What is a field stop. Is it a baffle in the ep? Does it limit the FOV. Why have a field stop. I don't have a clue and was just wondering what its all about. Thanks
Question about Field Stops
Started by david101, 05/22/2003 05:57PM
Posted 05/22/2003 05:57PM
Opening Post
Posted 05/22/2003 07:17PM
#1
It limits the field of view and also serves as a baffle against stray light. Without the field stop the edge of the field of view in most eyepieces yields a poor quality image along with an gradual and annoying fall off of the image rather than a well defined circle edge.
Joplin
Joplin
Posted 05/22/2003 07:51PM
#2
Placement/location is also a defining aspect of a field stop. In this regard, a field stop may be considered a specialized baffle.
A field stop is coincident with the eyepiece's image plane. Thus, it remains in sharp focus with the telescopic image and provides/defines the "frame" for that image.
Think of a field stop as being designed to limit the *use-able* field of an eyepiece. In a given eyepiece design (as well as its integration with a given telescope), the image plane *beyond* (outside) the zone defined by the field stop may be significantly aberrated in one or more ways. Astigmatism, distortion, and lateral chroma are perhaps the three "biggest" (most important; most destructive) off-axis aberrations in most eyepiece designs.
Best wishes.
-Dan
A field stop is coincident with the eyepiece's image plane. Thus, it remains in sharp focus with the telescopic image and provides/defines the "frame" for that image.
Think of a field stop as being designed to limit the *use-able* field of an eyepiece. In a given eyepiece design (as well as its integration with a given telescope), the image plane *beyond* (outside) the zone defined by the field stop may be significantly aberrated in one or more ways. Astigmatism, distortion, and lateral chroma are perhaps the three "biggest" (most important; most destructive) off-axis aberrations in most eyepiece designs.
Best wishes.
-Dan
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