Collimation tools (split from Lightbridge Updates)

[norm]

Hi Astronut,

The scope sounds very impressive. I am a newbie and just wanted to know what tools you will be using to collimate the scope. I went into Astro-Opticals and they basically said to me don't bother with a cheshire eyepiece or site tube and go straight for a laser collimator. I allways had the impression these were the basic tools to use and master?

Just wanted to know your thoughts or anybody elses. He also said something about putting a mark on the cover of the primary mirror so when the laser projects back up you don't get all those reflections.

Apologies now if I haven't clarified myself here:shrug: .

[janoskiss]

I would not listen to most dealers about the type of collimation tools you need. I was told a similar thing about the laser by staff at a scope shop :whistle: in Melbourne too. I was also told that once the scope is collimated, I should only ever need to make small adjustments on the secondary, yes the secondary! the small mirror near the focuser! I was told that when star testing I should be adjusting the three screws behind the secondary in the centre of the spider.

I am not kidding!! The guy showed me this in person and pointed out the adjustment screws for the secondary as the ones to tweak while star testing. He also told me not to touch the primary adjustment screws because that one stays put in transport, but the secondary goes out really easily. In case you don't know, this is all incorrect, back to front. See any good source on collimation, e.g., www.skyandtelescope.com. With this experience and their over inflated prices, they have lost me for good.

Cheshire/sighttube is the first collimation tool to get, and the only one you need. But a laser can be helpful in aligning the secondary. If you want one of those return beam lasers, they are on special at bintel for $79.

[janoskiss]

I've split this discussion from astronut's Lightbridge thread: http://www.iceinspace.com.au/forum/showthread.php?t=8814

[astronut]

Hi Norm, I was told the same thing by a very experienced astronomer, cheshire is the way to go;)

[cjmarsh81]

I had read this in reviews on the internet too. That is why I found collimation so confusing at first, I thought how in the hell do you adjust those three screws on the secondary in pitch blackness? It is only recently that I found a review that said the secondary is done pretty much once a year and the primary is adjusted each time you use it. This makes a lot more sense to me.

P.S. I have a chesire/sighttube and I find it is all I need. I have read too many reports on the laser collimators being inaccurate I have not wasted my time on them.

[Vermin]

A laser can be a handy tool, but can be considerably better with a few adaptors. I use,

1) a basic laser beam to square the focuser in the secondary cage

2) a holographic grid attachment on the laser to centre the secondary in the focuser and to rotate the mirror to face to the focuser

3) the basic laser beam to aim the secondary at the primary

4) A barlow attachment on the laser to aim the primary at the secondary.

When star testing after aligning with these tools, the primary does not have to be tweaked at all.

[cjmarsh81]

Maybe when I get into astrophotography I will get that piccy with my collimation. Until then, if it looks good through the EP it will do me.

[vespine]

So I went and got a 12" Lightbridge yesterday.. To cut a long story short, Astro Optical shipped one from Sydney for me, supposedly because they were going to collimate it for me... Yes: he didn't want to sell me the telescope that was in the shop because he wanted me to get a collimated scope and he'd sold out of the tools to do it himself .... He was getting the scope collimated, packed away and shipped from Sydney to Melbourne so that I could get a collimated scope, I'm not making it up.:screwy: He also said the laser is the way to go, but after this experience I'm even more convinced that the cheshire is the way to go ;) (I even called bintel, no cheshires there either :rolleyes:)

Anyway so after putting it together, to me it looks out. The bits are not lining up. To see the reflection of my eye right on the centre dot of the primary I have to move my eye towards the edge of the draw tube and then the reflection of the primary is far from centred in the secondary... But really, I got no idea and I've been reading about "off set" and finding it a little confusing so I thought I should at least do a star check or something before I touch anything, just in case I'm mistaken..

So I wait until dusk and just have to first point the scope at Orion's nebula, and even tho it wasn't even really dark yet I was stunned as to how NOT faint it is!! :eyepop: After I stopped gasping, I did a star test and sure enough it is definitely in need of some adjusting, thinking it would probably take me half an hour to do the 1st time and not even kidding myself that it's something I could attempt in the dark, the clouds came over so that I wouldn't keep torturing myself with a view that was now obviously impossible to bring to perfect focus and overly comafied..... Going to have fun trying to collimate it tonight.... without any tools...

[cjmarsh81]

If you have an old 35mm film canister you can drill a 1/16th hole in the center of the lid and cut the base off. This will give you a reasonable collimation tool if you have nothing else. Do a search on the internet about collimating. I would not even attempt it without some form of tool as you don't know if you are adjusting it in the right direction or not.

[cjmarsh81]

Try on of these

http://home.comcast.net/~astrohammer/tipscollimate.htm

http://www.schlatter.org/Dad/Astronomy/collimate.htm

http://web.telia.com/~u41105032/kolli/kolli.html

http://web.telia.com/~u41105032/myths/myths.htm

http://www.fpi-protostar.com/collim.htm

http://skyandtelescope.com/howto/scopes/article_787_1.asp

http://hometown.aol.com/billferris/startest2.html

[janoskiss]

Too much information CJ! :scared: There is enough pages there to make a book (or two). Are you a refractor dealer? :rofl:

[vespine]

I'll definitely be trying to "film canister" trick, doesn't look like a star test will be likely tonight tho :(

[janoskiss]

One trick with the film canister is to stick something bright around the pinhole facing the secondary so you can see its reflection when you look through the pinhole.

[barees63]

Well, FWIW.. here's the sum of my experience so far..

First, that selection of web pages will definitely confuse you, many of them confused me with their contradictions..

The thing is you need to treat collimation as a series of steps..

What has worked for me is to:

1. initially get the secondary correct by taping some bright colored paper opposite the focuser and some white paper in the light path (I was going to say to block the tube but you know what I mean), this lets you see the secondary very clearly and you can then use a sight-tube (or cheshire combo) to get the secondary centered and rotated so it appears perfectly round.

2. Then use a properly collimated laser to tilt the secondary so the dot hits the exact middle of the primary centre spot..

3.Then use a cheshire to set the primary tilt.

The theory is only the last step needs to be done on a regular basis..

Hope this helps, probably just more information overload ;)

Bruce

PS. Have a look at www.catseyecollimation.com (http://www.catseyecollimation.com)

[Vermin]

Because the Lightbridge is a truss tube scope, it is more likely that the secondary and primary will need adjusting if it is dismantled between sessions.

Numbering the truss tubes and putting them back in the same spots will minimise any secondary adjustment required.

If the truss poles are very similar or if the scope is not disassembled between sessions only the primary may need adjusting (after the initial alignment).

[Starkler]

Yes indeed and I thought it very misleading to suggest that one can dismantle a truss dob, ship it interstate and have it magically in collimation when reassembled.

Yes you most likely will have to tweak both secondary and primary mirrors each time the scope is torn down and reassembled. Tube dobs only need a regular primary collimation tweak.

FWIW, if I owned a truss dob I would use both a laser and a cheshire, with the laser only for the convenience of easier secondary aiming.

[cjmarsh81]

Nope. I just didn't want to fiddle with my scope until I knew what I was doing. I still don't, but I think my collimation is fairly good. I only tried Star testing a couple of days ago. hehe

[matt]

This is probably the nerdiest thing anyone's ever said but I actually enjoy collimating and star testing.:screwy:

I think it's actually really enjoyable once you've got the hang of it.

I need help:lol:

[Starkler]

In the other thread I suggested that the first lightbridge mod should be blackening those white inner tube ends but I have changed my mind.

I reckon the first mod should be gluing a washer on the secondary holder for the collimation screws to bare against. You will be tweaking the secondary often and the holder is only soft plastic. The screws will quickly gouge holes that they will always want to slip into so a metal surface will be a lot more durable.

[cjmarsh81]

Yes you are right. You need help:rofl:. I hate collimating my scope. I can't get over the feeling that I will change something and not be able to put it back to working order. Optics to me is a bit of a black art at the moment, until I get a little better at it.

[matt]

The only thing I can say that might be of comfort is that YOU WILL get better at it.

It's just one of those strange things in life where you get better at it the more you do it ...

I can't explain it. One day, the penny seems to just drop.

But you do have to do it, and do it, and then do it some more. And aim for only small improvements if you don't feel that you are making giant leaps forward:thumbsup:

[vespine]

Yes, when I get around to it I've got some incantations to try and already have selected a virgin bottle of beer that I'm going to sacrifice to the collimation gods :lol:

[Vermin]

Aligning my scope with the laser is a breeze, made even easier because I have motorised my primary collimation screws.

I Just stand opposite the focuser and press a few buttons until the ring binder shadow in the barlowed laser beam return lines up with the laser emitter. I love my gadgets :)

[matt]

nifty, mate. very nifty:thumbsup:

[vespine]

holy cow! That's awesome! :) I just had my 1st collimating attempt, I used a film canister and as I suspected, the primary AND secondar collimation was way out. I've had a fiddle now and everything looks nice and aligned, I was a little worried never having attempted it before but it all started to fall into place once everything started to look alined.

[a1120028]

Ok, this is my first post and it is due to utter frustration if I sound weird. I just bought an 8" lightbridge and am totally confused about the collimation. Especially about this 'offset'.

A few questions,

1. Can a lightbridge be collimated well with a meade laser collimater?
2. Does the offset mean your eye will not be center of the secondary when properly collimated.
3. Can someone post a pic of a collimated lightbride from down the focuser?

Or am I asking the completely wrong questions. HELP

[astronut]

I've just taken a photo of my 12"LB through the focuser. This is how it should look.
There is a great site called www.andysshotglass.com (http://www.andysshotglass.com) he has a very good video on collimation amongst other things.
If you need further help, PLEASE ASK!! :D :D

[Don Pensack]

You might start with my article here on IIS:
http://www.iceinspace.com.au/index.php?id=63,390,0,0,1,0

My point of view is that whatever gets you collimated, and if you have a scope you have to transport to use you WILL need to collimate, is fine with me.

Passive tools (non-electric tools that use ambient light) are generally easier to use and can correct more problems than a laser. Active tools (laser, Krupa) can work well, too, and MAY be easier to use at night for a "touch up" to collimation.

You have to :
--center the secondary under the focuser. This takes a sight tube, not a laser.
--rotate the secondary until it appears round. This is for even illumination of the field, NOT for collimation. This takes a sight tube, not a laser.
--adjust the tilt of the secondary until the reflected image of the primary's center mark lines up with the axis of the focuser. This can be done with a sight tube (center the dot behind the crosshairs) or a laser (adjust till beam hits dead center on primary's mirror centermark).
--adjust the tilt of the primary. This can be done with a cheshire or a "barlowed laser". It cannot be done with the simple return beam of a singlebeam laser unless you can accurately gauge the spot on the primary to a hundredth of an inch. Placing the laser in a barlow and centering the shadow of the return beam on the bottom of the laser (look up in Google: "Barlowed laser protocol" for multiple sites on how to do this).
--eliminate all residual errors. This can be done with an autocollimator, but no other tool. No matter how ell you've done the previous steps, there will be residual errors in your collimation. The autocollimator can eliminate those and give you perfect collimation. Other tools will get you close, but not quite to perfect.

Who makes the tools:
Laser: Only brand recommended: Howie Glatter.
Passive tools 2": Catseye Collimation
Passive tools 1-1/4": Tectron or AstroSystems (just ignore their instructions to center dot the secondary.....shudder:eyepop: ).

And, though I may regret this, send me a private e-mail if you would like help with an issue on collimation. I'll help if I can.

Clear skies to all.
Don

[a1120028]

Thank you for all the help. No problems so far except one, I live in Adelaide where does everyone get their collimation tools from. I only have one retailer here who is small. I am aware of Bintel, who else would you recommend?

[astronut]

This is not a paid ad:lol: but I have dealt with Bintel for a number of years and have found them to be reliable, competent and friendly at all times.
The other supplier that is very good to deal with is Andrews Communication here in Sydney www.andrewscom.com.au (http://www.andrewscom.com.au) :)

[rumples riot]

I bought a Catseye collimation tool set and obtained the image taken with the SDM in my solar system blog at Wartook Rise (latest entry). Truss dobs require collimation on each session. The collimation will be out if the truss is dismantled.

Using a barlowed laser in conjunction with the Catseye tools will provide the best collimation you have ever had.

[a1120028]

I've seen the cats eye page but was unsure what I needed. The "kit" you mentioned would seem like the best idea and can be used on any other Newts I may get in the future. The next question is price and delivery time.

BTW I'm green with envy, I just looked at your blog.:(

I want one!!!!!!

[rumples riot]

I have the Infinity XL triple pack kit with the 32mm length.

Price for that was around 270 I think and it took 2 weeks to have them at my door. Jim Fly makes everything as it comes up.

[PeteMo]

I was surprised that that shop Steve went to advised mainly to adjust the Secondary when collimating, since the Secondary is held rigid by Spider vanes, whereas the primary mirror is 'floating' on rubber and therefore has some play. Our club taught us the basics of collimation using a cheshire eyepiece and stressed that the secondary should hardly ever be touched once correctly aligned, whereas the Primary should ideally be collimated every time the scope is moved. Collimation is certainly easier using scopes where the primary has the centre marked.

I also understand that a laser collimator will itself need colimating every now and then. The blind leading the blind? One guy in the club that used both a laser and cheshire ended up ditching the laser.

