Celestron C130 Maksutov-Cassegrain

Let me clarify it prior reading: I do not have any commercial interest in Celestron, Meade, Orion or any of their distributors.

Disclaimer: I tested only one unit which might not represent the average optical and mechanical quality of the C130 MCs -- I might have got a lemon.

This summer Celestron announced a new series of spotters, the largest being the C130 mm Mak. Later, in August I had a chance to evaluate this equipment and compare it against the Orion Apex 127 which I had sold a couple of weeks before the Celestron Mak arrived. The C130 Mak is manufactured in China, just as most of the low-cost astronomical instrument nowadays. It features 130/2000 MC optics: the slow focal ratio (f15.4) yields a small FOV (max 0.8 degree) and smaller-than-average (at least among the Cassegrains) secondary obstruction (29.4%). The C130 comes with a 8x50 finder, a 45 degree amici prism and a 32 mm Plossl eyepiece - all housed in a nice carrying case. The case is water-resistant and is padded with relatively hard foam. All the accessories and the OTA, of course, fit into it plus you have some empty spaces for additional eyepieces. As the telescope weighs 10 pounds, is quite long and has a narrow FOV I can't recommend it as a grab-and-go spotting scope.

C8 left, C130 right

First impressions

The telescope and the accessories were properly packaged, the eyepiece comes in a cheap plastic container. The tube is surprisingly long - much longer than the Orion 127 Starmax and just a hair shorter than my Celestron 8. The purple coating on the corrector and the mirror were flawless, the glossy black paint on the outside however had one or two tiny errors in the paint job. The corrector is slightly (5 cm - 2 inches) sunk into the tube which means additional protection for the lens rather than a real dew shield. The back part of the tube is plastic and is very similar to that of the Meade ETX telescopes. The eyepiece holder and the thread on the rear-port are plastic too. The finish of the flip-mirror is very flimsy, if you look into the telescope and gently touch the flip-mirror button you can see the image move. The thumbscrews on the eyepiece holder and the amici diagonal are very small and their holes look homemade: they have poor finish and not painted black. The oversized focuser moves smoothly, effortlessly - it really appealed to me.

I was surprised to see that inside the rear-port and the eyepiece holder some kind of glass covered the holes to prevent dust from penetrating into the tube, I guess. As the specs don't claim the telescope is nitrogen filled I don't know why Celestron meant to insulate the tube hermetically. The glass definately degrades image quality more than some dust inside on optical elements .

There are no screws in the back to align the primary mirror which might be a problem if something goes out of collimation. The tube wall inside is well baffled, there are dozens of grooves to decrease reflection thus improve contrast just like in the Meade ETX telescopes. The tube of the Orion Starmax is smooth inside. The relatively small secondary and the good baffling forecasted excellent image quality, I was anxious the confirm it under the sky.

Accessories

Part of the standard package is a 8x50 finder which is a big plus compared to the standard 6x26 finder found on the Orion Maks. It attaches to the tube using dovetail base and can be adjusted using 6 screws unlike the Orion finders which are spring-loaded. The cross-hair is much thinner than that of the Orion finders but the optical quality of the lens is quite poor: it shows a lot of chromatic aberration and image degradation at the edges. One more complaint: Celestron didn't supply the finder with lens covers. The amici diagonal is ok, although the prism is not properly centered in the housing which causes some clipping at the edges in the eyepiece. The 32 mm Plossl is of a very low quality, it has blue coatings which suggests only one layer MgFl on the optical surfaces.

The Optics

I placed the telescope on a Synta HEQ-5 mount and pointed it at the Moon first. The Orion 127 showed significant reflections when Moon was just out of the FOV, the C130 didn't which confirmed the superior baffling. When I moved Moon into the center of a Televue 32 mm Plossl and positioned my eye at a certain distance and angle from the eyepiece I did notice weird reflections. It was not very disturbing, but still it was there. I guess the "cover glass" in the eyepiece holder accounts for it. In addition I spot some colour around the edges of the Moon which was caused by either the corrector or this "cover glass". After a short period I started to dislike the flip mirror mechanism: not only is it sloppy but you cannot rotate the diagonal to your most comfortable viewing position. (I must admit this is my very personal opinion.)

Next night I pointed telescope to Vega and epsilon Lyrae, the famous double-double binary. On Vega I noticed that telescope was slightly out of collimation and had some astigmatism. Epsilon Lyrae did split but the stars didn't focus to pinpoints and separation wasn't very clean. I was pleased to see that no image shift is visible. As it was a warm summer night (20 deg Celsius) and I waited approximately 1 hour I don't think cool down problems caused the low image quality. Anyway, I know how temperature currents degrade image quality: when I had the Orion Apex sometimes I went to locations with icy Hungarian weather (-10 deg Celsius) to stargaze. That time I really had to wait for thermal equilibrium. Due to the very poor optics and severe light pollution I felt it makes no sense to perform more sophisticated testing. Sorry Celestron, this telescope doesn't live up to my expectations.

Conclusion

It didn't take long to realize that I preferred the Orion Apex 127. It has much better optics, mechanical construction and is slightly shorter. My main complaint is the low quality optics and the sloppy back part. I feel Celestron should significatly improve the C130 Mak otherwise it won't be able to seriously compete with the Orion Apex/Starmax telescopes.

This is what I liked:

• excellent baffling
• big, 50 mm finder
• thin crosshair in the finder
• oversized focuser
• large, semi-hard case
• no image-shift

This is what I didn't like:

• poor optics
• some kind of glass inside the eyepiece holder
• sloppy flip mirror
• slightly uncentered prism in the diagonal
• very cheap 32 mm Plossl
• 6-screw-mechanism for aligning the finder
• optics are not user collimatable