University Lowbrow Astronomers

The Intes-Alter M703, Experience with a Mak-Cass.

by Charlie Nielsen
Printed in Reflections: August, 2009.

I still remember looking at the old Orion Telescope catalogs and being a bit more than just curious about their Maksutov/ Cassegrain and Maksutov/Newtonian telescopes that they used to carry. Orion’s sales blurb was not the only testimony that I had heard or read regarding the high optical quality of these designs. Perhaps the most prominent design parameter is the use of spherical primary mirrors. This would normally be very bad since a parabolic mirror is required to reduce the inherent aberrations that come with a spherical mirror. But, a spherical mirror is much easier to figure accurately than a parabolic. Both designs use a corrector (lens) at the very front of the telescope which introduces the opposite errors that the spherical primary causes. Therefore one cancels out the other and this allows the primary to be figured to very high accuracy. Having a corrector and semi-sealed tube provides the advantage of keeping the primary and secondary clean, but also throws in the disadvantage of having a front surface that could dew up, or be touched by something other than air and photons. Both of these designs are capable of producing very high contrast, coma free images with spot sizes that are just short of refractor category. Small spot sizes translate into very tight, small, high resolution star images. This feature as well as both designs’ high contrast makes them excellent planetary scopes.

There are some differences between the two designs. The Mak-Newt uses the Newtonian optical path, and the Mak-Cass uses the Cassegrain path. Another difference is that the Mak-Cass will be a slower focal ratio. Typically they are F/10 to F/15, while the Mak-Newt is F/5 to F/8. The Mak-Cass typically uses a secondary that produces less central obstruction than a typical Schmidt-Cass, while the Mak-Newt is smaller yet. Less central obstruction produces higher contrast. Given the same aperture, the Mak-Newt will be a longer optical tube and therefore heavier.

My reasons for selecting the Mak-Cass are that I wanted a slower focal ratio and it would require less mount than the Mak-Newt of equal aperture. My other scopes were all F/6 or faster, so I wanted something slower. A slower scope is more forgiving of eyepiece aberrations for one reason. But more significant to me was that given the same aperture a slower focal ratio will mean a longer focal length, and a longer focal length will produce higher magnification for a given eyepiece. This means that I could use my longer focal length eyepieces more, which usually have better eye relief. Being an eye-glass wearer with astigmatism this is of great benefit. Also, my dominant (right) eye is more astigmatic than my left, darn it. So I would now be able to produce higher magnifications easier and more comfortably. My final reason for going Mak-Cass is that it was shorter, lighter, and therefore easier to balance on a German Equatorial Mount than an equal aperture Mak-Newt. For mounting I went with the Orion Sirius EQ, which has a 30 lb. capacity. I will comment a little more about the mount later.

So, off I went looking at 6 inch Maksutov-Cassegrains. Orion’s, which was imported from Intes-Micro of Russia, was no longer available, and their current 6 inch Mak-Cass, which is made in Asia, was not yet available. From reading reviews and comments in ads on Astromart, it appeared to me that Intes was probably the way I wanted to go. Intes seems to have changed names a few times in their history, and at one time some of their employees split off and formed another company. My telescope sports the Intes-Alter name tag, which I think was the premium division of the original Intes or Intes-Micro company. Eventually I called ITE of Jupiter, Florida. They have imported and worked with Intes for a number of years, and I heard some positive comments from fellow club members about that company. ITE showed 2 versions of the 6 inch Mak-Cass. One was F/10 and the other was F/15. F/15 was a little slower than what I wanted. Now to start the confusion, they have a 6.5 inch. Aperture fever starts to set in. But the 6.5 was a little longer, slower, and more expensive. Besides, now that I am looking at 6.5, is it that much of a leap to 7.1? Well, cost wise it was. So, having settled myself back down a bit, I called ITE. Mike Palermiti, owner of ITE, answered the phone. I found Mike to be a very friendly and knowledgeable guy who will talk your ear off if you let him. Besides being a business owner, Mike is also an avid observer and astro-photographer, with a bit of “Lowbrow” thrown in. He is a true pleasure to work with. Well, it turned out that Mike was freshly out-of stock on the Intes M603! So, I gritted my teeth and asked about the M703. I apparently caught him in a low inventory time because he only had one of those in stock. However, I worked out a very nice deal on that scope and ordered it. Mike knew I would get over the extra cost above the 6 inch, stating that there is a very noticeable light gathering advantage with that extra 1.1 inch of aperture. When I told him what I intended to mount it on he started getting excited too, being a fan of this mount himself. He thought the combination would be first class all the way.

About a week later, the glorious brown truck pulled up to my office at Scio Township Hall. The scope was reasonably well packed and showed no shipping damage. Looking through the visual back revealed a perfectly centered secondary mirror, leading me to believe there were no large collimation issues. However there was one issue. On the bottom of the aluminum optical tube are two brackets welded to the tube, to which is attached a Losmandy style plate. My mount uses a Vixen style. Yes, for about 3.5 seconds I considered duct tape. I called Mike at ITE and he felt badly about not thinking about this himself when I ordered. So he custom drilled a Vixen style dovetail that matched two 1/4-20 holes in the bottom of the Losmandy plate, free of charge, and sent it to me with an extra counter weight for my mount that I anticipated needing. I even got a good price on the counter weight. Meanwhile, I used the 1/4-20 holes to set the scope on a heavy duty photo tripod, and prayed. But, it held well enough for me to spot some terrestrial objects and provide a hint as to how good this telescope’s resolution is.

