Pls help newbie trying to collimate 10" LB :( ...

[Kokatha man]

Well, it's pretty darn close: after a while you can start becoming really obsessive about "spot-on" - I'd recommend seeing if you can do a star test if you feel like it mbaddah. You'll need a pretty good "seeing" night and I'd suggest start with about 100 mags or so (the rule is double etc that, but I found that helped me get the gist first up.)

Get a star (not a dim one) focussed in your scope and then take it out of focus either side of focus; observing how the star appears to expand into a soft out of focus "disk." If there isn't too much turbulence etc in the atmosphere you should, on carefull obsevation, notice that there should/will be a dark central spot in this disk, which, as you go much further out of focus, develops into an image of your spider assembly. But well before this, in fact at about the time you see the tiny central spot, you'll see a number of "diffraction rings" like tiny black/dark circles (hopefully concentrically) surrounding this central dark spot.

I don't seem to get past seeing 5 of these concentric within each other rings (like an archery or rifle target around the central spot) but they should be, along with the central spot, centred and evenly concentric within your out-of-focus star disk. Bear in mind that these dark rings will be very close to each other and may take some discerning at first. If they're not uniformly concentric then they indicate more collimation tweaking.

Once you get the hang of seeing them, bung up the magnification for a more reliable indicator - but remember, if it's a lousy night you'll most probably have buckley's chance of seeing them! I'm sure there's links on IIS to star-test images and most manuals have something about them in them.

Cheers, Darryl.

[mbaddah (Mo)]

Since last night was one of the first clear nights we've had all week, decided to take the scope out and test out how she purrs...

Everything looked tack sharp, with one slight problem. If I move head little bit, I can see a ghosting effect. For example when looking at Saturn, i'd have to have my eye dead on the centre to see it as one, otherwise i'd see two saturns moving around each other!

Is this due to collimation or some other factor? Thanks guys.

[wavelandscott (Scott)]

I'd suggest that you start a seperate thread for this question in the eyepiece section below...I think that you will get more responses there than buried at the bottom of a collimation thread.

I would suspect an eyepiece for ghosts but, it could be a number of other things such as:

Some eyepieces are more sensitive to eye placement than others
Internal relection within the eyepiece (for a number of reasons)
Stray light from a steetlight or other
It might be the reflection off of your own eye too...

What eyepieces were you using?

[mbaddah (Mo)]

Originally Posted by wavelandscott

I'd suggest that you start a seperate thread for this question in the eyepiece section below...I think that you will get more responses there than buried at the bottom of a collimation thread.

I would suspect an eyepiece for ghosts but, it could be a number of other things such as:

Some eyepieces are more sensitive to eye placement than others
Internal relection within the eyepiece (for a number of reasons)
Stray light from a steetlight or other
It might be the reflection off of your own eye too...

What eyepieces were you using?

Thanks mate I've started a new thread on the matter (located here http://www.iceinspace.com.au/forum/s...376#post302376)
Cheers.

[mark3d]

got the hang of it! after some experimentation i would really suggest a laser collimator and a barlow! you just tweak the secondary until the laser is centred on the primary, then just tweak the primary until the laser lines up in the collimator eyepeice. doing a star test proved its that easy. a set of bob's knobs and it will be a piece of cake!

[mark3d]

having said that it would be really good to fabricate a small disc with a hole in the centre to make the barlowed laser a fine point, as outlined in the S&T article.

that is a bit of a problem though because if that is not precise the collimation will always be out. the one i made out of cardboard was rubbish.

[mark3d]

having said that it would be really good to fabricate a small disc with a hole in the centre to make the barlowed laser a fine point, as outlined in the S&T article.

that is a bit of a problem though because if that is not precise the collimation will always be out (and my collimator doesnt take threads so id need to make a 2" one for the barlow).