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Re- Collimation of the Vixen VMC200L (long)

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#1 Don Taylor

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Posted 06 July 2013 - 01:50 PM

I hope that others here on Cloudy Nights that own and observe with this telescope have not had to disassemble their scopes and therefore have no need to perform a ground-up collimation. Unfortunately if you do, this is a rather lengthy and detailed process. I apologize for the wordiness.

There have been various threads here on Cloudy Nights on collimation of R-Cs and other Cassegrain style scopes that utilize spiders to support the secondary mirror. One procedure is credited to Texas Nautical Repair (the Takahashi importer for the USA). There is also a procedure on the Vixen USA website. Finally, there are suggestions on the basic mechanics in Suiter’s book “Star Testing Astronomical Telescopes”.

Combining elements of these techniques I’ve developed the following procedure, which turns out to be very similar to one posted on Howie Glatter’s collimation website for use with Cassegrains. I’ve made a few changes and simplifications because of the specific design features of the Vixen VMC200L.

In essence, the procedure is:
1). Align the focuser to the secondary spider using a laser collimator.
2). Align the secondary mirror to the focuser by folding back the laser beam.
3). (optional) align the primary to the secondary using either a holographic laser, or a procedure from TNR.
4). Final primary alignment using a star.


Earlier in the year I purchased a used Vixen VMC200L Field Makustov OTA.

The mechanicals were in fine shape but my first (and second) light with the scope revealed severe astigmatism and defocused-star diffraction patterns that were somewhat pentagonal or “shield” shaped with significant changes passing through best focus. Images of Jupiter and of double stars were poor, far worse than my ETX90 and 4” refractor, and a friend’s C-14 used for comparison. Needless to say, such optical performance was unexpected, and not at all acceptable. Thus began an epic journey……


One of the advantages of this telescope design is that the alignment of principal elements are each adjustable using sets of push-pull screws (focuser and primary mirror) and 1 pull + 3 push screws (secondary mirror). Conversely this also creates the opportunity to render the telescope worse than it was previously

First efforts to improve the images and defocused-star diffraction patterns by collimation adjustments were largely ineffective. And nothing seemed to change the non-symmetrical patterns and obvious astigmatism.

After several attempts with little improvement, I disassembled the telescope and found a significant problem. The primary is held in a cast aluminum cell and restrained by mirror clips on the reflective surface (like most Newtonian scopes). These were found to be tightened down firmly against the face of the mirror. Secondly, the edge is restrained by 6 metal+cork pads and setscrews which were tightened down very firmly against the periphery of the mirror. The primary was overconstrained – basically warped into an odd shape.

While I had the scope disassembled I cleaned the primary, then reassembled with approximately 0.010” (0.25mm) radial float between the primary and cell, and made sure that the mirror clips were clear of the primary face by the thickness of an index card (0.006” or 0.15mm).

One of the nice features discovered is a ring baffle that sits on top of the mirror clips and serves as an optical stop – so there are no diffraction effects from the 3 mirror clips. Strangely one of the screws used to hold down the clips and baffle was missing – I would assume someone had disassembled the scope previously but don’t know for certain.

Next reassembled the scope and then attempted to collimate.

I would caution that you should not need to do a ground-up collimation on one of these scopes unless you have disassembled it, or someone had previously adjusted things incorrectly, as in the case of my scope.

Glatter’s procedure has you checking the centering of each element by measuring from the tube walls. Link here. The design of the VMC200L precludes this. The telescope’s backplane and spider are machined castings, and the secondary carrier is a machined part. None have adjustments for centering. So the following procedure uses the mechanical center of the backplane and spider to establish the mechanical axis of the telescope. The collimation procedure that follows will bring the optical axis to coincide with this mechanical axis. Therefore the tube may not be perfectly concentric with the mechanical axis however this is not detrimental and any deviation will be small as it is limited by the machining tolerances of the spider and backplane.

A few definitions:

“push-pull” screws: There are 3 sets of push-pull screws used for the focuser mounting/alignment and 3 more sets for the primary mirror alignment. These work just like collimation screws for refractor telescopes. These take a 2.5mm Allen wrench on the VMC200L.

“pull screws” means the screws with flanged heads.

“push” screws means the screws with no head, just a hex socket – like a “set screw” or “grub screw”.

“backplane” is the housing at the eyepiece end of the telescope that forms the support for the focuser and primary mirror.

