Tom Jonard, Astronomy Student

I took a part-time job during my second year as a student assistant in the Department of Astronomy and worked in the astrometry program.  The Department ran the second largest (in terms of data gathered) astrometry program in the U.S.  In this program the distances to the nearest stars were measured using trigonometry based on parallax.  It is the only method of directly measuring the distances to stars and is an important baseline for other more inferential methods.  The number one astrometry program in the U.S. was the one at Allegheny Observatory in Pittsburgh.  Dark skies are not particularly important for this work, as the closest stars are also the brightest so both of these observatories still engage in this work.  Traditionally long focal length refractors are preferred for this work and having libraries of photographs taken by the same instrument over long periods of time are invaluable.

Dr. Oswalds ran the astrometry program.  Each night was divided into 3 shifts and student assistants would rotate through this schedule.  Before your shift started you had to verify that it was clear and then climb Mount Jefferson just behind the new (then) dorms.  Climb was the operative word because we had no cars and it was too steep for a bike either going up or coming down.  Fortunately this was less a mountain than an oversized hill.  The third shift was the hardest because you were almost always asleep and had to wake up for it.  You could stay up for the second shift but not for the third.  Of course in a dorm with others (roommate too) not on this particular crazy schedule there was no possibility of sleeping before an early shift or not disturbing someone when arising in the middle of the night.

The work basically consisted of taking photographs of star fields at the prime focus of the telescope, acquiring the field, noting the time of the exposure and the condition of the sky.  We took three exposures of each field on the same plate and three fields on each plate.  This was done to save on the cost of plates which were 12” X 14” glass covered with photographic emulsion.  The way we kept things straight was to stagger the exposures for each field in a unique way.  The first field might be staggered horizontally.  The second vertically.  And the third diagonally.  In this way the person measuring the positions of the star images could distinguish all 9 exposures on the same plate.

The glass plates were taken from a supply kept in the dark room and mounted in a metal box by the assistant.  It was done entirely by touch and they had to be mounted emulsion side (sticky side) up!  This box attached to the back of the telescope with four screws.  The “shutter” was the front side of the box, which was pulled out to start the exposure and put back to end it.  During an exposure the student assistant looked through a secondary eyepiece and made constant adjustments to the position of the telescope.  This was necessary because while the telescope’s drive was designed very precisely to follow the stars it was not perfect.  Perfection was achieved by watching a “guide” star in the secondary eyepiece and adjusting as it drifted back and forth in response to minor irregularities in the drive.

In addition to the exposures and bookkeeping we made sure the dome slit was in position and that the telescope did not run into the pier it was mounted on.  If you didn’t do the former the telescope which was following the stars might end up trying to “see” them through the roof rather than the opening of the slit.  In the second case limit switches prevented the drive from damaging the scope by driving it into the supporting pier (the telescope could not move from the east side to the west side of the pier while pointed to most parts of the sky – a “feature” of the style of mount known as a German Equatorial).  Nevertheless it was disconcerting to be in the middle of an exposure and suddenly hear the sound of the little motor that unlocks the drive while the guide star starts to rapidly drift across your field of view!  Hopefully you remembered where you put the shutter and also don’t get so excited reaching for it that you knocked it to the floor.

Assistants who started the first shift also opened the observatory.  Those who worked the third closed it.  We worked alone.  It was astronomy the way astronomy was done in the late 19th and early 20th centuries – real hands-on stuff in unheated domes.  Today astronomers can remotely access telescopes on other continents.  On site crews are still needed to make sure they don't try to open the dome when it is raining but aside from an occasional peek outside they are usually confined to comfortable control rooms lined with computer monitors.  And astrometry is done from satellites much more accurately and quickly than ever before.  As a matter of fact before Hipparcus (the first astrometry satellite) only some 2,100 stars had been measured with programs like that at U.Va.  Hipparcus did 100,000 in 3 years.

If I had known that a revolution in accessibility was in store I might have stuck with the field longer.  As it was walking down the road from the observatory one evening I had the thought that this is what I would be doing with my life when others were out enjoying concerts or just sitting at home or sleeping.  It suddenly seemed a lot less appealing and in it made other factors that would prevent me from going into the field (I wasn't doing well in Math) seem more palpable.

Now I volunteer to stay up late at night and show others the stars as a hobby.