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Collimation - before and after experiences?


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Probably only really mainly applicable to Newts and cat/mak designs, but I'm interested in stories of people trying to see something, but not, then after collimation, it pops out! 

Plus, how did you collimate? Star test? Barlowed laser? 

All stories welcome! 

Mark 

 

Edited by Flame Nebula
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Are you seeking evidence, or otherwise, regarding the need for accurate collimation ?

I'm curious about the purpose of your question that's all ! 🙂

Anyway, this thread covers some points, with examples, and is only a few months old so worth a look:

Laser Collimation Guide for Newtonians - Discussions - Scopes / Whole setups - Stargazers Lounge

I've found that some refractors need collimating as well, although it's usually a one-off process.

 

Edited by John
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Hi Mark, not sure I can answer the question you have asked,  but from experience when I have put the effort in to getting collimation absolutely spot on. If the seeing is steady the level of detail can be exceptional on the Mmon, planets and splitting tight doubles. The sky always seems to be the limiting factor.

Cheers

Ian

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A few years ago I acquired a 150mm Mak, an Intes M603. It was somewhat “tired”, so I set about freshening it up. I replaced all the screw-and-bolt type fittings, some very worn, cleaned and re-aligned the primary to the focus-tube and otherwise had the scope completely dis-assembled into all its constituent parts.

On re-assembly, just as I was about to re-attach the secondary-mirror unit into the corrector plate, the secondary mirror fell off into my hand! Its glue had lost its stick.

So the whole scope, once put back together, was in a state of completely random alignment. Because it’s a Rumak-Mak, both primary and secondary are user-adjustable and collimatable.

Out of pure curiosity, I decided to have an observing session before any attempt at re-collimation. Just to see how bad it could be.

And it was BAD. During the day, local objects simply would not get sharp. During the night, “best focus” on a star was actually two separate brightish blobs connected by a streak. Out of focus patterns were a horrid hybrid of all the worst aberrations you can imagine. It was fascinating, actually. I drew diagrams of the in- out- and “at”-focus patterns:

IMG_6522.thumb.jpeg.b18603ea7d0e34008f0b3f32b97a0cc2.jpeg
 

When I did collimate it, all became good again and it’s a lovely scope. I still have it. I documented my travails with it

, if you need something to help you nod off 😆.

Cheers, Magnus

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1 hour ago, John said:

Are you seeking evidence, or otherwise, regarding the need for accurate collimation ?

I'm curious about the purpose of your question that's all ! 🙂

Anyway, this thread covers some points, with examples, and is only a few months old so worth a look:

Laser Collimation Guide for Newtonians - Discussions - Scopes / Whole setups - Stargazers Lounge

I've found that some refractors need collimating as well, although it's usually a one-off process.

 

Hi John, 

Just stories, not advice. 

I'm interested in what difference it can make. 

Thanks 

Mark 

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Here is one example. At an astro society observing event, I looked through an 8 inch SCT that could barely resolve the pairs of Epsilon Lyrae. The owner seemed to think the performance was OK but we did a star test and found the collimation a little off, not massively but definitely off. We adjusted the collimation and got a decent star test after a few tries. Both pairs of Epsilon Lyrae were duly properly, and rather nicely, split which seemed to rather surprise the scope owner. He later subsequently (a few weeks later) told me that the scope was now clearly showing Jupiter's Great Red Spot and Saturn's Cassini Division whereas he had not previously aware of these features being shown. 

Sometimes, it takes a look through someone else's scope to realise that yours perhaps has a little more that it could give 🙂

A lot of observing (probably the majority ?) goes on solo though so it is very helpful to read reports from other observers on places like SGL to get a feel for how you and your scope are doing and how hard you are pushing it. It is also reassuring at times to know that poor seeing is more likely to be the cause of lacking performance, if reported by others in your part of the world. 

 

Edited by John
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12 minutes ago, John said:

Here is one example. At an astro society observing event, I looked through an 8 inch SCT that could barely resolve the pairs of Epsilon Lyrae. The owner seemed to think the performance was OK but we did a star test and found the collimation a little off, not massively but definitely off. We adjusted the collimation and got a decent star test after a few tries. Both pairs of Epsilon Lyrae were duly properly, and rather nicely, split which seemed to rather surprise the scope owner. He later subsequently (a few weeks later) told me that the scope was now clearly showing Jupiter's Great Red Spot and Saturn's Cassini Division whereas he had not previously aware of these features being shown. 

