Collimation

[buzzlightyear]

Hi folks,

I have just brought as laser collimater and had a go using it tonight.

After adjusting all the screws I eventually got the red dots in the right places. So after doing this I ( for some reason) slacked of the focus EP holder slightly until I could turn the laser in a circle, and whilst looking down the tube I noticed the laser dot moved around in a oval rotation and was coming out from the primary centre circle then back in!

Is this normal? I guess it's not but would like a expert opinion.

Thank you.

[Charic]

Hold you finger on the end of the laser lightly and rotate. see if it still describes an oval. The focuser tube is a little to big for the laser ( this is normal, however not correct / satisfactory ) allowing for the rotation your observing. I found slight pressure aligns mine better.

ps. Hows your plumbing? build one of these   This helps to align the laser.

I had a similar issue, but only a slight mis-alignment. The best use of the laser for me is to use it with a Barlow to set the Primary mirror!

[buzzlightyear]

The red dot was around a good half inch out of the target circle on half a turn charic. This can't be normal can it..

[Charic]

If you construct a cradle or something with a 'V' in it, so that you can cleanly rotate the laser in this cradle, and point the laser to a wall as far away as possible, when you rotate the laser, the dot should remain central as a dot, when properly collimated. Once this is achieved, any other movement in the focuser is just due to the size of the focuser tube. Electricians tape around the laser may help, but too much and the laser won't fit?

Create a 'cross-hair' on a piece of paper and  stick this to the wall, aim the laser at it when you rotate. REMEMBER the laser tube has raised sections around its circumference, so have caution when you rotate. the laser has to be level.

If you have managed to collimate your telescope before buying this laser, then collimate it again using your usual method, but when it comes to aligning the primary mirror, place the laser into a Barlow? This 'spreads' the laser beam and illuminates the mirror surface, the centre spot then creates a shadow, which is visible on the face of the angled face plate, so now instead of chasing the laser dot back into the hole on the angled face plate, you now have a 'circle - shadow'  from the centre spot. You just align this to surround the hole in the face plate. Once central, you mirror is set.

[Scooot]

If you're holding it straight it should stay pointing at the middle as you rotate it. Try leaving the laser tight in the 1.25" adapter and rotate the adapter whilst ensuring its still flush in the focuser. What laser is it?

[Scooot]

If you construct a cradle or something with a 'V' in it, so that you can cleanly rotate the laser in this cradle, and point the laser to a wall as far away as possible, when you rotate the laser, the dot should remain central as a dot, when properly collimated. Once this is achieved, any other movement in the focuser is just due to the size of the focuser tube. Electricians tape around the laser may help, but too much and the laser won't fit?

Create a 'cross-hair' on a piece of paper and  stick this to the wall, aim the laser at it when you rotate. REMEMBER the laser tube has raised sections around its circumference, so have caution when you rotate. the laser has to be level.

A V block apparently doesn't work for a hotech

http://www.hotechusa.com/category-s/58.htm

I had to send one back.

[Charic]

Ok.....never asked what laser he had?

Just checked a  HoTech SCA laser, and yes it looks awkward, but a cradle can still be made by using crossed nails at differing heights to level the laser tube!

Whatever the mount for the laser, as long as the laser is horizontal, it should be possible to check its collimation.

[Scooot]

I just tried my hotech. Rotating the adapter isn't very successful, there's too much play in it. Rotating the laser itself is more successful, it still moves about a bit but not in a circle, but that's mainly because it's not possible to hold it perfectly in the same position. If you are getting a circle maybe it's faulty. If you can test it as above all well and good.

I'd contact the retailer you bought it from to discuss. They should just swap it for you if necessary.

[Dave In Vermont]

I recently purchased an Orion (USA) LaserMate Deluxe II and this evening was the "first-light" for it. First I checked it's collimation using a home-brew version of a v-block. It was perfect. Then I turned it around several times in the focuser after I had centered the secondary and the red-dot was perfectly in the center-mark of the primary - perfect again! Then I collimated the primary so the red-dot was dead-center back in the emitting aperture of the laser's bull's-eye. Perfect (This laser is boring me! I'd rather complain! ). This was too easy! Now to try to throw a monkey-wrench into the works.....

I found my Orion "Collimating Eyepiece." This is a mixture sighting-tube/Cheshire eyepiece - same animal as the one from Celestron, #94182. I then proceeded to check all the results from the laser, but using this "Collimating Eyepiece." Both the laser and the quasi-Cheshire were in perfect agreement.

