Re: [APML] new posts from new telescope with new format

[Chris1011@aol.com]

In a message dated 11/9/2001 9:23:48 AM Pacific Standard Time, bobm@koyote.com writes:


> The BRC also has a bit of a hotspot in the center of the neg 


"Hot spots" are an indication that the secondary mirror is too small for the field size and vignets the image. You can determine this for yourself by opening the back of the camera and with the shutter open, scan the entire format with your eye. look for the point where the mirror starts cutting off the main mirror. With no vignetting of the secondary, you should be able to see the entire primary mirror anywhere in your 6x7 camera field. You may find that the center of the field is fully illuminated, but toward the edge, the illumination may only be 1/2 that (in other words the center is F5, the edge might be F10).

Roland Christen