Recommend a Laser Collimator?

morls (Stephen) · #1 10-08-2010, 02:30 PM

Hi,

I hope I'm not duplicating any earlier threads.....

I'm wondering if anybody could recommend a laser collimator that would be best for my skywatcher 8" collapsible dob....I have an orion collimating eyepiece with the crosshairs, but I think I remember someone telling me this is best for the secondary, and that combining this with a laser for the primary is the way to go.

I'm just looking for something basic and accurate.....any suggestions would be much appreciated....

Thanks

Stephen

erick (Eric) · #2 10-08-2010, 02:45 PM

$s that you want to spend are??

norm · #3 10-08-2010, 02:46 PM

Hi Stephen,

Pick of the bunch (high end stuff):

Cats Eye collimation, Howey Glatter and Astrosystems.

I prefer the Astrosystems - pretty easy to use.

They're expensive, but you pay for what you get.

I'm happy to give u a demo of the AstroSystems, send me a PM

Cheers,

Norm

Jeeps (Sam) · #4 10-08-2010, 02:56 PM

I've got a saxon laser, it was about $70. It works fine.

cheers

morls (Stephen) · #5 10-08-2010, 07:41 PM

Thanks for the replies...
Eric, I was thinking around the $100-$120 mark, but I'm really not sure of what's available...
I'll also check out the ones you mentioned Norm....

erick (Eric) · #6 11-08-2010, 10:04 AM

You've picked a price point that is more than the cheapies (around $70-80) but well below the goodies ($150+). So I'm not sure which way you want to go. A cheapie that puts out a good beam and has its internal collimation checked and adjusted if necessary, can work well enough, especially if combined with a simple 2x barlow for the final primary mirror adjustment. The top end tools (Glatter, Catseye) have very good reputations. Here is a thread from the Archives that might help:- http://www.iceinspace.com.au/forum/a...p/t-38552.html

morls (Stephen) · #7 11-08-2010, 10:44 AM

Thanks for that Eric,

I think I need some further advice before I decide which way to go here...

I'm chiefly interested in visual observing. Does this mean I don't need to have quite the level of precision that someone into photography would need in order to get good results? Also, at what point does the 'seeing' limit resolution as compared to collimation, given that upwards of 50% of my viewing will be from light polluted urban Sydney?

Thanks...

Stu Ward · #8 11-08-2010, 10:50 AM

I bought a GSO Laser Collimator from Andrews $59 i think.

You just have to make sure that the collimator itself is collimated and the laser beam is tight and you are away.

Works perfectly for my 8" Dob ( or my eyes anyway)

Stu

erick (Eric) · #9 11-08-2010, 11:51 AM

Stephen, others will disagree, but I reckon you are looking for "good enough" collimation on your dob for visual work and I reckon you reach that point well before the photographers are happy with their collimation. I'm guessing that your 200mm dob is a GSO or Synta make? If so, any attempt at super accurate collimation is probably defeated by the mechanics of the scope (most are not bad, but we are not talking exquisite engineering here! Typically, the primary mirror sits on springs that sag somewhat as the elevation of the tube is changed. Many replace them with stronger springs. ps. a laser collimator is good for observing if you have that saggy behaviour!) A good idea is to collimate the scope at the angle of elevation at which you expect to be observing. Certainly, don't collimate it at zero degrees elevation, then go off looking for targets at 80 degrees elevation! Probably around 60 degrees is the best compromise if you are going to be up and down all night.

Now you should always collimate and get as close as you can to accurate, but, in my experience, bad seeing blows away resolution more than will being a bit out of collimation. Of course, bad seeing combined with bad collimation! - you might as well pack up for the night!

You shouldn't confuse light pollution with bad seeing. You might have wonderful seeing conditions in the big city (presuming you can get away from looking across large expanses of bitumen, concrete, metal rooftops which can give you horrible localised seeing conditions) and good transparency (no clouds, dust, smoke, mistiness), then you are then left to cope solely with the light pollution. Yes, if the contrast between what you are trying to see and the background sky is poor, that will surely make it more difficult to see detail and resolve fainter objects. Of course, anything fainter than the background sky is "invisible". But many people in such conditions focus on observing double stars and seem to have a great time - if the stars are bright enough to stand out from the bright sky. One can experiment with the various forms of light pollution filter to try and improve contrast. Splitting double stars? - Yes, you want your collimation as best as you can get it for your scope.

Why don't you go with a GSO laser. Not many dollars and you'll easily sell it here if and when you upgrade. But make certain it comes out of the box in the shop and is turned on and shone on a wall 2-3 m away. Inspect the spot and check it seems bright and fairly well focussed. It won't be a spectacular performer (a sausage shaped spot is the norm, it seems), but is better than no laser. BUT THAT IS IF you do check its own collimation, and adjust if necessary. Not too hard to do - search out some threads on IIS. Then check it fits snuggly into your focusser, or more likely in the 2"--> 1.25" adapter. My trick is to add a layer of "contact" around the barrel, if necessary, to get a snug fit.

