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Mak-newt collimation...

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#1 shredder1656

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Posted 26 July 2021 - 12:53 PM

Tried to locate and read a variety of info on this. Still not quite convinced I understand it all.

At this point my question is focused mainly on WHERE to start.

I understand there are 3 spots that allow adjustment for collimation. If your scope's defocused image is slightly, very slightly out of collimation, where should you start? Seems like you'd start at the primary mirror for miniscule or "finishing" adjustments.

Is this even close to correct?

#2 Jeff B

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Posted 26 July 2021 - 01:20 PM

Which Mak-Newt do you have?

 

For the Intes Mak-Newts, I always start by disengaging the secondary adjustment screws until the secondary is flush with the front of the holder, then pull the secondary holder assembly up flush against the corrector securing it modestly with the center bolt

 

I then slide the focuser forward/backwards until it is centered axially over the secondary.

 

Then adjust secondary rotation

 

Adjust focuser using a good sight tube to make sure it is square over the secondary.  Tweak secondary rotation if needed.

 

Use secondary adjustment screws to put quality laser in the middle of the primary mirror donut.  Lock secondary adjustments with the holder's center bolt.

 

Adjust the primary with any number of tools.  I use a barlowed laser and adjust the primary so that the shadow of the primary's center donut is centered over the laser's aperture.  

 

Works great for me.

 

Jeff


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#3 Paul Hyndman

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Posted 26 July 2021 - 01:55 PM

Years ago I put a how-to here on cloudy nights. Before you make any adjustments, you may want to just check to see if it really needs a tweak or two (an excerpt):

 

A quick and accurate check to determine the state of alignment is by observing the diffraction pattern of a defocused star. 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.

 

Once set, most MNs hold collimation extremely well seldom requiring so much as a tweak.

 

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#4 shredder1656

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Posted 26 July 2021 - 04:23 PM

Which Mak-Newt do you have?

 

For the Intes Mak-Newts, I always start by disengaging the secondary adjustment screws until the secondary is flush with the front of the holder, then pull the secondary holder assembly up flush against the corrector securing it modestly with the center bolt

 

I then slide the focuser forward/backwards until it is centered axially over the secondary.

 

Then adjust secondary rotation

 

Adjust focuser using a good sight tube to make sure it is square over the secondary.  Tweak secondary rotation if needed.

 

Use secondary adjustment screws to put quality laser in the middle of the primary mirror donut.  Lock secondary adjustments with the holder's center bolt.

 

Adjust the primary with any number of tools.  I use a barlowed laser and adjust the primary so that the shadow of the primary's center donut is centered over the laser's aperture.  

 

Works great for me.

 

Jeff

I have the Intes Micro MN65.  I purchased it used recently, and it is my first MN.  It is a little intimidating, relative to any collimation adjustments or other tasks. 

 

I appreciate the step-by-step.  I am really hoping it is not necessary to get that deep.  However, someday...SOMEDAY...not any time soon, if I can avoid it, I need to clean the scope.  There is a fair amount of dust inside.  Not enough to make me concerned about it, but enough that it gets me right square in my OCD.  When that time comes, these step-by-step instructions will be a huge help. 

 

I am not even sure that it needs ANY tweaking.  I intend to spend some time under the stars with it before doing anything.  I am just trying to do a little recon.  See below...

 

Years ago I put a how-to here on cloudy nights. Before you make any adjustments, you may want to just check to see if it really needs a tweak or two (an excerpt):

 

A quick and accurate check to determine the state of alignment is by observing the diffraction pattern of a defocused star. 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.

 

Once set, most MNs hold collimation extremely well seldom requiring so much as a tweak.

Thank you!  I read through your how-to.  I honestly will need to read it through several times, I am sure, before it sinks all the way in.  Lots of layers to pass before I comprehend it all. 

 

One question, which explains why I am not sure it needs any adjustment AT ALL, is regarding what the defocused "collimation check" image should look like.  Am I NOT looking for a bull's-eye image like I aim for with my SCT? 

