Celestron C-9.25 Inch (235mm) Aperture Schmidt-Cassegrain Telescope

We at Company Seven regard the larger cousin of the 9-1/4" telescope (the Celestron CG-11 telescope) as possibly the best value in a serious, yet one man transportable telescope in astronomy today! Ideally, this CG-9-1/4 telescope will fill the niche between the Celestron 8" models and the CG-11 telescopes more so for those who aspire to do serious astrophotography. This system is a good choice for those who require a relatively compact, and easily manageable system or for those who intend to employ the telescope German Equatorial mount with other optical tube assemblies.

The mating of a Celestron telescope with a Losmandy made German equatorial mount proved to be a successful formula with the CG-11 telescope. Celestron had Losmandy manufacture a variant of the Model GM-8 mount, termed the GM-9-1/4, it incorporated some cost cutting features. But our preliminary evaluation of the CG-9.25 has not been as favorable due to the unsteady Chinese made tripod and tripod to mount head interface that Celestron has furnished with the telescope. As Celestron was concerned about maintaining a certain price level, and as the other dealers and customers had made few adverse comments, we did not expect to see substantial improvements. Ultimately Celestron discontinued this CG-9.25 system and now offers even less sophisticated mountings which we find to be inadequate.

Regardless, Company Seven does offer the Celestron 9-1/4 optical tube assembly, and we can install it onto a variety of suitable third party mounts such as the Losmandy Model GM-8, Model G-11, or Astro-Physics Model 400 or 600E series computer controlled Go-To" German equatorial mounts. Optional mounting hardware is available to permits the quick installation or the removal of the optical tube from third party mountings.

The Celestron 9-1/4" telescope is about the largest Schmidt-Cassegrain telescope that can very easily be managed by any healthy person. It features a note worthy increase in light through put over an 8" f10 SCT; our measurements show a difference in actual transmission of 635X the light gathering power of the unaided human eye (predicated on a nominal 7mm exit pupil) versus 850X for the 9-1/4" model - all with very little difference in portability and no difference in ease of set up or use between the 8" and 9.25" models. The Celestron 9-1/4" system offers the best contrast of any of the production SCT models, this is particularly helpful to one in a suburban environment where clarity of image is more critical than sheer ligh gathering power. This telescope has a primary mirror focal ratio that is higher than that on conventional f10 SCT's where the primary mirror tends to be about an f/2. The secondary obstruction (by diameter) of a C-9.25 SCT of 86.06mm is about 37%. A typical f10 8" SCT will have a secondary obstruction of about 69.52mm which is actually 34%. So this alone does not account for the perceived contrast differences.

The Celestron 9-1/4" telescope optical tube assembly includes:

9-1/4" f10 Schmidt Cassegrain OTA with a nominal focal length of 2350 +-50mm (at 1.25" foci), Starbright Coatings (Magnesium Fluoride AR coatings on corrector, enhanced Aluminum on primary and secondary mirrors), Celestron 26mm Plossl ocular (1.25" Diameter from Taiwan providing 90X), 1.25" Prism Diagonal with Mgfl AR coatings, 1.25" visual back, 6x 30mm straight finder on standard mounting bracket, Celestron "G-5" mount pattern quick release dovetail plate, instruction manual (in English), one year limited international warranty.

The furnished 6x 30mm finder is adequate only for finding the brightest objects (planets, moon, etc.), we do suggest an upgrade to either the optional 9x 50mm straight through view finder. Or to the optional 7x 50mm straight finder with its Polar Alignment Reticle. In addition to improved finding ability, the finder has the integral pole finder reticle providing capability for use as a Pole alignment tool. A pole finder reticle illuminator, and pole alignment analog dial/scale are included with the 7x50 finder package for $175. Either finder should have an optional quick release bracket to facilitate removal of the finder for transorting the telescope.

An optional Telrad sight ($48.00) is also highly desirable accessory for those who intend to hunt out and learn how to find the most faint "deep-sky" objects possible. This sight is essentially battery powered (two "AA") a "Heads Up Display" type of sight, where three cocentric circles are projected onto a transparent window in an adjustable red light. From the observers position the view will show the night sky with circles of 4, 2 and 1/2 degree diameter "suspended" over the sight's window. This simple, adjustable brightness display helps one to learn how to measurure distances across the sky, and to "Star Hop" from one object to another.

There are a variety of other options which you are likely to choose to buy initially with the telescope, and many more can be added over time to further increase the versatility of this telescope. Please contact Company Seven for a more in depth reply either by Email, or by telephone, or at our showroom!

Company Seven offers the 9.25" optical tube with quick release hardware to permit use of the telescope on optional German equatorial mounts including our Losmandy GM-8 and G-11, and Astro-Physics Models 400 or 600E series computer controlled mounts.

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