Collimation

[ICR_2019]

Hi all another newbe with a collimation issue, I think?

It was my first travel to what was hopefully a dark sky site and as I undid the clamp for the tripod, bang! the scope hit the deck.A quick inspection and a spider vane was bent. I straighten as best I could and put it away.

I have since purchased a cap and proceeded to attempt alignment. I tried to undo the centre screw for the secondary but it was so tight I decided to remove the spider as it was getting bent trying.

I did undo the screw and once loose I found I could move the 3 allen screws. I did expect to be able to move the allens without loosening the centre.

Everything appears centred but in truth I don't know what I should see. I've read somewhere I should see the primary retaining clips but I can't, is that an issue?

The scope is a skywatcher 130p.

Any advice or pointers grateful.

Thanks in advance Ian

 

[cletrac1922]

Ian

Quickest way to make sure that the secondary mirror is centered

Using a bit of paper, measure each vain from inside scope to centre hole of secondary mirror

Mark, each vain on the paper, and should be equal distance

I use a laser collimator, and align secondary so that the red dot is located on dot centre of the primary

Then slightly loosen mounting screws of primary, and adjust so that red dot not visible target indicator of the collimator

John

 

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[Les Ewan]

Best to loosen the 3 allen screws first. Regarding the knock if there are no broken mirrors and all the adjustment screws are working freely then things are probably OK.

As far as collimation is concerned the best method in my opinion  is to press the eye as squarely as possible against the empty eyepiece holder and look down the tube and if the reflection of your eye is central to the centre ring of the primary and centred in the secondary and you can see all the clips of the main mirror with slight movements of the head that's close enough. 

[ICR_2019]

Thanks for the replies.

The secondary appears well centred, However I'm not so convinced its aligned properly as the primary clips are not of evenly located.

I can see the top and left but not the right. The donut and cap hole align perfectly.

I assume its the secondary thats a little out?

 

 

 

 

[spike95609]

If the secondary is centred in the focuser but you can't see the mirror clips then yes it's out of alignment. Slacken off each of the three little screws on the secondary a bit and then move them around until you can see the clips spaced evenly around the edge of your view. This will confirm that the secondary is angled with the focuser to look straight down the tube at the primary. When tightening the secondary screws back up, do each screw a fraction of a turn at a time until all of them are tight, otherwise you'll knock it out of position again. After that it's just a case of moving the primary around until you have the dot inside the circle.

[Skipper Billy]

Have a read here - http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

Everything you need to know - in simple language - for a newbie to achieve excellent collimation on a newt.

 

[Ships and Stars]

Starizona has an excellent online collimation tutorial. I have a 130PDS and I can say I've never been able to see all three primary mirror clips at once, perhaps due to the physical size of the tube in relation to the focuser. Someone else may have more experience with this particular scope, but I just do the secondary first with a Cheshire eyepiece, then adjust the primary with a cheap laser collimator and recheck. It's fairly sharp once that's done, but too much light now for a star test.