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Collimation on a MkV explained

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#1 daniel_h

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Posted 01 September 2011 - 06:07 PM

My Collimation story
The following post is designed to lay out my experiences with the MkV collimator that gets so much mention in threads which wont go away on this forum. Regular readers here will know where i had experience of this.

To begin with, the MkV itself



It is essentially the same size as a 8”-10” f5/6 Newtonian.
The parts, at the back is a reference grid, as shown in the below pic. There is a light at the back to illuminate the grid & the front has one of the 2 critical pieces of equipment for the whole process ; a lens (which for the moment i will say is like the corrector on a mak Newt - but it has the important job of providing parallel light rays from the glass to the back grid. If the light was not parallel your adjustments would be in all sorts of trouble.

Attached Thumbnails

  • 4782989-view thru MkV.jpg

 

#2 daniel_h

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Posted 01 September 2011 - 06:08 PM

here is a sample of the gird- it is printed on clear sheeting (we call it transparency film)

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  • 4782991-MkV_grid.jpg

 

#3 daniel_h

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Posted 01 September 2011 - 06:10 PM

The 2nd critical piece of equipment is the auxillary scope -for without it the MkV would be useless. It is a small low power (3-4x)scope, which has a rhomboidal prism (think of a tiny periscope) sitting atop in much the same manner as an off axis guider works when imaging- the beauty of this is you get a view thru the aux scope proper, but a small amount of light is coming from above the aux scope thru the all important prism.
(there has beena recent collimation thread whereby one member - i’ll call him Flash has been talking about rhomboidal prisms.

forgive the gratuitous product placement in the pic - NB this is the original navy model - i have been unable to show you Cory's new & improved prototype as I had to sign a confidentiality agreement & his lawyers have been all over me

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  • 4782993-aux_scope.jpg

 

#4 daniel_h

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Posted 01 September 2011 - 06:12 PM

So you secure the bino, doesn’t mater which barrel you work on first, with the premise that one side of the bino is fixed securely & does not move, it will be the reference point to begin with

i forgot this pic showing use of the aux. scope. In this pic I am checking the left barrel which is the reference is aligned to the centre of the target at the back of the MkV (RobertA i think thats your arm in the upper left)

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#5 BillC

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Posted 01 September 2011 - 06:43 PM

Daniel:

As a former hunter, I would like to know if

"doe snot" differs greatly from buck snot?

Beat, ya to it, Kenny!

BillC
 

#6 rydberg

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Posted 01 September 2011 - 08:02 PM

Daniel:
:ohgeeze: :poke: Flash?
:roflmao:
:grin:
Marco
 

#7 daniel_h

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Posted 01 September 2011 - 10:22 PM

OK I am now back from my 60km morning ride...


So you secure the bino, doesn’t matter which barrel you work on first, with the premise that one side of the bino is fixed securely & does not move, it will be the reference point to begin with - IE It will be aligned to the centre of the target at the back of the MkV.

You adjust the clamp housing the bino so the left barrel lines up against the centre -then check the view thru the right barrel - ideally it should also hit the centre target or be very close to it.

If it is way off there is probably a good chance the prism housing has shifted & the glue holing it has broken. So its probably a good idea to open up the eyepiece end, & check how the prism are seated, you will easily see a break in the goo holding the prism in place..if it has moved you will need to get some fixative & secure it back into place (keep in mind ideally when doing this you will place the prism on the MkV & check it is aligned BEFORE glueing it into place again. a prism pic is attached - you can see the black goo bottom centre

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  • 4783441-prism cluster.jpg

 

#8 daniel_h

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Posted 01 September 2011 - 10:23 PM

NOW you are into the nitty gritty, after double checking the left barrel is still at the centre point, use the auxiliary scope to look thru the right barrel at either min or max IPD, you should see two grids -as seen in my poor drawing below

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  • 4783448-aux_scope_results.jpg

 

#9 daniel_h

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Posted 01 September 2011 - 10:24 PM

It doesn’t matter which IPD you do first. Now you have TWO points on a graph, you will measure the distance between them with a compass, and proceed to draw an arc from both points. I have 1 & 2 on my diagram so you get the picture

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  • 4783451-graph.jpg

 

#10 daniel_h

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Posted 01 September 2011 - 10:25 PM

Terrific bit of advice at the bottom of my diagram - ALWAYS GO CLOCKWISE with your arcs -and you should build an image like that below

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  • 4783452-tail_arc.jpg

 

#11 daniel_h

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Posted 01 September 2011 - 10:25 PM

This is where the name of the method comes from. (Tail of Arc)

NOW the point of interection of your two arcs is where you are going to adjust the right barrel via either screws or eccentric objectives. DO NOT try & tweak it to the middle.

Once you have adjusted it to where you think it should be (the point of intersection of the arcs on your graph) You need to re-check your reference point (ie left barrel) then look through the right barrel again with the aux. scope. Hopefully the 2 points you can see at min/max IPD are now a little closer. YOu will continue to repeat the above process until there is virtually no difference between the points you can draw on the graph between MIN IPD & MAX IPD.

