Focuser problem

[kosh]

Currently I have a bushnell northstar GOTO 114mm and i'm having a problem with the focus.
To get a 20mm EP into focus, the focuser is ALL the way out! But I don't think that it's still 100% focused. Basically the focuser stops before the EP is focused. Is this a problem with the focuser or the mirrors?
Can I do anything about it?

[elusiver]

does u'r focuser have a tension adjust knob? with my crayford i found the same problem occured cause when the tension adjustment was done up too much it stopped the amount of travel i had... but with the tension adjust freed up it the focuser had about an extra 20mm of travel.

el :)

[ving]

failing that just pull the EP out of the focuser a couple of mm and lock it in place.

[kosh]

Ok i'll try all that, thanks.

[iceman]

Sounds like there's not enough out-focus, so if the above suggestions don't work, you can try getting an extension tube to fit between your focuser and your eyepiece, to give you the extra length needed to bring the eyepiece to focus.

[rmcpb]

Has the scope been collimated using all three knobs? If so, the mirror may be too far up the tube and need moving back toward the baseplate.

[kosh]

Bushnell say they collimate all scopes before they ship them. I myself have not tried (i'm just a newb) as i've got the scope on a "satisfaction guarrenteed" thing, so i dunno if i'll keep it and don't want to break anything. Probably won't because I really need something BIGGER. Anyway...

Actually, is there a collimation tutuorial on this site anywhere?

[ballaratdragons]

Hi Kosh.

If you want to get your EP a bit further up out of the Focuser barrel place an 'O' ring on the EP shaft. Move the 'O' ring up or down the EP to the desired distance you want it away from the focuser.

This is only a temporary measure as the scope really should be adjusted correctly, but if you don't want to fiddle with it just try the 'O' ring trick!

[davidpretorius]

played with the secondary last night and then noticed that the toucam prime focus position had changed considerably. (1 to 1.5 turns of the crayford)

[asimov]

Yup! Theres more to it than meets the eye...put a hartmann/aperture mask on? gotta re-focus...put a filter on the EP? usually gotta re-focus...put my camera on after getting perfect visual focus thru the EP? gotta re-focus.

[ving]

funny how that works. I visually focus then put my camera on (which has auto focus) and have to re focus it :confuse3:

[RAJAH235]

kosh, try these for a 'How-to guide' to collimating > http://skyandtelescope.com/printable/howto/scopes/article_790.asp
http://www.andysshotglass.com/Collimating.html This is a movie, so it might take a while to load.
HTH. :D L.