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Intes-Micro Mak-Newt Collimation Procedures
People are sometimes intimidated at the prospect of aligning or tweaking these scopes, but should not be. The
collimation process is relatively straight-forward, and your efforts will reward you with the high quality images
for which these scopes are known! Once adjusted, they tend to hold collimation very well, needing only an infrequent
tweak to retain perfection..
It behooves you to know how, what, and when to adjust things though. Before you actually make any adjustments, you may want to merely check it out. A quick and accurate check to determine the state of alignment is by observing the diffraction pattern of a defocused star.
Using medium to high power, locate a mag 2 star and center it in the field of view (it is important that it be reasonably centered, as the amount of error will otherwise be skewed). Defocus to about 5 rings and note the diffraction "bulls-eye" pattern. If the rings are concentric, you're all set! (Note: the shadow of the secondary may appear offset from center... this is normal and may be ignored).
For a quick overview of these scopes, you may want to download the Orion manual for the Argonaut (aka Intes MN61) Mak-Newt. The Intes and Argonaut models differ from the Intes Micro instruments in that they use a cored primary and three screw secondary, while the Intes Micro (MNx6) scopes use a solid primary and two screw secondary (as of this writing). The manual can be found at:
Some excellent sources for a more in-depth discusion of collimation procedures and theory can be found at the following sites:
This article however, will deal specifically with the procedures as they relate to the Intes Micro MNx6 series of scopes.
When reviewing information about collimation you may come across references to offsets. This term refers to the mechanical shifting of the secondary away from the mechanical centerlines so as to properly (fully) intercept the light cone from the primary and relay it to the focuser. Fortunately, we don't have to worry about offset calculations, as one component of this is established by where the secondary is mounted on the meniscus, and will never change so long as the meniscus is not rotated. The other is adjusted by moving the focuser base fore or aft on the tube... this is also set at the factory and won't change on its own. You can check it out but shouldn't have any need to change it.
The following adjustments are made in a methodical manner, and can be done from a ground-zero starting point or anywhere beyond, but please be aware that after you make ANY adjustment, you must check all the ones that would normally follow it.
STEP 1: ENSURING THE CORRECT PLACEMENT OF THE SECONDARY IN THE OTA
You can begin by inserting a sight tube into the focuser draw tube, centering the diagonal in it. When it is visibly centered, the correct mechanical longitudinal offset has been set. As noted above, you probably will not have to adjust this. Adjustment on the MNx6 scopes is usually accomplished by sliding the focuser fore or aft on the OTA (optical tube assembly) until the secondary appears visually centered.
NOTE: I personally like to use a laser collimator to do the rest of the alignment, although a Cheshire EP will suffice. I've also used an autocollimator for the final adjustment, but prefer the laser, as it lets me set up in one felled swoop, whereas you have to already be pretty darned close before you can use the auto-collimator. In any event, a defocused star test after the alignment has proven to me (in my case... your mileage may vary) that the laser alignment is extremely accurate, with the autocollimator providing no additional benefit.
STEP 2: SETTING THE SECONDARY TO THE CORRECT OPTICAL AXIS
You must now aim the secondary directly to the center of the primary. A center marked (donut) on the primary makes this easier to do. The secondary adjuster is probably different from anything you've encountered before. It uses two screws and toggles on a center post. Remove the adjuster cap. Carefully put some dry silicon lubricant or equivalent on this, and do NOT overtighten it later when re-installing... these can sometimes be a bear to get off and can cause your freshly adjusted diagonal to rotate!
Using a pair of hemostats or long nosed pliers (placing the tips along the adjuster screws) you can carefully rotate the assembly in an arc for one directional component. If you are using a laser, you will readily see the effects here. Rotate the secondary until the beam is closest to the primary's center mark.
Use the two adjuster screws to center the beam in the donut. I found that after I get where I want to be, both screws should be run in (or out) till snug. Since these adjust a pivoting toggle, it would otherwise be prone to "drift" a little.
STEP 3: ADJUSTING THE PRIMARY
You can now adjust the primary so that the laser beam hits the secondary and comes right back into the opening on the base of the laser unit that it exited from. ONLY adjust the primary for this... if you re-adjust the secondary, the laser will no longer be at the optical center of the mirror. Some units use an internal semi-translucent diffusion screen that will intensify in brightness when the returning beam strikes it, making it easy to realize when you are dead-on.
The primary uses three push-pull sets. You must loosen one of the pair before tightening its partner. Always turn (and tighten) both... I found that just adjusting one and going back later to "snug" it's partner changes the alignment...ALWAYS loosen one, tighten the other, then tighten both!
This sounds kind of hairy, but it really becomes quite intuitive. I have to re-iterate though... a laser is a great help here! If you are fine tuning with a real star, you might want to use a 33% (roughly) central obstruction mask. You can center this (measuring from the tube walls) and avoid being misled by the offset defocused image you will otherwise encounter. It also makes it easier to see what's going on, as your CO is very tiny... this will also help "standardize" your star test views with the published results in Dick Suiter's guide (which you will no doubt want to try), as well as making it easier to detect when the CO is emerging from either side of focus.
I check my collimation (with a "live" star) before each viewing session, but it never changes. As I've often said, you could probably roll these scopes along the lawn to your mount, without changing the alignment... they're built like tanks (almost as pretty but not quite as light though)!
If there is a discrepency, it is usually minor and can be corrected by a simple tweak of the primary. See the "trick" (listed below) to make this a little easier.
A few points to ponder:
The physical center of the primary is usually, but not ALWAYS the optical center.
When using a laser, position your OTA as level as possible (parallel to the ground), so that the machined collar of the laser rests on the accurately machined top of your focuser draw tube. Do not tighten it into position, this way you are assured it is squared with everything, as opposed to having an angular offset as a result of either being too loose or tightened to one side in the draw tube.
Always rotate the laser in the draw tube prior to making any tweaks for the night, to ascertain that it (itself) is in alignment (they DO get bumped out occasionally). Observe the dot as it comes back (hopefully) onto the base of the unit (from the laser, to the secondary, to the primary, back to the secondary, and onto the bottom of the laser body). When rotated, it should still present a fixed spot. If it moves (called an excursion) the cause must be found and corrected before proceeding. Usually this means the laser needs to be re-collimated (with the adjustment screws provided).
A little trick I use to make things easier... When checking with a real star, the importance of having it centered in the FOV was previously stressed (so as to not skew the error). This phenomenom can be used to our advantage, as it actually makes it easier to do a solo collimation. If the defocused image shows a non-concentric pattern (bulls-eye), move the scope so that the star is on the the side of the FOV that had the "thin" side of rings, noticing that the error has lessened (If not, try the opposite direction). With the error lessened, tweak the corresponding screws on the primary to move the star back to your center of field. This not only keeps the star in your FOV (making adjustment far easier), but as you re-center the star, the diffraction pattern is being adjusted closer to the ideal. Repeat till perfect.
BE ALERT AND AWARE!!! A laser is capable of producing severe eye injury or blindness if improperly used!