 

When you say "non-concentric", but also "bull's-eye", I confuse myself.  I assume we WANT a bull's-eye, which I would think would be concentric, not non-concentric.  What am I missing?

 

I started researching how to collimate the MN, because the very short time I had with the scope, I "checked" it on a star.  If I would have seen the same image in my SCT, I would have assumed it was slightly out of collimation, because the inner part of the image did not appear to be dead-center, relative to the outer edge of the defocused image. 

 

I apologize for not explaining well.  Believe it or not, English IS my FIRST language.  I am just struggling to describe things well. 
 

 

PS.  By the way, that scope looks like a monster, and awesome!


Edited by shredder1656, 26 July 2021 - 04:26 PM.


#5 Paul Hyndman

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Posted 26 July 2021 - 05:40 PM

... One question, which explains why I am not sure it needs any adjustment AT ALL, is regarding what the defocused "collimation check" image should look like.  Am I NOT looking for a bull's-eye image like I aim for with my SCT? 

 

When you say "non-concentric", but also "bull's-eye", I confuse myself.  I assume we WANT a bull's-eye, which I would think would be concentric, not non-concentric.  What am I missing?

When properly collimated with the star placed in the CENTER of the FOV, the defocused image should look like a bulls eye with all the rings concentric (sharing a common center). If not properly collimated, the bulls eye will be deformed they with thin rings on one side and thick on the opposite side (shifted left/right or up/erdown), when in the CENTER of the FOV. Repeat, when it is centered in the FOV! Nudging the scope towards the "thin" side of the rings image, should make them look better and the primary adjustment screws can be used to bring the image back to the center of the FOV where the image will be closer to fully collimated. Repreat until the image when in the CENTER of the FOV is a perfect bulls eye.

 

Again: it must be in the center of your FOV, as moving away from the center magnifies any errors.

 

Always check BEFORE diddling with adjustments, as these MNs hold collimation extremely well with little intervention. Also, don't get too persnickety, good enough often is much more than sufficient... enjoy the views! I've known people who've spent entire sessions "star testing" rather than enjoying their equipment.

 

For reference, the left image shows concentric rings while the right side shows non-contric rings with thin rings on the left side, thick on the right.

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#6 shredder1656

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Posted 26 July 2021 - 06:36 PM

When properly collimated with the star placed in the CENTER of the FOV, the defocused image should look like a bulls eye with all the rings concentric (sharing a common center). If not properly collimated, the bulls eye will be deformed they with thin rings on one side and thick on the opposite side (shifted left/right or up/erdown), when in the CENTER of the FOV. Repeat, when it is centered in the FOV! Nudging the scope towards the "thin" side of the rings image, should make them look better and the primary adjustment screws can be used to bring the image back to the center of the FOV where the image will be closer to fully collimated. Repreat until the image when in the CENTER of the FOV is a perfect bulls eye.

Again: it must be in the center of your FOV, as moving away from the center magnifies any errors.

Always check BEFORE diddling with adjustments, as these MNs hold collimation extremely well with little intervention. Also, don't get too persnickety, good enough often is much more than sufficient... enjoy the views! I've known people who've spent entire sessions "star testing" rather than enjoying their equipment.

For reference, the left image shows concentric rings while the right side shows non-contric rings with thin rings on the left side, thick on the right.


Thank you! I'm catching on, I think. Much appreciated, both of you. Thanks.

#7 Jeff B

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Posted 26 July 2021 - 09:25 PM

At focus, you should see no/scant coma at high powers (~200X or more).  But make sure you have decent seeing and the scope is thermally stable.

 

Here is an excellent reference to judge coma and its degree:

 

https://www.telescop...aberrations.htm

 

Number 4.

 

Where in Indiana do you live?  I live in Lebanon OH.

 

Jeff


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#8 shredder1656

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Posted 27 July 2021 - 03:09 AM

At focus, you should see no/scant coma at high powers (~200X or more).  But make sure you have decent seeing and the scope is thermally stable.

 

Here is an excellent reference to judge coma and its degree:

 

https://www.telescop...aberrations.htm

 

Number 4.

 

Where in Indiana do you live?  I live in Lebanon OH.

 

Jeff

Thank you.  All of this info is very helpful.  Much appreciated.

 

I am in the Fort Wayne area. 

 

I've been to the Lebanon area years ago.  I think it is around a 2.5 hr drive. 



#9 Jeff B

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Posted 27 July 2021 - 05:12 PM

I have lots of experience with the Intes scopes and I can help you through collimation but its best to do it in person.  I can also test your scope in double pass auto-collimation (DPAC) for optical quality. 

 

I just sold a gent a MN76.  He drove out from NM (!) to pick it up and demonstrated DPAC and how to collimate it. 

 

Of the dozen Maks and MNs I've owned, none have arrived in collimation except for a small M500. 

 

Does you MN65 have an aftermarket focuser?

 

Jeff  


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#10 shredder1656

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Posted 27 July 2021 - 07:09 PM

I have lots of experience with the Intes scopes and I can help you through collimation but its best to do it in person. I can also test your scope in double pass auto-collimation (DPAC) for optical quality.

I just sold a gent a MN76. He drove out from NM (!) to pick it up and demonstrated DPAC and how to collimate it.

Of the dozen Maks and MNs I've owned, none have arrived in collimation except for a small M500.

Does you MN65 have an aftermarket focuser?

Jeff


Very kind of you. I'm not opposed to that at all. It will just depend on timing, etc. In the meantime, I have work to do on the mount and go-to, so no rush.

I believe it's the Intes Micro MN65Q. I'm pretty certain, based on info provided by a few members on here, that the JMI focuser is original to the scope.

I picked it up in person from the original owner, so it has a chance, possibly slim, of being in collimation.

The mount, lack of a working drive currently, weather, and my obligations, have made it problematic to give it a thorough look.

I was hoping to go to the local public night at the astro club, in hopes that another member would have some experience. But, looks like we'll be out of town.

Regardless, at some point the dpac would be interesting.

Thanks!

#11 TG

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Posted 28 July 2021 - 02:00 PM

I used to have the perception that collimating a Mak-Newt was just like a collimating a Newt. This is true if only a small tweak is needed. In this case, leave the secondary alone and adjust the primary using a star.

 

However, if collimation needs to be done from scratch, we have to remember that the aperture stop of a Newtonian is the primary mirror, while that of a Mak-Newt is the corrector. Thus, in a Newtonian, we can be sloppy with squaring the focuser but get away with it because at the end of the process, we can still have a collimated system, but one where the optical axis and the tube axis don't coincide, which is no biggie since Newtonian tubes are generally oversized. In a Mak-Newt, unless the corrector and primary axes coincide, you'll have astigmatism, coma or a mix of both.

 

Because the corrector is fixed to the tube and has no collimation adjustments (thank Heavens!), we really have to make sure that the focuser is square to the tube. One way of doing this is to seat the secondary right against its cell by pulling in all the screws and then adjusting the focuser till the secondary looks centered w.r.t the focuser using a sight tube. Hopefully the focuser has a lateral adjustment along the tube axis and this can then be used to center the secondary in the sight tube. If no such adjustment exists (such as in the older Argonauts), you'll have to turn the collimation screws equally to move the secondary toward or away from the primary. After this, you can proceed with aligning the secondary using a sight tube or a laser but aligning the primary is usually problematic in Mak-Newts such as the MN65 due to the central plug holding the primary. In this case a barlowed collimator can be useful: just adjust till the shadow of the plug is centered. The final collimation can be tweaked on a star.

 

TG


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#12 sonny486

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Posted 28 July 2021 - 11:07 PM

I came up with this method for checking optical alignment for scopes that have been moved too far out of collimation due to focuser installation, or improper adjustments that have gotten the alignment so far out of alignment.

 

 

I ONLY recommend this for Mak-Newt scopes that have been put so far out of adjustment or secondary mirror has been 'adjusted to far out of alignment'

 

 

https://drive.google...iew?usp=sharing


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#13 Jeff B

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Posted 28 July 2021 - 11:20 PM

I used to have the perception that collimating a Mak-Newt was just like a collimating a Newt. This is true if only a small tweak is needed. In this case, leave the secondary alone and adjust the primary using a star.

 

However, if collimation needs to be done from scratch, we have to remember that the aperture stop of a Newtonian is the primary mirror, while that of a Mak-Newt is the corrector. Thus, in a Newtonian, we can be sloppy with squaring the focuser but get away with it because at the end of the process, we can still have a collimated system, but one where the optical axis and the tube axis don't coincide, which is no biggie since Newtonian tubes are generally oversized. In a Mak-Newt, unless the corrector and primary axes coincide, you'll have astigmatism, coma or a mix of both.

 

Because the corrector is fixed to the tube and has no collimation adjustments (thank Heavens!), we really have to make sure that the focuser is square to the tube. One way of doing this is to seat the secondary right against its cell by pulling in all the screws and then adjusting the focuser till the secondary looks centered w.r.t the focuser using a sight tube. Hopefully the focuser has a lateral adjustment along the tube axis and this can then be used to center the secondary in the sight tube. If no such adjustment exists (such as in the older Argonauts), you'll have to turn the collimation screws equally to move the secondary toward or away from the primary. After this, you can proceed with aligning the secondary using a sight tube or a laser but aligning the primary is usually problematic in Mak-Newts such as the MN65 due to the central plug holding the primary. In this case a barlowed collimator can be useful: just adjust till the shadow of the plug is centered. The final collimation can be tweaked on a star.

 

TG

Good stuff and I did not know that the primary was cored on this model.  My MN55 had a "conventional" primary holder with the mirror center spotted.

 

Yeah, my first move is to always square up the secondary and its holder flush against the corrector and use that as my reference to proceed.

 

If the stock focuser supplied is a JMI model, the scope was probably sourced from Teton Telescopes.  It should be a really ice scope when properly dialed in.

 

Jeff


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#14 TG

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Posted 29 July 2021 - 11:34 AM

Good stuff and I did not know that the primary was cored on this model.  My MN55 had a "conventional" primary holder with the mirror center spotted.

 

Yeah, my first move is to always square up the secondary and its holder flush against the corrector and use that as my reference to proceed.

 

If the stock focuser supplied is a JMI model, the scope was probably sourced from Teton Telescopes.  It should be a really ice scope when properly dialed in.

 

Jeff

I've owned two of these scopes and always been frustrated by the central plug till I realized it's the a larger version of the center spot mirrors usually have for collimation. I 3-D printed my own barlowed collimator to help with this collimation:

 

rlNqF3Wl.png

 

The method I use with it is to insert a bare laser first into the focuser and adjust the secondary. Then, to adjust the primary, I insert the barlowed laser and then adjust the collimation screws on the device to center the expanded diffraction pattern from the barlow w.r.t. the central plug, and then adjust the primary to center the shadow of the plug on the collimator.

 

Here it is in action in an earlier version on a regular Newt:

 

CYb3ka6l.png

 

3-D printer models and instructions here:

 

https://drive.google...uyt?usp=sharing

 

TG


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#15 TG

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Posted 29 July 2021 - 11:36 AM

Good stuff and I did not know that the primary was cored on this model.  My MN55 had a "conventional" primary holder with the mirror center spotted.

 

Yeah, my first move is to always square up the secondary and its holder flush against the corrector and use that as my reference to proceed.

 

If the stock focuser supplied is a JMI model, the scope was probably sourced from Teton Telescopes.  It should be a really ice scope when properly dialed in.

 

Jeff

BTW, these MN65 models were marketed by Markus Ludes.


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#16 Jeff B

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Posted 30 July 2021 - 08:51 AM

Ok TG now I get it.  Your collimation procedure is just like mine with the exception of the ability to adjust the laser holder.  I use a T-Blug.  Good stuff!

 

I imagine then the plug is rather small in diameter for its "shadow" to fit on the face of your centering surface.

 

Jeff


Edited by Jeff B, 30 July 2021 - 08:52 AM.

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#17 TG

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Posted 30 July 2021 - 08:12 PM

Ok TG now I get it.  Your collimation procedure is just like mine with the exception of the ability to adjust the laser holder.  I use a T-Blug.  Good stuff!

 

I imagine then the plug is rather small in diameter for its "shadow" to fit on the face of your centering surface.

 

Jeff

Exactly, Jeff. I wrote the abbreviated version above but the document at the 3-D files link explains more. The problem I had was that because of being 3-D printed, the alignment of the barlowed laser was usually off and needed to be made exactly equal to that of the bare laser. Hence the collimation screws and the procedure to align the barlowed laser.

 

I don't offhand remember the diameter of the plug but its shadow fits neatly on the centering pattern.

 

TG


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#18 Jeff B

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Posted 31 July 2021 - 11:39 AM

Exactly, Jeff. I wrote the abbreviated version above but the document at the 3-D files link explains more. The problem I had was that because of being 3-D printed, the alignment of the barlowed laser was usually off and needed to be made exactly equal to that of the bare laser. Hence the collimation screws and the procedure to align the barlowed laser.

 

I don't offhand remember the diameter of the plug but its shadow fits neatly on the centering pattern.

 

TG

Cool.

 

I had my Mathias Wirth/APM MN86 out last night for a test spin and it delivered.  Collimation was dead on and the star test showed no coma at focus up to the limit of seeing which was, last night, a little north of 210x. 

 

This scope was/is a bear to collimate.  It's secondary is tiny, with only a mm or two of fully illuminated FOV...if that (!).  This makes squaring of the focuser and centering it over the secondary more important than with a "normal" newtonian.  It also drives home the importance of the very first collimation steps you and I recommend to the OP:  Seating the secondary up against its holder then seating the holder up against the meniscus. 

 

This is impractical with my MW MN86 because the focuser is fixed on the tube and cannot slide forward and backwards like the Intes series of MNs, which is a huge convenience.  For my MN86, I had to precisely measure where the center of the focuser was then remove the meniscus/secondary assembly (it has its own precisely machined cell), then precisely move the secondary forward to match the center of the focuser, carefully adjust the holder and secondary so that they were precisely perpendicular to the center of the meniscus, and finally reinstall the meniscus cell to check where things were at.  I did this several time before I nailed it.  Collimation after those initial machinations, including final focuser squaring up, went quickly. 

 

One thing I have found rather common with primary mirror holders is that when properly adjusted for a tiny bit of lateral play between the mirror and cell, the mirror can indeed slide sideways a little.  While not really important for a dob mount, it is when using a GEM as the mirror will indeed shift sideways, throwing off collimation slightly as it slews around the sky.  My MN86 was no exception.  My simple solution was to put a dab of silicone caulk between the mirror and each of the "pedals" support the mirror.  This keeps the primary from sliding around.  

 

Jeff

Attached Thumbnails

  • MW MN86 A.jpg
  • MW MN86 secondary.jpg
  • Secondary Through Sight Tube at Focus.jpg

Edited by Jeff B, 31 July 2021 - 12:24 PM.

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#19 TG

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Posted 31 July 2021 - 02:10 PM

Nice MN86, Jeff! I've always wanted one but was never lucky enough to snag one when they come up for sale. 

 

I'm surprised they have a "regular" primary in the MN-86. The center mounted one is usually a conical primary with less thermal mass and keeps collimation rock solid. It's a bit of a pain to collimate but with the barlowed collimator, that problem is solved.

 

TG


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#20 Matt Looby

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Posted 03 August 2021 - 08:41 AM

I remove the primary mirror, adhere the catseye triangular reflective  arrow.

 

While the primary is removed, ensure the focuser is

centered on the secondary.  You can adjust the focuser axially  (forward  or back) until it looks centered.  

