Silly question?

[multiweb (Marc)]

I'm not much of an observer but I was start testing my C11 tonight after some major surgery and then I got carried away and spent 2 hours with my daughter looking around the moon, saturn and other stuff. The moon details were ultra sharp. Saturn was very clear too. I noticed that when jumping from the moon to saturn I had to refocus and vice versa. The collimation was spot on and it wasn't mirror flop either but because saturn is side on right now it was very obvious I could see two lines for the ring until re-focusing. The focus point was extremely tight and very obvious but clearly different for the two. Is this normal? I thought whether you looked at a star or a planet or the moon you still focused to the same point (infinity)?

[DavidU (Dave)]

That's a good question. I find my refractor does need a slight tweek between the Moon and a star.

[avandonk]

Your eye is compensating without any apparent effort on your part as both these objects are so dissimilar in extent and brightness. Bert

[multiweb (Marc)]

Originally Posted by avandonk

Your eye is compensating without any apparent effort on your part as both these objects are so dissimilar in extent and brightness. Bert

Thanls for the clarification Bert - just so I'm clear on this and got it right: you're saying it's just a perception and the focus is actually the same if I was using a CCD? The only reason I need to re-focus is because my eye is doing something?

[Paddy (Patrick)]

I thought that it would all be at infinity until I started solar observing and noticed that I need to change focus as I move from observing the solar limb to the centre of the disc and also between different solar prominences.