Understanding Spherical Aberration and Strehl Ratio
Posted: Fri Sep 15, 2006 5:30 pm
This is for 'Steves' only. 
I have read this article a long time ago and it has helped me in deciding what telescope to get and at what level of quality of optics meets my expectation. This article is written by Thomas Back (TMB).
Understanding Spherical Aberration and Strehl Ratio
To summarize it,
A 0.88 strehl telescope is much sharper and higher contrast than a 0.8 strehl telescope. A scope that is 0.95 strehl and above is a full planetary scope. The difference between a 0.95 strehl and 0.998 strehl is very small. Anything 0.95 strehl and above is limited by seeing on almost every night unless observing in a perfect place with perfect seeing, perfect transparency and perfectly trained eye.
I have done simulations (on the airy disc pattern/ aka Point Spread Function) on 0.8, 0.88, 0.95 and perfect strehl ratio telescope and it agrees very well with the article.
I have read this article a long time ago and it has helped me in deciding what telescope to get and at what level of quality of optics meets my expectation. This article is written by Thomas Back (TMB).
Understanding Spherical Aberration and Strehl Ratio
To summarize it,
A 0.88 strehl telescope is much sharper and higher contrast than a 0.8 strehl telescope. A scope that is 0.95 strehl and above is a full planetary scope. The difference between a 0.95 strehl and 0.998 strehl is very small. Anything 0.95 strehl and above is limited by seeing on almost every night unless observing in a perfect place with perfect seeing, perfect transparency and perfectly trained eye.
I have done simulations (on the airy disc pattern/ aka Point Spread Function) on 0.8, 0.88, 0.95 and perfect strehl ratio telescope and it agrees very well with the article.