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Intes-Micro Alter M603

About me

I am a 26 year old student, and have been interested in astronomy for as long as I can remember. The Intes-Micro Alter M603 is my first “real” scope, having owned a 60mm toy refractor years earlier. As a student I’m severely handicapped in the cash department, so I needed an affordable scope. I also want to take my scope with me on holidays, so it also had to be a compact scope. The M603 fit the bill perfectly, being 20cm/7.9 in. in diameter; 40 cm/15.8 in. in length; and costing around $950. It is an older (’96) version, newer models have a threaded front for a screw-on dewcap and an underside rail to fit Vixen mounts. To keep myself on track I’ll discuss this scope point by point, with the main areas being first impressions, optical performance, transportability and setup, and general comments.

First impressions

The M603 is a 6-inch F/10 Maksutov-Cassegrain. This scope is not as light as you might expect from a 6-incher, weighing in at about 6 kgs/13.3 lbs fully loaded. Most of this weight comes from the sturdy construction of the OTA, which is a one-piece machined steel tube. There are exactly two pieces of plastic on this scope: the finder’s focuser and its lens cap. I think it’s safe to say that the M603 is somewhat over-constructed, but at least it won’t fall apart anytime soon (and I’m not thinking in years here, more like decades or centuries). It is said that Russian scopes are dull-looking to downright ugly, and as you can see the M603 won’t win any prizes for its looks.

The M603 in all its glory

There’s a story on the internet that says that all Intes and Intes-Micro maks are derived from aiming equipment for tanks. When I look at the solid construction of the M603, I have no trouble believing the story. The M603 is kind of cream coloured with black accents, and the paint is rough to the touch. It has a no-nonsense, purposeful look to it, and it’s certainly not a work of art. My point is: what does it matter? If you want something flashy, buy a Ferrari. A scope is made to look through, not at, so that’s what I did as soon as I got it. The weather gods must have smiled upon me, since I had 4 clear nights in a row. At first light I was somewhat disappointed with my scope: stars wouldn’t come to focus, and the planets were blurry. When I popped in the laser collimator I had bought, I found out why. The laser didn’t even return to the collimator, striking the front of the baffle tube instead! I returned the scope to the store so it could be collimated, since I’m not skilled enough to fix this myself. As it turned out, the scope was indeed out of alignment, but so was the laser. Both are aligned now, but it shows the limitations of using a laser collimator. This scope is baffled very well, and the coatings on the corrector are very effective. On the picture below you can see this, it was taken at close range with full flash but still almost no reflection from the corrector.

Almost looks like the corrector was removed…

The central obstruction is 53mm or 36%. The secondary can be adjusted with 3 sets of push/pull screws, they are the white dots on the secondary. As you can see you need a surgeon’s hand to collimate, since the screws are small and awfully close to the corrector. Thankfully collimation stays the way it is for a long time, even when the scope is transported a lot. You can also see the five tube baffles, and the central baffle which holds the primary mirror. This appears to be the secret behind the M603’s zero image shift focusing: the mirror moves forwards and backwards on threads on the baffle tube. Initially I had some problems with this mechanism. The picture below shows the back of the OTA.

The silver ring is what holds the baffle tube in place, without it the tube will rotate when the focusing knob is turned. The ring is held in place with four *minute* screws (one of them indicated with a red arrow) the threads of which stripped out when focusing. I removed the screws and tightened the ring by hand, and the problem never occurred again. Strangely enough, the ring stays in place better *without* the screws. Focusing is smooth and gets smoother when it is colder outside. (Maybe because the gears shrink?) There is some play when you reverse the focusing direction, but it’s not much and you get used to it very easily. Sometimes I find that focusing is a bit too coarse, fine focusing can require minute tweaks of the focus knob and then the play in the mechanism can be a nuisance. The focus knob is made out metal with a fine grid engraved in it. It’s placed pretty well, although I would have liked it to be a bit more towards the edge of the tube so I could put on a bigger knob. All in all, despite some minor mechanical issues, this is a scope that is solidly built.

