Equipment Library

The Seattle Astronomical Society maintains a library of small and medium size telescopes that may be checked out for a period of 1 month by members in good standing. If you are new to astronomy, this is an excellent way to learn how to use a telescope and to begin viewing the wonders of the night sky, without having to invest immediately in a telescope of your own. To check out a telescope, please check out our equipment available for loan.

If you have any questions about borrowing equipment, or do not see a specific piece of equipment please reach out to our Equipment Manager.

See the complete equipment list in alphabetical order.

Available Immediately

The following list of equipment is immediately available to borrow.

Celestron Echelon 16x70 Binoculars

Currently there are 3 requests to borrow this.



Large-aperture astronomical binoculars are designed for viewing .star clusters, nebula, and galaxies. 16x magnification is sufficient to provide good views of many deep sky objects, It will provide pleasing views of the moon , and will show Jupiter and it's four Galilean moons. 

Celestron Echelon binoculars sport high quality 70 mm objective lenses made in Japan. BaK-4 prisms provide good contrast and sharpness, and all air-to-glass surfaces are multi-coated with Celestron’s proprietary XLT anti-reflection optical coatings.


Available Eventually

The following list of equipment is currently loaned out to a member, and may include other members waiting to also borrow.

Orion Resolux 10.5x70 Astronomy Binoculars

Currently there are 2 requests to borrow this.


Large-aperture astronomical binoculars are intended for viewing star clusters, nebula, and galaxies. 10x magnification will provide good wide field views of larger deep sky objects such as the Great Orion Nebula and the Pleiades star cluster. At a dark sky site it will provide good views of Milky Way star fields and larger objects such as the Andromeda and Triangulum galaxies (M31 and M33). 

Like any binoculars, the Resolux 10.5x70 will provide pleasing views of the moon.

The Orion Resolux binoculars feature BAK-4 prisms and anti-reflection multi-coatings on all optical surfaces. The eyepieces focus individually and provide 18mm or more of eye relief They.have a 5.0-degree field of view.

A binocular tripod mount is provided in the SAS loaner package, but these 10.5x70 Resolux binoculars are hand holdable for short viewing sessions, especially if you can relax in a reclining lounge chair (not provided) while stargazing..  

All our equipment is in good condition!

Telescope Types

Types of telescopes

Copyright NIAAS, North Ireland Amatuer Astronomical Society

What are those numbers?

Types of telescopes

Copyright 2008-2012

The f-ratio is the focal length divided by the diameter of the telescope. Magnification is the focal length of the telescope divided by the focal length of the eyepiece.


To find the f-ratio of a telescope 10 " in diameter with a 45" focal length:

Divide 45 " F.L. by10" D. to get an f-ratio of 4.5.

Compute Magnification

First, convert focal length to mm: 45" = 1146 mm, then:

1146 mm focal length divided by 35 mm eyepiece equals 33 magnification.

More Information

If you are interested in learning more about telescopes, we recommend: