This discussion arose peripherally to the North Pole discussion.
John Denker mentioned being able to find celestial objects by knowing where to look relative to easily observed stars. Bernard
Cleyet correctly referred to this as star hopping and mentioned how difficult this can be when you live in an area with "poor sky."
Poor sky is definitely my situation. Personally, this is complicated by vision imperfections that used to be fairly well corrected
by good rigid contact lenses that had to be abandoned when presbyopia caught up with me. However, even though many students see
better than I, many students do not. No amount of "see that bright star there... now move up and to the left about two hand
widths..." seems to get them to see things that even I see.
Because I teach at a small college (1100 students) and my astronomy class typically has 15 students enrolled, we can have a fairly
intimate, profitable, and fun lab experience if it isn't raining or snowing or doing something else downright miserable. Our goal
is to get outside and look at things about 2 or 3 hours per week. Sometime this is all at once and sometimes it is for an hour at 2
or 3 different times. Sometimes we do it during the day. I am quite surprised how flexible the students are. There are a few
whiners, but that is minor.
I do this in spring semester (for reasons unrelated to astronomy) so we start in January. We don't have an observatory or even any
type of shelter when we go out. One day early in the term (i.e. last January) we carried a surveyors transit into a field so we
could try our hand at measuring some angular separations and see how parallax can be used to determine distances. A snow squall
came up and we could barely see some of the trees, telephone poles, etc. that we were using for "reference points" and "unknown
points." We had to keep wiping snow off the transit lens, and our notebooks were getting wet and also blown all over the place. At
this point students preferred vanity over common sense and many did not have hats and gloves and their coats were chosen more for
style than warmth. (For subsequent labs this eventually improved.) We finished the lab, although I remember being worried that
some students might get sick and others might revolt. Surprisingly, many students looked upon that as one of many high points and
like to tell about it, as I am doing now.
Of course the supreme high point last spring was when we went out at sunset in late April, with the best weather we had all term,
and saw five planets all lined up along the ecliptic. We did this complete with a chili supper.
I think it is important to teach the students as many different observing techniques as I can. Star hopping ought to be the
easiest, but it is by far the hardest. We have a nice 10-inch Dobson telescope. Students working in pairs have to find something
with that scope. Aside from planets, we can find the Orion Nebula and that is often it. What it boils down to is, if you can't see
it in the finder scope, or there is a nearby star you can see in the finder and the desired object is close enough that you don't
have to move more than one finder field of view... you're not going to find it. We have so much water vapor and so much light
pollution that Andromeda Galaxy is not usually visible with the naked eye, and also typically not visible in a one-inch finder
scope. I want students to learn how star hopping works using this 10-inch Dobson, but they mostly find it a frustrating experience.
We also have a couple 6" Newtonians and also a nice 4" refractor all on equatorial mounts with usable (but not so good) setting
circles. I personally have a Meade ETX (pre-computer) that has pretty good setting circles. Students working in pairs must take
one of these, polar align it, then use the setting circles to find something. This is tedious and takes some understanding, but in
the end it it less frustrating than star hopping. A neat thing we did this way was find Venus in the daytime sky (not at sundown,
but 1:00 in the afternooon). We used my ETX, polar aligned it with a level and compass, put a solar filter on it and calibrated the
setting circles by aiming at the sun, then used the setting circles to move the appropriate offset to Venus. This method put Venus
into the finder scope, but it is just a small speck against the bright sky, and many students had trouble seeing Venus in the
finder. However, some of us could, so we could use the finder to center Venus, and then everybody was able to see Venus throught
the main scope (when we remembered to remove the solar filter).
We also have an 8" Meade LX200, a 5" Celestron Nexstar (both schmidt-cassegrains), and a 90mm Celestron Nexstar (refractor). These
are all computerized "goto" scopes. Students, working in pairs, have to align one of these scopes. They can take the 90mm ($300)
out on their own at any time to practice, then they show me they can do it either with that scope or with the 5" ($1300) or the 8"
($3000). Everytime we go out with the expensive goto scopes I have different students help me align them. These goto scopes allow
us to find things quickly that would take a long time to find by star hopping. If it's cold out, students won't wait very long
while you try to find something. These goto scopes have made a big difference when the goal of the lab is to see a specific set of
celestial objects in a particular viewing session.
Sorry to be so long winded, but I had to rise to the challenge that John Denker threw out about learning astronomy by going and
looking as opposed to learning it from a textbook. I think my students are getting a superior lab-based astronomy experience. But
it is really hard to do this in Ohio. It takes lots of patience, lots of time, and lots of luck with the weather. It is also
difficult with big classes. Last spring I had 16 students, and that was plenty. I am not sure how many more years I will be
willing to trek out through the mud or snow, carrying a bunch of equipment, and longing for the cup of coffee or hot chocolate that
awaits our return. Well... sometimes we take the coffee and chocolate with us.
If this posting were the position of everyone, we'd be in utopia, but it would probably be boring.
Michael D. Edmiston, Ph.D.
Professor of Physics and Chemistry
Chair of Sciences
Bluffton College
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu
This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.