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.


You can narrow your search of our equipment library by selecting any one of the below keywords.

Astrophotography Basic Binoculars Camera Dobsonian Go To Maksutov Newtonian Push To Refractor Schmidt Cassegrain

All our equipment is currently on loan to other members.

Available Eventually

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

DSLR with SCT Adapter

Newly added 11 days ago on September 12, 2020 (Saturday).

Loan ends in 32 days on October 25, 2020 (Sunday).

Older Canon XTi  DSLR camera body with T-ring and Adapter for attaching this camera to a Schmidt Cassegrain Telescope. Suitable for Lunar and Planetary photography.


ZWO ASI120MC-S Imaging Camera

Currently there are 3 requests to borrow this.


The ASI120MC-S is a color USB3.0 camera. primarily intended for planetary imaging, but it can be used for deep sky imaging with some limitations.

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: