A simple collimation method

[Pinwheel (Doug)]

Hi All, I've been having issues on and off now for a few years with bad collimation on my 8" newt. Well first off my main problem was the laser collimation unit was NOT accurate at all. In fact it was making things worse, anyway I've discovered a fast instrument free method that works, well for me anyway in 4 simple steps.

1/ Remove eyepiece & wind the focuser all the way in.
2/ Cover the Primary mirror with clean white paper.
3/ look through focuser tube & note if you can see the secondary mirror is concentric. If not adjust secondary until all is equally positioned though the focus tube while looking in.
4/ Remove the primary mirror white paper & again look down the focus tube. You should note the position of your eye's pupil in the reflection, now just adjust the Primary mirror only until your pupil is dead center of the reflection.

That's it, My newt has never been so sharp & the view so even. I hope this works for you as well as it did for me.

[barx1963 (Malcolm)]

Hi Doug
That method can work quite well on smaller newtonians, especially of the slower variety. The issue with it is that it is hard to know that you are holding your eye centrally in relation to the focuser. That is where a collimation cap or simply a film canister with a hole drilled in the base is usefull as it positions your eye exactly.

Malcolm

[Octane (Humayun)]

Someone come and do my 4" Newtonian for me. I'm hopeless.

H

[Pinwheel (Doug)]

Originally Posted by Octane

Someone come and do my 4" Newtonian for me. I'm hopeless.

Try what I did, It's fool proof!

[Pinwheel (Doug)]

Originally Posted by barx1963

Hi Doug
That method can work quite well on smaller newtonians, especially of the slower variety. The issue with it is that it is hard to know that you are holding your eye centrally in relation to the focuser. That is where a collimation cap or simply a film canister with a hole drilled in the base is usefull as it positions your eye exactly.

Malcolm

Well mines an f=4 and is a short tube too! so it's really no wonder the laser was so inaccurate. Anyway I learned so much doing it this way.
Totally worth it.

[MichaelSW (Michael)]

Doug,

G'day.

I also follow simple method with my 12" collapsable Skywatcher.

As an aide to help me determine if my Secondary mirror was centred within the focuser draw tube, I fitted a piece of graph paper in place to line the inside of the optical tube behind the Secondary mirror. (Had to cut notch in the paper for a spider vane and a screw head that got in the way). I aim to count the same number of 'squares' above and below the secondary to help assess its positioning towards the sides of the optical tube. (Can't count squares towards the outer end of the optical tube because the secondary mirror edge and holder get in the way).

I use a film canister with hole drilled in centre of the base to position my eye.

It seems reasonable to me that once you are satisfied with the positioning of your secondary, and you make any rotation and tilt adjustments of the secondary such that the reflection of the primary mirror is concentric within the secondary mirror, then you have achieved the desired result. With my scope I aim for the reflections of the three primary mirror clips to be equal in size and positioning.

It is useful to paint the inside bottom of the film canister with white paint. When I get to aligning the primary mirror, I hold a red torch carefully inside the optical tube shining it up into the film canister. This shows up the reflection of the hole in the bottom of the canister as a distinct black / dark dot. I then just adjust the primary mirror until this black / dark dot is centred within the reflection of the primary mirror centre-mark circle.

One astronomy friend gave me a tip about looking down the empty focuser draw tube at the reflection of your pupil lined up with the reflection of the centre mark on your primary mirror:- as you move back away from the from the draw tube, if you have done a reasonable job then they stay lined up and eventually fill the view.

Michael.

[ZeroID (Brent)]

I've been eyeballing my 10" from about 6 meters away to align the primary to the OTA. Just drop it down reasonably horizontal and step away and look back at the reflection. Centre the secondary in the reflective surface by adjusting the cell. Use a film can to finish off the secondary alignment as above. Works well. Check your secondary centre position first though the first time you do it, especially on DIY scopes.

[Pinwheel (Doug)]

Well I guess it's like a game of golf, different techniques work for different people. I had my newt out again last night much warmer than two nights ago and everything is still just perfect. For ages I started to think it was my EP's & then I thought it was my eyes, I'm just so happy now & can't wait for looking at old friends like M-42 etc.