Another Newtonian Collimation Question

[Glenhuon (Bill)]

After about 15 years of looking through my old 60mm refractor I decided it was time to go a bit bigger, but not being flash with cash bought a 150 newtonian on Ebay for $300. It sems well made, sturdy, settles down in a few seconds after a tap on the tube. Images are, wellll, kinda ordinary. I've ordered a cheshire from bintel, but in the meantime made up a film case with a pinhole in one end and crosshairs in the other. The secondary spider looks pretty well in line with the crosshairs, but I can't see the whole primary mirror. There is a dark crescent on the right side looking through both the pinhole and down the open focuser. I've just had another look and there is a lens screwed into the base of the focuser.
Newtonians are a whole new ball game to me and its apparent something is out of alignment, but what. Any help will be much appreciated.

[Starkler (Geoff)]

Could be that the secondary is too far up the tube and is not correctly placed under the focuser. Try putting a piece of paper between the 2ndary and the primary mirror to block view of the primary. Does the 2ndary look round and placed directly unde the focuser?

Take a look in the articles of this site for a recently written collimation article by Don Pensack.

[mill (Martin)]

"there is a lens screwed into the base of the focuser"
That lens is an barlow, and it is in there to make the scope a shorter lenght.
It will be harder to collimate than an normal newtonian, even with an cheshire.
I know because i have owned an meade ats2114 newtonian.
And collimating it was an nightmare.

[Glenhuon (Bill)]

It does now Starkler
Adjusted the secondary and removed the primary to mark the centre. Tight as a ducks bum, but got it out eventually. Can now see the whole mirror. The barlow lens (thought it might be summat like that) can be unscrewed easily so might make things easier for setting up when the cheshire arrives. Its specified as a 700/1400 focal, think the barlow extends it to the higher figure but might also be the reason the field of view in the supplied 6.5mm EP is so narrow. Will give it a test tonight with and without the barlow. Thanks guys
Glenhuon