Altomar718

I went for the first time to the meeting of local astronomy club here and they had a guest speaker who was talking for an hour about radio astronomy - I didn't understand ANY of it until he mentioned he had got a shed to keep his gear in and I have got a shed as well !!!

He was talking about baseline inferfeometry and put formulas up like P=I(p d²/4)(1/r²)(p D²/4)

Some clever people out there or I am really thick !!!

As I like to put it, the depth of field at infinity is infinite

Put mathematically, the distance d between optical centre of the scope and the image plane, for a given focal length f and distance to target D is

d = f D /(D+f)

At huge distances D this simplifies to d = f

For example, if D is a million kilometres (close by by astronomical standards), and f is one metre, the change in focus needed is about one nanometre. I doubt the average focuser would manage that.

Eh? - I have only just got into this astronomy lark and failed my 'O' level in maths Ha! Ha!

Thanks anyway

Interesting stuff and thanks for the replies ........ it may sound dumb - but - if you focus on a star as suggested, and then slew to Jupiter which is much, much closer, would the focus be the same as the star may be 1,000's of light years away ???

Hi All

Can anyone advise me on Bahtinov Masks and Planetary Imaging? - I know that the mask cannot be used for planets as they are supposed to be used for focusing on stars, but I wondered if the scope was focused on a nearby star and then the scope slewed (with Synscan) would that work and improve focusing on the planet?

Thanks