Intes Micro Maksutov Newtonians – Some thoughts on mechanical improvements and alignment and collimation





1. I own or have owned three Intes Micro Maksutov Newtonians, the MN56, MN66 and the MN78. The top picture shows the two smaller models. All three were bought secondhand and arrived with no documentation. The MN66 in particular was in a poor mechanical state, in fact the main mirror cell was misfitted and jammed onto the tube. I had to use a hammer and chisel to free it. The secondary was loose and rotating as well. As a result I had to strip and rebuild the whole scope. It now takes some quite good images – see above. Experience with these telescopes has led me to produce the following notes, which I hope will be of use to others, and possibly lead to more discussion.

2. The scopes are generally quite robustly constructed. The main tube is fabricated from a rolled aluminium sheet, rivetted and welded. All screws are metric sizes M3 M4 or M5. The following suggested procedure for realignment assumes that the scope has been extensively stripped and needs to be rebuilt and collimated.

3. The main mirror is supported by three pairs of screws. One of each is used to push and the other to pull its suspension point. Each pair may be adjusted independently of the other two without putting any strain on the mirror. The smaller of each pair has no head but merely a slot cut in the end of the screw thread. On the MN66 I replaced these with a panhead M4 bolt. This struck me as more robust, and would allow easier access for collimation in the field. Later experience showed me that such recollimation was hardly ever necessary. After rebuilding the main mirror assembly this is the time to clean the mirror. Only do this if it’s necessary. It’s easy to do more damage to the optical surface then you recover by cleaning.

4. The secondary mirror is supported on a pillar that fits inside a hole drilled in the meniscus lens. The pillar is secured by a locknut which tightens down onto the glass. This should normally be tight and need no attention. As it was loose on the MN66 I made a special spanner to tighten it – see below (a drawing is available if necessary). On the MN78 you can grip the nut by hand.


5. Having tightened this, it is still possible for the secondary to rotate. This happens if the collimation screws are loosened too much. There is a central screw and three outer screws. Normally they should be adjusted in small steps and in such a way that they oppose each other and thus hold the secondary tightly.

6. If for any reason the secondary has slipped there is no obvious way to reset it, but I have used the following procedure with good effect. Remove the whole front assembly: for the MN56 and the MN66 by undoing the six M3 cheeshead screws at the front of the tube; for the MN78 by undoing the 3 screws that hold the diffuser ring and removing the ring, then loosening the 3 screws that secure the meniscus and removing the meniscus assembly. Place the assembly on the bench and tighten the locknut as above if necessary. Using a suitable spacer, the shank of an M3 drill works fine for the MN56 and MN66 or an M6 drill for the MN78, adjust all four collimation screws so that the gap between the movable part and the fixed part of the pillar is exactly the same all the way round, and the centre screw is done up tightly. This assumes that the telescope drawings were designed correctly by Intes Micro to achieve symmetry when collimated; it seems to work on all three scopes that I have tried. Temporarily refit the assembly to the telescope but don’t fit any screws yet. Use a suitable instrument to check that the focusser is correctly adjusted longitudinally. If not, then move it backwards or forwards as necessary and retighten the screws that fix it to the main tube. You could use a longish Cheshire eyepiece for this, but the one I ordered from the UK supplier never arrived. I made a suitable tool from a piece of 31.75mm fibreglass tube sanded down until it was a tight but sliding fit in the focusser. (Note that sanding fibreglass may have safety implications). A small circular piece of cardboard was cut and a hole pierced in the centre. It was then taped to the outer end of the tube so that the viewing hole was dead centre. When this tube is pushed down inside the focusser the right distance you can look through the pinhole and gauge quite exactly the longitudinal position of the focusser.

7. Insert a collimation laser in the focusser. Rotate it while looking down the front of the telescope to make sure that the spot doesn’t wander. If it does then the laser itself needs centring. It is now possible to rotate the whole front end assembly in the main tube and watch the laser spot traverse an arc on the main mirror. It should pass its nearest point to the centre when the front assembly is correctly located, i.e. so that you can do up its fixing screws. If not then slightly slacken the secondary centre collimation screw and rotate the secondary by hand the required amount. For the MN78 you can rotate the meniscus slightly instead, but I would recommend leaving it near to where you found it, as it may be matched rotationally to the main mirror (I don’t know). Repeat this sequence until the laser spot passes nearest to the centre of the main mirror when the front end is correctly located. Make sure everything is tight and fit the screws to hold the secondary assembly in place.