 

If the secondary needs adjustment turn the tube downwards and carefully unscrew the secondary cap.

This will ensure the cap does not fall onto and scratch.

 

Adjust the secondary.

 

Reinstall the primary and make adjustment until the triangle is perfectly center in the sight tube ring.

 

Once all this is accomplished, the MN should never 

go out of collimation.

 

The Catseye is designed to reflect light, shine a light

down the tube, like at night and check collimation, if there is a misalignment,  you can easily a rapidly acquire perfect collimation.

 

Make sure you focuser extension tube are set at approximate height that is used for observing.  Mine

is set for Orthos.  Than do all the above.

 

Hope this helps.

 

Matt 


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#21 Matt Looby

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Posted 03 August 2021 - 08:42 AM

I remove the primary mirror, adhere the catseye triangular reflective  arrow.

 

While the primary is removed, ensure the focuser is

centered on the secondary.  You can adjust the focuser axially  (forward  or back) until it looks centered.  

 

If the secondary needs adjustment turn the tube downwards and carefully unscrew the secondary cap.

This will ensure the cap does not fall onto and scratch.

 

Adjust the secondary.

 

Reinstall the primary and make adjustment until the triangle is perfectly center in the sight tube ring.

 

Once all this is accomplished, the MN should never 

go out of collimation.

 

The Catseye is designed to reflect light, shine a light

down the tube, like at night and check collimation, if there is a misalignment,  you can easily a rapidly acquire perfect collimation.

 

Make sure you focuser extension tube are set at approximate height that is used for observing.  Mine

is set for Orthos.  Than do all the above.

 

Hope this helps.

 

Matt 


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#22 shredder1656

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Posted 15 August 2021 - 03:59 PM

Thanks to everyone on this thread, but specifically to Jeff B.  He sacrificed his Saturday morning to spoonfeed me the details of collimating this style of scope.  Beyond that, he opened his home, and showed me his huge and impressive collection of scopes and mounts.  I forgot to take a picture, so I could use his collection as proof to my wife that I do NOT have too many toys.  LOL

 

His technique and attention to detail were a huge benefit and eye-opener for me.  Thank you, Jeff!



#23 Jeff B

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Posted 15 August 2021 - 09:01 PM

You're quite welcome Scott and it was my pleasure.

 

Scott's MN65Q is an excellent, well thought out MN and is a solid notch above the typical Intes MN (either Standard or Deluxe).  Scott's sample has a conical quartz primary supported in the center and quartz secondary along with a nice JMI focuser, boundary layer fan, Wilcox style rotating rings, adjustable rear vent and two finder shoes.  The tube is powder coated, rather than painted.

 

Very nice.

 

It took about three hours starting from scratch, however, that included complete disassembly of the OTA, except for the meniscus/ secondary assembly, cleaning (spider webs and spider dung and the secondary...the primary and meniscus needed no cleaning ), reassembly collimation and DPAC testing.  

 

The most tedious part was the alignment of the focuser over the secondary, getting everything squared up.  Fortunately, the secondary was already quite square with the meniscus, but it still took a bit of time to get the focuser adjusted.  But we nailed it.  Once that was done, adjustment of the secondary to fire the laser beam at the center of the primary and the adjustment of the primary with the barlowed laser went quickly.

 

The only challenge for the secondary adjustment was finding the center of the center plug that holds the primary mirror to the cell.  We guessed as to its center (got pretty close really) but in retrospect, we should have applied a dot of some sort to the center of the plug, while the primary mirror and cell were out.  We could have nailed it then.  

 

The scope was a real performer in DPAC (sorry, no shots).  A very smooth figure, no zoning(!), a very clean edge and ever soooooo slightly undercorrected as a system, better than 1/8 wave spherical in my estimation, probably closer to 1/10 wave.  No astigmatism was seen.  Very, very nice.

 

Scott, if you ever want to sell this guy, just give me a call.

 

Jeff


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