Astronomy Day - 1999
Astronomy Day: May 22, 1999
Clear skies all day and all night! A good turnout for a very exciting day.
Thanks to the following companies that donated items for our drawing: The Naturium (Silverdale Mall, Meade dealer); The Book Stop (Poulsbo, used books); and Eagle Harbor Books (Bainbridge Island).
A computer video camera mounted on the front of a Mars Sojourner model served for the Rover contest. Students watched the computer screen as the rover was driven toward the rock "Yogi", and directed it to stop attempting to get as close as possible without hitting the rock. The winner, a second grader, received a Planisphere as a prize. These pictures show the rover on the edge of the gravel parking lot ("Mars" had a little green grass on this day). Photos by Anna Edmonds.
The little ball on the rover is one of those cheap color digital cameras that people put on top of their computer monitor and use with NetMeeting. Paul mounted it (with a rubber band!) on the rover (which actually is a toy model and is battery powered, the solar panel is fake) and ran a cable to a PC. The PC screen was updated a couple of times a second, and by looking at the PC screen you could see "what the rover sees".
One difference from the real rover is that the real signals took about 10 minutes to travel from Mars to Earth, but we didn't program in a delay. Another difference is that the model is about half as long and half as high as the real sojourner rover. You can find two images of a NASA full-scale engineering mockup of the real rover on this page (the images have a soda bottle for scale).
The real rover ran onto a rock nicknamed "Yogi", and then it had to back up and try again in order to use its probe. A prepared handout explained it, using an image from the NASA web site.
Each student took a turn watching the PC screen and verbally instructing the "rover" (Paul with the control box) to start and stop, to see who could get closest to the rock without hitting it. Photos by Anna Edmonds.
The contest turned out to be pretty popular, although later that night "flying" over the moon by controlling the telescope hooked up to the video camera and laptop screen was even more popular (see pictures farther down on this page).
Maybe next year we'll get a radio controlled model constructed, or perhaps a model that can be programmed, and get a camera that has an infrared connection. Then the students could drive the rover around and we could have a driving contest.
The solar observing area is always popular on Astronomy Day. This year Jim Young set a gnoman up on the roof to add another interesting item, as we tracked the sun's shadow throughout the day. All day, a table out front was staffed with helpful volunteers who distributed handouts and sold raffle tickets, gave directions to the solar system walk, reminded folks of the potluck, and explained the schedule of talks held in the meeting room in the observatory.
Jared Barnhill getting set up in the morning. photo by Anna Edmond
left to right, Jim Vaughan, Gina Ritchie, and Bill Edmonds.
An array of telescopes were pointed at the sun and the moon.
Preparing for one of the talks held in the observatory.
That night, we held a Star Party. The Messy A Report tells the story from the viewpoint of one of our master gardeners who is a star party attendee.
The following 10 pictures are the cream from the night's (Astronomy Day 1999 Star Party) Moon Video.
These were taken using the Club's Vidicon on Dave Warman's Celestron GP-C8. He never had time to polar-align the telescope (we were busy answering questions from the crowd), so it spent its time trained on the moon, but drift was tolerable anyway.
Some of the shots using the teleadapter fully extended were taken by some of our younger attendees, probably without any supervision. Fortunately the telescope seems to have survived the experience; having the real time video feed at high magnification turned out to be a hit with the young ones. Dave bravely let them have the controller paddle to rove about the surface of the moon on their own, and showed them how to save a snapshot.
It is fairly clear which ones were taken at prime focus (they are the ones that are at low power, showing the curve of the moon). The others were taken using eyepiece projection, with an 18mm eyepiece. Some had the projection tube fully inserted, and the rest had the tube fully extended. (Dave was using the Universal Teleadapter from Orion). Weather was 55 degrees, wind 5 - 10 gusty, humidity was low. Perhaps because it was the first real Spring day, the seeing was markedly affected by thermals. It was especially illuminating observing these effects real time on the TV monitor.
(left)Crater Aristillus on left, Autolycus on right, crater floors in shade. East is up. (right) Mare Figoris to the right, Mare Serenitatis to the lower left, Montes Caucasus near middle of image. West is up.
(left) Crater Walter (a walled plain 132x140 km), with crater Aliancensis to upper left. (right) Vallis Alpes and Montes Alpes on the edge of Mare Imbrium.
(left)Flooded crater Caille to left, walled plain Purbach to right. (right)Walled plain Posidonius in Mare Serenitatis.
(left) Highlands, with Rupes Altai on extreme right. (right) Flooded Crater Cassini.
(left)Walled plain Ptolemaeus, with crater Herschel in lower left. Small crater Ammonius (9km wide) is on left side of floor of Ptolemaeus. (right) Crater Herschel with floor in shade, edge of walled plain Ptolemaeus in upper right. Southeast is up.
Knowing that the above images were taken between about 9pm and 11pm on May 22 1999, a few good exercises for those who might be interested:
- Identify as many craters as you can and have the energy for.
- Choose one that is shown with a nice shadow, and calculate meters/pixel image resolution of the moon's surface.
- See if you can find another one which was taken with the projection tube at the other end of its travel, and repeat the computation above.
- Starting with the photos, compute the height of some features, then verify them against the official info.
- Also compute meters/pixel for the prime focus case.
- Given a focal length of 2100mm, compute the limiting resolution of the telescope objective, or if you think something else was limiting state it and your reasons.
- For each of the three resolutions, compute the approximate eyepiece focal length that would be needed to observe with eyeballs at the same level of detail. A hint: an ultra-wide 35mm eyepiece has a field of view of about 0.7 degrees. A standard (super-Plossl) eyepiece of 35mm has a field of view of about 0.55 degrees.
All photos by Paul Below, unless otherwise noted.