Now that I was ready to really use the scope, you can guess what happened; clouds. Eventually, after sufficient punishment by the gods, I got a clear night. I had already used my mount with my Orion 80 ED refractor, so it was now just a matter of setting the M703 on top of it, and balancing everything out. When I talked to Mike about the dovetail he made, I asked for one as long as the optical tube. This provided me with plentiful balancing range, and an area toward the front of the tube where I could mount extra equipment to the area of the dovetail where there is a gap between it and the optical tube. One time I used this to rubber band a green laser to the dovetail. When someone asked me where I was pointing (which I was hoping they would), I just flipped on the laser and it pointed right at it.

Back to balancing; it was very easy and fast. The Orion Sirius mount handled the scope and the extra stuff mounted to it with ease. It passes the “bump test” beautifully. I like this mount and highly recommend it. It is a GoTo mount with Celestron style hand controller. The controller is Internet upgradeable and can even be operated while disconnected from the mount. This could be handy for entering your own user objects during the day, for example. The included, illuminated polar alignment scope works well and is easy to use. The first night out with this mount I achieved very good polar alignment, and had the GoTo placing every object near the center of the field of view; and it only took a few minutes to get to that point. Later I added a GPS unit, which plugs into the hand controller. Now, after doing the polar alignment I only need to tell the controller if I am still in this time zone, and still on DST. Then it acquires several GPS satellites. Next is selecting either 1, 2 or 3 alignment stars, doing the alignment, and we are good to go, or “go to”. This mount also tracks very well. Once I have an object centered I can return hours later and it has not moved, even at high power.

Since this article is really about the telescope, I should return to it. I expected that I would need some amount of cool down time before I could really judge the optics. This is one of the common remarks about this design, that it has a long cool down time, mostly due to the rather thick corrector lens. Having now used the scope in all seasons, I have not had an issue with cool down. Even in winter it is pretty much less than an hour. I was already used to that time range or longer with my 8 inch DOB. The scope has a small cooling fan mounted on the back plate. It is filtered, as well as the ventilation holes at the front around the corrector. However, I have only used this fan a couple of times, and it was mostly just because it is there. The interior of the tube is painted a pretty effective flat black, and it features several baffles. The secondary mirror is also well baffled. The corrector shows no blemishes and displays very good looking multicoatings. The primary mirror is spotless. When using the telescope, two things always impress; resolution, and contrast. Both of these characteristics are so strong, that the view often makes you have to remind yourself that this is not a refractor. On many objects it will outperform my 8 inch DOB, which has an outstanding primary. Occasionally, on globular star clusters, I am amazed at how close it approaches my 12 inch DOB. At comparable magnifications the 12 inch image will certainly be brighter, but the 7.1 inch will be very close on resolving the core. On planets and double stars, this scoped is a monster. My first view of Saturn almost dropped me to the ground. Everything was razor sharp and colors were outstanding. I saw a cloud band on the disk that actually displayed a light brown against yellow background. Jupiter displays a similar high resolution, high contrast, and on good nights, colorful image. A couple of years or so ago I was set up for an open house at Peach Mountain, and happened to be right next to the Eastern Michigan University 14 inch Celestron Schmidt-Cass. That night Porima (a tough double star in Virgo) was well placed so I decided to try it. At that time I believe the separation was lass than an arc second, and it was not ideal weather for double star splitting. But, the Intes split Porima easier and more consistently then the 14 inch, and also beat an Obsession 18 inch DOB a few steps away! Yes, I did say that, and I have witnesses. On another night up on the hill several of us decided to go for the despicable NGC 5053. For any reader that is not familiar with this dreaded globular, it is fairly large and has a very low surface brightness. That combination makes it very hard to pick it up against the sky background, even on good nights, which this one was. We did see it in a very high quality 12.5 inch and 14.5 inch DOB just before I wheeled over to it. I saw it immediately! I was dimmer than the already dim image we saw in the DOBs, but it was there with direct vision. We were all pretty blown away by that.

In conclusion, you may have the impression that I really like my Intes M703, and that is certainly true. I have since “tricked out” the scope by replacing the original finder with a very nice Stellarvue 9x50, correct image model. I rarely use it as a finder, but instead more often use it as a small wide field telescope since it is of very good optical quality. It also has the ability to change eyepieces and it will focus with most of my 1.25 inchers. I added a Rigel finder, which I use mostly during my initial GoTo alignment. I installed a William Optics SC type rotating Crayford focuser, followed by a William Optics dielectric diagonal. The stock focuser is now used just to set the focusing range for the Crayford. The telescope uses a moving primary to achieve focus. The focus motion is very smooth and I have not experienced any image shift or mirror flop at all. I added the Crayford because I wanted fine focus (it is a 2 speed) and to be able to rotate the focuser conveniently. Now when I move to a different part of the sky, and my eyepieces ends up upside-down, it is really easy to remedy. For dew prevention I added an Astrozap heated dew shield. This dew shield is long, very dark inside, and so effective I rarely need to use the heater part. I found that by attaching two small pieces of Velcro to my Rigel, a 1.25 inch eyepiece dew strap fits perfectly over the top of it and sticks in place via the Velcro already on the dew strap. This actually seems to work, but I have not tried it under very severe dew conditions yet. Since I now had 2 dew heaters I purchased a 4 port, 2 channel variable controller which Velcro’s to a very convenient location on the mount. Me like Velcro! The whole system (mount, scope, and accessories) is optically excellent, very stable, easy to set up and operate, and user friendly. This combination makes it very fun and satisfying to use, and it has yet to disappoint me. Every time I use this setup I pack up for the night with a smile on my face.

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Copyright © 2013, the University Lowbrow Astronomers. (The University Lowbrow Astronomers are an amateur astronomy club based in Ann Arbor, Michigan).
This page originally appeared in Reflections of the University Lowbrow Astronomers (the club newsletter).
This page revised Sunday, March 9, 2014 4:30 PM.
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