collimation on Laser Collimator

[ggodetucsamoht]

Guys, i am doing my collimation for my new 8" but found out my laser collimator was actually out of collimation. Now, i did the collimation for this device and got a result of laser dots landing around 3mm and placing my collimator from a wall of 2.5m, is this make a satisfactory collimation standard for the laser collimator?

[starfinder]

Hi, can you elaborate or explain what you mean by "got a result of laser dots landing around 3mm..."

[ggodetucsamoht]

Hi, can you elaborate or explain what you mean by "got a result of laser dots landing around 3mm..."

Hi, yes my mistake for not explaining more on how I perform the collimation.

I stick a piece of paper around 2.5m away from the laser source, by diy a fixture so that the laser collimator able to rotate on this fixture. While the collimator is on and durinf rotation you can see the laser dot on the piece of paper running in a circular motion forming a big circle. The larger the circle the more the laser collimator is off alignment. So after I did all the adjustment of the 3 screws on the collimator I get the dots landings 3mm apart. If the laser dot is spinning on its center then it is a good collimation. I am enquiring whether my standard able to works for the use on scope collimation later on.

[starfinder]

Hi, I think a diameter distance of 3mm at 2.5m distance should be alright for use to collimate your scope well. I think it means that it would be max 1.5mm off from the centre at 2.5m, or 0.75mm off at around 1m distance which is probably too small a difference to see anyway under usual circumstances.

However, I'm not an expert on this. Anyone else has same/other views on this?

[Mariner]

Can this be considered a product defect? Or is the 3mm "error" non-consequential for collimation, especially for bigger or longer FL Newts?

[cloud_cover]

Depends on your tolerance for miscollimation. Having said that, the margin of error for collimation in faster scopes is exceedingly small, measured in fractions of a millimeter.
Your laser is probably OK for aligning the secondary, but for collimating the primary you really should use a barlowed laser. This also eliminates the miscollimation error on your laser, since the barlow autocorrects any misalignment

[Gary]

It is good to have accurate laser collimators to speed up the process.

To achieve the best performance, still need to do the final star test collimation which is base on an actual star.

So perhaps should spend more time improving star testing skills than getting overly obsessed and reliant on laser collimators alone to do perfect collimation.

[ggodetucsamoht]

Hi guys, my scope is celestron C8NGT so it has a f/5. For f/5 wise it should not be so strict during the collimation process.

After my collimation on the laser I use it to do a trial on the scope, insert into the focuser and screw the locking screws to a secure tightness so that I am still able to rotate the laser collimator on the focuser holder. But unfortunately the laser spot landing on the primary is still landing around but not on same spot. Got to redo the laser collimator collimation again. Tricky, this type of thing is really not easy comparing to scope collimation.

[Canopus Lim]

Hi,

For f/5, using barlowed laser collimation is sufficient to get very good results. Note that all lasers have some form of misalignment and also the 1.25"-2" adapter also have its own errors which will contribute in some way. However, using barlowed laser collimation technique for the primary mirror is very important as most of the error actually comes from the primary mirror collimation. I use my own barlow (Televue 2x) and put the laser collimator (Howie Glatter 1.25" red) to it and have a white screen in front of the barlow lens. Or alternatively, if you really want good laser collimation with barlow, you could get from Howie Glatter. The TuBlug should be good as it allows adjustment of collimation without having to look into the scope mirror.

I would think for adjusting the secondary mirror, some slight error of 1mm on your primary mirror is good enough. The reason is, to centre the beam 'exactly' centre to the primary mirror has already an error of estimation.

Focal length: 8x25.4x5=1016mm
Bore-sight error of laser to the 1.25" adapter=1mm: Converting to angle=1/1016rad=about 3 arcmin

If you use a distance of 2m, your error of the laser must be 2mm or less.

Just for reference Howie Glatter laser is better than 0.5 arcmin. This laser can be used without barlow collimation for the primary. I would still prefer to use barlow though because of adapter tolerances and tilt which can contribute significant error to primary mirror collimation.

[ggodetucsamoht]

Guys, thanks for all your advices....helpful and informative guidance for newbie like me........

Anyway i just got a celestron cheshire collimator and after following the steps from this site;
http://www.astro-baby.com/collimation/a ... 0guide.htm
i am able to get an overall image thru this cheshire which looks something like this



Is my collimation ok? wanted to test with star but unfortunately after i complete the collimation the sky is too cloudy to see any star on the sky...