TEC MCT 250

09/20/05

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My 250 mm (10 inch) F12 TEC Maksutov Cassegrain arrived on the 20th December 2004. Why did I buy this telescope? well several reasons actually. I like the design of a closed tube such that the optics will never likely to need re-coating, collimation is held and this was proven visually after a bumby transatlantic journey. It is therefore, relatively maintenance free. Secondly, MCT's offer high resolution with a smaller (30% in this case) secondary obstruction and I opted for a Quartz primary with better thermal characteristics (more later). Also Yuri from TEC moved to the US from the Ukraine, the heart of MCT manufacturing. His knowledge on this design is second to none, and he is also a nice fellow with a dry sense of humour having met him at the WSP in January2003. At that event I looked through Yuri's 12 inch prototype MCT which gave the best ever views of Saturn and Jupiter I have even seen, even compared to all other scopes present. We used silly powers of 1500x without image break down and breathtaking views. I just had to have one! Lastly I am a deep sky imager, particularly high resolution imaging. The TEC MCT offers a not too slow focal ratio of F12 and gives a flat field covering the ST10XME - perfect.

Here are photo's of the TEC 10 inch MCT on a Paramount ME. There is a TMB115 piggybacked

My first impressions after unwrapping, were the robust looking nature of the telescope, attention to detail throughout and very professionally made. I opted for an AstroPhysics rear thread so that I could use my AP accessories. The micrometer focuser is a joy to use, perhaps not as smooth as a feather touch but very accurate and there was no discernable focus shift when focusing with a CCD camera, a must! The tube rings are solid and open via a quick release clamp. I like the quality of the dew shield which snugs firmly onto the OTA. There is also a "wheel" on the rear of the OTA allowing one to rotate the tube when required.

The day the TEC MCT arrived, the forecast was poor for that evening, indeed a cold front quickly passed though with a little rain and amazingly left a clear spell for 2 hours. I firstly star tested the scope confirming that collimation was dead on and there was one residual heat plume, but thin and I doubt had much effect on the in focus star pattern. One concern with these larger MCT's is cool down time and TEC offer a cooling system utilising a peltier device. My first experience was that I might get away without it, although the larger swings of summer temperature would be more of a test.

Star test - The seeing wasn't great after the cold front, but in and out of focus images were very similar, just a trace of spherical aberration visible. In focus, at times I could just see parts of the first diffraction ring, but the star was boiling quite a lot. I hope to repeat this with better seeing. I turned the scope to Saturn which was over my neighbours house, but it gave a surprisingly crisp and steady image. Several belts with subtle colour could be seen, Cassini's division was obvious all the way round with the top of the globe now visible. The Enke minima was clear and colour of the rings quite striking. Lastly a quick look at the moon where Plato was well illuminated, I could see 2 cratelets which was not anticipated in this seeing.

Next onto a CCD camera. I cobbled my ST10 onto the back of the OTA, went through the usual routine of focusing, calibrating and tried short exposures of the Eskimo nebula.  I tried this because it is bright and the gibbous moon was in the west. I measured the FWHM at 2.2 arc secs which is excellent from my site and given the atmospheric conditions. I am therefore optimistic that future images will have better resolution.

Below is the Eskimo image - 5x6 minute exposures

 

Are there any negatives of the TEC MCT? The rear opening of the back plate is small so vignetting might occur with large format CCD camera's, but i suspect this is part of the design. The OTA is made of aluminium so focus may change with dropping temperatures. There is less back focus than for SCT's, but initial use of binoviewers and CCD equipment suggests this will not be an issue. Lastly, I thought I was buying a 10 inch scope, but in fact the mirror is 250mm in diameter which is 9.85 inches, so I will ask Yuri for a refund!

Finally, I purchased the Scopeguard case that is of real quality and essential if transporting a quality scope around.

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This site was last updated 09/13/05

   

09/20/05