TOA130 colimation assistance

[tempestwizz]

Aware of all the learned advice saying that a TOA130 can only be successfully collimating by Tak in their factory, I am attempting the impossible.
For a number of reasons is is just not economically or physically feasible to ship the scope from my current location without a strong chance of damage and or loss, plus horrendous fees.

I am seeking input from any TOA130 owners who believe their scope is well collimated, and who may have a laser collimating tool such as a Howie Glatter.

Firstly, I would like confirmation that the contrast of the airy rings is the same either side of focus.
And secondly, with a laser beam centred in the eyepiece holder, that the major internal reflection is seen to be at the centre of the laser. Like for a collimated Newtonian.

I purchased my scope second hand a number of years back, and when it arrived, the front element was rattling around. Hoping that the set screws hadn’t moved, I tightened the larger retaining screws and hoped for the best. It sort of worked. I got sidetracked from resolving the issue with more new toys, and a lot of travel for work, so I didn’t get back to it until now. Unfortunately I’ve also relocated to the wilds of Laos and don’t have access to the same level of shopping and shipping any longer.
If I can’t fix it, I’m no worse off really, if I can, then it is an ideal scope for this part of the world.

I spent some hours with the scope yesterday and am climbing the learning curve of how things work.
I’ve made myself an artificial Star to check the airy Discs and have a Howie Glatter laser collimater that works well.

On first view, I noted that there was a sort of airy disc on the inside of focus that turned to mush on the outside of focus. (Using the word focus loosely here).
With the laser inserted, I noted the reflected laser points from the various lens surfaces were scattered all over the place on the collimater.

I learnt that one set of adjusting screws affected all the reflected dots, and that the other only affected some.

My suspicion is that the inner of the three elements is fixed solid in the tube and cannot be adjusted. The major reflection from it is strait back into the laser and cannot be identified.

The first set of adjusting screws (which are the ones set further into the scope) seem to move the two outer elements together.
The second set move the two outer elements with respect to each other.

I adjusted the second set of screws to place the brighter dot that moved with it over the brighter dot that wasnt moving. With the other set of screws, I moved the two superimposed brighter dots to the centre of the incoming laser beam.

It couldn’t be that easy. And, it wasn’t,

Checking the airy Discs, they were terrible, but there was some form in them.

With a lot of iterations, viewing the airy disc I managed to form a circular airy disc that shows either side of focus.
The airy disc on the outside of focus is still quite faint, but a disc now, and not mush.
I checked with the laser again, but the major dot was no longer in the center. Every attempt at moving it back toward the centre messed up the airy discs.

Hence my questions above.

After a night’s sleep (or maybe during it) I now realise that I have been adjusting basically only the angular orientation of the elements.

By stepping all three set screws either in, or out together, I have the ability to move the inter-element spacing while still maintaining the angular alignment.

So that’s where I’m at now.

Grateful for advice on the questions above, and any other feedback.

Cheers.

[Logieberra]

Brian, I hope you are well mate. Contact "Art" at Texas Nautical Repair (TNR) in USA. He can supply the advice and PDF instructions that you need.

[Exfso]

Seriously having had a TOA130 that was out, you really do need the pros to re-collimate. I sent mine to a Sydney mob who were recommended by the Aust distributor a few years back and they absolutely trashed it. It is no wonder they went down the gurglar:screwy: They really did not have a clue, I ended sending it back to Takahashi who were astounded at the mess the whole cell was in after these clowns wrecked it. The whole front end needed re-building. I had mine done under insurance, so it was not too bad financially. Art is the man to contact at TNR, I was in touch with him once and he and his mate were extremely helpful.

[garymck]

Hope this helps:

http://www.celestialportraits.com/cp_project_collimation-toa130.html

cheers
Gary

[sharpiel]

Gary,

That article refers to a number of attached diagrams...but they don't seem to be included. Have you seen the full document including the referenced diagrams?

[garymck]

Hi Sharpiel,

had that link from ages ago, (when I was a Tak owner) can't remember if the pics were there or not. There is an email at the bottom of the page, so I'd suggest contacting the page owner....

cheers
Gary

[Merlin66]

Brian,
Just a comment...

Did the laser hit the centre of the lens before you did anything??

This test is usually only used to align the focuser with the optical axis.

I've successfully used a Cheshire eyepiece to re-collimate a doublet - See Suiter's "Star testing", p 121

[tempestwizz]

Thanks for the article Gary, I’ve sent an email to the page owner.
I’ll absorb the contents meanwhile.

Merlin, when I first used the laser down the focuser, the reflections were scattered.
After my most recent attempts, I have the reflected laser to a single spot, however it is not back in the centre of the focuser. Attempts to ‘move’ the laser back to the centre seem to throw out the airy Discs that I currently have.
Live test last night showed that my stars aren’t bad, but have what looks like a small flare in the direction that the laser beam was off centre.
More adjustment required.

Cheers

[Merlin66]

Brian,
Not sure what you mean by:
""I have the reflected laser to a single spot, however it is not back in the centre of the focuser""

It's more usual to adjust the focuser relative to the OTA to align the laser spot on the centre of the objective. A greaseproof paper with centre marked, across the front of the objective will confirm the alignment.

[tempestwizz]

Sorry, perhaps I did not explain well. When I adjust the angular position of the elements, the internal reflections from a laser located in the focuser bounce around and some come back to the focuser, when viewed from the front of the scope.
I have a couple of times now concentrated on getting those internal reflections to all meet up at a single spot in near the centre of the focuser, and then adjust whatever was necessary to move that single reflected spot back to the centre of the focuser (right down the throat of the laser producing the beam, as for a Newtonian scope)
When I have attempted this, I cannot seem to get all the reflections back to a single point. I can merge what initially starts out as two dots, one way brighter than the other,but as I make adjustments to shift those two merged points back to the centre of the focuser, another faint dot becomes visible. And it is not at the centre.
If I check the airy pattern when the laser dots (but not the new faint one)are at the centre, the Discs are rubbish and way off.

If I readjust and get the airy patterns to look hallways reasonable, and check with the laser again, the reflected dot, and its faint companion is way off the centre.

I’m guessing that when it is right, all will come together, airy Discs and the central reflection.

[Merlin66]

I think you’re using the wrong tool for the wrong job.
The laser is for alignment, not for collimation.
You really need to use the Cheshire eyepiece. Elements at the rear will give brighter disks/ doughnuts, fainter for other elements towards the objective.

[tempestwizz]

Hi Ken, sorry to disagree, but the Howie Glatter collimation works just the same as a Cheshire. Difference is the Cheshire has the 45 degree cutout to view from the focuser end whereas the HG has a white plate on its front face, and you view the reflections through the front of the scope. In any case I tried my Cheshire in case I was missing something but it gives the same result.

I’ve not had confirmation from any source that the rear element of the TOA assembly is fixed in the OTA. I’ve been working on the assumption that it is, and that the two sets of adjusting screws work only on the front two elements.
But looking closely at the assembly today, it appeared as though all three elements were moving with one set of screws. I can’t fathom how you can individually adjust three elements with only two sets of screws. I’d be grateful if someone could enlighten me on that.
After another day of fiddling about moving one set of adjusting screws through ther range of motion, I think I have found a sweeter spot than I’ve seen before. Airy Discs balanced on either side of focus. But, the point of focus is a little vague, and my laser reflection is back where it was at my last two attempts, and not in the centre where is expect.
I’ll try it on some real stars a little later tonight.

[Merlin66]

Brian,
OK.
My comments were based on a laser pointer collimator....I overlooked the reference to the Howie Glatter. I've no experience with this collimator.

[thebonz]

I looked into the toa collimation some time back and I can recall that one set of screws tilts the whole cell and the other set tilts and sets the distance from the single element against the other 2 elements.
There was a hard to find web page that explained it all.
Cheers. John

[sharpiel]

John...any chance you'd be able to re-find that web page?:D

[thebonz]

One website is celestialportraites.com It has some info but the diagrams are missing. I cannot find the lens cell diagrams.
Cheers

[tempestwizz]

Thanks guys; the bonz is right. I worked it out for myself today.
Now need to work out how critical the spacing of the front element from the other two fixed ones is in the scheme of things.
First trial didn’t give even airy Discs either side of focus.
Trial and error if all else fails.

[sharpiel]

Keep us updated. I have a toa and would love access to all the literature and experience you gain from your experiments. Just in case one day...Sometimes things go bump in the night....

