[Mr Spock]

After much deliberation, I finally bought a laser collimator a few weeks ago. After years of my trusted method of holding my eye two foot away from the eyepiece holder and getting my eye in line, then doing fine adjustments via a defocussed star, I thought this would be easier.

The laser worked fine for the secondary, but the primary was horrible out of alignment... bleh! My first viewing was just awful.

I quickly resorted to a defocussed star test to get the collimation right and everything was fine.

I'll be going back to my old method. It's worked ok for me for the last thirty years.

Sometimes old dogs don't need new tricks

[Astro_Baby]

I bought one when I restarted the hobby assuming the hi-tech approach was more accurate. I found them horrible. The Hotech is good though.
Part of the problem I think is the poor secondary structures on modern telescopes where messing with the tilt adjusters introduces bad rotation errors which the laser cant deal with.

I went back to a Cheshire quite quickly myself and figured if a colli cap mwas good enough 30 years ago then even a Cheshire represented a techno leap for me

[dweller25]

Agreed.

I still use an aluminium collicap I bought from Astro Systems in 1986, gets me very close visually and then a quick tweek on a star to get spot on.

[calibos]

The problem isn't Lasercollimators per se but cheap laser collimators. More often than not out of collimation themselves. When you feel you can't trust your laser collimator to be in collimation itself and need to check its collimation or re-adjust it before you even go near your scope, well then they have the opposite to the desired effect which is quick collimation.

Pay the readies for a quality tool like the Howie Glatters or Hotechs though and you get the best of all worlds. Very accurate collimation in literally seconds and in the dark without messing about with torches in one hand, an eyeball in the focusser and the other hand on the primary collimation knobs. Beyond a certain focal length you start to need the arms of an orangutan or put up with a 5k walk back and forth from one end of the scope to the other over and over until collimated

[Moonshane]

I don't know half as much as most guys on here but I collimate secondary (just laser - I check the collimation on the laser from time to time with a 'L' block) and then the primary (barlowed laser) in about a minute with my dob. I have just made some 'Shane's knobs' for my secondary adjustment so this should be even quicker soon.
I have checked this with both a Cheshire and a star test and it's spot on in both cases so lasers (even well collimated cheap ones - mine was £35 new) work fine for me (I am visual only). all that said, I have never got someone who knows to check my collimation so maybe I am doing it wrongly but I am getting everything lined up on the Cheshire, the dot in the donut etc, a nice round, well-lined up concentric ring and perfectly concentric circles on the star test so I think it's right.

[Chris H]

What laser collimator did you get Spock?

[Moonshane]

Originally Posted by Kris77

What laser collimator did you get Spock?

just a word of warning - make sure it's 'set to stun'

[dweller25]

Originally Posted by shanefarrell

just a word of warning - make sure it's 'set to stun'

[albedo0.39]

I agree with the general tone of this thread. Indeed, when I did my overview of collimation at SGL 5 people who had previously set up with lasers were reporting (after using the cheshire) that they were now getting much better views.

It's not the concept of a laser that is at fault (as has been mentioned) but the fact that some of them are "out" to begin with.

Collicap + Cheshire + Star test = happiness !

Good luck

[ollypenrice]

I'm a laser fan (Astro Engineering) and with a 20 inch Dob I can do it single handed. With three or four instruments to get going on some nights the speed and simplicity of the laser is a godsend. The results are usually fine and if we want to get it tweaked a bit more then a two-handed star test can be done later. I wish the imaging rigs could be fired up as easily but Bill Gates likes to turn things blue whenever he can!
Olly

[Mick UK]

I have just recently purchased the 2" Hotech about 3 weeks ago and i just love using it!..im getting as much pleasure out of using my Hotech, as i do looking up into the heavens with my scope!
If anyone wants thier scope collimating for free..just PM me!


Shane.....

[SAB]

When it comes to lasers, I suggest avoiding cheap lasers like GSO, Orion, skywatcher etc- they'll liekly be out of collimation themselves. Go for a Glatter or Astrosystems unit. Sure, these cost alot more, but are machined to fit in your focuser properly and the laser itself will be aligned. For primary mirror collimation, only the barlowed laser method will provide accurate results like a cheshire.

[ZOG]

I use a Howie Glatter laser and blug. Collimate with this set up and then check with a cheshire and it's spot on every time.
Like most things in life, you get what you pay for.

