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Concise thread about autocollimators+improvements

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#251 Harveymeister

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Posted 30 December 2010 - 02:02 AM

Jason,

PM sent.

#252 Jason D

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Posted 30 December 2010 - 03:09 AM

replied...

#253 Anthony Cochetti

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Posted 30 December 2010 - 08:02 AM

This is excellent! Two questions, the first one Jim Fly might need to answer:

Is the cost of the CAM plus recessing the inner edge of the autocollimator lower than the cost of the cheshire? Would this new design represent a cheaper but just as effective way to collimate with the Catseye system?

And Jason, do you find that using the XLK-C with the CAM installed to be faster than using two separate tools? I have not been following the development of the CAM so I'm unfamiliar with time/ease of use, etc.

#254 CatseyeMan

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Posted 30 December 2010 - 11:36 AM

...Is the cost of the CAM plus recessing the inner edge of the autocollimator lower than the cost of the cheshire? Would this new design represent a cheaper but just as effective way to collimate with the Catseye system?...


The cost of a "CAM" equipped XLK (the XLK-C) will no doubt be significantly less than the curent cost of the 2 tools combined. Once a person gets "comfortable" with assessing the visual queues and has comprehended a methodical "adjustment" approach to correcting the observed errors, based on Jason's analysis, the XLK-C does appear to eliminate the need for a separate Cheshire. Keep an eye on the "Vendor's Announcement" forum for an XLK-C realease notice expected sometime in January if all goes well in ironing out some minor CAM manufacturing issues.

#255 Jason D

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Posted 30 December 2010 - 12:15 PM

And Jason, do you find that using the XLK-C with the CAM installed to be faster than using two separate tools? I have not been following the development of the CAM so I'm unfamiliar with time/ease of use, etc.


For an experienced user like me, collimating with the CAM is faster mainly because I do not have to switch tools back and forth.

Jason

#256 UmaDog

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Posted 30 December 2010 - 04:56 PM

Would existing users be able to send in their XLKs to add the CAM?

#257 nsldvd

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Posted 30 December 2010 - 06:22 PM

Would existing users be able to send in their XLKs to add the CAM?


Good question! I"m building a collection of Catseye tools!

#258 CatseyeMan

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Posted 30 December 2010 - 09:10 PM

Would existing users be able to send in their XLKs to add the CAM?


The jury's still out on that one but there is a possibility there may be an upgrade option offered.

#259 UmaDog

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Posted 31 December 2010 - 06:33 AM

Ah, well. Let us know if it makes up its mind. ;)

Please tell the jury that I'd pay to upgrade my XLK but I wouldn't buy the new model since I also have the Blackcat.

#260 Jason D

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Posted 31 December 2010 - 12:19 PM

I need to emphasize to those who already own the XLK and the Blackcat, the XLK-C will not add more accuracy to your setup.

#261 UmaDog

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Posted 01 January 2011 - 07:33 AM

Confused: Don't you say in post 3539475 that you get slightly greater accuracy in PAE reduction with XLK-C than with a Cheshire?
The XLK-C doesn't get a tick mark for measuring PAE in your table on the first page. Is this intentional?

#262 Jason D

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Posted 01 January 2011 - 01:33 PM


Confused: Don't you say in post 3539475 that you get slightly greater accuracy in PAE reduction with XLK-C than with a Cheshire?
The XLK-C doesn't get a tick mark for measuring PAE in your table on the first page. Is this intentional?