Optical performance

This is a scope that will perform right up to its theoretical limits, even under less than perfect circumstances. And “less than perfect” doesn’t even begin to describe my observing site. Lots of streetlights and heat-hoarding buildings. If I have a magnitude 4 sky I consider it a good night. On the planets all this light pollution doesn't seem to matter all that much. In fact, when watching Jupiter I have to look right past a streetlight. Through the eyepiece the sky is still black though, so score one point for baffling. On Jupiter I can see so many cloud bands it almost looks like a barcode, and on Saturn the rings look like an old record with all the grooves. On a decent night this scope will easily resolve details of less than 2 arcseconds. To test this I watched Callisto pass before Jupiter and tried to keep it in view, while I checked the separation with Redshift 4. The moon seemed to merge with the planet’s limb at about 2.2 arcseconds, measured from the center of Callisto’s disk to the edge of the planet. A little later I could see Callisto silhouetted against the planet. A few nights later, I set out to watch Io move across Jupiter. First the shadow appeared on the planet, and then I watched Io slowly move before Jupiter.

I can't comment on deep sky (yet), since that's one area where light pollution IS a problem. On a good night I can see point sources down to magnitude 9-10, but extended objects disappear from view when they’re dimmer than magnitude 6 or 7. Despite this, my impression is that the M603 will do just fine on deep-sky, since it clearly shows me the Orion nebula (wisps and all, even at 150X) and the Andromeda galaxy takes on form. That may not sound too impressive, but keep in mind that my observing circumstances are about as bad as they get. Other deep sky objects disappear in the glare, so further testing will have to wait until I go on holiday again.

Transportability and setup

I’m using this scope on a Vixen Great Polaris mount, which does a very good job. The M603 is near the upper limit of the GP’s 7kg/15.4 lbs carrying capacity, but I’m not going to do any astrophotography anytime soon. Despite its weight the M603 is remarkably compact, you can literally take it for a walk. I’m right in the middle of light pollution hell, with a limiting magnitude of 3-4 being a good night. To get to a somewhat dark spot I have to walk ½ a mile, and even there I can read my star charts without a flashlight. I can move all my equipment in one haul: the OTA in its padded bag on my shoulder, a backpack with the counterweights and eyepiece case, and the mount under my arm. Once I get there, I set up the mount, put on the OTA and I’m ready to go. The handle on top of the OTA is a nice feature that makes setup a lot safer. Total setup time with polar alignment is about 10 minutes.

General comments

So, the M603 does very well on the planets, at least decent on deep sky, is affordable and transportable; nothing but good news here. Sounds like there is a catch? Indeed there is. This scope takes ages to cool down, and on a nice clear night it seems to take longer than forever. On average 2 hours of cooling down is sufficient, with usable images after 1 hour or so. Only on really cold nights do things get complicated. A cooling fan would speed things up nicely; I’m going to try making one myself from an old PC fan.

A bit surprising is that I haven’t yet needed a dewcap. I live 7 meters below sea level, and 80% humidity is quite normal. Under these circumstances you would expect the objective to dew over in less than no time, but on average the window of my red dot finder dews up long before my scope does. I’m not sure why, but I’m thankful for it all the same. Despite this I might just make a dewcap myself, to block stray light and squeeze even more contrast out of this scope.
The last thing I’d like to mention is the finder. Simply put, it’s a piece of junk. First off, it isn’t sharp. Then there’s so much play in the focuser that the crosshairs wander across the field. At least, they do so when they’re visible. The crosshairs are small and thin, so I find myself in the strange position of actually NEEDING some glare to see them. I intend to upgrade to a better finder, preferably a 90 degree model.

By now it’s probably obvious that I think very highly of this scope. The Alter M603 is great for planetary and lunar observing, provided that you replace the finder with something halfway decent and that you’re not in a hurry to have a quick 5 minutes of observing. If there’s anything else you’d like to know about this scope, feel free to e-mail me.

