|
Centering the secondary mirror - you'll know just looking at it. Not towards the spider, not towards the primary mirror, but centred. And also looking round, not elliptical.
Use Andys' video. Look on the site for "Collimating a Newtonian..." It is a 3.7MByte down load, but a great movie. (One point - in one photo he is talking about adjusting the primary mirror tilt, but he has his fingers on the primary mirror locking screw.)
Do you have a collimating cap, or a sight tube (often combined with Cheshire, eg. Orion's)? If not, get a 35mm film cannister and drill a 1mm hole in the centre of the bottom. This will fit where a 1.25" eyepiece will and will centre your eye in the focusser (put it in from under the adapter and nip it up firm - don't want it falling out into the OTA. Not the best solution, but it will do. A long sight tube is better (eg. the Orion) since you can adjust it so the view of the secondary mirror just fits inside the circular end of the tube making it easier to get it well centred (and correctly rotated to a fully circular view and not elliptical).
|