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My Howie Glatter Laser Collimator Experience

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#1 Jason D

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Posted 04 April 2011 - 12:38 AM

I received my Howie Glatter laser collimator, TuBlug, and several attachments last week http://www.collimator.com – Thank you Howie ;)

I will share with everyone in this post and the following ones my “Glatter” experience.

I have 2 other Orion laser collimators which I bought 4 or 5 years ago. I thought it would be interesting to compare my new Glatter against my mass produced laser collimators and publish the results. By the way, I hardly used my Orion laser collimators over the past couple of years.

In terms of build quality, there is no comparison. See the photo below.

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In terms of the laser beam quality, Glatter is brighter and narrower. See the following photo. These photos were taken at a distance of 25 feet.

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In terms of accuracy, I had to build a robust V-block and I had to anchor it. At 25 feet distance, I was amazed with my Glatter’s accuracy. See the animation below. NOTE: If you want to put your Glatter to the same test, make sure your V-block is sturdy -- and I mean sturdy.

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Glatter fit perfectly in my Moonlite focuser. Years ago, I had to tape my two Orion lasers to improve their fit.

#2 Jason D

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Posted 04 April 2011 - 12:39 AM

The Glatter fit perfectly inside the TuBlug. You can even hear the air wheezing out as you slide the Glatter inside the TuBlug. The reflected shadow of my Hotspot was sharp on the TuBlug window. I could not see the internal edge of my Hotspot reflection to align it with the TuBlug laser central opening. This issue was pointed out by Vic last year and now I have experienced it firsthand. To get the most out of my TuBlug, I drew a template with a properly sized oval then taped it on the TuBlug window. Now I can align the outer edge of the Hotspot reflection against the oval. I borrowed the idea from Catseye Blactcat XL. Before cutting the template, I laminated it using a regular package tape to protect the template but more importantly to add stiffness. Check the template at the bottom left corner in the following photo. The photo includes additional templates which I will cover later.

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Referring to the outer edge of the Hotspot against the oval made it easier to observe at a distance.

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I recommend racking the focuser almost all the way in with the TuBlug to minimize potential focuser/OTA flexing/sag.

#3 Jason D

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Posted 04 April 2011 - 12:42 AM

To use the 1mm aperture stop and the self-barlow attachments, I needed a mirror since I could not see the bottom of my Glatter in the focuser. I bought a $2 antenna mechanics 1” mirror from my local auto-parts store. It came with a pocket clip. I clipped it to the spider vanes then adjusted the antenna length and mirror tilt. It was perfect. I did not like the idea of holding a pocket mirror inside the OTA. It is an accident waiting to happen. Sooner or later I will drop that pocket mirror on the primary. But with my new “clipped” mirror, I can keep my hands outside the OTA.

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Check the following photo with the 1mm aperture stop and self-barlow attachments.

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I taped templates with darkened rings. Again, I am using the same idea as Catseye Blackcat XL. I laminated the templates using package transparent tape. I used a “single hole punch” to punch a clean hole in the templates. Then I used the drawn inner circle to align the templates.

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The self-barlow attachment works similarly to the Tublug but would require the user to move back and forth between both ends of the scope. It is cheaper but physically more demanding.

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Then I removed the self-barlow attachment and replaced it with the 1mm aperture stop attachment. Now this is one neat attachment. It is an attachment with a precisely drilled 1mm central hole. The hole will cause the laser to diffract but will maintain a central beam. The central beam will be used to align the secondary mirror and the diffraction concentric rings caused by the hole will cover the primary spot and provides a similar functionality to the self-barlow attachment. Refer to the following photo. The left photo is with the barlow laser for comparison and the right photo is with the 1mm aperture stop. The self-barlow laser image is clearer and brighter but the 1mm aperture stop allows you to collimate both mirrors without the need to remove/reinsert attachments. The self-barlow laser attachment can’t be used to align the secondary mirror – unlike the 1mm aperture stop attachment.

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Note that the template I used for the 1mm aperture stop attachment uses a different ring size compared to the template I used for the self-barlow attachment. This is expected. The 1mm aperture stop attachment virtual source is located at the opening of the attachment but it is located few inches behind the self-barlow attachment. That is why the ring is smaller for the self-barlow laser attachment.
There is no one fit-all template. These have to be customized per scope model.

#4 Jason D

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Posted 04 April 2011 - 12:43 AM

Moving to the holographic square grid attachment. It is an attachment that will diffract the laser beam to a 9x9 square grid yet maintaining a central beam. For Newtonians, this attachment is mainly meant for centering/rounding the secondary mirror under the focuser – the same purpose a sight-tube is used for. The following two links describe how to use this attachment:

http://w1.411.telia....holographic.htm
http://dandjreed.hom.../lasercoll.html

The first link from Nils Olof Carlin describes how to use the attachment for truss scopes. The second describes how to use it for tube scopes. But I did not feel comfortable taping a sheet of paper across my OTA between the secondary and primary mirrors. I wanted to come up with a better method to use the attachment for tube scopes like my XT10. Here is what I came up with:

STEP 1: I drew a template as shown below. The large solid circle has a diameter equals to my secondary mirror size and shifted by the proper secondary offset for my scope.

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STEP 2: I aligned the template using the 4 focuser screws then taped it. If I had to do it all over again, I would laminate the template to increase its stiffness.
Note I rotated the secondary mirror 180 degrees to avoid bumping into it accidently.

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STEP 3: I inserted the laser collimator with the square grid holographic attachment. I racked the focuser all the way out. You will see a circular glow. I used it to fine tune the alignment of the template. This is another advantage for keeping the secondary mirror rotated to avoid any distracting returned laser reflections.

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STEP 4: I rotated the secondary mirror then collimated. I racked-in the laser collimator almost all the way in. I used the central beam to align the secondary mirror then the central grid square to align the primary mirror.
The scattered laser dots indicated how accurate my secondary mirror was aligned in reference the large solid circle of the template. You might have to adjust the spider vanes thumb knobs and/or the secondary holder central bolt to ensure the scattered dots are well-aligned with the large shifted circle of the template. Try to me meticulous. IMPORTANT: Every time to move the secondary mirror, you have to re-collimate both mirrors before evaluation.

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Here is the end result

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With some patience, anyone can do that above. The good news is that aligning the secondary mirror under the focuser is NOT a frequent alignment.

#5 Jason D

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Posted 04 April 2011 - 12:45 AM

After aligning the secondary mirror described in the previous post and before removing the template, I took a photo. I was amazed to see how well the outline of the secondary mirror coincided with the outline of large shifted circle of the template.

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When I looked down the OTA, I noticed the OTA wall opposite to the focuser showed less of the grid as opposed to the side closer to the focuser. See the following photo. The left hand photo is for the side opposite to the focuser.

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This was not a surprise because my secondary mirror is oversized. Here is a diagram that discribes this observation but I will not explain it to avoid unnecessary confusion.

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The technique attempting to balance the grid across the secondary mirror reflective surface is not optimal for oversized secondary mirrors.

#6 Jason D

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Posted 04 April 2011 - 12:45 AM

There is another application for the holographic attachments which is locating the optical axis with respect to the OTA/UTA mechanical axis. Then it is a matter of simple math to calculate the angle between them.

I attached a template with concentric circles in front of the OTA then I used my concentric circles holographic attachment. Given a well-collimated scope, the concentric circles projected on the template represent where there primary mirror is pointing. The center of drawn concentric circles on the template represents the location of the mechanical axis. The distance between the centers of both sets of concentric circles will tell us how far the optical axis from the mechanical axis at the OTA opening is. Note how the optical axis is shifted towards the focuser for my scope – as expected with “new model” setups.

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I can get the same info using the square grid holographic attachment.

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I see two main advantages for locating the optical axis:
1- Measure the angle between both axes to figure out the amount of DSC error
2- Ensure there is no front-aperture vignetting
In addition, the grid holographics attachment will show the shadow of any obstructions along the light path that could intrude inside the OTA.

#7 Jason D

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Posted 04 April 2011 - 12:46 AM

Here is a photo of all the components I described in this thread

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A) TuBlug with a custom template taped on the return window
B) 2” 635m Glatter collimator
C) Self-barlow attachment with a custom template taped on the top
D) 1mm aperture-stop with a custom template taped on the top
E) Concentric circles holographic attachment
F) Square grid holographic attachment
G) Antenna mechanic 1” mirror purchased from a local store
H) A template used to optimally place the secondary mirror under the focuser
I) A template used to measure the angle between the optical and mechanical axes

#8 Jason D

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Posted 04 April 2011 - 12:48 AM

Attachment is a PDF file which includes the templates I have described in this thread. But these are customized to my XT10.

Jason

Attached Files



#9 dbx

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Posted 04 April 2011 - 01:47 AM

Well done write up. good job

#10 Jon Isaacs

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Posted 04 April 2011 - 02:26 AM

Jason:

Thanks for the write up. It looks to be quite comprehensive and a good resource for collimation using Howies's collimators along with the various added tools like the holographic attachment.

I have been using Howie's collimators for at least 10 years, he does nice work.

Jon

#11 meteorite

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Posted 04 April 2011 - 05:29 AM

Hello Jason,

Do you see a significant improvment in the quality of your observations?

-Walter

#12 denodan

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Posted 04 April 2011 - 06:22 AM

Great info, I love my Howie Glatter laser and find it fits my focuser perfectly no wobble, etc and fits perfectly everytime. Have tried other lasers without much luck.

#13 hiddenwolf

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Posted 04 April 2011 - 06:38 AM

amazing writeup glad you like howie glatters tools. Mine will be here thursday both 2 inch laser and tublug for my xt10, i see you went with red as well for your cr2 SNAZZZZZZZY :cool:

#14 Vic Menard

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Posted 04 April 2011 - 07:01 AM

...Note that the template I used for the 1mm aperture stop attachment uses a different ring size compared to the template I used for the self-barlow attachment. This is expected. The 1mm aperture stop attachment virtual source is located at the opening of the attachment but it is located few inches behind the self-barlow attachment. That is why the ring is smaller for the self-barlow laser attachment.
There is no one fit-all template. These have to be customized per scope model.

I wonder if instead of using a custom sized ring template, you might consider a radial line template instead. If the radial lines could be aligned to the three radial lobes on the HotSpot, a "one size fits all" template might be possible? Or, instead of a single dark ring, perhaps a pattern of thin concentric rings in incremental steps (perhaps 0.1-inch diameter steps) that could be read to good precision relative to the HotSpot?

The CatsEye triangular center spot (with its larger perforation options) works quite well with the Glatter self-Barlow accessories and 1mm aperture stop without additional templates. But I do like the easy-read with the ring template/HotSpot (that mimics the CatsEye BlackCat).

FTR, how clear was the diffraction pattern with your 1mm aperture stop setup. Were the return diffraction rings clearly visible on your template (it's not clear from the image you provided)? If so, how close were the ring steps?

Interesting write up and nice supporting images! :waytogo:

#15 Howie Glatter

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Posted 04 April 2011 - 08:14 AM

Thank you Jason, for your edifying report. Your dedication to theoretical and experimental collimation science is truly awesome.
Please remember to leave some time for eating, sleeping, and observing.

#16 calibos

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Posted 04 April 2011 - 08:20 AM

Question 1:

In relation to the diference between the mechanical and optical axis and DSC's. How much will the everage offset effect the accuracy of Push-to/Goto's. At what magnification would you find the DSC putting an object at the edge or just outside the FOV as a result of the offset (assuming of course an accurate initial star alignment, adequate encoder resolution without slippage and orthagonal mount.)

Question 2:

Whats that on the side of your secondary mirror. Flocking, a back up holding your secondary should the silicone holding the mirror to the stalk fail or is it to emulate the secondary holder of premium dobs which is seen when rounding the secondary mirror in a sight tube?

