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Won't You Lend Me a Telescope?


[Editor's Note: In November we asked if any club members who had spent time with one of the club loaner telescopes had a story to tell about their experience. Here are two stories from the SJAA loaner program. Do you have a story about your time with a particular telescope? Send it on to the Ephemeris! Email to: ephemeris@sjaa.net]

Using the H-Alpha Solar Scope Loaner

Steven Nelson

One of the enticements for joining the SJAA is the extensive loaner scope program. I had helped set up and run a loaner program at a club, so I know the work Mike Koop does to organize is often "behind the scenes." It is much appreciated!

I had used solar H-Alpha (Hydrogen Balmer-Alpha spectral line) systems before and was eager to test out the equipment. The system I was familiar with (at Foothill College) has an electric (line power) heater control of the "fine tunning" of the wavelength. These systems have extremely precise wavelength settings! The task of the special solar filter is to isolate less than 1 Angstrom of wavelength out of the sun's image. At a wavelength of 6356.5 Angstroms that 1 A will get you the emission line light of hot hydrogen gas blasting off the sun. These are the famous "solar prominences."

The SJAA filter controls the wavelength with manual tuning. A knob slightly tilts part of the precision optics. When I started observing, I found this much nicer to use than the electric system. I could "tune" the filter across the wavelengths while watching in the eyepiece. This allows very quick selection of the view you want. Once you are on the sun's image, there is not much temperature drift. Besides prominences (or detail surrounding sunspots) this system is good for sunspots. Just tune "off-line" and you get much more contrast for picking out small sunspots. This is because off-line you are looking at the "continuum" or temperature related part of the sun's light. Sunspots are much cooler in temperature, so you get less of this "continuum light" from sunspots than from the surroundings.

The equipment worked fine for solar surface work. The many elements in the optical train (red prefilter, doublet objective, internal tele-extender) tend to scatter light a little for prominences. Still easy to see brighter ones. The battery drive system is a bit primitive and tended to slip before I spent some time adjusting it. As you may have seen in an earlier Ephemeris - this system is very portable and I took it up to our Yosemite Park public program. The drive worked fine there.

One trouble in the teaching of concepts can occur with a solar scope: "It looks like fire." The H-Alpha line is extremely red light. A glob of hydrogen plasma blasting out of the sun looks a lot like a lick of flame. "I saw the fire burning on the sun" is a very natural response to seeing a prominence. I always try to precede a novice's view with a short review of their own experience with "emission lines" - yellow and blueish street lights and "neon" lights. The energy in these different colored lamps comes out as different colors, depending on the gas. Low-pressure sodium (yellow), mercury (blueish white), and neon (red) all glow when we put them in bulbs and add energy. The hydrogen on the sun glows brightly in red light when energy blasts it off the surface!

I don't even try to explain about the view directly on the "surface" around sunspots and filaments! Absorption lines, continuum bound-free emission from plasmas, thermal line-broadening, Dopler shifts, etc., really only have a place at the college physics level. Keep it simple (boiling and magnet line patterns)!

Starting with Ole Number 31.

Jamie Dillon

This started on a December night in 1998, when my boy Liam and I went on up the Peak with binocs and tripod. Figured we'd likely run into some stargazers, having noticed that there's a community of people who gather at such places. It was socked in drippy fog. First we ambled over to the observatory and met up with Robert Hoyle, who showed Liam, then 7, the sights. He said, "You guys haven't heard yet of TAC?"

By chance, just a bit later while we were sitting in the car in the main lot eating our supper, two cars came down in the fog from the SW lot, with Mark Wagner and Marsha Robinson. So we got some encouragement and a TAC address. A half hour down the line, other lights went by in the then dense fog, which later turned out to be Jay Freeman.

Signing onto the TAC list, within a day or so I got an e-mail from a certain Jim Van Nuland, who told me to join SJAA and get a loaner scope. Within two weeks, I'd gotten hold of Mark Taylor and Mike Koop and picked up an 8" f/8 dob. We dubbed it Oscar.

By 11 January we'd gone to our first star party, the one in fact where Marsha finished her first Messier survey. Looked at M31, M34, the Double Cluster and M42, as well as Saturn thru Oscar. Spent a solid hour trying to find M37, finally packed the effort in and mooched views thru Rashad al-Mansour's and Mark Taylor's scopes. Oscar has good clear optics but had a diagonal on the finder which I learned to cordially loathe.

Within a month we were propelled and bought our own scope from Lumicon, an 11" f/4.5 Celestron dob to be named Felix.


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