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Need help collimating a laser collimator


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Hello, I purchased a laser colliator but unfortunately I'm facing a problem, I knew that I need to collimate the laser before I purchsed it, and I got something just for that at home, so I thought it wouldn't be a problem, but for a reason I don't seem to be able to collimate the laser, at first the laser was a bit off, so I tried playing with the screws, but it just didn't really worked, no matter when I did the laser was just not going to the direction I needed it to.

A bigger problem is that after about 30 minutes of trying to collimate the laser, the screws worn out and it was just unusable, so I just used regular screws instead, it should work in theory, after all its only laser with screws that push it to whatever direction you need, the weird this is, when 1 specific screw is not screwed at all, the laser circle(when you spin the laser to check if its collimated) is not so big, but after screwing the screw(is that how you supposed to write it? o: the gap is widening, eventually, no matter really what I try, I just can't seem to manage to collimate it. Maybe I'm doing something wrong possibly? Hopefully someone will be able to help me and give me some advices.

Just one more thing, I know the long debate about laser vs cheshire, please spare replies such as "get a cheshire" or "you should've bought a cheshire" and so on, maybe its true, maybe I learned it the hard way, but its still not helping my situation, so thats just it, thanks a lot :)

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I have two threw the first one in the bin no matter what I did could not get it right.

The second one a friend well more advanced than me collimated it for me but he even said done the best he could and it is only slightly out, I know you won't like this but I then check with a Cheshire/ sight tube.

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I use the "V-block" method as described here (my laser collimator is the same design as shown here):

http://www.stark-labs.com/craig/llcc/llcc.html

The laser unit is held in the machined housing with a rubber "O" ring type thing at one end and three grub screws that go through the housing press against the laser unit at the other end of it. On some models you need to remove a label to reveal the grub screws I believe. You might need to loosen one grub screw a little to allow adjustment to another. You need to remove the screw on battery cover section and spring from the end of the collimator to allow the last unit inside to be free to move as well.

It is a fiddly operation I agree and it can be more "miss than hit" at times.

 

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9 minutes ago, John said:

I use the "V-block" method as described here (my laser collimator is the same design as shown here):

http://www.stark-labs.com/craig/llcc/llcc.html

The laser unit is held in the machined housing with a rubber "O" ring type thing at one end and three grub screws that go through the housing press against the laser unit at the other end of it. On some models you need to remove a label to reveal the grub screws I believe. You might need to loosen one grub screw a little to allow adjustment to another. You need to remove the screw on battery cover section and spring from the end of the collimator to allow the last unit inside to be free to move as well.

It is a fiddly operation I agree and it can be more "miss than hit" at times.

 

Thanks, one important question, the laser doesn't need to be "10 feet away" to do it right? I'm not failing to do it because of the distance I'm trying I assume?..

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13 minutes ago, jinchuriki said:

Thanks, one important question, the laser doesn't need to be "10 feet away" to do it right? I'm not failing to do it because of the distance I'm trying I assume?..

It needs to be at least that I feel. The further the laser dot is projected, the easier it is to see where it varies as you rotate the laser around it's axis and the more accurate the collimation is, when you achieve it. I try and get around 30 feet and when adjusting, try and get the laser dot to stay within a 10mm circle, or better if possible.

 

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1 minute ago, John said:

It needs to be at least that I feel. The further the laser dot is projected, the easier it is to see where it varies as you rotate the laser around it's axis and the more accurate the collimation is, when you achieve it. I try and get around 30 feet and when adjusting, try and get the laser dot to stay within a 10mm circle, or better if possible.

 

So if you insert the laser in the focus tube and spin it, how vast the gap should be? Do you mind filming a really short video showing that when you're free?

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5 minutes ago, jinchuriki said:

So if you insert the laser in the focus tube and spin it, how vast the gap should be? Do you mind filming a really short video showing that when you're free?

You just need to have the laser spin evenly around the polo mark  so irrelevant how far the laser is out of collimation  . 

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1 minute ago, bottletopburly said:

You just need to have the laser spin evenly around the polo mark  so irrelevant how far the laser is out of collimation  . 

Well the problem is no matter what I try its just not really working, the screws are not going to the direction they should.

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23 minutes ago, jinchuriki said:

So if you insert the laser in the focus tube and spin it, how vast the gap should be? Do you mind filming a really short video showing that when you're free?

I don't have the facility to film it I'm afraid. You turn the laser collimator slowly around 360 degrees, stopping every 90 degrees and marking the position of the laser dot on a piece of paper taped up around 30 feet from the laser unit. The V-block and laser unit must stay completely still in one place of course during this rotation. That shows you how far out the unit currently is. Then you pick a grub screw, hold the laser collimator in place in the V block (and the V-block exactly where it was as well) and make an adjustment to the screw noting which way the laser dot moves - hopefully towards a spot at or near the centre of your 4 90 degree marks. The repeat the rotation, mark accordingly and adjust again as necessary. It is a bit trial and error I'm afraid.

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2 minutes ago, John said:

I don't have the facility to film it I'm afraid. You turn the laser collimator slowly around 360 degrees, stopping every 90 degrees and marking the position of the laser dot on a piece of paper taped up around 30 feet from the laser unit. That shows you how far out the unit currently is. Then you pick a grub screw, hold the laser collimator in place in the V block and make an adjustment to the screw noting which way the laser dot moves - hopefully towards a spot at or near the centre of your 4 90 degree marks. The repeat the rotation, mark accordingly and adjust again as necessary. It is a bit trial and error I'm afraid.

That's a really nice explanation, I'll give it a try :)

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I have a laser collimator that looks like this. 

Z-LC.jpg

The instructions below are valid for this type of collimator, but will probably also be useful for other designs. 

  1. Internally, there is a smaller metal cylinder that comprises the laser diode and the battery compartment. This cylinder is quite stiffly pivoted at the bottom end and the three screws at the top simply push against the sides of this cylinder to adjust the position. The pivot in mine is stiff enough to hold the cylinder in a fixed position without the adjustment screws being in use. You can use this to start your collimation procedure with the screws backed out.
  2. Some sort of target or grid on the wall you are pointing the laser at might be useful so that you can more easily tell how far off centre you are at any point.
  3. When collimating start with all the screws backed out so that they are not touching the internal cylinder. Rotate the collimator until the laser dot is at the lowest point of the circle traced by the laser. If you tighten the screw that is now top-most it will bring the laser dot upwards. Tighten the screw a touch and rotate the collimator again until the laser is at the lowest point in the new circle. Tighten whichever screw is now nearest the top. Repeat this procedure until the laser is collimated. You will probably find that you are only tightening two of the screws. Once you have the laser collimated carefully snug up the screw that you haven't really touched to lock the laser in position.
  4. Don't tighten the screws too tightly as the internal cylinder is quite delicate and you could either deform the cylinder or cut through the plastic film that insulates if from the outer body and create a short circuit. (This might not apply if your adjustment screws push against a solid part and not the sides of the battery compartment like mine.)

Edit: Even with my laser collimated I mostly use a sight tube to collimate the secondary mirror, with the laser just to check/tweak. To collimate the primary mirror I use the barlowed laser method (just put a barlow between the focuser and laser). This turns the laser into a torch which illuminates the central part of the mirror and the centre spot. You then collimate the primary by centring the shadow of the primary spot on the collimator face. This method reduces the effects of inaccuracies in the collimation of your laser and secondary mirror.

Edited by Ricochet
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9 hours ago, Ricochet said:

I have a laser collimator that looks like this. 

Z-LC.jpg

The instructions below are valid for this type of collimator, but will probably also be useful for other designs. 

  1. Internally, there is a smaller metal cylinder that comprises the laser diode and the battery compartment. This cylinder is quite stiffly pivoted at the bottom end and the three screws at the top simply push against the sides of this cylinder to adjust the position. The pivot in mine is stiff enough to hold the cylinder in a fixed position without the adjustment screws being in use. You can use this to start your collimation procedure with the screws backed out.
  2. Some sort of target or grid on the wall you are pointing the laser at might be useful so that you can more easily tell how far off centre you are at any point.
  3. When collimating start with all the screws backed out so that they are not touching the internal cylinder. Rotate the collimator until the laser dot is at the lowest point of the circle traced by the laser. If you tighten the screw that is now top-most it will bring the laser dot upwards. Tighten the screw a touch and rotate the collimator again until the laser is at the lowest point in the new circle. Tighten whichever screw is now nearest the top. Repeat this procedure until the laser is collimated. You will probably find that you are only tightening two of the screws. Once you have the laser collimated carefully snug up the screw that you haven't really touched to lock the laser in position.
  4. Don't tighten the screws too tightly as the internal cylinder is quite delicate and you could either deform the cylinder or cut through the plastic film that insulates if from the outer body and create a short circuit. (This might not apply if your adjustment screws push against a solid part and not the sides of the battery compartment like mine.)

Edit: Even with my laser collimated I mostly use a sight tube to collimate the secondary mirror, with the laser just to check/tweak. To collimate the primary mirror I use the barlowed laser method (just put a barlow between the focuser and laser). This turns the laser into a torch which illuminates the central part of the mirror and the centre spot. You then collimate the primary by centring the shadow of the primary spot on the collimator face. This method reduces the effects of inaccuracies in the collimation of your laser and secondary mirror.

Going to try that on mine much easier to understand thank very much.

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Ok, I do it like this.

I place the collimator in a v-block (anything that supports it in a fixed orientation is fine) aimed at a wall about 16 feet away.

Bear in mind you need to  alternate tightening and loosening screws to avoid over-tightening. This is one way

Rotate the collimator and the dot describes a circle. Get the dot at the bottom of the circle. If a screw is more or less at the top, tighten by half a turn. If a pair of screws are either side of the top, turn one of them to the top and tighten by half a turn.

Now rotate the collimator again but aim to get the dot at the top of the circle, and choose a screw the same way and loosen it.

Now bottom and tighten, followed by top and loosen. If at any point the screw feels tight, don't force it but do a top/loosen cycle twice instead. If it a screw feels loose, retighten it and do one or two bottom/tighten cycles

The circle should keep getting smaller. As you it gets really smell reduce the amount you turn to a quarter turn or less.

This may seem long and drawn out but you always move towards a better setting and will get on point faster. Doing large adjustments is actually slower in the end.

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On 15/09/2018 at 21:03, wookie1965 said:

I know you won't like this but I then check with a Cheshire/ sight tube.

Absolutely. IMO this bit really isn't optional if you want to ensure good collimation. An unbarlowed laser can be useful for rough alignment of the secondary, but that's about it in my view. On its own, I'd rather use a basic collimation cap than a laser.

Billy.

Edited by billyharris72
Typo
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  • 1 year later...
  • 3 years later...
On 15/09/2018 at 17:38, John said:

It needs to be at least that I feel. The further the laser dot is projected, the easier it is to see where it varies as you rotate the laser around it's axis and the more accurate the collimation is, when you achieve it. I try and get around 30 feet and when adjusting, try and get the laser dot to stay within a 10mm circle, or better if possible.

 

A well-collimated laser collimator when rotated on itself, will generate a 10 mm circle on a wall when at a distance of 30 feet (9.144 meters). Adopting this criterion it's clear that the collimator has a deviation angle from the centerline (circle's center) equal to alfa, where alfa = 1.8 arc-minutes. So: A well-collimated collimator must have a deviation < 1.8 arc-minutes.
Let's simplify and assume a maximum tolerance of 2 arc-minutes of deviation for any laser collimator. In that case, the deviation r [mm] at a distance L [mm] will be:

r [mm] = L [mm] x tan ( 2 arc-minute) = L [mm] x tan (1/30) = L [mm] / 1719
r [mm] = L [mm] / 1719

Therefore, on a collimator with alfa < 2 arc-minutes at 30 ft (9144 mm) from a wall, we are considering it generates a circle with a diameter < 10.6 mm.
A 10 or 11-mm circle is quite small so we need to increase the distance by at least 20 meters to have a circle of 23 mm, which has enough room for the laser dot and will let us draw the circle easily on paper and center it to make the proper corrections!