[thebonz]

I am also very interested in the end results. I can recall that the distance between the 2 sets of elements may be critical to eliminate CA. If I was to do it, I would use a step approach like you are doing. I have had great success collimating doublets with the Takahashi collimation tool that is an advanced Cheshire eyepiece.
Some photos of lens cell and steps would be invaluable

[sharpiel]

Lewis sent me this link once. It's in Japanese but at pp 18, 19, 20 there are some collimation diagrams...not sure how you'd translate it.

Perhaps it will help...

http://www.takahashijapan.com/ct-products/prod-pdf/TOA-150B.pdf

[tempestwizz]

Thanks Les. It seems the pictures in the Takahashi .pdf are the ones missing from the CelestialPortraits website document. Also that the CelestrialPortraits document is a translation of the Japanese on the Tak site. Classic Jinglish!

I was hijacked by ‘she who must be obeyed’ today, and so have made no progress. Tomorrow!

I do have photos by the way, I’ll post them when I can work out how to do it successfully. My first attempt failed.

[tempestwizz]

Update: I’m still adjusting, and awaiting darkness again for another real star test.
My latest theory is that there are two points of focus that need to be brought together with the spacing of the front element from the two at the rear.
In earlier adjustment attempts I noted that when inside of focus, the adjusters for the main assembly seemed to have most affect on the airy disc pattern, and when outside of focus, the front element adjustments seemed to have most affect on the pattern.
As I have progressed, it seems I am getting interference patterns set up from two sets of airy Discs rather than just one.
I am also reconciled to my ccd camera set up not providing a clear enough view of the Discs. Perhaps because too small, but I’m now resorting to making an adjustment and then visually looking through the scope with my 3.6mm Tak eyepiece. Hopefully these are signs I’m getting closer.
Meanwhile I’m going nuts. I can see airy Discs in everything now. I can understand the photographic term ‘circles of confusion’ much better now.

[tempestwizz]

After all my tweaking, a live star test showed the scope is now apparently working reasonably well. I wasn’t sure how to test it out, but I thought I’d go through some doubles. I can easily resolve gaps between a mag 3 and mag 6 star separated by 2 arc seconds. I have nice small round and coloured stars that correspond to the descriptions in my atlas. It is working the best I have ever seen it.

But in the back of my mind, I’m thinking that when I shine a laser collimator through the scope, the reflections from the elements should all be central. And for me they are not. Not even close.

In my first post I asked if someone with a TOA could do this test and report what they see to me to confirm my supposition. So far, no one has come back to me with that information. And I’m thinking it must be critical to the whole process.

So again, please, can somebody carry out this simple laser test on their good TOA and let me know what they see?

Cheers Brian

[sharpiel]

Brian,

Have you confirmed your laser is accurately concentric and squared?

[tempestwizz]

Yes. Many times and at great length. It is one of the solid 2” Howie Glatter variety.
As a confidence check, spinning the laser collimator in the focuser does not alter the positions of the reflections.

[tempestwizz]

Sharpie graciously offered his assistance a couple of nights ago, and we were able to ascertain that the laser reflections within his TOA did not select to the central spot of the focuser either, although they were within less than 1 cm by eye, and closer to the centre than mine were. Sharpie advised that he does not photograph through it, but his scope performs very well visually.

This seems to infer that maybe there is a range within the collimation adjustments that returns acceptable viewing results. Maybe there is the one perfect setting, but around it a region of acceptability .

Armed with this information I decided to have another attempt to align the central reflections better than what I had. Mine consisted of one major reflection about 1.5 cm from centre at 12 o’clock position, and another lesser on about 2 cm out at 10:30.

I again completely removed the lens assembly. Initially I checked the reflections with just the front element removed and I was greeted with an asterism of a three dot pattern. One fainter dot up at an 11 o’clock position and two brighter ones at about 3:30 and 4:30 position but closer to the centre.
As another source of confusion, I noted that when I held the assembly(only the two rear elements) against the mounting plate, and rotated it, the asterism did not rotate with the assembly. As I rotated, the asterism moved around as a whole with a small circular motion, but did not itself rotate.??

I rotated the laser source and racked the focuser in and out, but it had minimal affect on what I observed.

