Marine grade ply also isn't necessary to be used. Common everyday exterior grade pine plywood will perform just as well. All that hardwood ply's do is resist dings a lot more than the softer pine. Mechanically they offer nothing more than extra weight. Not my thoughts - this is stated in the Kreige book "The dobsonian telescope". Better water resistance with hardwood or marine grade ply -
nope! That's what the varnish is for.
The benefit from pine ply is reduced weight and cost. Some people may not like the look of it or its tendancy to yellow with age, but I make the most of the knots to make a highlight of the timber when I make dobbie mounts.
Ebony star is expensive stuff - though Dave found the bargain of the century (I hate you, Dave
). But there are also cheaper alternative laminates that can be used. You'll find these noted in post No. 14 of the
ATM non-astro sources sticky, along with many other material and source alternatives.
Careful consideration of materials and you'll be able to make a dobbie mount for half what Dave quoted for his, and work equally well.