NavList:

Hello, Frank (and other NavList members)!

Frank, you recently wrote:

“This is an example of a well-collimated scope, and in my (long!) experience, very few observers can detect that "tiny gap at center" once the scope is collimated.”

If you observe angles at 100°…120°,  this gap is considerable. It is impossible not to see it! It would be hard to detect a gap 0,1’…0,4’, but at such a large measured distance the gap is really large.

As I mentioned before, I have observed this with 7x power inverting telescopes. Of course, if someone use 3x or 4x power scope, the gap is visually smaller. But even in this case the gap is considerable.

I am wondering, if it is possible to apply the same formula which is used for calculating collimation error, to calculate the value of the gap for well adjusted scope? Intuitively I think this formula could be used. But I am not 100% sure.

If the angular distance between two wires is 2°, then the offset from the center will be 1°. Let’s suppose I observe distance between two stars that are seperated by 110°. In this case the gap in the middle should be 1,5’. If the observed distance is 125°, then the gap should be about 2.0’. 

Here I used formula:

E=A²*tan(B/2), where

E-error in radians;

A- inclination angle in radians;

B- measured distance in degrees.

Any coments will be appreciated.

Modris Fersters