[albedo0.39]

Zog - for sure, if you go Barlowed then you get a totally different result for primary miirror and as you mentioned, with that kind of result it's worth paying for.

However... I still love my Cheshire ! - Am I warped and twisted ?

;-)

[Astro_Baby]

I dont think so albedo - I prefer a Cheshire. If I had a huge long scope I might feel different and get a laser but when you have to worry about the laser collimation, batteries etc a Cheshire just seems reliable and simple and fuss free though they are confusing to newbies.

[PaulB]

I came across a thread on another forum about laser collimator's which I found helpful, so I was able to use this with my Orion Optics Laser collimator.

Collimate your telescope's optics using a star and high power eyepiece.

Then when you are satisfied that your telescope is in perfect collimation. Replace the eyepiece with your laser, first making sure that the focuser is locked up and hasn't moved.

Switch on the laser and simply adjust the laser beam using the three cap head adjustment screws. When you see the laser shining back into itself the Laser will now be lined up with the mirror.

I have done this, and found that it did work with my Orion SPX 200-800 F4 "AG". And I am now able to get the collimation reasonably accurately. I then just need to make a few final tweaks on a star and I'm ready.

I am pretty hopeful that this will also work on my OD250S which will need to be laser collimated, because it isn't on a tracking equatorial mount.

[Astro_Baby]

Umm - sorry to sound pedantic but arent you using a star test to set up a laser collimator there ? It all sounds a but round about and a hassle. I prefer to use my collimator to get the scope ready for star testing not get a perfectly aligned scope so I can collimate the collimator

[johninderby]

The method being described is a way to check the collimation of a new laser collimator to make sure that the collimator itself is actually properly collimated. Just a one time procedure.


John

[johnkirkpatrick]

I've never understood the star test, i use a coll cap for secondary, barlowed method for primary, it seems ok but never really happy with it, also study astrobabys guide millions o times as it the best one there,
but when i do star test its round and looks good then i move the primary mirrior screws i see no change at all, even when i make collimation miles off lol so now i dont even bother.

[TheThing]

Having purchased a collimatable laser at SGL5, I'm never going back to the 'old fashioned' ways. It's so much quicker and easier!

But, each to their own. If we were all the same, astronomy would not be the vibrant, interesting obsession that it is!

[johninderby]

The focuser also plays a big part in collimating with a laser. If your focuser has a bit of slop in it (as with many focusers fitted as standard) then the laser may very well be thrown off and a good old cheshire might work better for you.

I'm very satisfied with my Hotech laser which has proven to be far more accurate than ones I have used in the past. I've tried collimating with a cheshire or collimating cap and then checking with the Hotech which then usually shows a small tweak is necessary to get the collimation spot on, so now I just use the Hotech.

John

[sgazer]

Originally Posted by johnkirkpatrick

I've never understood the star test, i use a coll cap for secondary, barlowed method for primary, it seems ok but never really happy with it, also study astrobabys guide millions o times as it the best one there,
but when i do star test its round and looks good then i move the primary mirrior screws i see no change at all, even when i make collimation miles off lol so now i dont even bother.

now you mention it, I've noticed that too. I have to turn the main mirror bolts a lot before I notice a movement in the star test. It's not just a fraction of a turn which is all the Cheshire requires. So if it looks reasonably ok on the star test after using the cheshire, I don't bother with any more adjustments either as it thows the Cheshire collimation way off.

[Jason D]

Miscollimated laser collimators always get more negative feedback than they really deserve. They are not as bad as most think. Let me clarify – see attachment.

Figure “A”: Let us insert a miscollimated laser collimator into a perfectly collimated scope. Let us assume we do NOT know that the scope is perfectly collimated. The miscollimated laser forward beam will hit the primary mirror off-center and its returning beam will be off. Based on the laser readings, we conclude that the scope is “miscollimated.”

Figure “B”: We adjust the secondary mirror to align the primary mirror center spot with the forward laser beam. The returning laser beam is irrelevant in this step.

Figure “C”: We adjust the primary mirror to coincide the returning beam with the forward beam. Now we believe collimation is done and “perfect” – which is not the case. But how far off is collimation?