Then follow supplied instructions.

But you can add the "barlowed laser" method easily (Eric's poor astronomer's method!) after you have done the best you can with the instructions. You need a barlow lens (2x will do.) Place the laser in the barlow and all in the focusser. Look at the primary and you should see a diffuse patch of laser light. If necessary, tilt the laser a bit to ensure that the diffuse patch covers the centre ring. Punch a small hole (paper holepunch size should do, maybe a bit smaller if you can) in a piece of paper. Now hold the paper inside the tube unit in front of the focusser and move it until the laser beam coming through the barlow and out of the focusser passes through the hole. You should immediately see a reflected diffuse spot back on the paper. You should see the shadow of the centre ring, hopefully with that exiting laser beam nicely centred in that shadow. Try tipping the laser a bit in the focusser and observe that the shadow is rock solid on the paper - how about that! If the shadow is not centred, tweak the primary mirror collimation adjustment screws until it is (it helps to have a friend with you).

You might find this does all you need? Or you might move up and spend that $200+ for a super-duper Glatter sometime.

Cheers
Eric

Quote:

Originally Posted by morls

Thanks for that Eric,

I think I need some further advice before I decide which way to go here...

I'm chiefly interested in visual observing. Does this mean I don't need to have quite the level of precision that someone into photography would need in order to get good results? Also, at what point does the 'seeing' limit resolution as compared to collimation, given that upwards of 50% of my viewing will be from light polluted urban Sydney?

Thanks...

morls (Stephen) · #10 11-08-2010, 02:00 PM

thanks Eric, that's seems like excellent advice...

I've gone and ordered a GSO from Andrews, so I'll keep my fingers crossed it'll be good (not too big a sausage!)....

thanks everyone for your time and help

erick (Eric) · #11 11-08-2010, 02:54 PM

Hope it works well.

There is a mod that makes it easier to internally collimate a GSO laser collimator. See here:-

http://www.iceinspace.com.au/forum/s...d.php?p=523122

morls (Stephen) · #12 11-08-2010, 03:44 PM

Brilliant! Thank you....

ausastronomer (John Bambury) · #13 13-08-2010, 06:10 PM

Quote:

Originally Posted by erick

Stephen, others will disagree, but I reckon you are looking for "good enough" collimation on your dob for visual work and I reckon you reach that point well before the photographers are happy with their collimation.

Hi Eric,

That depends on how serious you take your visual observing. When you have the very best of equipment for visual observing, with a lot of $$$$$ tied up in it, you don't do a 1/2 pied job of collimating the telescope when you wheel it out. I will guarantee you, my scope is collimated as well as anything on the field, each and every time I set it up. But that is just how I like to be. I know plenty of visual observers with plenty of $$$$$ tied up in their equipment and they don't bother to spend any time collimating their scope. FWIW I don't spend much time looking through these.

To the original poster:-

If you intend to get serious about your observing, buy a high quality collimater now. You will still have it long after your current telescope has gone to greener pastures and you have progressed to high end equipment. The Astrosystems, Glatter and Cat's Eye are all good. Like most things in life you get what you pay for. The cheaper units are hit and miss. Somtimes they are out of collimation themselves, they do not produce a circular beam and the lasers in them can suddenly stop working and they go straight in the trash.

Cheers,
John B

stephenb (Stephen) · #14 14-08-2010, 09:35 PM

Stephen,

I agree with Eric's suggestion 100%. Although I have used a few different types of laser collimation tools, a GSO will do the job for you. In my opinion there is no absolutely no need to go out and buy the biggest and best of everything based on the theory that it will last you for the rest of your life.

Let us know how you go.

morls (Stephen) · #15 15-08-2010, 08:06 AM

I've got the GSO, done the mods and while I can see it is not going to be a highly accurate tool, I think it's made a clear difference to the accuracy of my collimation....

I think down the track I probably will move on to a higher quality laser collimator, but for the stage I'm at this is a good compromise for me. If I still have this level of enthusiasm in another 6 months I will be more confident buying high-end equipment, knowing I will indeed be doing this for a long time.

For now, I'm very happy with the results I've got vs money I spent on the GSO collimator. If I get some of this back selling the GSO when I upgrade that is a bonus, but 6 months of clearer viewing than what I had before for $60 is a bargain to me...

Thanks again for all the advice...choices aren't easy, but this forum makes it much less of a mystery.

Stephen

erick (Eric) · #16 15-08-2010, 08:12 PM

Quote:

Originally Posted by erick

Stephen, others will disagree, but I reckon you are looking for "good enough" collimation on your dob for visual work .......

Quote:

Originally Posted by ausastronomer

Hi Eric,
That depends on how serious you take your visual observing........

, I felt that you would have a view, John. I think that degree of seriousness comes with time, after a learning curve? But I cannot disagree with your recommendation, if one has the money. Morls was pitching at around the $100-120 mark. Also for an 8" collapsible Dob? - I suspect the mechanics won't really do justice to the capability of the high end collimators.