Not to be put off, I removed the rear element and replaced the assembly (with just the central element now). I noted a single returned reflection not far from the centre.
I used the adjusting screws to centre this reflection, and now noted that when I rotated the whole assembly, this central dot remained in place.
I then replaced the rear element, and noted again that I had a three star asterism again, although the two brighter reflections were much closer to the centre now. Rotation the whole assembly produced the same result as before. The asterism did not rotate but moved (now slightly) as a whole around the centre.
In an effort of completeness, I removed the rear element, and rotated it 90 degrees before replacing it. The affect on the observations was again minimal. I rotated it a further 90 degrees and again minimal change (if any).
Convinced that the rotational placement of the rear element has no major affect on things, I replaced the assembly into the OTA and secured it with the mounting screws.
Now I loosely held the front element onto the assembly, and noted that I now had my major reflection very close to the centre of the focuser. Rotating the front element had no affect on location of the reflection.
I fixed the front element back on with the mounting screws, and then went through the fine alignment with the artificial star.

The settings for the adjusting screws were not far off, and I quickly achieved alignment again. (5 previous days of practice helped too).

With fine adjustment set, the laser major laser reflection is within about 4 mm of the centre. The earlier second and fainter reflection is no longer visible.

Although the sky conditions were not good last night, Star tests showed the scope appears to be working well. I managed to visually split a 2 arcsecond double star despite the unstable conditions.

I’m quietly confident that I now have the scope back to better than I have seen it before. I have demonstrated to myself at least that it is possible to completely strip it down and rebuild it with minimal equipment. Artificial star and Howie Glatter laser collimator.
I’m still to work out how to get iPhone pics small enough to post here.

The words of my father echo in my brain,
“ you’ll never know if you don’t have a go”

[Tinderboxsky]

Brian, there is a way to resize images using your IPhone. Simply email the images to yourself. Mail will ask you whether you want to resize the file to save data etc. The "small" option offered is too small and very low resolution. I have used the "medium" option successfully to resize to fit IIS and still have reasonable resolution. The "large" option will work too depending on the number of images and the total file size.

[The Mekon]

Well done Brian. Taking on a challenge like this takes some courage. And a big raspberry to all the naysayers (they seem to have all disappeared)

[Kunama]

Well done indeed !!!

Don't forget to put some desiccant sachets to dry out any moisture .... I usually put some velcro on the inside of the dew cap and then stick a bag of desiccant to the other half of velcro...

[Atmos]

Took me a while to build up the courage to fiddle with the collination screws on my focuser let alone strip down a triplet objective.
I bow before your magnificence ;)

As for iPhone size, I have a 6S and I find the Medium size when emailing is perfect for IIS getting it to ~150kb.

[sharpiel]

Any further updates on testing Brian?

I'm very interested to see your step by step dis and re assembly journey in all the pictures you took along the way. Not many of us will have seen the internals of a TOA.

[tempestwizz]

Sorry, nothing further to add yet. We’ve been clouded over pretty solid the last few days. Quite cold for Laos. I will try and get my photos into a postable file meanwhile.
Thanks for the words of support..

[tempestwizz]

As promised some pictures of the lens elements from the TOA 130 during the collimation exercise.
Basically shows the system exposed with the lens hood removed.
The front element has a ring of plastic tape around its circumference making an air/dust seal between it and the second element.
Can see down the throat of the OTA.
Can see the assembly in a couple of angles, and with the front element removed.
Also looking into the scope with a Howie Glatter laser collimator inserted. Trying only to show what is reflected back onto the collimator face.
One pic has two obvious reflections, one brighter than the other. At that stage, the airy disc patterns looked quite acceptable, and the ‘live ‘ test produced good stars, . I could separate a 2arc second double. I couldn’t see any colour fringing on the edges of the moon.

After removal of the assembly and replacing only the centre element for alignment firstly, and then without changing the alignment positions for the inner elements, replace all the elements and re-tweaked the front element for good airy Discs again, I got the second Howie Glatter picture. The Brighter of the two earlier reflections is now almost spot on the centre. There is still another (in real life much fainter) dot visible.

But in actual viewing, i cannot really notice a difference after my second attempt. Everything seems to be quite OK still.

I’ll stew on it for a few months, but I think I’ll be happy with it.

[sharpiel]

How's it performing Brian? Still happy?