Question 3:

Come on, you know the question that we are all thinking!! What if any collimation tweaking did you have to do when you put in your Catseye tools to verify afterwards. We all know you did it dude!!

Question 4 for Howie:

When did you start supllying a cool concentric circle holo attachment? :D Got my Glatter tools in '08.

#17 94bamf

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Posted 04 April 2011 - 08:27 AM

Nice write up Jason. One thing I find is the aperture stop works better with the Tublug. I don't think Howie recommends using it like that, but I find I can easily see the inside edge of the hotspot to align with the central opening in the tublug with the aperture stop screwed onto the laser. Without the aperture stop the beam from the laser brightens up the central hole of the tublug, making it harder to see the inside edge against the inside edge of the hotspot..

Ken

#18 Vic Menard

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Posted 04 April 2011 - 08:52 AM

Question 1:

In relation to the diference between the mechanical and optical axis and DSC's. How much will the everage offset effect the accuracy of Push-to/Goto's. At what magnification would you find the DSC putting an object at the edge or just outside the FOV as a result of the offset (assuming of course an accurate initial star alignment, adequate encoder resolution without slippage and orthagonal mount.)

Depending on the focal ratio, the location of the focuser on the OTA (side, top, in between), and the location of the GoTo object (for example--at least five or ten degrees from the zenith for a Dob), the typical error is less than two tenths of a degree (and often less than one tenth!). Considering the resolution of a 4000 count encoder is about one tenth of a degree, the error usually falls within this threshold. The closer you get to the zenith (or the pole for an equatorial mount), the more likely the error will reach its maximum effect (about two tenths of a degree at f/5, or three tenths at f/4).

Question 2:

Whats that on the side of your secondary mirror. Flocking, a back up holding your secondary should the silicone holding the mirror to the stalk fail or is it to emulate the secondary holder of premium dobs which is seen when rounding the secondary mirror in a sight tube?

I'll leave this one for Jason...

Question 3:

Come on, you know the question that we are all thinking!! What if any collimation tweaking did you have to do when you put in your Catseye tools to verify afterwards. We all know you did it dude!!

I use a Glatter laser and CatsEye tools. I prefer to use the Glatter after dark for routine axial alignment assessment and correction. In daylight, I often verify the Glatter results with the XLK autocollimator--and while there is often a small tweak available with the XLK, it's surprising how often the two agree--if you're willing to spend a few extra moments getting the laser right to start with. For secondary mirror placement (a daylight procedure), I prefer the visual cues offered by the CatsEye sight tubes. The CatsEye BlackCat Cheshire and Glatter self-Barlowed accessories give more or less identical results...

#19 okieav8r

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Posted 04 April 2011 - 11:27 AM

As usual Jason, you've added to our collective knowlege of the art and science of collimation. Thank you. Well done!

#20 Jason D

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Posted 04 April 2011 - 12:10 PM

I would like to thank everyone for the kind comments :bow:
Jason

#21 Jason D

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Posted 04 April 2011 - 12:12 PM

I wonder if instead of using a custom sized ring template, you might consider a radial line template instead. If the radial lines could be aligned to the three radial lobes on the HotSpot, a "one size fits all" template might be possible? Or, instead of a single dark ring, perhaps a pattern of thin concentric rings in incremental steps (perhaps 0.1-inch diameter steps) that could be read to good precision relative to the HotSpot?

Your suggestions might work with the self-barlow attachment but will they be as readable as the simple Blackcat-XL-like ring? Only an experiment will answer this question.
But I highly doubt concentric circles will work well with the 1mm aperture stop since it will be hard to differentiate the template rings from the laser natural diffraction dark rings.

The CatsEye triangular center spot (with its larger perforation options) works quite well with the Glatter self-Barlow accessories and 1mm aperture stop without additional templates. But I do like the easy-read with the ring template/HotSpot (that mimics the CatsEye BlackCat).

Can you see the internal edge of the triangle? What do you reference when you align the triangle shadow?

FTR, how clear was the diffraction pattern with your 1mm aperture stop setup. Were the return diffraction rings clearly visible on your template (it's not clear from the image you provided)? If so, how close were the ring steps?

I am attaching a magnified photo. I do not reference the laser diffraction rings when I aligned.

Interesting write up and nice supporting images! :waytogo:

Thank you

Attached Files



#22 Jason D

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Posted 04 April 2011 - 12:14 PM

Please remember to leave some time for eating, sleeping, and observing.

:lol:

#23 dvb

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Posted 04 April 2011 - 12:15 PM

Jason, this is an awesome write-up, with exceptional illustrations.

I have all the Howie Glatter gear you refer to, except the concentric circle hologram, but haven't used the 1 mm or the grid hologram. Now I will.

As I am currently building a 10" f/4.5, your tips on positioning the focuser and secondary will be very interesting.

I especially appreciated the attachment of the templates.

I am using a perforated CatsEye triangle - I likely would have chosen the HotSpot (which you designed), but I already had a spotting template for a triangle.

I also have a CatsEye XLK autocollimator (and sight tube) for when I want things "just right", but the Glatter kit is what I usually use for a night's observing.

#24 Jason D

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Posted 04 April 2011 - 12:15 PM

Question 1:

In relation to the diference between the mechanical and optical axis and DSC's. How much will the everage offset effect the accuracy of Push-to/Goto's. At what magnification would you find the DSC putting an object at the edge or just outside the FOV as a result of the offset (assuming of course an accurate initial star alignment, adequate encoder resolution without slippage and orthagonal mount.)

I am not using DSC; however, had I been using one then the error would have been around 0.4 degree. How did I come up with this number? I measured the distance between the optical and mechanical axes to be 10mm at the OTA opening template. Assuming the primary mirror is centered in the cell, then the angle is arctan(10/1100) where 1100mm is the distance between the primary center and the top of the OTA. Bear in mind that some DSC computers are smart enough to compensate for this error.

Question 2:

Whats that on the side of your secondary mirror. Flocking, a back up holding your secondary should the silicone holding the mirror to the stalk fail or is it to emulate the secondary holder of premium dobs which is seen when rounding the secondary mirror in a sight tube?

It is a piece of flock material with two extensions. I have a secured string running through these extensions in case the secondary decides to drop. But my secondary has been in place for years and I am no longer concerned it will drop any time soon. I came up with the formula to figure out the shape of the flocking material. See attachment.

Question 3:

Come on, you know the question that we are all thinking!! What if any collimation tweaking did you have to do when you put in your Catseye tools to verify afterwards. We all know you did it dude!!

Keith, Catseye is the best passive collimation tools you could buy. Glatter is the best laser collimator you could buy. I do not see how collimation errors could be traced back to either Catseye and Glatter tools since both are virtually perfect. Mismatches are introduced by user readability errors or scope flexing errors. The few minor mismatches I noted between both tool sets were traced to one of these two error categories.

Attached Files



#25 Jason D

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Posted 04 April 2011 - 12:16 PM

Nice write up Jason.

Thank you, Ken

One thing I find is the aperture stop works better with the Tublug.

I believe I tried this combination but I do not recall an improvement. I will try it again and pay closer attention.
IMPORTANT information about the center spot shadow size. It is highly depended on two parameter: The distance between the barlow laser virtual point location and the focal plane versus the scope’s focal length. The first is about the same for all scopes but the second varies. The smaller the scope’s focal length the smaller the shadow. For my 1200mm focal length scope, I can’t see the internal edge of the shadow even if the actual Hotspot perforation diameter is a little larger than the Tublug laser opening. For 1800mm focal length scope, the internal edge of the shadow might be visible.
Based on my experience, the largest shadow I get is with the 1mm aperture-stop attachment. The self-barlow attachment reduces the size of the shadow by around 15%. The Tublug provided the smallest shadow size which happened to be around 25% smaller than the one I got from the 1mm aperture-stop.






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