Hello Rob,
First, thank you for your thoughtful questions.
When FAE=0, the CAM sensitivity is twice that of the cheshire since the CAM measures CAE at twice the focal length when the cheshire measures PAE at one focal length of the scope. But the catch here is that FAE is assumed to be zero. Practically, if you take into account residual FAE errors, then the cheshire and the CAM accuracy would be comparable. In addition, since that 1 year old post, I have come up with the HotSpot idea which made the HotSpot/Blackcat is tough contender to beat compared to the Triangle/Blackcat. Therefore, I feel comfortable with by recent statements that the new HotSpot/XLK-C is comparable to the HotSpot/XLK/Blackcat combo in terms of accuracy.
With respect to the following table, it has a check mark next to what each tool is capable of measuring directly. The XLK-C does not have practical means to measure PAE directly and that is why it did not get a check mark by PAE. But eliminating any two errors of (PAE/CAE/LAE/FAE) accurately will also eliminate the remaining two errors. The XLK-C does a good job in eliminating CAE and LAE which will indirectly eliminate PAE and FAE with great accuracy.
Posted Image
Jason

#263 Kokopelli

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Posted 02 January 2011 - 07:36 AM

For an experienced user like me, collimating with the CAM is faster mainly because I do not have to switch tools back and forth.


That's reason enough for me to upgrade. I'm fast with the XLK and Blackcat combo but this all-in-one tool will be a great convenience.

And to anyone collimating in the dark, the CATSEYE red LED light is terrific. Another alternative is a red Photon Freedom LED which allows you to set the beam strength.

Many thanks to you and Jim Fly!

#264 Jason D

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Posted 21 January 2011 - 06:16 PM

I thought of an interesting corner case I wanted to document for XLK users. Check the following. Notice how the top two photos – each taken from a different pupil -- are similar to what you would expect from a collimated scope. (ignore the CAM throughout this post). This corner case is more prevalent at night under a red light. It is not as prevalent in the daytime as shown in the 2nd row photos.


Posted Image


The above setup has a large collimation error but under the red light it looks eerily similar to the following perfectly collimated setup.


Posted Image


The corner case occurs when a user completes executing CDP from the central pupil but for a brief second get confused the thinks he/she is looking through the offset pupil -- after all, the CDP view looks quite similar to the collimated offset pupil view under red light at night. Now the user moves to the actual offset pupil thinking it is the central pupil and the view MIGHT look quite similar to the collimated central pupil view under red light at night. This condition happens when the actual central pupil axis runs through the primary mirror center and the actual offset pupil axis runs through the COC. as shown in the following diagram.


Posted Image



To summarize: The user might get confused when using the XLK at night under red light and "mentally" swap central/offset pupils. There is a corner case where the actual central pupil view will look similar to a collimated offset pupil view and vice versa.
If you pay closer attention, you will see that reflections P+3 are actually stacked from the pupil that is perceived as the offset pupil – NOT reflections P+2 as it should be. In addition, in the same view, reflection 1 is not stacked with any reflection .
During daytime, the above corner case is easily detectable. During evenings under red light, it could happen especially when the user loses track of which pupil he/she is looking into. Just be careful.
Jason

EDIT: Corrected several statements and the 3rd diagram…




#265 lightyear44

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Posted 21 January 2011 - 07:49 PM

Jim is constantly updating the collimation experience, and indeed improving it, along with his friends like yourself. Is there anyway that you can think of, that this insight could be detected under red-light, foolproof? -David.

#266 Jason D

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Posted 21 January 2011 - 08:45 PM

Is there anyway that you can think of, that this insight could be detected under red-light, foolproof? -David.


Hello David,

Good question. Yes, there is a foolproof method. Check the following enhanced photos (same ones I referenced in my last post). If you look closely, you will see reflection 2. Only a camera can see it -- it is too dim to be seen by the human eye. All you need to so is decollimate the scope by a little and reflection 2 will appear.


Posted Image


To demonstrate this point, check the following photos which came from a different setup. See how when the scope is decollimated by a little, reflection 2 will pop up (going from top left photo to bottom left photo)


Posted Image

Jason


EDIT: The easiest method to detect this condition is by shinnig a red light at the XLK to identify the pupils.
Another method is rotating the XLK by a small amount




#267 lightyear44

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Posted 22 January 2011 - 05:43 AM

Thanks, Jason. There's always something new to wrap your head around with the subject of collimation. Fascinating. I have yet to fully read the posts about the new CAM, but look forward to it. Printed out the pages, so as to not forget. -David.

