Crooked dovetail

[Liz]

Had my new collapsible Dob for about 3 months now, barely used it cos of the weather, and when I did, it was/is very frustrating as cant align scope and finderscope. Tried my little red dot finderscope, but still way out, despite much turning of the screws.
Had a look at the dovetail this am, and is not on straight!!
This would account for the problems???
Will I need to take it off and somehow drill another hole to align correctly?? Thanks :help:

[gbeal]

Looks like it will be a good idea Liz, not too difficult, and if you place the new holes right they will be hidden under the existing base. Plus another two holes will lighten the tube a bit, tiny bit, LOL.
Gary

[Dennis]

Hi Liz

You’ve probably tried this already, but I’ll ask the question just in case, to save you drilling holes!

Is your finder scope a typical optical finder, mounted on a stalk with either 3 or 6 adjustment screws? If so, have you tried adjusting the finder scope position in the stalk, by trying to align scope and finder on say, a tree or pole 2 or 3 kms away in the daytime?

Cheers

Dennis

[gbeal]

And in addition to what I posted earlier, take one screw out completely, and with the other remaining screw in place but not absolutely tight, "reposition" the finder unit so that it does do what you want.
Better to check this BEFORE you bore all those holes.
Gary

[Dennis]

Another possibility would be to shim the (female) dovetail slot with a thinly tapered wedge, to “force” the (male) dovetail on the stalk to be more parallel to the optical tube?

Cheers

Dennis

[Liz]

Thanks Dennis - with the red dot one, there are 2 adjustment screws, but they wont get me on the target ... even on the Moon.
Havent tried the daytime thing though.



Thanks Gary .... will keep that in mind.



Ok ... will have a think about that one too Dennis, thanks again. :)

[mithrandir]

Liz, don't trust the sides of the focuser to be straight on the tube either.

I presume the dovetail is held on with bolts and nuts? You might find it simpler to make one of the holes into a short slot so that side can slide up and down. It might already be like that.

Then put in the finder with its alignment screws all centred. Twist the dovetail to get the finder close then tighten the dovetail screws.

[asimov]

As Andrew suggests, making one hole into a small slot will work. A small diameter file (a chainsaw file) is ideal.

[Liz]

Thanks guys for your help .... have taken off the dovetail, and then put it back on - and it looks OK!! It wasnt straightened properly when screwed in.
Hopefully now AOK, and what a relief :thumbsup: