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Old 24-11-2021, 08:17 AM
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mldee (Mike)
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OCAL collimator has arrived

My OCAL collimator arrived yesterday, and tested functionally OK with a NUC. For those not familiar with this gadget, it is claimed to be for reflector-based OTA collimation using a highly calibrated focusser -mounted camera, USB coupled to software on your laptop or smartphone to allow accurate lineup of secondary and primary mirrors.

Website:https://tinyl.io/5Ce8

There are a few factory intro videos on Youtube, featuring the most nauseous music and random bird twitterings ever made, and a new user-generated Youtube video is now posted, https://tinyl.io/5CeR, which gives a slightly clearer description of how to go about things.

I haven't yet had a chance to do a real collimation check due to weather, but it seems to be good quality, with a user-friendly approach, sort of like a combination of an electronic Cheshire and Howie Glatter concentric rings, basically done in software. Watch the above video to get more of an idea, although I confess that I found the tester's approach a little "flexible". But at least he's tried his out, which I have yet to do.

I'll post a review after trying it on my 10" f4 Newt. After that I want to try my 8" RC. Yes, Peter, still trying to get the damn thing adjusted....
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Old 24-11-2021, 08:48 AM
Hans Tucker (Hans)
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Looking forward to reading your follow up report. I notice Testar sells these in two versions, Standard and Pro. Price looks good.
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Old 24-11-2021, 09:17 AM
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mldee (Mike)
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Standard vs Pro version

I bought the Pro version from Ali express, although I would recommend Testar now they have them in stock.
Dunno why I got the Pro, it's the exact same unit and software with a couple of thread size adaptors and a USB-A f to USB-C m adaptor in the box, but with my eyesight, I doubt I will ever try to collimate anything using a smartphone screen! There is also a smartphone App, but I haven't bothered to download it.

Last edited by mldee; 24-11-2021 at 09:25 AM. Reason: Added app info
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Old 25-11-2021, 04:10 PM
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First setup on 10" f4 Newt

Set it up on the Obs Newt out of the rain, a very simple two minute job just like mounting a normal camera in the focusser tube with a USB2 connection to the NUC.

Pix show setup, before and after shots. Adjustment took all of five minutes max, as the scope was pretty well in collimation according to the first pic. I used the green circle to fit the mirror reflection, blue as a focus tube circle and yellow as the OCAL image within the focus tube. You can see the silver and red bits on the outside of the tube, which are actually the internal bits of the Moonlight due to the wide angle of the OCAL lens. The second set of pics show the OCAL rotated 90 degrees in the tube just to see if there was any change. There wasn't.

The white square is the OCAL lens and the black primary mirror donut is almost on top of it. I then adjusted the secondary screws to superimpose the donut on the lens, which then required slight readjustment of the green circle offset settings to again overlay the primary mirror edge. While it is only about 99% perfect overlay, good enough for a first attempt until a star test can be done. But all the bits seem to align well, for very little effort or frustration. Also very convenient to be able to see things on a big computer monitor while adjusting.

Very happy so far.
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Last edited by mldee; 25-11-2021 at 04:15 PM. Reason: splleing
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  #5  
Old 26-11-2021, 12:20 AM
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Would this work with the Skywatcher MN190 or Mewlon?
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Old 26-11-2021, 09:32 AM
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Although familiar with the MakNewt design concept, I've never actually seen one, so am just basing my reply on Mr Google's results.

Since it appears the secondary mirror is adjustable, sort of like an SCT, it would suggest that the answer would be yes, it would be suitable, as the Mak meniscus lens at the front is basically simply mechanically locating and supporting the secondary mirror and has no impact on the collimation of the primary and secondary mirror alignment. A very elegant approach.

Obviously it has a major effect on optical "distortion correction", but not on collimation.

I'm sure if you were to ask Testar, they would be able to confirm this before you purchased. As I stated in an earlier post, I have yet to star test mine, and the rain is coming down in buckets today, so it may be a while before I confirm my initial results
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Old 26-11-2021, 10:00 AM
Dennis
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Quote:
Originally Posted by toc View Post
Would this work with the Skywatcher MN190 or Mewlon?
Hi Tim

I did try the OCAL Pro on my Mewlon 210 but when I then did a real world star test, it was way out of collimation, despite only making a few small adjustments to the Secondary Screws, just the pressure of a small tweak rather than a definite turn.

From my understanding, the OCAL device requires a centre spot on the secondary mirror (the primary mirror is not adjustable in the M210).

Have a look on CN

https://www.cloudynights.com/topic/7...ic-collimator/

There are reports on RC's and DK's which suggest that the OCAL device is not suited to these scopes.

Cheers

Dennis
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Old 26-11-2021, 01:18 PM
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How was the collimation star test before you tried the OCAL? Any thoughts then on which parameter was off after collimation of the secondary? A photo of the setup and results would be handy for others.

The Mewlon (Google says) that all Mak Newts use a spherical primary mirror, like an SCT, so the primary should not need adjustment or a center spot. I presume then that all Mak Newts would then have a spot on the secondary. I may be wrong. The standard Newt with OCAL requires a spot only on the primary. See my pics. The RC pics shown on CN suggest it should work, as they normally have a spotted secondary, but no doubt far more critical than a Newt. But I think ALL RC collimation techniques fit that bill.

I must admit that without some reference on the primary, it would be difficult to decide when collimation is "correct" with a Mak Newt, although due to the spherical primary shape, secondary mirror dot and front Mak lens, I have no idea on how critical all that ray geometry is to final collimation, nor what you're supposed to see.

CN as usual had a million different questions and answers, few of which were useful, perhaps the most interesting thing was the openness and service of the manufacturer in his replies.

I still think the Newt collimation looks most promising, we'll see after the rain. I also have a C8 hyperstar and an RC8, so plenty of testing still to be done.

Last edited by mldee; 26-11-2021 at 01:23 PM. Reason: added more RC comments
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  #9  
Old 26-11-2021, 04:20 PM
Dennis
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Okay, these are my experiences “as is”.

Prior to using the OCAL Unit indoors, the M210 was in good collimation based on previous star testing and imaging results.

I then used the OCAL Unit indoors and made adjustments to the collimation based on the OCAL results. Test 01 is pre-adjustment and Test 02 is after adjustment using the OCAL Unit.

A couple of days later I took the M210 outdoors and performed a star test and found the collimation to be significantly off. This is poorly shown in a screen capture marked Test 03.

I then corrected this in the field and produced the attached intra-focus and extra-focus star tests using FireCapture SER stacks under less than average seeing.

When I then re-tested indoors using the OCAL Unit, I could not see any significant change to the OCAL pattern to alert me that “something had changed” as a result of my star test collimation in the field.

I was hoping that for the Mewlon 210, the OCAL Unit would be a killer accessory, much like the QHY PoleMaster where Polar Alignment is repeatable, definite and unambiguous.

EDIT:
I just added Test 04 Indoor OCAL Unit test after I had made collimation adjustments in the field based on star testing. I could not easily see an unambiguous change between OCAL results prior to the star test and after the star test.

EDIT 2:
Added an image using the Tak Collimation Telescope where I haven't yet quite worked out which ring/feature is what.

Cheers

Dennis
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Last edited by Dennis; 26-11-2021 at 04:38 PM.
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  #10  
Old 26-11-2021, 07:37 PM
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Based on your results, there certainly doesn't seem to be much need for an OCAL with the Mewlon,

As there is only the secondary mirror adjustment on the Mewlon, it would appear to be quite sensitive relative to the small change in the before and after OCAL pics.

I notice that there is also very little OCAL ring offset needed, just -1H on pic2. I was needing 6 before then -14 after adjustment on the Newt.

My eyesight has let me down with the TC tool, I'm looking forward to my star tests if the rain stops. 60mm today.
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Old 26-11-2021, 07:59 PM
Dennis
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Originally Posted by mldee View Post
Based on your results, there certainly doesn't seem to be much need for an OCAL with the Mewlon,

As there is only the secondary mirror adjustment on the Mewlon, it would appear to be quite sensitive relative to the small change in the before and after OCAL pics.

I notice that there is also very little OCAL ring offset needed, just -1H on pic2. I was needing 6 before then -14 after adjustment on the Newt.

My eyesight has let me down with the TC tool, I'm looking forward to my star tests if the rain stops. 60mm today.
I think that the Mewlon’s have an elliptic primary mirror with a spherical secondary mirror. The collimations screws are so tight I tend to go by how they "groan" rather than say, 1/30th turn.

I suspect that with a spherical secondary, any adjustments made to the secondary collimation screws may still produce an acceptable pattern to appear in the OCAL view, but may lead to the optical axis of the secondary becoming misaligned with the primary mirror axis. This might be why I got the poor star test.

As for the Tak Collimating Telescope, there are so many circles and also, I notice that the “X” formed by my spider vanes is offset from the centre, but the scope still produces sharp views and images, so I’ll stick with the star test.

Cheers

Dennis
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Old 26-11-2021, 09:24 PM
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Ah so! My apologies on not knowing the Mewlon was a Dall Kirkham Cassegrain design. Way out of my league and knowledge base. (Your comment re spiders is what aroused my curiosity!)

Sort of negates a lot of my comments which actually pertained to Mak Newts.

One lives and learns.
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Old 27-11-2021, 09:29 AM
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So at least with the MN190 it has spots on both the Primary and secondary mirrors, although some wags on CN have commented that they think the secondary one is not accurate.
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Old 27-11-2021, 11:44 AM
Dennis
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Ah so! My apologies on not knowing the Mewlon was a Dall Kirkham Cassegrain design. Way out of my league and knowledge base. (Your comment re spiders is what aroused my curiosity!)

Sort of negates a lot of my comments which actually pertained to Mak Newts.

One lives and learns.
Hi Mike

No worries, I'm more of an end-user who reads enough to get by with, rather than someone who is interested in taking a deep dive into optical theory.

Cheers

Dennis
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Old 28-11-2021, 01:30 PM
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Looking forward to the day when they create a collimator for Meade ACF scopes…😩
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Old 28-11-2021, 05:14 PM
Dennis
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Looking forward to the day when they create a collimator for Meade ACF scopes…😩
Hah, I've reverted back to using the original Mk I Eyeball that so far, has proven to be quite versatile and reliable.

Cheers

Dennis
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Old 30-11-2021, 08:51 AM
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Originally Posted by Dennis View Post
Hah, I've reverted back to using the original Mk I Eyeball that so far, has proven to be quite versatile and reliable.

Cheers

Dennis
Yes in the end I find collimating my Meade via a star test and a camera to be the most effective approach.
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Old 12-12-2021, 11:13 AM
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Good video on the OCAL here:
https://www.youtube.com/watch?v=cVVX...%2CTheLazyGeek
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Old 12-12-2021, 12:01 PM
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Reinforces the point that for any method of collimation, you may get a wonderful result until you add or subtract elements in the optical train, and then everything changes, especially if you don't have threaded connections all the way.

As Dennis commented above, the MK1 eyeball and a star test with your final setup should always be the end assurance of good total system collimation.

However for me the OCAL does a fast and effective job of getting in the optical alignment ballpark, so the star test final tweaks should be far easier, while also perhaps helping highlight any mechanical misalignment issues in the camera connection side of things, hence my comment (and Cuiv's) on threaded connections.
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