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Celestron C130 5.1 inch Maksutov OTA

Posted by Tom Nicolaides   03/25/2005 08:00AM

Celestron C130 5.1 inch Maksutov OTA
I've always wanted a Maksutov. So after selling several mounts and telescopes on AM, I started casually looking around. I have a CG5 mount equipped with Meade motors and Autostar for it to ride on, so I wanted something fairly light for a quick setup scope. I was leaning towards Orion's Apex 127. I almost bought one when I saw an ebay ad for Celestron's C130 Maksutov, 130mm (5.1 inch) F15.4 at a price quite a bit less than a new Apex. I ended up buying the OTA from Adorama for 320.

It arrived yesterday and I was impressed with the case - It's a nylon case, but it has a hard rubber molded insert to accept the OTA, Finder scope, several eyepieces and a few other accessories. It's a really nice case. The finish was pretty good - it looks like a new scope should look.

The C130 has an internal flip mirror to switch between the built-in 90 degree celestial 1.25 inch EP holder or a threaded rear aperture that can accept the supplied 45 degree correct image diagonal. Celestron supplies a 32mm Plossl that provides 62x with a fov of just under one degree. It's a LONG focal length scope (2000 mm)! Both EP holders have a glass barrier between the outside world and the interior of the OTA. This seals the interior of the OTA from humidty and dirt and is a nice feature - if the glass doesn't introduce any optical aberations!

The tube weighs about 10 lbs with the supplied 10x50 finderscope. The finderscope is nice. It has a dovetail type mount but the 6 screw push-pull alignment mechanism. I really prefer the two screw and spring type, and maybe I'll replace the finder mount later. Which leads me to the first noted problem. I couldn't align the finderscope. Didn't have enough adjustment range. I looked at the dovetail mount on the OTA and discovered a little pry-off plate that covered the two mounting screws. I was able to loosen the screws,
move the dovetail receiver and get the finder aligned fairly easily.

First Light - Old Luna - Last night was a full moon, so I wasn't expecting much. I used my 40mm plossl first - Since my other scope is an 8 inch F5 newtonian I haven't used that EP much because of exit pupil. With the 40mm EP, The moon fit easily into the FOV (50x, 1.1 deg FOV). There's a LARGE focus range on this OTA and it actually took me a minute or two to find the focus. Once i did I immediately looked for evidence of CA on the edge. I saw none. I put in my 15mm Antares W70 in (133x, 0.5 deg FOV). The view wasn't bad. Even with full on lighting contrast was reaonable and around the terminator I could see a fair amount of detail. More importantly, I was interested in off axis lighting problems. I moved the scope so the moon was slightly out of the FOV and while I could see a glow, I didn't see any flashes and splashes of light that might be seen on other scopes when
performing these tests. Indeed, looking into the tube, it does appear to be well-baffled.

Next stop - Saturn & Jupiter - I kept my 15mm EP in and slewed over to Saturn. I was pleasantly surprised. Cassini visible all around with planetary bands evident. Seeing wasn't the best, but occasionally more ring detail popped in and out hinting of better performance to come. I putin my 7mm Siebert Standard (285x)- too much - Saturn was a big fuzzy mess. Don't know if it's the scope or seeing. Stay tuned.

Over to Jupiter - Again with the 15mm EP Jupiter showed as a nice large orb. The detail was very nice, comparable or even a little better than I typically get in my 8 inch F5 newtonian. Given the seeing last night (fast moving clouds, occasional clear patches), I was impressed once again. The equatorial bands were obvious. Polar region was visible also, with detail popping in and out. I think this is going to be a good planetary scope.

On both planets I looked carefully for reflections that might be coming from those glass barriers in the EP receivers. I didn't see any. So far, so good.

Focusing - This is a tough one for me. For me it's quite good, but I have little experience with folded catadioptrics. The focusing knob is large and turns easily and smoothly. When focusing at high power (133x, that is), the image moves a bit and when the knob stops turning
it retuns to where it was. Is this the "image shift" I've read about? But for me focusing was much easier with this little scope than my newtonian equipped with crayford - probably because of the long FL. So for me it's quite nice and pleasureable to use. But I suspect an experienced catadioptric user might not like it.

Finally, I wanted to try a DSO. Given the very bright full moon I didn't expect much. I tried M3. I used the 32mm EP, slewed over and there it was, a fuzzy patch on a bright background of moonglow. I didn't try higher power to try to "bust the globular." I was just pleased that it was visible.

The flip mirror - I'm not sure I like it. While it works and didn't cause any apparent misalignmnent, it doesn't sound right. Sounds plasticy. My experience is that if something sounds like it might break, it probably will. So I'll be watching this.

Star tests - I didn't spend a lot of time doing those, but Arcturus showed identical inside and outside focus rings with no sign of astimatism and very good collimation (I'd expect good collimation from an F15!). Seeing wasn't good enough to judge for spherical aberration and I'd need to get out my chart for that anyway.

Overall I'm pretty well pleased. I could recommend it just based on this first night out. As I discover more, I'll post it here.

Click here for more about this subject. -Ed.