I'm just about to start.

Its probably the Bushnell telescope reviewed here.

www.mav-magazine.com/Dec1999/Contents/bushnell/index.htm

Spherical optics!
Dont touch if you want to magnify above 25!

It's worth noting that there's nothing wrong with a spherical mirror as long as the spot diagram fits within the Airy disk. For an 8" Newt, this is true at f/12 and slower. I'm not exactly sure how this scales, but I think a 4" Newt with a spherical mirror is fine down to about f/9.

-- Jeff.

It's worth noting that there's nothing wrong with a spherical mirror as long as the spot diagram fits within the Airy disk. For an 8" Newt, this is true at f/12 and slower. I'm not exactly sure how this scales, but I think a 4" Newt with a spherical mirror is fine down to about f/9.

-- Jeff.

Is it not the case that the mirror in an SCT is spherical and that the huge variety of variations on the theme come from the use of different corrector/secondary treatment? It's only in Newts that the mirror needs to be strictly parabolic.

I know, I know. I'm only asking!

JMP

That's true. Maksutov's and Schmidts use spherical mirrors. Newts should use parabaloidal ones so that all wavelengths get focused to a single point.

As mentioned above spherical mirrors are serious nono on newtonians. They are much easier to make, hence the price difference.

I would go for a 6 inch dob or a 80mm refractor as a starter scope. Don't make my mistake and start with something with a huge focal ratio (skywatcher mak). It is much much easier to find your way around the sky with a faster scope, say f6 or so, because you get a larger field of view.

Skywatcher make some great starter scopes.

Trev

In my opinion, i think the skylux is well suited to you! Its aperture is 70mm. its a great scope! i have one! great optics, every christmas there in lidl for €69! cheap as chips! but im sure you wouldnt want to wait that long! also there is an etx 70 for €170 which is also cheap for this scope! this scope is motorised! well hope i helped somewhat!

Good luck with your scope search!
Matthew

It's worth noting that there's nothing wrong with a spherical mirror as long as the spot diagram fits within the Airy disk. For an 8" Newt, this is true at f/12 and slower. I'm not exactly sure how this scales, but I think a 4" Newt with a spherical mirror is fine down to about f/9.

-- Jeff.

Is it not the case that the mirror in an SCT is spherical and that the huge variety of variations on the theme come from the use of different corrector/secondary treatment? It's only in Newts that the mirror needs to be strictly parabolic.

I know, I know. I'm only asking!

JMP

Yes, that's correct. Spherical mirrors are much cheaper to make, so the various CAT designs use various correctors to allow a spherical primary to function as if it were a paraboloid.

(As a really minor nit, a "parabolic" curve is 2D (similar to a circle, not a sphere) -- a "paraboloid" is the 3D shape.)

If anyone's interested in all this nonsense, I highly reccommend Rutten & van Venrooij's "Telescope Optics". You can't beat it.

-- Jeff.