"secondary carrier" is the assembly of secondary mirror, menisicus corrector, baffle, and housing that holds these together.


So, to get started:

This is best done indoors in a darkened room. Place the telescope approximately level. A table works OK but my preference is to use my Duo-T mount so that I can control the position via slow motion controls.

Suggestion: Start with the focuser push screws retracted then turned in approximately 1 turn from initial contact. Do this by loosening all 3 sets of push pull screws through the focuser, then unscrew the push screws until they protrude from the focuser flange. Press the focuser against the telescope backplane with the focuser held against the backplane and turn in the screws until you feel them touch. Then turn in 1 complete turn further. Snug up the pull screws. The intent is to have the focuser start roughly parallel to the backplane, with some room for adjustment provided.

Mark the secondary carrier. I use pieces of removable sticky paper labels but just about anything removable will do. I put markings on the outside of the carrier/baffle and the adjacent spider vane so that when reinstalled it will be in the same orientation as previously. This is not really necessary because we will fully adjust the secondary in due time – but it may reduce the amount of adjustment required if the collimation is not that far off.

Remove the secondary mirror and carrier by removing the central (pull) screw from the spider while holding the secondary carrier. Remove from the telescope tube by working it between the spider vanes and set aside.

Make sure the washers installed between the secondary and spider are accounted for and set aside. These set the spacing between primary & secondary mirrors and also determine available back focus. These fit on the pull screw between the spider and secondary carrier. My scope had two.

Fashion a target and place over the central hole of the spider. I use a piece of self-adhesive label. Place a laser collimator in the focuser and fire the beam towards the spider. Place the focuser nearly (but not quite) to the in focus limit. (On my scope this is about where it is when using a 2” diagonal & eyepieces).

Adjust the push-pull screws that mount the focuser to the telescope backplane until the laser is centered in the spider hole. You can see the shadow of the hole. Adjust the push-pull screws to place the beam centered in the shadow. Loosen the pull screw, adjust the push screw and then snug up the pull screw to hold the adjustment. The correct screws are the 3 sets of push-pull screws closest to the focuser (not the ones near the outside of the backplane – those are for the primary mirror).

I use a magnifier to get a clearer image of the shadow. Once the laser beam is centered make sure the pull screws are firmly tightened – but don’t get carried away here. Recheck the laser/shadow centering after tightening the pull screws.


One suggestion: I place tape or similar over the primary mirror (outer) push-pull screws because it’s easy to use them by mistake.

Another suggestion: If your adjustments result in the focuser mounting flange being above (not flush with) the telescope backplane there is a risk that not enough threads are engaged in the pull screws.

Before finishing up the focuser alignment move the focuser to almost (but not quite) the out-focus limit and recheck. The laser pattern and shadow should still be concentric as seen previously.

Next reinstall the secondary carrier. Place the pull screw in the spider central hole, and don't forget to reinstall the washers on the screw. Thread the carrier between the spider vanes and align with the pull screw and tighten the screw into the secondary carrier with a Phillips screwdriver. Make sure the washers are not dislodged before engaging and tightening the screw. It’s a bit fiddly. Tighten the pull screw (but again don’t get carried away). As I tighten the pull screw I rotate the secondary carrier until I can feel the push screws engaging the small divots from previous use and obtain the original rotational alignment (the purpose for marking the secondary carrier and spider vane as described previously).

Next turn on the laser and adjust the push screws by loosening and tightening adjacent screws as needed to center the laser return beam precisely back into the laser collimator itself, i.e. “fold” the beam back on itself. You have to loosen one screw slightly to create enough play for the desired screw to be tightened. This process is exactly like adjusting a Newtonian telescope secondary. Once done all 3 push screws should be snug and both the outbound and return beams should coincide.

Remove the laser.

Next, the primary is adjusted. This can be done purely with a star (I use Polaris) or you can do a preliminary alignment using a variation of the TNR collimation process. Link here. This process uses your eye to align several reflections of the spider vanes with the vanes themselves, kind of a “hall of mirrors effect”. Alternately a holographic laser (I have the Glatter concentric circle attachment) can be used to set the primary by examining the image projected on a wall or ceiling. If you do a preliminary alignment of the primary by either method you should do the final alignment on a star anyway.

Suggestion: if performing a preliminary alignment of the primary tip the scope up slightly to make sure the primary is resting against it’s back. With the holographic laser you could point it at the ceiling.

Whatever you do, at this stage adjust only the primary push pull screws using the same loosen-tighten method as was previously used to align the focuser, only apply it to the outermost sets of push pull screws. Do not re-adjust the focuser or secondary screws or you will just have to start over. In fact this entire procedure starts at one end of the scope and moves through the optical elements to the other. Once an adjustment is complete, leave it alone and move on to the next adjustment. Don’t go back.

There are plenty of descriptions in the literature and here on CN of final primary collimation using a star. Essentially it’s getting the out of focus diffraction pattern of a star to appear circular and symmetrical, notwithstanding potential seeing and thermal effects. Obviously the final adjustment may not be possible until the conditions are very steady and the telescope is at thermal equilibrium. The procedure is repeated with smaller amounts of defocus, dimmer stars, and higher magnification. The amount of defocus needed becomes very small when nearing perfect collimation so that you can judge the centering of the Airy disc in the diffraction rings.

Again, at this stage only adjust the primary mirror push-pull screws, otherwise you will have to start over.

The above procedure has resulted in excellent collimation. Combined with correction of the constrained and deformed primary, the scope is now a joy to use.

I hope this procedure is of some help to users and owners of these and similar telescopes.

Clear skies and good seeing!

#2 DaveG

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Posted 06 July 2013 - 03:18 PM

Wow, great job detailing this process. Thanks!

#3 coopman

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Posted 06 July 2013 - 08:33 PM

Thanks for the info Don. I hope that I never have to go thru that!

#4 Don Taylor

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Posted 07 July 2013 - 09:46 AM

Thanks for the info Don. I hope that I never have to go thru that!


Actually, once you get into it - it's not that bad. Part of the problem is trying to describe an intricate process using only words.

There are lots of little details and when writing up something you either put in tons of details or assume that others know what you're talking about. Try to describe changing a tire on an auto (using only words) to someone not familiar with the process.

In retrospect the procedure I posted would probably be better if it was illustrated with drawings or photographs

Having gone through the process a couple of times and learning from my mistakes.......I could probably do the first 3 phases in less than 30 minutes without rushing. (The last phase obviously requires the night sky).


The key is working carefully and going through the basic steps in order. Collimating the secondary without first squaring the focuser is a waste of time. Likewise adjusting the primary without the secondary and focuser being aligned will just make you pull your hair out. You will not get a good result.

Hopefully you won't have to go through all this - but if you do don't be afraid of it. All the adjustments are reverseable. They can be undone. Just go step by step. If fhe result isn't quite right then just re-do it. You will get there.

#5 jjack's

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Posted 08 July 2013 - 02:15 AM

On mine i disasemble the 6 metal+ cork pad and put some thick adhesive tape (1mm) around the baffle. Because it's better to maintain the primary Mirror by the center (like SCT's)I put the same thickness between the adhesive tape and the hole in the Mirror. It's an absolute performer now.

#6 Don Taylor

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Posted 09 July 2013 - 10:48 PM

On mine i disasemble the 6 metal+ cork pad and put some thick adhesive tape (1mm) around the baffle. Because it's better to maintain the primary Mirror by the center (like SCT's)I put the same thickness between the adhesive tape and the hole in the Mirror. It's an absolute performer now.


This is a clever idea!! I agree - anything that eliminates stress on the mirror and allows it to take it's natural shape is a good thing. (and it's still supported on its back face as designed). I like it!

#7 bremms

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Posted 11 July 2013 - 12:08 PM

Good job Don, I had a VMC200l and sent the first back because it was just as you described. The replacement was better but could have been improved as well.

#8 Orion58

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Posted 12 July 2013 - 05:15 PM

A very informative and timely post Don. Although I have the VC200L I shared some of the same issues as you did in early June.

