Quote:
Originally Posted by aerobrake
When you build the upper cage and see the size of the bloody thing you will appreciate the larger tubes!!!
Krieges book explains the mathametics of a smaller diameter which scarred me into the bigger tubes.
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*And yet the formulae he gives in the book suggests one inch tube for an 18" F4.5* . I think its really a case of people go for 1 1/4" tube to visually match the over built top end. For a 60" tube span on an F4.5 18" , 1" tube easily satisfies Kreiges 1/80 rule.
My attitude is to make every square mm of a telescope justify its existance. The primary enemy of large scopes is thermal mass , as you don't always have time to give your scope a long cooldown. Building your scope becomes a compromise on how heavy you are going to build vs the winds you intend to observe in.