8. It’s now time to perform an ordinary collimation procedure. Insert the laser into the focusser and adjust the secondary collimation screws to centre the spot on the main mirror. Then adjust the main mirror collimation screws to return the spot to the centre of the laser face. When this happens you will see the spot become noticeably brighter. I assume this is because the laser cavity consists of two horizontally opposed mirrors, and by returning light centrally into the laser the laser action is reinforced.

9. An alternative and I think easier way to adjust the main mirror is as follows. Obtain an old fashioned 35mm film canister. This is made of plastic or metal and is exactly 1.25” in diameter. Drill a small (approx 1mm) hole in the lid and glue a shiny metal washer centrally on the inside of the lid. Cut a larger (approx 10mm) hole in the base of the canister. See below


Reassemble the canister and insert it into the focusser. Point the telescope at a bright sky, but not near the sun, and look through the 1mm viewing hole of the canister. You will see a reflected image of the washer. Adjust the main mirror collimation screws to center this.

10. That’s it! But unfortunately, it isn’t! Every time you take the scope out and set it up on the mount you should check the collimation, using the laser and film canister. What you will find is that the main mirror doesn’t shift, but every time you move the focusser, especially to accommodate different eyepieces or cameras, the laser spot falls in a different place on the main mirror. It even moves when you tighten or slacken the focusser friction adjustment knob. These are inevitable weaknesses of any telescope that has moving parts, and as far as I am aware, that means all telescopes. It arises because the focusser assembly on these scopes wobbles to a greater or lesser extent.

11. The focusser is attached to the main tube by a saddle plate. If you look carefully you will see that there are two extremely small screws buried in holes at the back and front of the saddle plate. Tighten these as best you can with a jeweller’s screwdriver. The focusser is pinned to this plate by two internal screws and these need to be tight too. On the MN66 I went further and drilled two angled holes and inserted two more grub screws to pin the focusser in four places at 90 degrees, as two are obviously not enough. This stopped the assembly rocking about the two points.

12. That isn’t the end of the story, because the three draw tubes that constitute the focusser itself also rock. Each is clamped by a single screw with a knurled head that you can loosen and retighten when you need to change the range of adjustment to accommodate widely differing focal distances. On the MN66 I fitted two more screws to each draw tube by drilling and tapping extra holes at 120 degrees from each other. The extra screws with their knobs can be seen in the photo at the top. This assembly was then much better than before, but even then the centre line shifted with changes in draw tube distances.

13. My current procedure to overcome this when observing is as follows. Set the telescope up and make a preliminary focus on the object of interest using the chosen eyepiece or camera. Remove the eyepiece or camera and insert the laser and see if the spot is on the centre of the mirror. If not then move it there if possible by adjusting the tension on the three draw tube knobs, and rotating the tubes if necessary. Usually this is possible. Only if you can’t achieve this is it necessary to adjust the secondary collimation screws. Insert the film canister and check that the main mirror is aligned. It usually is, unless you have had to adjust the secondary mirror. Everything is now perfectly set up for your observing session. This procedure is actually quite quick to perform.

14. Another mechanical improvement is to fit handles to the MN56 and MN66. These can be seen in the top photograph. They make it easy to manhandle the scopes without grabbing any vital bits, and easy to rotate the scope in its clamping rings when observing. I strongly recommend the use of these handles. They have revolutionised my observing sessions. They are not necessary for the MN78, which has rotating tube rings.

15. Further suggestions along these lines are always welcome. Despite the above, I consider that these are excellent scopes. I have never used an SCT, but understand that they have their own mechanical problems. The optical quality of the Intes Micro Mak Newts makes the above procedures more than worthwhile.

Feathertouch Focusser

16. Since writing the above, I finally got fed up with the wobbly focusser, so took the plunge and have fitted a Feathertouch focusser (model FTT20BCR) to my MN78. This can be done by retaining the existing Intes Micro saddle plate and drilling and tapping four M4 holes in it, see below:

The Feathertouch base is attached by four M4 x 12 caphead screws and washers. These are the maximum length that can be accommodated without protruding through the saddle plate. The next picture shows the focusser in place, with my fibreglass sight tube inserted for collimation:

And here is another view:

17. The focusser grips the eyepiece or laser collimator rigidly – no more wobble! Also the focussing movement is very smooth in action. I bought the adjustable base option as a precaution, in case things weren’t square after I’d fitted it. In fact I was able to achieve alignment by rotating the focusser in its holder to find a suitable position, without using the levelling screws. Fortunately this coincided with where I wanted it – see above. The literature warns that if the brass knob is knocked it can damage the reduction gear and that means a return to factory, so I placed it pointing along the tube as shown, to protect it.

Last updated 29th July 2005

John Moore

Fleet, Hants, England