Geissberger Observatory, Panorama


Forecast and Current Conditions for the Geissberger Observatory.



The Saint Mary's College Geissberger Observatory is the vision of the Prof. Ronald P. Olowin (1945-2017), and was created with a generous gift from the Geissberger family in memory of Norma Geissberger.

In 2017, with undergraduate researchers Katherine Damiano and Justin Robinson the observatory took its first steps toward differential photometry of variable stars beginning with eclipsing binaries. Thanks to additional gifts in memory of Prof. Olowin, in 2018 an upgrade of virtually all of the astronomy equipment used for both teaching and research was undertaken.

Today, the observatory's largest instrument is used to record exoplanet transits, and its current local team consisting of Brian Hill and Ariana Hofelmann is part of the Transiting Exoplanet Survey Satellite (TESS) Follow-Up Observing Program. For a brief introduction, see the video produced by Haley Nelson of the College's Communications Office: Summer Research: TESS Follow-Up Observing Program.


Thanks to the aforementioned gifts, the observatory is blessed with four Stellarvue 102T and two Stellarvue 115T refractors, a Questar 7 Maksutov-Cassegrain, and in its dome, a Meade 0.4-meter Schmidt-Cassegrain. Below, two members of the Saint Mary's community study Jupiter rising in the southeast at the beginning of a May, 2018 astronomy night. The Stellarvue 102T they are using is riding on a Losmandy GM8 mount affixed to one of the observatory's six permanent outdoor piers.

Photo Credit: Brian Hill

In the dome, the imaging train on the 0.4-meter is an Optec TCF-S3i with an Optec NGC 316 0.75x reducer/flattener. These are followed by a Starlight Xpress Mini USB filter wheel with an integrated holder for a Starlight Xpress Lodestar X2 autoguider. The filter wheel contains an Astrodon Clear Blue-Blocker and 2nd-generation Sloan g', r', i' and z' filters, all made by Optical Structures Inc., and at the end of the train is a ZWO ASI 1600 MM-Cooled CMOS camera. Calibration is performed using a Gerd-Neumann D420 Aurora flat-field panel.

The 0.4-meter rides a Paramount ME which has been upgraded to Software Bisque's current-generation MKS 5000 electronics. Controlling the entire system is the latest build of TheSkyX running on macOS.

Photo Credit: Gerry Serrano

For further details about how this equipment will be used to record exoplanet transits for the TESS Follow-Up Observing Progrm (TFOP), see the presentation by Ariana Hofelmann and Brian Hill at the November, 2018 meeting of the American Association of Variable Star Observers: Stepping Stones to TFOP: Experience of the Saint Mary's College Geissberger Observatory (YouTube, Slide Deck).


The campus and observatory are located in Moraga, California which is east of Oakland and the first range of the East Bay’s coastal hills. These hills delay the arrival of the coastal fog that the Bay Area is well-known for. The dome is at 37° 50' 21.1" N and 122° 6' 8.7" W, and at an elevation of 277 meters.

On the satellite view below, the Geissberger Observatory Pad is at center-right and the Geissberger Observatory Dome is at upper-right. The satellite view is sufficiently detailed to show the outdoor piers at the Observatory Pad. Clicking on the satellite view opens Google maps.

Image: Google Maps

The pad is in a slightly protected position and has good horizon except to the east where targets must rise to about 25° to be visible. The dome is situated on the top of a small hill that is far enough from nearby hills so as to be limited principally by airmass in choice of targets rather than any obstruction. Relative to a major city, Moraga is about 16 miles east-northeast of San Francisco. During standard time, local time is UTC-8, and during daylight savings time, local time is UTC-7.


For questions about the Geissberger Observatory, please email Brian Hill.

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