Figure “D”: Well, collimation is not bad!!! An eyepiece focal point is very close to the primary mirror focal point which is the most critical alignment. However, the eyepiece focal plane is tilted with respect to the primary mirror focal plane – this is the typical error introduced by miscollimated laser collimators which happens to be the less critical error. Actually, if we insert the colli-cap or a cheshire, both will agree that collimation is “perfect.” Even the star test will indicate a “perfect” collimation. In a way, this miscollimated laser collimator produced results comparable to the colli-cap, a cheshire, and the star test. See, all these tools check for the proximity of the primary mirror focal point to the eyepiece focal point. HOWEVER, none of these tools, including the star test, will flag a focal plane tilt error between the eyepiece and the primary focal planes.

Figure “E”: If we re-insert the laser collimator with 180 degree rotation, the forward laser beam will hit the primary mirror way off-center and the returning beam will also be way off. But collimation did not get worse – it is still the same.

In summary:
1-Miscollimated laser collimators are not as bad as many state
2-Their accuracy is comparable to the colli-cap, the cheshire, and the star test
3-It is important to re-insert the laser collimator exactly in the same orientation each time

I believe those who own mass produced scopes should be more concerned about the location of their primary mirror center spot as opposed to how well is their laser collimator collimated. My scope had its center spot off by 1.5mm which meant even had I used the most expensive and perfect collimation tools, I would have had an error of 0.75mm – the distance between the focal points of both the primary and eyepiece. This is borderline to the coma zone for my scope’s F-ratio.


Jason

[calibos]

Originally Posted by Astro_Baby

Umm - sorry to sound pedantic but arent you using a star test to set up a laser collimator there ? It all sounds a but round about and a hassle. I prefer to use my collimator to get the scope ready for star testing not get a perfectly aligned scope so I can collimate the collimator

Certainly using a star test for this purpose seems to defeat the object of the excercise but it has merit. JUst before I sold on my 12" dob and Orion Lasermate deluxe after reading some of Jasons posts on CN I learned that this was a very handy way of making sure the laser was collimated before a dark sky trip.

First of all I had a cheshire combo tool but didn't like using at night with all the torch holding (especially as work always made me last to the field and setup thus annoying others with the torch) and backwards and forwards while collimating the primary. Neither could I setup in daylight. Thus my cheshire combo tool never got used. I relied on my Orion Lasermate to collimate at night. However the thing was miscollimated from day one and I found the collimation of a laser proceedure (where one sets up the laser in a lathe type aparatus and target on a far wall etc) a pain in the proverbial. Collimation would only hold for a few sessions before drifting again so I was never sure of I could trust the lasermate on any given night.

So I upgraded to a Howie Glatter laser and Blug. It was a revelation in easy of use and accuracy and speed.

However just before i sold the old scope and lasermate I tried to research whether I could provide the new owner with a reliable collimation proceedure and like I said came across Jasons postings on CN on the matter. Before a trip I would collimate the scope in daylight inside the house with the Cheshire. Then insert the lasermate in a known repeatable position, ie with say the L on the label in line with the focuser drawtube set screw. I know the scope is perfectly collimated with the cheshire thus any miscollimation of the laser dot and return beam is in the laser(for that focuser orientation) So I would then centre the laser dot in the donut ring with the three adjustment screws of the laser. I tested that this was a reliable method by miscollimating the scope again and doing it over with the cheshire and with my Howie Glatter laser and then the lasermate. All tools would agree. Then just a quick tweak with the lasermate after setup on site after the bumps in the car knocking the scope collimation out a bit.

Thus should the new owner start to feel the lasermate was out of collimation again, instead of messing about with the lathe and wall target malarkey they would just have to pop the cheshire into the scope, quick tweak to get the scope collimation right and then pop in the lasermate and within about 5 minutes have the lasermate back perfect.

[Jason D]

Hello Keith,

I do recall both of us discussing the method you have described in your post.

The method outlined in your post is indeed the best way to collimate a mass produced laser collimator. I did the same. I used my quality Catseye tools to collimate my scope to perfection as much as possible. Then I inserted my Orion Deluxe Lasermate in the focuser and adjusted the laser setscrews until the forward beam hit the center of the primary mirror spot. Finally, I ensured the returning beam coincided with the forward beam.

Each time my scope needs collimation, I start off with the lasermate to attain good results. Then with few tweaks using my autocollimator and cheshire, I am done. Now my lasermate always provides consistent good results.

Interestingly, if I rotate the lasermate 180 degrees in the focuser then the forward and returning laser beams slightly shift. This is due to the lower machining quality of a mass produced laser collimator compared to the superb machining quality from Howie Glatter.

Jason