Quote:
Originally Posted by Quickxb
It's a foco, 114x900 I think it's a refractor? Not sure what you mean by what's described on the tube as there is nothing but foco written on it. Thanks for the reply..Uhm how do you collimate?
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That's a reflector - long tube, little mirror in vanes just inside the top of the tube, eyepiece goes into the focuser at the side, near the top of the tube - right?
Assumimg no one has fiddled with the secondary mirror, collimation is pretty simple (a lot simpler in practice than what it sounds like when I describe it).
Aim at a star, get it sharp, then throw it out of focus a bit and you should get a bullseye pattern - just like this member has posted in another thread,
http://www.iceinspace.com.au/forum/s...d.php?t=119622
But if the dark centre of the bullseye is off to the side of the disc, so that it looks like a little comet, then you have to collimate the telescope and bring that dark bit back into the middle.
The back of the telescope has three or six screws. Where you have six screws, you unscrew slightly the three shallower ones which are locking the mirror down. Going back to the eyepiece, stick your finger in front of the tube so that you see it in the defocused disc - move it around till it's in line with where the distance between the dark central bit is Shortest to the edge of the ring. See where that finger corresponds to the screws at the back end of the telescope. If there is a single screw there screw it Out (i.e. anticlockwise) and screw In the other two which correspond to the dark bit being Longest away (i.e. clockwise). That's how I remember it, Out Short, In Long - OS, IL.
And when I say "screw" I mean no more than a quarter turn, less as you get close to your target.
But if your finger corresponds to a point in between two screws, do the same - screw them Out, and screw the opposite one In.
Eventually, you will get a nice bullseye pattern and the images will be the best you can get out of the telescope with those eyepieces. Just remember to do up the three locking screws (not too tightly).
If someone has fiddled with the secondary mirror, you have to wait till daylight, and get a film cannister or cannister lid from somewhere, put a little hole in the middle of it, put it over the focuser without an eyepiece in it, and look into it - you should see the secondary dead centre, with the reflection of the primary mirror totally filling it.
If you are well collimated and the images are still bad - it could be that,
a. the atmosphere is bad, twinkling stars are bad atmosphere or
b. it could be that neighbours have heaters going and you are looking through heat haze, or
c. initially, the telescope is cooling down and you have tube currents.
You can actually see these effects in the defocused star image if you look closely in the disc.
Good luck,
Renato