After so much collimation frustration, I've bought a Concenter

[BrendanC]

I've tried numerous different ways of getting my secondary sorted, without much success.

So, I decided to invest in a Concenter. Hopefully it's going to help me get the bally thing central, and aligned, and aligned to the primary, once and for all. That plus my Cheshire and hopefully I will be collimated. End of.

This is more a statement than anything. I just want someone to tell me I've done the right thing because I always feel guilty buying more kit.

[bottletopburly]

Bought one not so sure 🤔

Edited December 7, 2020 by bottletopburly

[johninderby]

There is no better tool for getting the secondary set up properly. I consider it an essential bit of kit. 👍🏻

[AlexK]

Kinda expensive for what it actually is (a trivial sighting tube for an arbitrary sized newt). But I guess you are buying a peace of mind  Unless I'm missing some hidden ingenuity in that carved polycarbonate front disk?

[johninderby]

The Concenter shouldn't be confused with a simple sighting tube. It’s a lot more than that. 

Once ypu’ve used one you realise how poor a Cheshire is for setting up a secondary. Simple idea but simply alows for perfect setup which makes collimation much easiers as you aren’t compensating for a poorly set up secondary when adjusting the primary.

Edited December 7, 2020 by johninderby

[BrendanC]

I do actually think it's stupidly expensive for what it is, but I can also see that it's a kind of niche item with limited production runs.

I've been trying to use my 'concenter-like' method - in which it seems I sort of re-invented the Concenter without realising it existed at the time - and whereas it does kind of work, it's extremely fiddly. and not very reliable.

I just decided to treat myself to something that should sort me out. I've been going through all sorts of daft ideas in my head about trying to make one using printouts of concentric circles on clear acetate and sticking them into eyepieces etc, but decided, well, like the L'Oréal ads say, I'm worth it.

Edited December 7, 2020 by BrendanC

[johninderby]

FLO should bring out their own version for say £35.00. 🤔

Edited December 7, 2020 by johninderby

[AlexK]

When you start using that concenter you will quickly realize that all you need from that wonder-disk is just the center hole and a single ring (just use the focuser to go from the secondary edge to the primary. There are many rings there just to cover more telescopes. Otherwise, that's just a glorified sighting tube. There is no secondary offset gauge either (how come they are saying it is addressed too?).

I have just 3D printed a combo tool  (see the first link in that blogpost for the guide I've been following) when I needed to adjust the secondary in my Astroscan once (~10 cents cost  ). Works the same as that concenter I believe, but custom-tailored to the target aperture.

[Craig a]

I’ve just bought one of these today and carnt wait for it to arrive to give it ago, expensive? Yes but in my opinion worth every penny if it helps my images look better in the long run , my f4 scope can give me a headache when it comes to collimating it if this cures it it’s better than buying a box of paracetamol once a week 😂

Edited December 7, 2020 by Craig a

[runway77]

6 minutes ago, Craig a said:

I’ve just bought one of these today and carnt wait for it to arrive to give it ago, expensive? Yes but in my opinion worth every penny if it helps my images look better in the long run , my f4 scope can give me a headache when it comes to collimating it if this cures it it’s better than buying a box of paracetamol once a week 😂

I have just bought one as well. I should not have read this thread 😉 what should help as well is a twist lock adapter. It centers a laser collimator inside a focuser tube. I have tested it and it works perfectly.

Edited December 7, 2020 by runway77

[AlexK]

Please, report your findings when available! Who knows?

The ideal approach, I think, would be to make that disk custom-tailored to the particular telescope. Following the BrendanC idea (the post he has linked above) the ideal sighting collimator can be made on a transparency film from the contoured image of the internal edges/reflections view shot through the piphole when perfectly aligned by other methods. If workable it might speed up a travel truss collimation task (for example) tremendously. That's what delaying my DIY air-travel 8" prestressed truss project, as I see the every night collimation as a serious challenge of owning such an instrument.

Edited December 7, 2020 by AlexK

[BrendanC]

I'll certainly report back on the results.

 

[Tiago Ferreira]

One more for the concenter club. Ordered yesterday a Concenter Ray to see also in dark and a APM deluxe eyepiece adapter 2"/1,25" to help the laser i also have to be aligned. Will post the results later.

[amaury]

@AlexK 

On 07/12/2020 at 17:40, AlexK said:

There is no secondary offset gauge either (how come they are saying it is addressed too?).

Even if there is an offset, the edge of the focuser tube, the edge of the secondary mirror, and the edge of the reflection of the primary mirror into the secondary mirror are concentric. Just ignore the vanes and the shadow of the secondary holder, and focus on the concentricity of those three elements.

I think the concenter is by far, the simplest most accurate way of collimating the secondary. At last in my very very short experience with collimation. Just from a conceptual point of view.

@BrendanC I've been trying the phone + laptop/PC method, it's very fiddly indeed but it works. 

[BrendanC]

Hey, glad it worked!

I never came back to give my opinion of the Concenter...

So, what I found was, that it's good for getting the secondary in the centre, as the name suggests, but not initially for getting it round. This is because my secondary was a bit too far up the tube. That's where the phone method worked for me - I could move the Mire de Collimation circles so that they were over the secondary, and then get it nice and round. Then, I used the Concenter to get it centered.

I suppose I could have done this the other way around ie use the Concenter to get it centered, and then use it again to get it round. However, I also found that, when the secondary was ALMOST centered, I would get 'lost' when following the concentric rings in the Concenter. It was hard to tell whether they were crossing sometimes.

Anyway, the combination definitely did work - Mire de Collimation for roundness, Concenter for centrality and then precise roundness, and now for quick checks. Over the past three months I've used it twice to make sure the secondary is in position, and it's been fine. All I do now before each shoot is quickly check the primary with a Cheshire, and I'm good to go. I guess the cost of the Concenter was something ideally I wouldn't have paid for, but just for the peace of mind knowing it's sorted, it made a big difference.