Hi all,
Been thinking of planning my next newt astrograph.
I have been on the lookout for some cheap blanks etc around the 7-8" size.
Can anyone point me to a site or some info on the differences between plate/pyrex and other low expansion materials for a mirror this size..
Would it make much of a difference in small mirrors as they cool down.
Plate is easy to get while pyrex is rather hard to find except buying from the states. What about BK7 glass?, how does this rate?
I`m planning on a 1/20 pv mirror if all goes well to get nice crisp stars!!
cheers Gary
oh....where to get blanks over here at reasonable prices?