Fine tuning the Finderscope

[Bilvers]

I have a refractor scope and have aligned the finderscope to the tube - however I can place an object in the finderscope but it is ever so slightly out in the main scope. 

I use a water tower that is about a mile away as the target to align too, I use the central mass of the tower (that's coming from my day's in the RM's and zeroing my weapon).  

The question is; should I be align to something smaller on the tower, like the top of the radio mast on the top to get more accuracy from the alignment?

Many thanks

Stuart

[michael.h.f.wilkinson]

At the start of any session, I just fine tune the finder scope on a bright star: After course alignment, centre the star within the scope, and then recentre the object in the reticle of the finder. My mount does track, so that leaves me with ample time to align. If your mount does not track, you need a small stationary object at a large distance for accurate alignment

[triton1]

I have a sw200 with a 9x50 finder scope which I leave attached to the tube.However I still adjust slightly nearly every time I use it just to make sure it's bang on.This I always use any star that's in the middle of the fov which I,ve found more accurate than a terrestrial object.Hope this helps

Regards Jonn

[Bilvers]

Thanks Guys, I haven't been aligning it at the start of each session and will do from now on.

[brantuk]

Set it up on as small a subject as you can see as far away as possible. The aerial on the water tower or even a corner of it will be fine. Then at the beginning of a session refine the accuracy on a star or planet. You can refine further by increasing magnification.

Start with a 20mm-25mm eyepiece in the scope and adjust, then use a 12mm-15mm one and you'll see it slightly out - readjust. Lastly pop in an 8mm-10mm eyepiece and center up the finder.  You'll then find any eyepiece longer than the shortest one used, will be very accurate.

(I find a zoom eyepiece very useful for aligning my finder)

[Astro Imp]

A tip I picked up from another recent thread, when trying to centre a star in the eyepiece it helps to de-focus, this seems to work very well.