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Laser Collimation


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Hi,

Just used the Baader laser collimation tool (brand new out the box) on my O/O 250mm f4.8..

Adjusted the secondary to align the red dot dead center on the primary. Moved onto the primary and adjusted the mirror until the laser beam returned back to dead center on the collimation tool.

Problem is when I look through a colli cap or just down the focusing tube it looks way off from the diagrams and instructions I have seen on the web...

Any idea what it could be or do I just need to wait and do a star test?

:)

Acme

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Thorny old subject this - is the laser collimator itself correctly collimated? Unfortunately the otherwise excellent Baader unit is not user collimatable so you have to assume that it is correct straight from the box but this *might not** be the case. Other reasons that things might not 'look right' are secondary mirror offset (a big subject!). The only real way to check that the laser has done its job correctly is to carry out a real star test.

I only use a laser for collimating my Newtonian but I can check and calibrate my laser collimator first so that I know I am starting from a good place.

Edited for typo although I still not sure how to spell collimatable!!

Edited by steppenwolf
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I'd do a star test before jumping to any conclusions. I have the same scope and used a (well collimated) laser to collimate the scope. Looking down the drawtube with no collimator in place things did not look lined up but when I tested the scope on in-focus and out of focus star images it was clear that the laser had got things pretty well aligned an I just needed to do some fine tuning. Thats about the best I expect a laser to be able to do.

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Thanls for the replies..

I did a star test, best ever veiws sharp focus and no trails on the brightest objects....

Strange but I will just go with it for now..

Question about the Baader laser..Is the switch moody, works one minute then for no reason it just will not switch on and then at times the beam is so dim it won't project more than 6 inches...

Never used one before so just not sure about the product..

Acme

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Hi,

Just a quick update, I orederd the Hotech laser from FLO yesterday and it came first thing this morning (Thanks Steve great service)

Worked like a dream, collimation in less than 5 mins. Showed up how far out the Baader laser was..I looked down the draw tube after using the Hotech and it was all alligned just as it should be (See first post)....Another star test is necessary but I have faith in the Hotech. :)

The Baader is my new paper weight.....:eek:

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Hi,

Just a quick update, I orederd the Hotech laser from FLO yesterday and it came first thing this morning (Thanks Steve great service)

Worked like a dream, collimation in less than 5 mins. Showed up how far out the Baader laser was..I looked down the draw tube after using the Hotech and it was all alligned just as it should be (See first post)....Another star test is necessary but I have faith in the Hotech. :)

The Baader is my new paper weight.....:eek:

You should try and get a refund from the seller if the baader is that new and you still have all the original packaging.

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Long Story.

I was putting it back into the packaging for that very reason...Like a plank I turned the box upside down, it fell about 6" onto the kitchen table..Agghhh it has left a small indent/chip in the finish.

I might offer it up as trial object to UK SGL members if anyone thinks it can be collimated correctly, just pay the postage from who borrowed it last, just a thought or I could keep all my Astronomy equipment bills on my desk in one place with it..lol

Live and learn.....:)

Acme

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Am I right in assuming that when you rotate the laser collimator in the drawtube and the collimator is not properly collimated, the laser spot on the primary mirror would move?

(a bit like adjusting a polar scope?)

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Yes, that certainly would be one of the symptoms....

but it also depends on your focuser and the clamping of eyepieces.

I've seen many focusers which "push" the eyepiece off centre when the knurled screw is tightened. This is a common problem ( and worries me at times) where the laser collimator may be 100% spot on but the eyepiece will still sit off centre and give image distortions.

The 100% reliable method is to do the final collimation check with an actual star!

Ken

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I just collimated my 300P with my Hotech with the draw tube all the way in and got it spot on. Then wound the draw tube all the way out and it was showing the primary way off again. I guess its down to play in the focuser but is there any way to get rid of this?

Would a moonlite focuser suffer from less play than the standard one that I have?

Cheers.

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As the Hotech is good at centering itself in the focuser, it sounds like the focuser may not be sitting absolutely square to the OTA and the optical axis.

You may have to consider putting a couple of small shims ( cut up an aluminium drink can) to re-position the focuser body on the tube.

A much cheaper option than an upgrade to the focuser ( which may have exactly the same problem!!)

Ken

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