[Den (Dennis)]

Hi Brian,

To collimate, In my case I put a laser in the 2” focuser and the light passes through the secondary mirror (The tal has a section of mirror uncoated in the centre of secondary) so the light passes through it, I then place clear tape on a centring bolt to see if the focuser is on centre. In my case I placed a thin shim in between focuser flange ( this focuser is separate from the primary mirror attachment ). I then place the TAL on a mini mount and prepare to adjust the secondary mirror by making an artificial star light made up of a pin hole on black paper and shine a led torch through it, place this light box as far as you can from the telescope, in doors. ( With the Tal200k you line up the light using the unmirrored centre and the centre of the focus tube, this brings multi circles of light together, see pictures). . If you do this outside on a sunny day you can use a RED or GREEN xmas ball only instead. Using the light I aim the telescopescope on centre (you can use a illuminated eye piece to help centre it) and use a low power eye piece with a defocused circular star pattern (winding the focuser towards the secondary it is very bright). If collimation is close you will see lots of circular rings like a bulls eye. When not collimated (see below: a picture of diffraction rings) you will see the rings leaning to one side. My scope was only a little out so adjusted the secondary bolts till it was like a bulls eye. Then I winded the focuser outwards to check the primary mirror it needed only a slight adjustment. Then I took the scope outside on a real star and use higher powers to do a fine adjustment.

Den