As I’m sure you’re aware the main knock on these OTAs is the thick spider vanes which results in bloated square stars when imaging. As I mainly image through the scope I had been contemplating grinding the vanes as many other Vixen owners have done. After June’s new moon I jumped into my project which involved taking the entire OTA apart including focus tube and mirror cell. In addition to grinding the spider I wanted to clean the primary and check the mirror cell for proper “play” as you described. The grinding took quite a bit longer than planned but turned out well. My vanes averaged over 5mm in thickness prior to grinding. When I was done they averaged slightly over 1mm. The primary cleaning went fine and I did discover that the mirror had no lateral movement in the cell – I adjusted the screws so it has between 0.5mm and 1.0mm of movement. Things were going quite well until reassembly/collimating. I had never collimated a telescope before but was confident that I had read and studied every single manual/article/blog that was ever written on the subject... :grin: For the sake of brevity I will summarize by saying that I experienced everything you did. To top it off after I had the focuser to spider and secondary back to focuser collimated I picked the scope up and heard something rattling around in the OTA…not good... :bawling: Of course it didn’t fall out when I tilted it forward – it didn’t matter at that point as anything that would have fallen out belongs somewhere. So….I dismantled the OTA again, including the mirror cell. What I found was one of thespacer washers that should be positioned between the secondary and the spider assembly…So after several hours of disassembly/reassembly/collimation I had things back on course. During the collimation process I did use a laser but I also used the visual method described in Vixen’s documents to verify I was on the right track.

The project turned out great, no more square bloated stars and the collimation has helped tremendously.

I just wish you would have published your comments about 3 months earlier! ;) All kidding aside you did a fine job on this.

#9 Don Taylor

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Posted 12 July 2013 - 08:46 PM

Glad you worked things out as well! I'd like to see some images taken with your modified Vixen.

I've actually gone through the collimation process numerous times - but my old 1 1/4" laser used in a 1.25 - 2" adapter was just enough off (even trying various orientations) that the focuser was not really looking at the center of the secondary.

Doesn't sound like too big a deal until you adjust the secondary to fold back an off-center beam. That results in a tilted secondary and elliptical defocused images I struggled with slightly elliptical images for quite a while.

Just before writing the original post I picked up a 2" Glatter laser and it showed no variation when rotated in the clicklock visual back. Centering the beam in the spider correctly then effectively centers the secondary and the rest was easy. Now nice symmetric images.

Ya gotta start with the focuser and then progress through the optical path. You can't jump around or start with the secondary etc. just doesn't work. Just as you found out.

Also, there have been several reports now of these scopes arriving with tightly mounted primaries. Whoever was assembling these must have been having some bad days!

Thanks for the nice comments and for sharing your experiences with these unusual scopes.

#10 Orion58

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Posted 13 July 2013 - 09:25 AM

Glad you worked things out as well! I'd like to see some images taken with your modified Vixen.

I've actually gone through the collimation process numerous times - but my old 1 1/4" laser used in a 1.25 - 2" adapter was just enough off (even trying various orientations) that the focuser was not really looking at the center of the secondary.

Doesn't sound like too big a deal until you adjust the secondary to fold back an off-center beam. That results in a tilted secondary and astigmatism. I struggled with slightly elliptical images for quite a while.

Just before writing the original post I picked up a 2" Glatter laser and it showed no variation when rotated in the clicklock visual back. Centering the beam in the spider correctly then effectively centers the secondary and the rest was easy. Now nice symmetric images.

Ya gotta start with the focuser and then progress through the optical path. You can't jump around or start with the secondary etc. just doesn't work. Just as you found out.

Also, there have been several reports now of these scopes arriving with tightly mounted primaries. Whoever was assembling these must have been having some bad days!

Thanks for the nice comments and for sharing your experiences with these unusual scopes.



After putting the OTA back on its pier in my observatory and as soon as conditions allowed I did a star test. I had done a visual check of the primary – as described in Vixen’s literature – so I hoped collimation would be relatively close. Seeing wasn’t the greatest but I could make out the diffraction pattern and it was very close. After staring at the pattern long enough I detected they were not completely concentric and made very slight adjustments on the primary. I will add that I did have electrical tape covering the collimation screws for the focuser… ;)

After I had made these adjustments I mounted my camera gear and swung up to M3. I did not put my focal reducer in because I did not want another optic in the imaging train. I took about 1.5 hours of 240 second subs. Below is the stacked result straight out of DeepSkyStacker. I used levels to brighten the stars a bit but nothing else.

I was generally pleased on two counts. First: the bright stars are not bloated and square. Before grinding the spider vanes there would have been 4-5 stars (at least) that would have been that way. Second: It appears my collimation is very close – guiding at f/9 can be a bit challenging for my system but the stars appear OK to my eye. Here is a link to a larger version of the (processed) image:

http://www.flickr.co...set-72157628...

