Archive for November 18th, 2015


A truly tiny scope – the Synta MC90

November 18, 2015

MC 90 set up for birding

I realized in conversations with Doug and Terry recently that I have not blogged about the Synta MC90. I got one of these way back in the spring of 2009, on my quest for the perfect travelscope. I only used it for about a month before putting it on semi-permanent loan to my brother Todd. I did briefly mention the scope and show the photo of it set up on the hood of the car in this post.

In the early 2000s it was offered by a variety of vendors – I’ve seen units online labeled Synta, Orion, and Omcon. There’s a review of the scope on Cloudy Nights here, and the same article appears verbatim here.

MC 90 business end

It’s an odd little thing: a 90mm Maksutov Cassegrain, but operating at a fast f/5.6 (500mm focal length) instead of the more typical f/13.9 (1250mm). The most obvious con is that with such a steep light cone, the secondary mirror has to be quite large, which degrades contrast. Pros are that it can get a much larger true field of view than the ~1.3 degrees that the f/13.9 scopes are limited to – I’ll have to check, but unless it’s somehow vignetted it should be able to do over 3 degrees – and that it is incredibly compact.

MC 90 length

It is the same ‘barrel size’ as the longer 90mm Maks, but only about 2/3 as long. Take off the diagonal, eyepiece, and strap-on finder (in this case, a red-dot gizmo from StellarVue) and the scope almost disappears, which has two nice effects. First, just about any mount will be sufficient. In the photo at top I have it mounted on a Manfrotto MKCOMPACTACN-BK tripod and the whole setup weighs only 5.5 lbs (2.5 kg).

C90 orange tube in cooler

Second, if you need a case for this scope, you probably can’t do better than to get a six-pack cooler from Wal-Mart, which will set you back about six bucks. In this photo the scope in the “case” is my old orange-tube Celestron C90, but the MC90 fits inside just as easily. The black drawstring bag holds the finder.

Given how much I’ve written about them in the past, you may fairly wonder where my love for little Maks has gone. Each one got killed by a different problem.

SW 90 on tripod 1

My 90mm SkyWatcher Mak got out-competed by other scopes. The Apex 127 is no more trouble to set up but performs significantly better on just about everything, and if I’m in the mood to roll with a smaller scope, the C80ED has better contrast (as demonstrated in this post), takes magnification about as well, and is more versatile. I still have the little SkyWatcher Mak, mostly because I haven’t gotten around to selling it, but I haven’t used it in well over a year and I don’t imagine that I will miss it.

Happiness is--

From left to right: XT12, XT10, AstroScan, C90, XT6, SV50, 5″ SkyWatcher Newt on homemade dob base. Out of all of these scopes, the only ones I still have are the XT10 and SV50.

I sold the orange-tube C90 a long time ago. I really, really wanted to love that scope. I like the idea of that scope. It’s built like a tank, and since it focuses by rotating the barrel like a giant camera lens, there’s almost nothing that can go wrong with it. If that focus action ever does get sticky, there are instructions online somewhere showing you how to disassemble and regrease it. Basically, as long as our civilization can produce grease, and the scope doesn’t get dropped or left out in the rain, it should never, ever wear out.

BUT that rugged, rotating-tube focuser is also the problem. With such a long focal length, you start at medium powers and go up to high power pretty rapidly. That’s just the natural métier of a long focal length Mak. My problem was that it was almost impossible to focus the scope at high powers without nudging it off-target, and in fact the shakes that were induced by having my hand on the OTA were usually enough to make precise focus a guessing game anyway. It wasn’t a mount problem, it was me needing to paw at the scope to get it to do anything. Don’t know how many other people had the same problem, but I note that for its current, popular, and inexpensive incarnation (still around $160), Celestron has gone to the same rear-mounted focus knob as everyone else.

Synta MC90

Image borrowed from Cloudy Nights.

Finally there’s this MC90. I never really gave it a fair shake back in the day. I only had it about a month before loaning it to my brother, and I’ve only used it on one or two evenings since, neither of them in the last five years. Also, my observing interests have changed. Back in 2009 I did a lot more lunar and planetary observing, and now I’m more interested in DSOs and low-power, widefield scanning, where the MC90 might do better. I’m going to borrow it back this Christmas and give it a serious workout. I’ll let you know how that goes.