G'day.
Joined this community to pose a discussion.
Sky Watcher have on the market their Stargate 500P Dobsonian
This Dobsonian has a 20 inch primary mirror with a relatively short focal length.
The secondary appears to be unusually large when compared with other Newtonians of similar aperture..
I have included two shops in Oz for the following links, so you know it's not blatant advertising
Link here.
...or here:
The 18 inch version the 450P, has been around for some time now and this beast is kind of new to our neck of the woods.
The 450P also has limited information regards quality of optics.
My biggest concern with this primary mirror for the 500P, is that there are no optical tests made with the mirrors or even made public.
Tests that are specific for each mirror.
I am aware that the primary is mass produced, but surely Sky Watcher could spare a few minutes and test each mirror and publish results for each mirror sold?
One would think that for almost 10,000 grand that a telescope manufacturer would at least provide such information?
I know that for the same price, I could get a custom made scope complete with optical specs from the USA, but the postage is a deal breaker.
I have looked hard and long on the internet for user reviews, seen a few but none regards optical quality to their primary or why the secondary in my opinion is unusually large.
I suspect that for such a short focal length combined with a larger aperture, some correction is needed at the eye piece end...yet again no information available.
Thought I would discuss your thoughts regards this 20" Dobsonian, before I confront Sky Watcher with some pertinent points and before I fork out the $$$ for such a beast.
As I live in Townsville, I have no way of seeing one of these scopes in the flesh, so any thoughts will be greatly appreciated.