And the processed image/description:
http://www.flickr.co...t58/9161573588/


You remarked about using the clicklock system – that is exactly what I used and for the same reasons as you mention. I used a Hotech SCA laser but rotated it like you did as a check.

It had been a project that I had been dreading for quite some time but after doing it I feel a lot more confident about collimating and adjusting this OTA. FYI I have printed out your “tutorial” and filed it in my Vixen folder. :grin: Thanks again for putting the effort into creating it.

Attached Files



#11 jjack's

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Posted 15 July 2013 - 01:49 PM

Like i said earlier, the big problem seem to come from the primary support. When i tightened the push-pull screws i saw very bad astigmatism. releasing the 6 metal+cork pads and setscrews around the miror can solve the problem, but on mine i got slight miscollimation when i moved the scope along the sky.
The first try , as you see on the picture was to support the Mirror on 3 points @ 80% and not at the edge to avoid flexion. But the result was only marginal.
The second was to remove the 6 metal+cork pads and setscrews around the Mirror and stop it by the center with 3 thick parts of adhesive (red)tape. the last try (not seen) was to put the adhesive all around the primary baffle. let a little loose between the inner part of the primary and the adhesive tape And this method give the best result. no sign of decollimation in all directions.

Attached Files



#12 Don Taylor

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Posted 15 July 2013 - 06:16 PM

Thanks for the photos - I'm surprised how few stars show diffraction spikes.

#13 Don Taylor

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Posted 15 July 2013 - 06:21 PM

Thank you! I plan on trying your method the next time I disassemble the scope. I assume the 3 edge clips and ring baffle are used as originally designed by Vixen?

#14 jjack's

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Posted 17 July 2013 - 10:32 AM

Yes Don, the 3 edge rubber clips and ring baffle are originaly designed by vixen. However i put them again to avoid the Mirror escape. But tight the screws only just a little.

#15 DaveG

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Posted 19 July 2013 - 06:52 PM

Don, I can't thank you enough for posting these directions. After purchasing a glatter collimator and the concentric attachment, this evening I finally decided it was time to tackle this procedure. Following your directions made this process so much easier, and it only took about an hour or so. I didn't even have to collimate the primary, only the secondary and focuser were off, and they weren't off by much. Hopefully I will get a star test soon to verify that everything is aligned. Thank you again!

#16 Don Taylor

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Posted 20 July 2013 - 12:48 AM

You are welcome!

I have the focuser & secondary dialed in. After then doing the primary with the hologram reticle in the Glatter I did have to adjust the primary a bit based on star test. I'm really close but we have bad awful, unsteady skies for months now. With my shortest eyepiece (4.7mm ES82) I can still see just a smidge of decentering but it's so unsteady I'm just going to use it as is until I get a steady night.

Here's another tip ( I think from Suiter's book)........

When you are doing the final adjustment of the primary on a star if you do see some decentering when almost focused... You can figure out the correct collimation screw to adjust by defocusing a lot ( big donut) then placing your hand over part of the sky end of the scope and you can see the shadow of your hand. Move your hand ( shadow) until it lines up with the direction of decentering. The adjust the screw in line with your hand (or if between two Collimation screws - then adjust the screw diametrically opposite)

Sounds kinda confusing until you try it . This tip is only to figure out which primary screw to adjust - you need to be very nearly focused to be sensitive enough to get it fully collimated.

Also don't forget to get your star back in the center of the fov when finalizing the adjustment.

Like I said - mine is close with nice round (slightly) out of focus patterns - but I see a very slight decentering when almost perfectly focused. Nearly there. :jump:

#17 DaveG

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Posted 20 July 2013 - 12:59 AM

Whew... What a long night. I thought the primary was centered, at least it looked like it. I star tested it tonight in unsteady skies and sure enough, it was way off. I was out for 3 hours tonight trying to get the thing perfect but there is no way that's going to happen with the wind and boiling skies. That's a great tip about placing your hand over the end of the scope. I'm hoping Sunday night things will settle down and I will be out to try again. It's pretty close right now, but I can see a little bit of decentering like you, but it's not too bad. Wow, what a process.....

#18 ohioalfa64

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Posted 24 July 2013 - 08:32 PM

Don, did all your effort result in longer lasting collimation and better visual observation? You mentioned that in your introduction and reasoned that the collimation was the problem. My question poses, what are your observable results? Does your scope keep better, longer-term collimation? You stated you have repeated this practice several times. We're these done to improve the process or because you have continuing de-collimation issues that need continual addressing. Or, perhaps you travel and take the scope up and down form the mount. Something must be going on. Please elaborate on this. Thanks for your long but greatly appreciated tome on "how to". You are correct. Photos would be greatly beneficial and probably result in shorter text.

