Re: [APML] Medium format wide field scopes

[Chris1011@aol.com]

In a message dated 3/27/2002 10:46:10 PM Pacific Standard Time, shekhar@prodigy.net writes:


> Is this true for just red (H-alpha) or is that true for the entire visible
> spectrum?  Is the problem with an uncorrected scope that it can 
> focus accurately within narrow passbands across the entire visual 
> spectrum, but it cannot focus different wavelengths together? 
>
> In other words, if I use a 400-410nm filter on this scope, will the star
> sizes be as good as the ones using a 650-660nm filter?


The short answer is yes. The stars will be sharp. The long answer is that the images will not register correctly because the focal length changes. This can be overcome with software manipulation. Also, you will miss a lot of photons, and you will be doing some very long and painful exposures to register any kind of density.

Roland Christen