  While the sun and moon were rising and setting too far north to be seen over water, I was not disappointed!  We were able to spot several instances of Fata Morgana - a mirage effect caused by layers of air at different temperatures.  In the cases below, I believe cooler air is trapped near the Sea of Cortez or the ground with an inversion layer and warmer air above.  The effect of this is a vertical magnification or stretching caused by bending of light rays by the temperature differences.

The first instance was on our first evening there, on eclipse night.  After taking the picture mosaic of the rising full moon in our last post, I whipped over and took a shot of Bird Island to the southeast (shown at left), about 25 miles (40km distant).  So far, so good...  About 2.5 hours later, just before the eclipse started, I went looking for Bird Island again to try imaging it by moonlight (shown at right).  Wait a minute - they appeared much higher from the exact same viewpoint!  Even though they are reproduced at the exact same scale here, they appear at least twice as tall!  I'm thinking that a cool layer of air formed over the water, and magnified the height of the island vertically.  At Christmas I observed them to float over the Sea (see link above), in a more complicated mirage effect, but this version was interesting too!  Both of these pictures were taken with the William Optics 11cm diameter F/7 APO (770mm focal length), with the moonlit image a 10 second exposure.

The next night found us near downtown Puerto Peñasco, at a popular restaurant with a spectacular view of the harbor and sea.  From our vantage point, even a casual look to the north showed an interesting mountain range.  The distant mountains were stretched vertically into a nearly impossible profile.  This shot was taken with the 70-200 zoom (set to 200mm), and is another example of Fata Morgana.  Taken again, shortly after sunset, it slowly dissipated over 20 minutes.

After taking the above mountain picture, I noticed another example to the west over the Sea of Cortez.  Here, with just the horizontal line of the sea marking the horizon, the vertical displacement due to the Fata Morgana is easily identified.  I actually took a time lapse of it, but likely won't display it (I didn't get the frame very level), but at right show how it dissipated in 30 minutes time - nearly, but not totally back to normal.

The interesting thing about all these examples of Fata Morgana is that they depend on stable layers of air at different temperatures, but for nearly our entire stay in Mexico the wind was blowing pretty steadily, and I would have predicted there would be too much mixing of the air to produce these effects.  But I'm glad I was able to see and document them.

Some of the finest examples of Atmospheric optics, as well as written explanations for their cause is at the excellent website by Les Cowley - Optics Picture of the Day.  He has some great images of Fata Morgana shown here and here...