 |
| Above: The Orion 3.25-inch doublet crown and flint coated lens refracting telescope is f/5 and can show large sky areas. With a 1-inch or 25mm focus eyepiece gives only 16 power. A half inch FL EP (12mm) or a 2x negative projection barlow takes it to 32x or a 3x to 48x. It can be used as an RFT rich field telescope, a finderscope, guider and tracker or a main telescope. A plastic finderscope with a dovetail mount will keep it lightweight. |
Orion CT80 80mm (3.25") f/5 Doublet Refractor Telescope
I'm really excited about these small telescopes that are lightweight, easy to carry and transport, and only take moments to easily set up. The class of these telescopes include tiny Dobsonians, tripod mounted OTAs and OTAs that share resources mounted onto an existinging telescope - for example to take advantage of a GOTO mount. Some examples are the Orion f/5 3.25-inch diameter refractor with a 14.7-inch tube, and the Acuter 60mm f/12.5 Maksutov which is a mere 8-inches long with the star diagonal attached. The CT80 is 2.25 lbs and the Acuter Mak is only 1 lb.
Orion CT80
The Orion CT80 is a 3.25-inch diameter f/5 coated doublet achromat refractor OTA with a 400mm focal length. A 1-inch focus eyepiece will give about 16 power and a very wide view of the sky. The OTA has a dovetail mount for a finderscope, and up until this time it was unknown how to mount the OTA. Upon close examination today, the OTA has a photographic standard 1/4" hot shoe mount for attaching to a tripod. An HF-3110 long four level tripod was found in inventory to make this telescope complete at no extra cost.
The CT80 will also attach to the Celestron Nexstar 6SE using the Celestron camera mount. The CT80 weight is listed as 2.25 lbs. The optics are coated crown and flint glass mounted in a metal tube with a rack & pinion focuser. The tube is 14.7-inches long. Resolving power is 1.45 seconds of arc. It's short FL low power makes a fine addition to the Nexstar 6SE long focal length Schmidt Cassegrain scope and it gets to share the GOTO mount.
Left: a finderscope is added to the OTA using ring mounts on a dovetail shoe. The finder is all plastic with resin lenses and extremely lightweight. The rings and dovetail mount are metal and much heavier than the finderscope. however, these are capable of maintaining the rigidity needed for holding precise calibration.
Without central obstructions compared the Schmidt Cassegrain design, generally refractors are said to be equivalent to a Newtonian reflector or catadioptric about double the aperture. In this case, the 3.25 becomes a 6.5-inch telescope. The CT-80 has potential as its own telescope, and when mounted on the Nexstar - a guide telescope or dual telescopes on the single GOTO mount. At f/5 it can give 16x with a 1" EP. Many of these small telescopes are used as the main scope in astro imaging. Note: the 3.25-inch CT80 refractor is larger than a Celestron 2.99" reflector Firstscope.
Above Left: The tripod is an HF-3110 which is at just the right height when used with a 90-degree diagonal, but ends up being a bit wobbly along the axes until properly adjusted with four adjustment points. After moving the telescope, doing focus, a fair amount of time is required for the vibrations to subside. If not for testing, temporary usage and the ultimate in lightweight tripods for transportation, a larger and more sturdy tripod is recommended.
