Re: Effects of Central Obstruction

Actually, anyone with a refractor can find out for him/herself. I did it with my old 4" C102-HD on Jupiter with a cardboard 33% mask to simulate the obstruction. The effect was very eye opening: a very noticeable loss of contrast and **brightness**. I didn't do a critical test at the time to find out which feature I could see and which I couldn't. But the one thing I most personally didn't like was the lack of contrast when the mask was on.

Ron B[ee]

Ron, it takes more than one brief "test" to determine what is the effect of c.obstruction. Seeing is a factor that can play games with us. Also, we all have our biases: if you want to be really objective, such test should be a "blind" test (you don't know when the c.obstruction is on, when off).

A 33% obstruction causes nearly 11% light loss. It is equivalent to 5% increase in magnification. I am yet to experience "very noticeable" loss in brightness from a 5% magnification increase.