Do refractors have to be collimated?

[DobDobDob (Ron)]

I've read lots about collimation, but can't figure if you can or have to do it to a refractor telescope, any one tell me?

[ballaratdragons (Ken)]

not sure about others refractors but you can collimate ED's when they need it. The collimation on ED's is done by slightly loosening the 3 screws holding the focuser in, and moving the focuser body, then re-tighten the screws.

[DobDobDob (Ron)]

Originally Posted by ballaratdragons

not sure about others refractors but you can collimate ED's when they need it. The collimation on ED's is done by slightly loosening the 3 screws holding the focuser in, and moving the focuser body, then re-tighten the screws.

Sorry mate, but what do you mean by 'ED's', and I don't suppose you have a picture to make it even clearer, by any chance?

[JohnG (John)]

Depending on the type of Lens Cell the refractor has, it can be collimated by using the 3 sets of push/pull screws located around the front lens cell. This type of collimation is normally done on a bench and you use a Cheshire Eyepiece to center the yellow and blue coloured rings, using the 45 degree cutout in the Cheshire Eyepiece, you shine a light into the cutout and the rings are superimposed onto the front lens, you then adjust the push/pull screws until the rings are centered.

Note, not all refractors have these push/pull screws as the manufacturers don't like people playing with them, any misadjustment can cause you a lot of work to get your collimation back.

Also, most refractors can tolerate a large amount of miscollimation and still provide a good image.

Hope this helps a little.

Cheers

JohnG

[DobDobDob (Ron)]

Thanks John, that is helpful

[ballaratdragons (Ken)]

Sorry Ron,

'ED' as in ED80, ED100 scopes. They come standard with Crayford focusers which can be adjusted to aid in collimation (if ever needed)

It doesn't help with objective lens collimation though.

1. ED80

2. lines showing the screws that hold the focuser in, which you loosen to collimated then re-tighten.

[DobDobDob (Ron)]

Thanks heaps Ken, you have been a really great help. I have also located the manufacturers website and they have a reasonable manual, which I have downloaded and am reading right now: http://www.skywatchertelescope.net/

Thanks again