Regards
Andy

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On 16/09/2018 at 11:17, Stub Mandrel said:

Ok, I do it like this.

I place the collimator in a v-block (anything that supports it in a fixed orientation is fine) aimed at a wall about 16 feet away.

Bear in mind you need to  alternate tightening and loosening screws to avoid over-tightening. This is one way

Rotate the collimator and the dot describes a circle. Get the dot at the bottom of the circle. If a screw is more or less at the top, tighten by half a turn. If a pair of screws are either side of the top, turn one of them to the top and tighten by half a turn.

Now rotate the collimator again but aim to get the dot at the top of the circle, and choose a screw the same way and loosen it.

Now bottom and tighten, followed by top and loosen. If at any point the screw feels tight, don't force it but do a top/loosen cycle twice instead. If it a screw feels loose, retighten it and do one or two bottom/tighten cycles

The circle should keep getting smaller. As you it gets really smell reduce the amount you turn to a quarter turn or less.

This may seem long and drawn out but you always move towards a better setting and will get on point faster. Doing large adjustments is actually slower in the end.

Exactly what i do and you describe it so well 

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Another factor is securing the laser in your focuser. A single screw will knock the laser off centre. For this reason I prefer the Hotech with it’s expansion rings which keep the laser centered. My HoTech came perfectly collimated and when used it’s in perfect agreement with my Cheshire and cap.

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On 18/03/2023 at 15:45, bosun21 said:

Another factor is securing the laser in your focuser. A single screw will knock the laser off centre. For this reason I prefer the Hotech with it’s expansion rings which keep the laser centered. My HoTech came perfectly collimated and when used it’s in perfect agreement with my Cheshire and cap.

I agree with you,  bosun21! A very important point you mention by the way! Indeed this is a problem with many drawtube's eyepiece holders...😢 Laser collimators and Cheshires will show this off-centering when we tighten the retention screw... A partial solution is to make the collimator body fit more tightly (a scotch tape around usually will do), being the recommendation not to tighten the screw when we achieve a tight fit using this method.

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On 18/03/2023 at 13:32, Mike Q said:

Exactly what i do and you describe it so well 

Right, Mike! 👍🤜🤛🔭 Your description of how to proceed is excellent! I just wanted to give some numbers and the general formula so our colleagues would understand why it's essential to put a reasonable distance between the laser and the wall, I'd like to use 10 to 20 meters. 
I forgot to mention narrowing the laser beam even more!
1st - Regulate the laser lens to have the point focused at the calibration distance.
2nd - Open the collimator and under the 45º diagonal, just in front of the laser exit (internal) glue an aluminum foil, press your finger on it so the central hole appears, and with a needle, punch a small hole at its center. This will reduce considerably the laser dot diameter, which is not a dot because the solid-state laser beam is generated at a rectilinear junction. The laser point should have an internal diaphragm, which has not. So we make one at the exit.  This mod really improves the laser collimator performance making the dot smaller!

Regards and clear skies for us all!🙏🔭
Andy

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Fortunately I have a lathe which makes collimating your collimator easy.  Mount the collimator in the chuck, tape a piece of paper on the far wall and slowly rotate the chuck. Word of warning though: many modern 3 jaw chucks do not run true, so you may have to use a 4 jaw & dial it in.

Rob

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Some of the China made budget lasers and cheshires are a bit naff imo and are just not made well enough to be totally accurate out of the box. I ended up buying a Baader and it was spot on. The reason Howie Glatter and Hotech kit is so expensive is because they manufacture high quality, precision made devices. 

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