Sometimes, it takes a look through someone else's scope to realise that yours perhaps has a little more that it could give 🙂

A lot of observing (probably the majority ?) goes on solo though so it is very helpful to read reports from other observers on places like SGL to get a feel for how you and your scope are doing and how hard you are pushing it. It is also reassuring at times to know that poor seeing is more likely to be the cause of lacking performance, if reported by others in your part of the world. 

 

Nice account! 👍

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2 hours ago, Captain Scarlet said:

A few years ago I acquired a 150mm Mak, an Intes M603. It was somewhat “tired”, so I set about freshening it up. I replaced all the screw-and-bolt type fittings, some very worn, cleaned and re-aligned the primary to the focus-tube and otherwise had the scope completely dis-assembled into all its constituent parts.

On re-assembly, just as I was about to re-attach the secondary-mirror unit into the corrector plate, the secondary mirror fell off into my hand! Its glue had lost its stick.

So the whole scope, once put back together, was in a state of completely random alignment. Because it’s a Rumak-Mak, both primary and secondary are user-adjustable and collimatable.

Out of pure curiosity, I decided to have an observing session before any attempt at re-collimation. Just to see how bad it could be.

And it was BAD. During the day, local objects simply would not get sharp. During the night, “best focus” on a star was actually two separate brightish blobs connected by a streak. Out of focus patterns were a horrid hybrid of all the worst aberrations you can imagine. It was fascinating, actually. I drew diagrams of the in- out- and “at”-focus patterns:

IMG_6522.thumb.jpeg.b18603ea7d0e34008f0b3f32b97a0cc2.jpeg
 

When I did collimate it, all became good again and it’s a lovely scope. I still have it. I documented my travails with it

, if you need something to help you nod off 😆.

Cheers, Magnus

An excellent example 👍

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16 hours ago, Flame Nebula said:

Nice account! 👍

One part that I omitted was that even after collimation of the SCT my ED120 was putting up sharper views of Epsilon Lyrae with 4 perfect airy disks while with the (collimated) SCT the stars were still a bit fuzzy around the edges. At least they were clearly split now though.

 

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Hey Mark, it's the story of every time I tried to see something I should have been able to see, couldn't, checked my collimation, touched it up, and bang it was there. Close doubles are my typical test object. Izar, Rasalgheti, Algieba, Epsilon Lyrae, … they'll all let you know if something's wrong. 

For the SCT user and even more for the Newton user, collimating should become as easy and routine as tuning your guitar every time you pick it up. Can't say I'm there yet, especially with my fast Newt, but getting there.

Besides, as John says I will practically always prefer the star images of my refractors. But a well-collimated reflector can give very pleasing images, and have much more to offer. 

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3 hours ago, John said:

One part that I omitted was that even after collimation of the SCT my ED120 was putting up sharper views of Epsilon Lyrae with 4 perfect airy disks while with the (collimated) SCT the stars were still a bit fuzzy around the edges. At least they were clearly split now though.

 

Which I think adds further weight to why I've deviated away from choosing  a sct for visual, at least in uk seeing. 

Thanks John, 

Mark 

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2 hours ago, radiofm74 said:

Hey Mark, it's the story of every time I tried to see something I should have been able to see, couldn't, checked my collimation, touched it up, and bang it was there. Close doubles are my typical test object. Izar, Rasalgheti, Algieba, Epsilon Lyrae, … they'll all let you know if something's wrong. 

For the SCT user and even more for the Newton user, collimating should become as easy and routine as tuning your guitar every time you pick it up. Can't say I'm there yet, especially with my fast Newt, but getting there.

Besides, as John says I will practically always prefer the star images of my refractors. But a well-collimated reflector can give very pleasing images, and have much more to offer. 

Hi radiofm🙂

It might seem strange, but I'm actually looking forward to collimating my F5 reflector(or rather my future, 90%+ probability 🙂). I'm also brushing up on upgrading my optics theory too. Very interesting. I have a 5" apo refractor on my list of possible future buys, most likely used, and as John and others have said, the SW 120ed looks like a solid scope with lots of good history behind it, in terms of quality. I saw a used one for £700 the other day, so in future I'll be watching out for these bargains. 

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