Clear skies,
Jarno Craamer
Rotterdam, Netherlands (52º 55’N, 4º30’ E)
June 2001-December 2001

update 05/25/2003

Well, it’s been two years since I wrote my review of this scope and a lot has changed. My “complaints” with this scope were the following things: 1) cool down time 2) the finder. I’ve taken steps to make improvements with both of these issues, and added some other helpful accessories. Read on for more information.

My M603 now

First, the cool down issue. Not much can be done about this, it’s simply an issue inherent in this type of telescope. Whenever I think the skies might be clear, I put the OTA outside before dinner so it will be ready when it’s dark. Sometimes, when I need to speed things up a little, it put the scope out on the mount. I point the scope down vertically and remove the cap on the back (the one covering the threads on which the star diagonal attaches). This way, warmer air can rise out of the tube. To prevent all kind of dirt blowing in I leave the diagonal attached, so it can act as a dust trap. I’m not concerned about the diagonal getting dirty, more on this later.

With the finder I have had to concede a partial defeat (or claim an incomplete victory, depends on your point of view). I’ve given up on all my attempts to improve the original finder. It has been taken apart and I might do something with the optical components some day, but right now the empty tube makes an excellent solar finder. To replace it I bought an Antares 8x50 right angle finder since I heard a lot of positive comments about it. However, having used it, I don’t know why so many people like it. There’s a lot of coma, and you can’t focus the crosshairs and the image at the same time. It’s an improvement on the original finder for sure, but I won’t buy another one. For my next step I decided to forgo a magnifying finder entirely and added a Telrad to my scope. This was truly an eye-opener for me. I can’t describe how easy it is to simply swing your scope around and see those red circles float in the sky. Objects that take me minutes to find with a magnifying finder can be found in seconds with the Telrad. One word of caution: a Telrad doesn’t do well under light polluted skies, since it has the same limitations as your eyes. If you can’t find things with the naked eye, the Telrad won’t help much either. This is why I still use the Antares finder. The Telrad gets me close, and with the 8x50 I use stars not visible to the naked eye to get to the desired object.

Now I will make good on my initial promise: why am I not worried about dirt getting on the diagonal? Simple, I don’t use it anymore. As I got better at star testing and collimating, I saw a triangular pattern to the stars. The more experienced astronomers will immediately recognise this of course, it means that an optical component is deforming under pressure. Once I became aware of this, I made certain that the primary and secondary mirror adjustment screws weren’t too tight. This didn’t solve the problem, so it HAD to be the diagonal. The Intes-Micro diagonal is made out of two tubes at right angles to each other, so they form an “L” shape. The short leg attaches to the scope, the eyepiece goes into the long leg. Where the two tubes connect there’s a hole in which the diagonal mirror is mounted. When taking the diagonal apart I saw that the mirror was glued in place, with what looks like epoxy (see picture).

The gutted diagonal, or how NOT to mount a mirror

When the diagonal cools, the metal contracts and deforms the mirror. I don’t have the equipment to do something about this (and I was thinking about getting a 2” diagonal anyway) so I took the plunge and ordered a William optics diagonal from APM in Germany. This is a refractor-style diagonal, so I also bought an SCT to 2 inch adapter. Miraculously, the sky was clear when they arrived. The improvement is amazing, everything is brighter and sharper than ever before. I also bought a Pentax XL 10.5mm from APM. As a side note, I’d like to say that I can wholeheartedly recommend APM. Markus may sometimes seem a bit unfriendly in his e-mails with his answers being really short, but I suspect that this is only because he’s a busy man and cannot spend too much time on e-mails. Everything I bought from him arrived quickly, well packaged and was exactly as promised. Now, back to the Pentax: this eyepiece works really well with this scope. Easy to use, a large FOV, bright, excellent contrast, you name it. This eyepiece only blacks out when you are intentionally trying to make it do so. A star in focus is a thing of beauty now, so much so that I might take up double star observing. I should have upgraded the diagonal a long time ago. Now I finally believe that my scope is performing at or near its maximum capacity.


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