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Manastash Ridge Observatory

The 30" Boller and Chivens Ritchey-Chretian telescope at MRO
The 30" Boller and Chivens Ritchey-Chretian telescope at MRO

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About MRO

Manastash Ridge Observatory (MRO) is managed by the University of Washington Department of Astronomy, and is located on a ridge above Ellensburg, Washington. The location of the site was carefully chosen to allow UW students reasonable access to the dry and dark skies available on the eastern slopes of the Cascades. Owing to its remote location, the observatory was built with its own water supply and accommodations sufficient for groups of students to stay for multiple night observing runs.

Underneath an Ash Dome sits a 30" Boller and Chivens telescope. They would look familiar to anyone who has used MRO since it was dedicated in 1972, but many other things have changed since then. Originally observers used photographic plates to record their images, but now we rely on computers and digital CCD cameras. You can read the history, and some of the best stories, on the MRO 40th Anniversary page.

Today we work to involve UW Astronomy undergraduates in all operations of the facility.

Our current instrumentation includes:

  • An Andor thermo-electrically cooled CCD camera.
  • A filter wheel (designed and built by UW students) with Sloan, Johnson-Cousins, H-alpha, and other filters available.
  • UW students also designed and built a new backend for the telescope which provides a mount for this equipment.

The observatory was built in 1971 at the initiative of George Wallerstein, the first chair of the UW Astronomy Department. Construction was funded by grants from the National Science Foundation, as well as by funds from the state of Washington. The current instrumentation was designed and continues to be integrated with the telescope by the Astronomy Undergraduate Engineering Group, thanks in part to funding from the UW Student Technology Fee (see Manastash Ridge Observatory Imaging Camera Upgrade). Along with funding from the UW Campus Sustainability Fund, this work will help ensure MRO is productive for years to come (see Conservation and Sustainability at Manastash Ridge Observatory: Planning For the Next Forty Years). Central Washington University generously provides us with internet access via a microwave link. 

Information for Observers

The 30" Boller and Chivens Ritchey-Chretian telescope, focal reducing optics, and the Evora science camera produce a field of view of 8 x 8 arcminutes and a plate scale (with 2 x 2 binning) of 0.93 "/pixel.

The observatory is located approximately 9 miles West-Southwest of Ellensburg, WA at an altitude of 3930' (1198 m), a longitude of 120.7278 degrees West, and a latitude of +46.9528 degrees. The facility offers a full kitchen and a grill. Although there is running (cold) water, observers should plan on bringing drinking water.

The observatory is usually open by mid-May and stays open through September. The observing class, Astro 481, has priority for much of the time from late June through the middle of August, but for other times please contact Oliver Fraser ( with your observing proposal!

Safety Checklist

  • Keep the gate locked so animals don't get trapped within the fence, and so you can choose who visits you.
  • First Aid kits are on the telescope pier and in the safety kit. You will find small amounts of over-the-counter pain medication, and even a snake bite kit, in the kitchen. The medicine cabinets in each bathroom have other supplies you may need.
  • In case of any accident, report it to the observatory staff.
  • Summer is wildfire season, and it's not unusual to see smoke on the horizon. If you feel concerned, call 911 and prepare to leave. For unconcerning fires, check the Northwest Fire Locations map (click on the fire for more information, including its outlook) and the Western Fire Chief's Association Fire Map (claimed to be updated quickly).
  • Once you have the name, twitter is a great way you to stay up to date (e.g. #riggscanyonfire, #lefthandfire) but you can also check WildCAD.
  • Smoke from distant fires isn't a safety issue, but does affect observing. You can check the Real-time Air Quality Index for Ellensburg.



Save your log of facility or telescope issues, any grocery store items that we need to buy (or need to stop buying!), and water tank levels each day. Measure your water use with the gauge marked "Inches of Water" mounted above the water pump, and confirm that exterior rainwater catchment tanks are draining.


Coming Soon!

Things to Do

Coming Soon!

Observation Procedures

Checklist available here.

Septic System

Our septic system is a secret superhero, but its superpowers are limited to naturally occurring materials (and toilet paper). Do *not* put wipes or anything else into the system, or else you may experience what life was like before flushing toilets.

Evora Crashes

The Evora GUI has a stability issue and you may find it crashes unexpectedly. If this happens run '$' before you restart. See the Evora Documentation for details.

Telescope Closure Conditions

Weather conditions can make it unsafe to operate the telescope and its instruments. Cover the telescope mirrors and close the dome if any of the following weather conditions arise:

  • Sustained winds in excess of 30MPH, or gusts in excess of 45MPH;
  • Humidity in excess of 95%;
  • (Temperature - Dew Point) < 5° F.

Weather data for wind speed and humidity are available from the wireless station located to the left of the control room monitors. Data for (Temperature - Dewpoint) are available from the same station. If sustained wind speeds exceed 20MPH, or you are experiencing gusts in excess of 35MPH, you should work with the telescope dome opening pointed downwind (away from the direction that the wind is blowing from).