Oakland Astronomy Club
McMath-Hulbert Solar Observatory Tour

The OAC occasionally organizes tours of various astronomical points of interest for its members. One such tour was of the historic McMath-Hulbert Solar Observatory in Lake Angelus, Michigan. Construction on the observatory began in the late 1920s in partnership with the University of Michigan. By 1936, it was considered to be the second-best solar observatory in the world. One of the most significant achievements at McMath-Hulbert was the production of the first time-lapse motion pictures of the sun using a home-brewed device called a spectroheliokinematograph. Research continued at the site until the late 1970s, when it was sold to private individuals.

The site is currently being restored by The McMath-Hulbert Astronomical Society. OAC members Tom Hagen and Richard Champine are part of the restoration team, and have made significant contributions to getting Towers #1 and #2 operational. The observatory is no longer open to the public.

The observatory consists of three towers, each containing different instruments. This picture shows Tower #1, home to a 6" refractor. This tower is the shortest of the three at 30 feet, and was the first one built at the site in the late 1920s. It's currently in working order.

Here's the 6" f/12 refractor that resides in Tower #1. This scope had one of the early Hydrogen-Alpha filters as part of its instrument array to deliver enhanced views of solar activity, such as flares and prominences. Unfortunately, that filter has been lost over the years. The mount restricts the declination travel of the scope to near the ecliptic due to its original role as a solar observing tool.

Tom Hagen points out key features of Tower #2's coelostat, a 22" flat mirror and associated hardware that acts as the primary for this tower's instrument. The coelostat tracks the sun over the course of the day, reflecting raw sunlight on to three other mirrors and a lens, which channels the beam into a spectroheliograph. Tower #2's entire instrument system was nearly functional at the time of the tour.

Tom is a member of both the McMath-Hulbert Astronomical Society and the Oakland Astronomy Club. Tom has been spending many Sundays, often late into the night, at MHSO working towards restoring the historic site. "It's a real labor of love" says Tom.

Tower #2

Tower #2 is the middle tower, standing 50 feet high. This tower contains a coelostat, which acts as the "primary" for its spectoheliograph instrument. Solar movies were made in this tower from 1936 onward.

OAC Members in Tower 2

Mark & Alex Webb look on as Tom Hagen explains the workings of Tower #2. The tower is also home to this 12" f/15 Maksutov-Cassegrain telescope built by renown telescope maker, the late Max Bray.

Tower #1 Dome and 6" Refractor

Close-up of Tower #1 and its 6" refractor. This tower and telescope are functional, though a replacement Hydrogen-Alpha filter is sought by the restoration crew. The earliest movies of the sun were made in this tower with a 10" Cassegrain and the spectroheliogkinematograph.

Tower #3

The top of tower #3. Tower #3 is 70 feet high, and contains another system of mirrors that channel sunlight into a vacuum spectrograph. In this case, the spectrograph is located at the end of a 50 foot vacuum chamber. The vacuum eliminates contamination of the sun's spectrum by earthly airborne particles. This tower and its instrument are not operatonal.

That thing in the middle

That thing in the middle

Mirror Aluminizer

The copper colored cylinder is an aluminizing chamber. This device was was used to apply reflective coating to observatory mirrors.

Images © 2000 Oakland Astronomy Club

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