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  • Tom

Technical Projects and Volunteering at Mount Wilson Observatory

Updated: Feb 20

(The mighty Hooker Telescope Dome on the night of October 7th , 2023 100 years since the 1923 VAR! Plate. Andromeda is located to the right above the dome.)

This is going to be a bit longer of a blog post than usual so I hope it's not too much to digest but I really wanted to share and hope some find it interesting.

Firstly I need to start this post with the the 100 year anniversary (10/6-7/2023) of the VAR! Plate which was made during observation/imaging on the night of October 6-7th 1923, a big deal for Mount Wilson Observatory and for our understanding of our place in the cosmos. This plate was made by Edwin Hubble and is of a Cepheid variable star in the Andromeda Galaxy which proves that the Andromeda Galaxy is indeed millions of light years away and not contained inside our own galaxy making the cosmos a lot larger place than previously thought.

Cepheid variable stars were discovered by Harvard Computers (Astronomers) which was a team of women astronomers most notably in the discovery of Cepheid variables was Henrietta Swan Levitt. They serve as cosmic lighthouses and give astronomers the ability to calculate distance given the huge scale of the cosmos where other methods are not well suited for.

(From the left, Henrietta Swan Levitt, the VAR! Plate, and Edwin Hubble)

Since 2016 I have volunteered my time at Mount Wilson Observatory as a photographer for events which I feel so fortunate to have had the opportunity to do so. This past year I signed up to volunteer for events and to help with technical projects at the observatory and it's been an amazing experience so far!

(Attendees of a telescopes and talks night lining up for the public viewing through the 100in Hooker Telescope)

By all accounts the past viewing and events season has been a great success with very good attendance and interest. There were a couple talks and events I attended and volunteered for which were great.

I got to hear Bethany Ehlmann speak about the Lunar Trailblazer mission which is going to be a crucial tool in determining the water content of the moon. During this talk in the Q&A when Bethany was asked about the challenges they faced when building the spacecraft she discussed the problem of tin whiskers, something I never heard about before her talk. More info on that can be found here.

I also attended Brother Guy’s talk on Discarded Worlds: Astronomical Ideas That Were Almost Correct. A fascinating depiction of the ways in which humans interpreted astronomical observations and how they used them to base their conclusions, which were sometimes, or often times, incorrect or incomplete. I think the message in this talk really rang true to me especially when you think about our current incomplete understanding of the universe, for instance dark matter/dark energy, just to name a few examples.

 (Inside the dome with attendees of the talks and telescopes lining up to view through the 100in Hooker Telescope)

I also volunteered for a concert in the dome performed by the Los Angeles Reed Quintet, working to direct traffic and greet guests to the observatory. I was lucky enough to be able to attend the second concert that day and the experience was truly amazing. I really want to attend more next year. I also worked in the same capacity for a talk given by Hal McAlister about the CHARA Array up at the observatory.


(Attendees of the talks and telescopes night lining up outside the 60in telescope dome)

In addition to the events and concerts this year up at Mount Wilson Observatory, Bill Leflang the Lead Engineer for the observatory and Tom Meneghini the Director of Telescope Operations assembled a group of technical volunteers, myself included, who spent many days working on various projects to keep the observatory functioning.

(Bill Leflang demonstrating the telescope controls to the technical volunteer group)

The first task we tackled was to fix dome rotation slippage that was occurring with the 60in telescope dome. Basically, when you would move the dome either left or right in some cases the dome would not move ! You can imagine how this is a problem when trying to run an observing night.

To understand what was occurring a brief description of how the dome rotation mechanism works is needed. The dome rotates by way of a metal cable that is gripped by 60 cast iron grippers spaced evenly along the dome circumference. This cable is driven by a motor on the first floor that worked through a gear reduction system and then to a pulley system. The group looked at possible issues and causes. When this issue was first witnessed several years ago a fix was put in place to shore up grip in the grippers by adding material inside the grippers. Rubber was mostly used, and the grippers were scored and then had adhesive used to attach the rubber to them. This worked for a time, but the rubber was starting to come off and the slippage problem appeared again. Our group then ran tests and made observations as to what could be the cause, we also searched the library archives of the original observatory plans.

Based on this we were able to see that the original design used a clutch system to ramp up the speed slowly so that when the motor was activated the cable didn’t go from a stop to very quickly full speed. The original design was not in place and at some point, when upgrades were made to the observatory a soft start device was used to safely ramp up the speed of the motor. This device had failed and was bypassed. Our group made the determination that indeed this lack of control of the speed/acceleration/deceleration of the system was the root cause of the slippage. Basically, the cable was yanked hard at first and the grippers couldn’t hold. Much like how a rope is pulled quickly out of your hand as you clench it if it’s pulled quickly enough. (don’t try this at home unless you want rope burns lol).

(The technical volunteer group that worked on the VFD drive implementation (located in the boxes in the center), from the left, Colin Conley, John Thompson, Tom Masterson (me!), Michael Lichtenberger, Bill Leflang, and Shawn Chatman)

Based on this determination our group suggested using a modern Variable Frequency Drive to control the power delivered to the motor that would allow us to set whatever parameters we would like. Through the summer our group worked step by step to implement this VFD into the system and the Friday after Thanksgiving this past year we finally were able to test it and it worked!! The slippage was not observed as had been before and the strain on the cable seems to be greatly decreased.

Some more tests and phases to this project are going to be done over the next couple months during the offseason in the hopes of having it operational for the summer of 2024.

(Members of the Kollmorgen Servo Motor technical volunteer group inspecting the 100in Telescope, from the left Chris Barrus, John Thompson, Bill Leflang and Mariah Birchard)

I also worked with another group to put in safety barriers in the 100in telescope observatory, and to tackle a major issue with the mercury pump on the north tower of the HA/RA bearing, a group that would be in charge of knowledge about the Kollmorgen Servo Motors, another group that would be working to sell old equipment from the observatory and a couple other projects. The one thing about a telescope observatory is that there is never a lack of things to work on! More on that as these projects progress in the future.


Needless to say, it has been an amazing opportunity to work as a volunteer for the observatory this past year. I’m really looking forward to what 2024 will bring 😊


C L E A R  S K I E S




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