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The Webfooted Astronomer - June 2001


New Rattlesnake Lake Observing Site Opens to SAS Members

By Greg Donahue

THE Seattle Astronomical Society (SAS) has recently concluded negotiations with the City of Seattle Cedar River Watershed and the North Bend Sheriff's Office for use of a new observing site at Rattlesnake Lake. This site is separate from the turn-around/cul-de-sac site that many of us have used for years.

The new site: backside of the lake

The new site is at the back (northwest) side of Rattlesnake Lake, behind two locked gates. The SAS now has combination locks on both those gates. Unlike the turn-around site, access to this new site is carefully controlled. There are three main requirements for using the new site:

  • You must read and sign a copy of the Use Agreement, and agree to abide by its terms, at which time you will be given the combination to the locks.
  • You must agree to park only in the lot that is outside of both locked gates, and not at the back of the lake.
  • You must prominently display an SAS ID tag in your vehicle's front windshield.

The SAS Secretary, Greg Donohue, will have copies of the Rattlesnake Lake Use Agreement and SAS ID tags at the monthly general meetings.

The back side of the lake offers darker skies and lower horizons to the east. Those who have used the turn-around site are aware of the sky-glow from Seattle. In addition, there are now two motion-sensitive streetlights at the turn-around. There are no lights at the back side of the lake, and Rattlesnake Ledge blocks the sky-glow from Seattle.

Use of the new site is a privilege granted to us by the Cedar River Watershed. The site is environmentally sensitive, so it is important that members follow all of the terms of the use agreement carefully. Failure to do so by one member may result in closure of the site to all members. You will be given a copy of the Use Agreement, so be sure to leave it in the glove box of your car for reference when you use the site.

Finally, if you do use the new site and happen to run across one of the Watershed personnel, please take time to thank them for opening this site up for astronomical viewing. In a time when many officials are placing more and more restrictions on public access, the folks at the Cedar River Watershed are bucking the trend. We need to encourage such behavior both by expressions of our thanks, as well as by respecting and following the guidelines for use of the site.

The old site: turn-around/cul-de-sac

SAS members may continue to use the turn-around site for observing. However, you should be aware of these new guidelines:

  • An SAS ID tag should be displayed prominently in your front windshield. This helps the Sheriff's department, charged with patrolling the area, to easily distinguish those who are there for astronomical viewing from others who have no business in the area after hours.
  • Officials at the Watershed have indicated that we may disable the lights in the turn-around. Since the lights are 9-10 feet off the ground, you will need at least a six-foot stepladder to reach them. Please be careful, and do not climb the light poles themselves to disable the lights.
  • You can disable the lights by wrapping heavy-duty aluminum foil around the two motion sensors. The lights go off about 5 minutes after you cover the sensors. Alternatively, you may place a large bag or sack over the lights, as they are not high temperature fixtures. This will probably require a taller ladder though.
  • These lights illuminate the locked gate at the end of the cul-de-sac. So, if you do cover the lights, it is your responsibility to watch for and warn on-coming motorists about the gate. Please be sure to uncover the lights when you leave the site.

If you have any questions about use of either site at Rattlesnake Lake, contact Greg Donohue by e-mail at, or by phone at (206) 701-2097 (work) or (425) 487-2187 (home).

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