Sorry to hear of the trouble with the HoTech SCA. But it's not surprising. This is what happens just about every time somebody/company joins the "Innovation-Of-The-Minute Club." The design can be the greatest feat of engineering ever seen on Earth! As was the R.M.S. Titanic. There's always that one, teensy, tiny, little, widdle detail.....

Bon Voyage & Clear Skies,

Dave

[buzzlightyear]

If you're holding it straight it should stay pointing at the middle as you rotate it. Try leaving the laser tight in the 1.25" adapter and rotate the adapter whilst ensuring its still flush in the focuser. What laser is it?

It's called a next generation.

[nicoscy]

Most of the laser collimators available actually need collimation themselves.

My first collimator was a Baader Collimator which was awful straight out of the box.

Tossed it away and replaced it with the Glatter Laser and Tublug. Pay "dearly" once but get a proper tool for life.

[buzzlightyear]

Think I might send it back if this is the hassle it gives. Only got it to collimate the scope when in the dark.

I use the cheshire somehow from now on,

Thanks

[nicoscy]

A Cheshire is all you need. Being lazy and wanting to finish with collimation asap without going back and forth, I use the laser to center the secondary and the laser and tublug for the primary without all the back and forth at the eyepiece.

Glatter tools are really accurate. I remember the first few times I would always check with my Cheshire to confirm collimation. Haven't used the Cheshire in months, although I am still sufficiently "old school mentality" material to always carry it with me 

[buzzlightyear]

I'm going to make the block of wood and nails v shape holder later and see if I can collimate the laser. I won't be defeated easily lol

[buzzlightyear]

Ok now I have realised that the 3 screw holes on the laser for collimating it are packed with some type of resin. Now should I scrape away and risk loosing the warranty, or just send it back.

[nicoscy]

Either send it back for a refund or a replacement with Howie Glatter laser.

If you ask for a replacement with the same brand you have, you are likely to receive a unit that is out of collimation again.

You would thing that companies would be a bit more careful rather than keep coming out with collimating tools that need user end collimation to work.

As if customers are obligated to do QC for the manufacturer or set up a v block and invest an hour or two to correct collimation...

[buzzlightyear]

I agree with you that selling a collimating tool that needs collimating first is a bit odd indeed.

[Gomtuu]

Tossed it away

Never toss a laser away!  Even a badly collimated laser can be barlowed to collimate the primary.

[buzzlightyear]

Never toss a laser away!  Even a badly collimated laser can be barlowed to collimate the primary.

As half a rotation whilst in the focus tube sends the red dot half an inch out of the primary centre circle, then I can't see how a Barlow can help?

[nicoscy]

Bar lowed collimating of the primary is insensitive to laser mis collimation.

[Lowjiber]

I've used a Hotech for a couple of years with a 10" Dob and an f/5 150mm Newt, which is very sensitive to good collimation.  Mine was dead-on right outta the box, and I've not checked it since.

I still carry a Cheshire in my eyepiece case for a backup, but haven't used it much... mostly at star parties on other people's scopes.

My main complaint about the Hotech is that it is either "on" or "off".  There is no way do dim it down for collimation at a very dark site.  I think the fairly new Orion laser can be dimmed.

Clear Skies

[jetstream]

The red dot was around a good half inch out of the target circle on half a turn charic. This can't be normal can it..

Glatters equipment is the Rolls Royce of laser collimating tools. A sight tube for secondary alignment + Glatters laser + TuBlug is among the best and most accurate tools out there.

Your laser not being collimated is only one of the problems you will encounter when trying to use it (unbarlowed). The TuBlug provides the barlowed method with a target screen.

[buzzlightyear]

Not sure how the Barlow will work on the primary if the seconds is out? Please tell me as can't get my head around it lol

[nicoscy]

After collimating the secondary, try this:

https://www.cameraconcepts.com/barlowed%20laser%20collimation.pdf

Even if your laser is not collimated, the projected ring of the center spot bounced back from a barlowed laser is not affected.

[The BFJ]

I use a laser colli and 2in - 1.25in self-centering adapter to ensure it lines up with the center of the focuser-tube and have never had a problem getting the colli just fine. I got my adapter from Tring Astro but I'm sure other retailers will also have them. It's def more reliable than trying to use the 1.25in eyepiece holder in the focuser tube anyway.