Have some smaller optical glass blanks...3 inch give or take.
In terms of color correction is there any advantage of a triplet made of a glass with an abbe number of 35 ish and an abbe number of 55 ish over a doublet made of the same glass types?
I guess there is one advantage in that you can oil the inner surfaces of the triplet for better light transmission and or no ghosting. Also I suppose the additional degrees of freedom allow you to correct for coma and or other abberations.
Plus good practice for a larger refractor project later that uses the good and expensive stuff.
Also....in the f15 ish range plus or minus 5.
Can give better optical glass numbers later if needed.
Oh...or a triplet that uses three different glasses but none of them are abnormal dispersion to any great extent.