[a1120028]

So how do I know if the laser is collimated, this seems like it goes round in circles. My retailer assured me the best way to go is laser, probably more so to his profit margin than the good collimation of my scope. I think I'll start with a chesire and sight tube all in one first and see how I go. Adelaide optical said the lasers he has are made my meade but rebadged, anyone confirm if this is the case. He's asking $120 for them which is $50 more than Bintel's, my head is starting to spin.:shrug:

[JethroB76]

I think all retailers I have spoken to have suggested a laser first.
Get the chesire/sighttube. Next step after that is the Catseye system I reckon. A laser on its own won't do all that is required but may be useful in conjunction with the cheshire.
Re-read Don's post, he has covered the major points nicely

[a1120028]

Thanks Don for your help, It would seem that a laser is not the way to go first off. I think I'll be getting the chesire. I think I could use the practice this will give me. Then when I can afford the laser I can use it to double check the chesire collimaton.

[rumples riot]

First don't go to him, he is way too expensive and not trustworthy. I and several others here in SA have had bad experiences with him. He always adds 30% onto everything and sometimes as much as 50%.

To check if you laser or a laser is collimated. Make a jig with two "v's" and use these as a craddle to hold the laser. Then turn the laser on and about 15 feet away have a door with some white paper stuck to it. Point the laser at the paper and rotate the laser a little at a time. Go and make it after each rotation. You will see if it is collimated. Most lasers for this type of thing have collimatino screws.

However, I recommend getting a barlowed laser as this is more accurate and will present the centre dot image at the face of the barlow. It will not shift when you rotate the laser, thereby removing the need for great collimation of the laser.

[Sentinel]

I have a Howie Glatter barlowed laser. Which of the Catseye products would compliment the Laser?

I am thinking that a INFINITY XL Autocollimator would of some assistance.

[Tannehill]

I have a glatter laser, also, and the Catseye triad of tools. A barlowed laser serves the same function as the Chesire, so if you want to avoid duplication, then you can avoid buying a Chesire.

A sight-tube and an autocollimator complement the Laser + barlow attachment nicely. Each has a purpose not served by the other two. So, if you want a high quality sighttube - one with a telescoping inner tube so as to make secondary placement very simple, get a sight-tube from him...it's quite nice, really, and easily adjusted for different scopes.

The autocollimator is great for fine tuning collimation by adjusting the secondary screws. It's really valuable for faster f-ratio scopes, and less noticeably beneficial for f6 and greater scopes. But if you dial in the AC, you'll be spot on. When using the AC, the fine adjustments you make to the secondary often require you to repeat the primary collimation a bit, then again to the AC. 2-3 iterations at most is necessary for this, but then you are about as perfect as you can be. Assuming your center dot is centered!

if you get the Catseye autocollimator, I'd suggest requesting the WHITE reflective triangles rather than red. Red is fine, but in truth, it's harder to see depending on lighting conditions. If it's daylight, the red is harder to see in the eyepiece, whereas the white reflective is visible in all conditions.

Scott

[Starkler]

You can live without ever owning a laser and have a well collimated scope with just a combo cheshire sight tube. The reverse cannot be said.

[Sentinel]

Scott,

I have a 1 1/2 Orion Sight Tube/Cheshire for placing the secondary. Once that is showing the secondary in under the focuser, I then switch to the Laser, adjust the secondary till the laser is inside the reinforcing ring. Then switch the the Barlowed Laser.

Surely the Sight tube gets used the least. Once the secondary is even/circular under the focuser, surely this is a fairly redundant item. I always store the 1 1/2 Orion Sight Tube/Cheshire in the scope when not in use.

The Orion Sight Tube/Cheshire has too much parallax error really for collimation, however this was my only form of collimation aid for nearly 7 years.

Thanks.

[Tannehill]

Yep, I agree with Geoff, the laser is not a critical, if I had to have just one single tool it'd be a sight-tube/chesire dual tool. But I like the lasers. And it is - as you point out - real slick for that first-off adjustment of the secondary using the straight beam. I know what you mean about the parallax issue. Catseyes are as good as any, but that still is present to some degree, the separate tool for each is better I reckon. I, too, don't use my sight tube much, except when I've removed the secondary for a reason and replace it. In fact, I use it more for helping others position their secondary than on my scopes, now. And my daughter runs around with it pretending it's a telescope (like I'm gonna let her run with any of MY real stuff...NOT!)

there are so many schools of thougth out there, it's easy to see why the newbies get confused. 25 years ago, when an f5 newt was "fast", it was all eyeballed. Now we have whole websites and instruments devoted to collimation using one of no less than three possible and distinct "religions" of collimation practice. Sheesh.

Cheers,


Scott