#268 Kokopelli

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Posted 22 January 2011 - 10:35 AM

I'm ready to buy the new CAM. Any idea when it comes out?

#269 Starman1

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Posted 22 January 2011 - 10:52 AM

The hotspot is a step forward in creating a situation where a slight miscollimation is visible.
I also found that the visibility of all 4 reflections was significantly enhanced by:
--making the centermark a reflective white. This made reflection 3 MUCH easier to see.
--Because I prefer to use a circle as my centermark, I also found that thinner and larger circles were easier to use as collimation marks. First, because the outside diameter of the mark and the inside diameter of the cheshire center were easier to see as concentric [though a very small central area in a cheshire could fit within a large ring--an interesting idea I'd like to test], and second because the overlap between two thin, but large, circles was very easy to see errors in. In the same way the CAM shows even tiny errors in overlap because of the differences in color and sizes of the central holes, two large rings easily show minute errors in overlap because of the fact they are not (at least in my eyes) exactly the same size due to differences in focus and slight differences in illumination.
I tried triangles and found them confusing to gauge very small errors with. I had some reflective white rings with slightly larger-than-normal central holes and tried those and found them incredibly easier than the normal paper-reinforcement rings (which have a small central hole in relation to their outside diameters).

But I agree the Hotspot shows minute misalignments easily, and I may change on the next mirror cleaning. I love that all four reflections seem easy in twilight with reflective white marks, though. Is the Hotspot available in reflective white?

One other troubling thing: the use of the acetate template to install the centerspot:
--due to its stiffness, and the deep sagitta on my mirror, the acetate does not sag uniformly into the mirror to allow the centermark to be installed EXACTLY in the center of the mirror. I use a pencil with an eraser to push the spot directly down to the mirror surface. Inevitably, the acetate slides sideways a tiny bit when it is pushed down to the mirror surface. I have had to install, remove, and reinstall the centermark a few times to get it anywhere close to exactly centered. I use a compass to gauge exactness, though a tape measure reveals the same thing: because the acetate does not sag onto the mirror surface uniformly, the spot gets installed slightly off-center by pushing the center down to make contact with the mirror about a quarter inch below it. I start out with the rings on the template perfectly centered on the mirror, but after the center of the template is pushed into contact with the mirror, I look at the edges of the template and the rings are no longer perfectly lined up--the template moved slightly sideways when the center was pushed down.
If the acetate were thinner it might sag easier. Has anyone else had this issue?

There is another technique for marking the exact center of the mirror that may allow the installation of a centermark a little more exactly (though it is a slower technique):
--place the mirror over a piece of grade-school "construction" paper and draw a pencil circle on the paper around the mirror. Cut out the paper, fold it in half, and fold it in half again. Use a scissors to nip off the tip of the pie slice. Open the paper to show the square central hole. It should not exceed 3/16" in size.
--tape the paper over the mirror surface using scotch tape in a few places around the periphery of the mirror so the paper is taut and centered above the mirror.
--Carefully stick the tip of a Sharpie pen directly vertical through the central hole in the paper to make a tiny dot on the mirror.
--remove the paper and measure the centering of the dot. I've been able to get it centered to a tiny fraction of a millimeter.
--using tweezers, hold the centermark above the mirror, carefully aligning the central hole in the mark with the tiny Sharpie dot. With your other hand, use a pencil or pen to push one tiny bit of the centermark into contact with the mirror. Using the tweezers, carefully lay the rest of the centermark onto the mirror and gauge the centering of the mark around the dot. If it appears perfect, carefully push the rest of the mark into contact with the mirror. If it doesn't appear centered, use the tweezers to carefully lift the mark and replace it with a better centering.
--If you use a laser, clean the center dot off the mirror with a q-tip with a tiny drop of alcohol on it.

