Skyliner 200P Dob Collimation

[Ian J]

Being new, this has been a very steep learning curve.

I started out with an eflea bought laser collimator which done more harm than good, then a cap which I found easy enough to use then a combination of cap and Cheshire after reading Astro Baby's guide.

The one thing that really stumped me was although relgiously going through the steps was that when I came to the Cheshire I could line up the doughnut perfectly by adjusting the primary mirror screws but the cross hairs of the Cheshire were well and truely out.

After some time scratching my semi bald head which made it even balder and searching  through the forum posts and online without too much success I decided to start from complete scratch.

What I did was to loosen off the three allen screws on the secondary holder all the way and tighten the central screw until the holder was seated closest to the vanes.

Very gradually and with a lot of patience I realigned the seconary by easing off the central screw little by little whilst at the same time adjusting the allan screws until the seconary was showing a nice round circle using a card to block off the primary mirror view, Using the cap some minor tweaking to make sure all three clips in view and recheck secondary still nice and circular.

Cheshire Collimaor inserted and immediately the cross hairs were more central, after a bit of tweaking with the primary mirror screws all shows spot on.

I have yet to do a star test due to poor skies but I'm hoping this has solved the question of why the crosshairs so often do not line up on the dougnut when using the Cheshire.

My guess being that the secondary mirror although aligned is just a few too many mm down the tube for the cheshire cross hairs to align up.

Being newb to all this I really don't know if getting the cheshire cross hairs lined up as I did makes a vast amount of differance when all else is showing true but it just annoyed me not to have it just right.

I would be interested to know  what your thougts are.

[bingevader]

Everything should line up as in the pictures in Astro Baby's guide that you mentioned.

It's a quite daunting process at first, but sounds as if you may well have cracked it.

Understanding how to adjust the 2° is definitely the hardest part.

Once you have the spider vanes sorted, knowing that the 2° adjustment is a 3 stage process does help.

It's basically rotating, tilting and adjusting the height of the mirror to get it central and round in the collimator.

Makes it sound so easy!

[Pondus]

At risk of beeing lost in translation : Is your focuser squared properly with the tube?

Rune

[Coastliner]

Hi Rune,

I am not having difficulty collimating because of mechanical problems, I am having difficulty because of lack of intelligence!  I was just asking for a recommended collimator to make things easier.

[Pondus]

(got a bit confused now, not even sure whom or what I was commenting to)

Rune

[Coastliner]

Rune, my fault!!! It's me that's replied to the wrong thread - I'm following two at once, both related to 200P collimation.

I need a lie-down.

[Ian J]

At risk of beeing lost in translation : Is your focuser squared properly with the tube?

Rune

All looks good with focuser, have been outside observing moon  with a 6mm ep and a 15mm ep and ok, real test will come later if the clouds stay away.

Hoping to give my light pollution filter a try out.