If you can achieve this you have succeeded in aligning the right barrel to the centre of the bino or hinge point. YOU HAVE A 2 POINT ALIGNMENT

Once this is complete - which can take some time, all you need do is flip the bino over,-NOW THE RIGHT BARREL & HINGE ARE ALIGNED THEY BECOME THE REFERENCE POINT and all is left is to now align the left barrel to the right barrel by adjusting it (as you know the right side & hinge are already aligned) and this will achieve your 3 AXIS or 3 POINT ALIGNMENT


Once you have finished you can get one of these

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  • 4783453-cert.jpg

 

#12 daniel_h

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Posted 01 September 2011 - 10:27 PM

now go out & do this
(PS there is a skippy badge for anyone identifying the bins in the pic)

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  • 4783456-handheld kk.jpg

 

#13 BillC

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Posted 01 September 2011 - 11:01 PM

I'm glad he put you through all that geometric kwarp we had to learn; as a curmudgeon, I just love to see people suffer! :ooo:

BillC
 

#14 Jawaid I. Abbasi

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Posted 01 September 2011 - 11:08 PM

Daniel,
What a tremendous tutorial and examples you provided to the astronomy community. Thank you

Oh, one thing; take care of your hand writing :)
 

#15 BillC

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Posted 02 September 2011 - 01:14 AM

"(PS there is a skippy badge for anyone identifying the bins in the pic"

Could it be the 4-inch (25 power & 40 power adjustable)Chinese Army surplus binocular that is imported into the western states by Jimmy Chin and which has the less than color-balanced objectives that give a yellow hue, which some people believe are to enhance contrast, but which are just the result of a less than perfect glass choice for the flint element?

Of course to get my Skippy badge, I'm sure I must say that the eyepieces have been modified to something I can't see at this angle and from this distance. However, the mounting pin and altitude adjustment knob are pretty tell-tale, though you could never tell if you didn't know what you were looking for . . . they're so tiny in the photo.

But of course, that's just a wild guess.

BillC

PS Dan, you've done a great job!!!

Years ago, Cory and I wanted the ins and outs to be (though they never were difficult) held pretty "close to the vest." Now that we're getting close to our "dirt nap," we want everybody to know. And with the quality (actually the lack thereof) coming from so many plants, we hope to get AT LEAST some people to stop being gullible—believing everything they hear or read— roll up their sleeves, and stand for the quality, across the board, that only the more expensive instruments provide, today.

 

#16 KennyJ

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Posted 02 September 2011 - 02:01 AM

Thanks Daniel ,

One thing though that you didn't clarify .

Is the 60km. morning ride an essential part of the process ?

Kenny
 

#17 Man in a Tub

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Posted 02 September 2011 - 02:44 AM

Very interesting. A few practical run-throughs would improve my understanding.

I'm adding this thread to my favorites. Thanks!
 

#18 mercedes_sl1970

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Posted 02 September 2011 - 03:05 AM

Hi Daniel - great report. Did you manage to bring a MKV collimator back to Australia in your carry-on luggage? And when can we send you any binos needing repair?

Cheers

Andrew
 

#19 daniel_h

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Posted 02 September 2011 - 06:42 AM

Kenny the morning ride keeps me sane & stops RSI

Bill, you are right on the objectives, as for the ep's someob might kno of a certain mod..a clue they are big & I would say buttery smooth ( as compared to cheap margarine)
 

#20 eklf

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Posted 02 September 2011 - 04:01 PM

Daniel h,

What an informative and well illustrated thread! I have often wondered about the steps during collimation process, and this has been very enlightening. Many thanks!
 

#21 marcelof

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Posted 02 September 2011 - 04:47 PM

Thank you for sharing your experience with us!!!
Finally I see a colimator!!!!!
 

#22 Joad

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Posted 03 September 2011 - 12:04 PM

As those who have been following this thread have seen, the discussion has gone off the rails into yet another slag-fest that is only partly related to collimation. Since Daniel has provided a valuable and appreciated photo essay of his own experience with a particular collimation device, I want to preserve the thread, so I have removed that section that ran off the rails (including a post of my own). At that, I am locking this thread. If further slag-fests about collimation occur, they too will be stopped. We've seen enough of this sort of thing.
 

#23 Joad

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Posted 03 September 2011 - 09:55 PM

Post deleted by Joad
 

#24 Cory Suddarth

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Posted 04 September 2011 - 01:47 AM

While there is much information regarding this topic in print I wanted to offer a "hands-on" experience, at least for this method for those interested. Reading and doing are often two different things. It's always fun for me to see the light bulb go on, and hear "OK! Now I get it". While the first couple sets are actually plotted out like Dan showed, this step eventually becomes a mental process. With 3 rookies in the shop, it was important to see that we were all on the same page.

Perhaps we'll do it again sometime.

Cory
 

#25 daniel_h

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Posted 04 September 2011 - 04:18 AM

Todd, I will make up some more graphs for you showing the points & where to adjust to - Gordon & Cory are right, once in practice you can see in your mind where to adjust the bino alignment

Thanks to joad (strangle my iPad changes the name joad to ipad when i type it) for letting me add some more diagrams tomorrow by unlocking :jump: so play nice :foreheadslap:
 


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