Collimation

[emyliano2000]

Hi guys. I have a laser collimator that is not properly collimated. I purchased a cheshire collimator to allign the mirrors on my 200p and I followed all the steps on Astro Baby's website until I have managed to properly collimate the ota. What I'm trying to do is collimate the laser collimator using the perfectly collimated ota. So after a perfect collimation with the cheshire I want to insert the laser one into the focuser with some tape stuck around it to avoid having any play and turn it's 3 little hex screws until the laser beam points exacly on the center of the primary mirror and comes back in the center of the collimator. Will this method give me a good alignment of the laser collimator? I find it so much easier to allign my mirros using the laser collimator and that's why I wanna collimate it.

Cheers Emil 

[dweller25]

Use two identical V shaped wooden blocks to hold the collimator, then point it at a distant wall and rotate it. The size of the rotation circle will equal the amount of miscollimation, adjust and recheck until you are happy with the results.

[Timebandit]

23 minutes ago, emyliano2000 said:

Hi guys. I have a laser collimator that is not properly collimated. I purchased a cheshire collimator to allign the mirrors on my 200p and I followed all the steps on Astro Baby's website until I have managed to properly collimate the ota. What I'm trying to do is collimate the laser collimator using the perfectly collimated ota. So after a perfect collimation with the cheshire I want to insert the laser one into the focuser with some tape stuck around it to avoid having any play and turn it's 3 little hex screws until the laser beam points exacly on the center of the primary mirror and comes back in the center of the collimator. Will this method give me a good alignment of the laser collimator? I find it so much easier to allign my mirros using the laser collimator and that's why I wanna collimate it.

Cheers Emil 

 

Hi . People have so much trouble with laser collimator giving incorrect results, even when they think the laser is collimated or they have recollimated theI lazer. It really does drive some people up the wall?

If it was me I would stick to the Cheshire or a cheap quick but effective collimation cap and instead use the time enjoying the telescope views under the stars?

[emyliano2000]

15 minutes ago, Timebandit said:

 

Hi . People have so much trouble with laser collimator giving incorrect results, even when they think the laser is collimated or they have recollimated theI lazer. It really does drive some people up the wall?

If it was me I would stick to the Cheshire or a cheap quick but effective collimation cap and instead use the time enjoying the telescope views under the stars?

I have a home made collimation cap, made from an unused focuser cap (sugestion taken from Astro Baby's website also). The trouble I have with the cheshire is that I can't reach all of the 3 primary mirror collimation screws when I look through it and I can't get a good reflection on the cheshire collimator as it doesn't have a mirror and it's only made of polished aluminium or something like that. 

When I go out in the field I'm pretty sure the mirrors will be misaligned again because of the vibration from the car and I don't know how I would be able to use the cheshire out there. That's why I would like to properly align the laser collimator.

I wish I could enjoy the stars but unfortunately it's always cloudy cloudy cloudy?☁??☁?

 

[emyliano2000]

I booked a 4 day trip to Exmoor National Park which is supposed to be an international dark site and I wanna make things as easy as possible so I can enjoy as much as I can of the starry skies, if I'm lucky enough to get clear skies that is.

[Ricochet]

I would make a v block. Just knock four nails into a block of wood in two V shapes spaced to hold your laser nicely. You can then take that with you to Exmoor because if the car journey miscollimates the telescope it coukd do the same to the laser too. 

[John]

You need to adjust the laser collimator so that there is (ideally) no movement of the beam at around 15-20 feet distance as you rotate the unit through 360 degrees. This web page shows a simple jig to test this:

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

[wookie1965]

You can shine a red torch on the shiny surface of the Cheshire to collimate in the dark. 

[Tiny Small]

2 hours ago, emyliano2000 said:

The trouble I have with the cheshire is that I can't reach all of the 3 primary mirror collimation screws when I look through it and I can't get a good reflection on the cheshire collimator as it doesn't have a mirror and it's only made of polished aluminium or something like that. 

 

I might be misinterpreting what you're saying here, but you're not supposed to get a reflection on the Cheshire from the primary. You point a light at it and it reflects that light onto the primary.

[iapa]

Lookout for the Astronomy Shed tutorials on YouTube - one of these covers "Laser collimators lie" and show how to correct

sorry, can't find which one just now

edit

 

[Charic]

On 10/13/2016 at 19:12, emyliano2000 said:

 The trouble I have with the cheshire is that I can't reach all of the 3 primary mirror collimation screws when I look through it.................  That's why I would like to properly align the laser collimator.

Do you have by any chance a Barlow lens?  For field testing of the primary mirror, place the Barlow  in the focuser, then bung in the Laser. The reflected shadow (  created from the centre spot on the primary ) is visible on the laser's  target face, you now just need to adjust the collimation screws until the shadow is concentric around the laser  hole in the centre of the target face. Once the shadow is central around the hole, you wont get any better, the scope is now collimation checked for your session. By all means use the guides to calibrate the laser tool itself, but a Barlow negates the need for 100% laser accuracy. Check here https://www.cameraconcepts.com/barlowed laser collimation.pdf 

I use a Barlowed laser,  and my laser is 99.99999% accurate ( according to me! ) but of all the methods, available,  eye's alone, film cap, Cheshire and laser, ( I cross reference them all if I've removed any of the mirrors )  If I could only have one, its my longer reach Cheshire.

[N3ptune]

On 2016-10-13 at 13:40, Timebandit said:

If it was me I would stick to the Cheshire or a cheap quick but effective collimation cap and instead use the time enjoying the telescope views under the stars?

I use a cheap quick collimation cap and it's providing only good results. I can watch the moon at 212x the image is really clean and sharp. The cap is working no doubt about it.

[Dave In Vermont]

Any and everyone should have a copy of this, regardless of how they collimate a telescope:

http://www.astro-baby.com/collimation/astro babys collimation guide.htm

And the author, Astro_Baby, is also a member of SGL. I'm sure she'd be happy if you also send others to find copies and give away. Her instructions are about the clearest and understandable I've ever read - and that's a big number!

Have fun,

Dave

 

[emyliano2000]

Thank you very much for all the lovely replies. I think will just stick with the cheshire method of collimation then.