I've been able to get the centermark centered using this technique to a slightly better accuracy than the acetate template. Now, as I said, the acetate template is a lot faster. Perhaps a gentle heating of the template would make it softer and allow it to sag more uniformly into the mirror. Or perhaps the use of a thinner acetate would be better. But I have had problems with the template as it stands because it is as stiff as a piece of paper and it needs to be a lot more flexible.

I need to disclaim, here: I am being incredibly fussy and picky. I want a better technique to align the centermark to an accuracy better than .1mm. If Jason would put his mind to it, perhaps a better technique for installing the centermark could be developed. The Tools are accurate enough. The marks on the mirrors are illustrative and usable. Now we have to address the installation of those marks on mirrors smaller than 15" (above 15", the acetate would easily sag under its own weight until it came into contact with the mirror), or shorter than f/4 (i.e.with deep sagittae).

#270 sixela

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Posted 22 January 2011 - 11:05 AM

Yes, the HotSpot is available in reflective white. In fact, the other colour is yellow, not red.

#271 Jason D

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Posted 22 January 2011 - 02:19 PM

OK, my recent posts about the new interesting corner case could be confusing. Let me try again.
See attachment.
It is possible at night under a red light to confuse both pupils. It is possible for the central pupil to give a misleading collimated offset pupil view and for the offset pupil to give a misleading collimated central pupil view simultaneously.
The likelihood of running into this scenario is small – assuming you confuse both pupils in the first place.
However, if you are careful with identifying the pupil you are looking through then you would eliminate this scenario. It might be a good idea to shine a light at the XLK to double check the pupil locations.
BOTTOM LINE: IF YOU DO NOT CONFUSE BOTH PUPILS AT NIGHT THEN YOU WILL NEVER RUN INTO THIS SITUATION.
That is what I wanted to convey.
Jason

Attached Thumbnails

  • 4332222-corner_case7.jpg


#272 FirstSight

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Posted 22 January 2011 - 02:43 PM

If this is the "concise" thread, I fear to wade into the "in-depth" explanation thread on auto-collimators. :graduate:
:grin:

#273 Jason D

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Posted 22 January 2011 - 02:54 PM

Is the Hotspot available in reflective white?

All my photos in the last few pages of this thread use a white HotSpot. I like the white HotSpot but be warned it will not work well with the collimation cap or a typical sight-tube/cheshire combo (other than Telecat).
I guess the camera White Balance can be adjusted to make them more white – they do look whiter in real life compared to the photos. Below are photos with the right White Balance.
Posted Image
Posted Image
Posted Image

But I agree the Hotspot shows minute misalignments easily

Sure does..
Posted Image

With respect to center spot placement, I place two wood blocks with about the same height as my primary mirror then place Catseye spot template on the top of the wood blocks and the primary. Then place weights on the template above the wood blocks to keep it steady. When it is time to press at the center of the template, I go slowly while looking for potential template slippage. In fact (something I did not do), you can place referecne markers on both wood blocks below the transparent template to easily detect any slippage while pressing down the middle. If you do not feel comfortable, stop! If thing are OK then press all the way.


Click here for an interesting animation showing the placement of my HotSpot versus the original triangle. I referenced the adhesive residues of the original donut placed by the mirror maker to stack both frames for animation. Of course, I did not reference these adhesive residues during the actual installation. As you can see, my center spot placement consistency is pretty good.

#274 Jason D

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Posted 22 January 2011 - 02:59 PM

I'm ready to buy the new CAM. Any idea when it comes out?

That is Jim Fly's area ;)

#275 Jason D

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Posted 22 January 2011 - 03:01 PM

If this is the "concise" thread, I fear to wade into the "in-depth" explanation thread on auto-collimators. :graduate:
:grin:


:lol:


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