Springfield Schmidt-Cassegrain Telescope (SSCT), a compact portable fixed eyepiece telescope that can be constructed in a modest shop using readily available parts
Nasmyth focus for camera works at f/7.2 (f/6.4 for an eyepiece)
Fixed eyepiece(Springfield) used visually works at f/10 to F/11
The above drawing shows the generic SSCT which can readily be configured as a Springfield, Nasmyth (for camera), stock SCT, or SSCT with transfer lens for a warmed room.
Designed for quick setup on portable tripod and it’s a joy to use!
This Springfield telescope evolution modernizes the design for portability, with light pollution being a motivating factor. The modern SCT makes this possible. Quick, tool-free setup is a design goal.
The joys of being seated, holding comfortably onto a stable eyepiece can’t be overstated. This makes brighter viewing due to the ease of holding the user’s pupil precisely over the scope’s exit pupil. Nothing ruins your ability to see like having to twist and strain to look through the eyepiece. A user friendly telescope having a fixed eyepiece and capable of having the observer in a warmed room. A real godsend to those in wheelchair or with muscle deficiencies.
Russell Porter invented his famous fixed eyepiece telescope(later named Springfield) about 1920, but he died before the evolution of the popular SCT. This document shows how easy it is to modify a SCT tube assembly for use with a Springfield mount. The Springfield mount, like all others, can be simple or complex. The most simple is made from pipe, see "The Turn-on-Threads 8" F8 Porter Springfield", easy to make Springfield(40% down page). The state-of-the-art design now would be direct drive(no periodic error, or backlash) with control by planetarium on an iPad.
SSCT tube showing camera on Nasmyth light path location near OTA center of gravity. For a balanced Springfield, a hole is required in baffle and main tube. The previously used overhead counterweight is now gone, important for safety reasons.
SSCT, Portable Springfield Telescope - 2 min put away, 3 min setup at home, 15 or 20 minutes away from home.
Shown here is a DSLR camera attached to the Nasmyth port. In this case the f ratio is f/7.2.
Switching between the Springfield eyepiece and camera port only takes a few seconds.
Link to Flickr set (photo blog) : http://www.flickr.com/photos/edhiker/sets/72157624186145557/
Web page with SSCT details and variations: http://edhiker.50webs.com/ssct.htm
Useful internet search words: SSCT, “fixed eyepiece”, “Russell Porter”, “Springfield SCT”, edhiker, Johnson SSCT, SSCTelescope
I place this telescope concept in public domain for non-commercial use, Springfield Schmidt-Cassegrain telescope, SSCT.
Email Ed Johnson at: SSCT@edhiker.com
Edit Date: 10/6/10 by Ed
This page is: http://edhiker.50webs.com/SSCT_flyer/SSCT_flyer_of_100918.htm