Bruce, did you radius or debur your machines edges of your spider? Are they rounded or 90 degree angles with the flat surfaces? Did you paint them or leave them bare metal?

Many thanks to both of you. I am sure I will figure more questions before I try this for the first time.

#19 Don Taylor

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Posted 24 July 2013 - 09:10 PM

Too early to judge how stable the collimation will be. From the mechanical bits I expect it will be very stable. (But time will tell).

The reason for doing the process several times (and learning from my mistakes)....is that I initially tried to solve the pinched optics problem through collimation. I didn't know how the primary was restrained.

Once that was fixed (requiring complete disassembly) then the scope improved but I still had some trouble. Turns out it was a slightly out of alignment laser collimator. Since using that resulted in a slightly tipped focuser ( the first step) the collimation was never quite right.

Finally I bought a Glatter 2" (with Barlow attachment) so I can use it in the Vixen and my other scopes.

Once getting the Glatter everything improved - but as in my last post the final star adjustment of the primary is not complete due to seeing.

Again, I'm looking forward to finishing and expect the adjustments to be very stable (2 adjustments are just like refractors, and the 3rd like a Newt secondary).

I hope I don't have to do the entire process again, but if I do I will get out the studio lights and camera and take some proper pics.

#20 Don Taylor

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Posted 24 July 2013 - 09:47 PM

And just was this tome really needs......another refinement:

When reinstalling the secondary (make sure to install the washers).....you want to make sure the center screw does not tighten the secondary hard against the spider. If you do then any adjustment of the secondary will be hard because you are bending the spider. So what I've done now is to retract the secondary push screws, install the pull screw, washers, and secondary carrier. Snug up the pull screw then loosen approx 1/4 turn. Then extend the push screws and collimate as described in the original procedure. ( by loosening and tightening alternate push screws.

This makes sure the secondary can pivot about the pull screw. You want it to allow the secondary to move slightly - you don't want the pull screw to bolt the secondary to the spider.

When finished the tension in the pull screw will balance the compression of the 3 push screws (and they all will be fairly tight). The washers should have a little play - but I don't know how you could determine that - its just about impossible to see. I guess you have to trust that snug and then back off 1/4 turn will get you there.

Now - don't go off and redo collimation - this might be needed only if your secondary adjustment doesn't respond to your adjustments. It's probably ok otherwise.

#21 ohioalfa64

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Posted 25 July 2013 - 06:20 PM

What did you use to clean the primary mirror? ISO alcohol with kewtip? Blow off first with clean air from small bladder? Did you wrap the central hub (baffle) with the tape so the fit with the primary mirror was snug? No tape under (backside) the primary mirror? You said the 3 plastic shows holding down the primary mirror were not snug but has a 1mm gap. Does this mean you snugged them and then backed off 1/4 turn of screws? Again thanks for sharing your valuable experience and knowledge.

#22 bremms

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Posted 25 July 2013 - 10:59 PM

I was told the mirrors are dielectric coated. Don't know if that is true. If so, they would be difficult to scratch.

#23 Don Taylor

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Posted 26 July 2013 - 05:55 AM

I was told the mirrors are dielectric coated. Don't know if that is true. If so, they would be difficult to scratch.


I understand the coatings on the VC200 VISAC are dielectric, the VMC uses normal coatings I believe. The coatings appeared to be normal aluminum.


I cleaned the primary when it was removed from the scope using the normal techniques use for Newtonian mirrors. I rinsed with running water in the sink prior to using the distilled water (+drop of dawn) and cotton balls method. I have not cleaned the secondary but would use methods same as refractor objectives.

To set the mirror clips I placed a thin piece of paper between the clip and mirror face and then tightened down the clips just to the point where I could still move the paper. I bent up the edge of the paper to allow me to remove the paper without touching the mirror face.

Did not apply tape - just made sure the cork+metal pads around the outside of the mirror allowed a small amount of play so as to avoid deforming the mirror. The back face of the mirror is supported by 3 round pads in the mirror cell.

Another poster to this thread has used tape around the baffle to allow elimination of the 6 cork+metal pads around the outside of the mirror.






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