Celestron C9-1/4 Telescope Systems
By Chuck Hawks
Perhaps you or some of your friends have an 8" Schmidt-Cassegrain telescope (SCT) from Celestron, Meade, Orion or the equivalent and you would like to try something a little bigger. However, you have read on Astronomy and Photography Online and elsewhere that an 8" SCT is about the biggest telescope that is reasonably portable by one person who is not a fitness freak and you would rather spend your time observing than setting-up. 11" and 14" SCT's are notorious for being awkward to transport and set-up, and portability is a requirement for driving to the local dark sky location.
Enter the 9.25" SCT. The rationale for this size telescope is that it is between the 8" and 11" SCT's in physical size and weight. For comparison, a Celestron EdgeHD 800 optical tube weighs about 14 pounds, while an EdgeHD 925 optical tube weighs 21 pounds. The next step up, an EdgeHD 1100 optical tube, weighs 28 pounds.
It is a truism among amateur astronomers that aperture rules. After optical and mechanical quality, clear aperture is the single most important factor determining what you can see in the night sky. If you can stretch the upper limit of portable telescopes from 8" to 9.25", you can increase the light grasp from 843x to 1127x times that of the unaided human eye.
The least expensive way to order a Celestron 9-1/4" SCT package is on the CG-5 go-to German equatorial mount, in the form of a C9 ¼-SGT (XLT) #11046-XLT. The same scope is available on the larger CGEM go-to German equatorial mount as the CGEM 925 #11098. If you want the flat-field EdgeHD 925 telescope package, it is the CGEM 925 HD #11081 on the same mount. (Illustrated at left, courtesy of Celestron International.) This is probably the optimum 9.25" telescope/mount system for visual astronomy. It is worth noting that standard C9 1/4 telescopes come with a gloss black finish, while the EdgeHD 9.25 scopes wear a striking ivory pearl finish.
Alternatively, either telescope can be ordered sans mount as an optical tube assembly (OTA). The standard C9 OTA is the C9 ¼-A XLT (w/CG-5 mounting rail) #91020-XLT, while the HD version is the EdgeHD 9.25 OTA #91040-XLT. If you prefer to choose your own mount, or simply want to avoid a go-to mount, this is the way to go. However, it is usually more expensive in the end.
With telescopes of this size, 2" mounting diameter oculars begin to make sense and Celestron provides their EdgeHD 925 scopes with a 2" star diagonal and 2" Axiom 23mm eyepiece. The standard C9 ¼ models come with 1.25" star diagonals, but are easily upgraded to accept 2" oculars with the addition of a Celestron 2" XLT diagonal #93527 ($129.95 from Orion). Celestron states that, "The 9 ¼" was specifically designed for visual infinity focus when using 2" eyepieces."
The Celestron 2" Eyepiece and Filter Kit ($249.95 from Optics Planet) includes a 2" star diagonal and three moderately priced E-Lux (three element) oculars of 26mm, 32mm and 40mm, as well as a set of five colored Wratten filters and an aluminum hard case. This is the cheapest way to get into 2" eyepieces. A better, albeit more expensive, way to acquire oculars is to buy higher-grade eyepieces individually, along with a hard case in which to carry them. That is the approach used for the following lists.
The accessories listed below are applicable to any of the Celestron C9 ¼ telescopes, as well as the Orion SkyView Pro 9.25 (made by Celestron for Orion). The C9 ¼ (non-EdgeHD) scopes come with 1.25" star diagonals; you do not need to purchase 2" oculars unless you choose to do so. I am assuming that if you are buying a 9.25" telescope, you already have the required general observing accessories, such as a red flashlight, sky map, observing chair and so forth. The prices that follow are quoted from Celestron, Optics Planet and Orion Telescope in 2010 U.S. dollars.
Here is a sample EdgeHD 925 telescope system with 2" eyepieces
Here is a sample C9 ¼-SGT (XLT) telescope system with 1.25" eyepieces
Copyright 2010 by Chuck Hawks. All rights reserved.