Dob vs Refractor

If you are concentrating only on planetary and lunar observations then the Skymax is an excellent scope. For deep-sky it won't perform so well as the focal length is very long and the field of view very narrow.

I think an 8" dob is the way to go, it's not heavy, can be easily transported, offers great views and the price is very reasonable. For deep-sky you won't go far wrong and for planetary work you can build a mask to reduce the aperture to 4" or so to give better views.

Are you close to any astronomy club? If so go along to a meeting or observing seesion and the people there will be only too glad to help and show you views through their scopes.

Whatever you end up buying the best of luck with it and wait for aperture fever to strike.

Paul

Efla, sound advice there from all, if planets are your thing then the skywatcher is a decent scope. But certainly go for as much aperture as you can afford

Keith..

Why does masking make for better view of planets?
It may do - I don't know to the contrary. My understanding is that if the mask is off-axis one can increase contrast by avoiding interference from the spider viens - but on the flip-side - resolution goes down with decreasing aperture. Benefits outweigh costs?

BTW efla, I went the 8" DOB route - one can remount it later on an Equatorial mount if you wish to do so later on. Good luck.

Mark

The Nexstar was just the first one that came to mind as an example. The Skymax is a sound scope.

www.opticalvision.co.uk/astronomical_tel...rs/explorer-200p_eq5

I believe I may compromise with an 8" reflector....

I'll certainly keep my options open r.e. all of your suggestions whilst I'm shopping around

mjc wrote:

Why does masking make for better view of planets?
It may do - I don't know to the contrary. My understanding is that if the mask is off-axis one can increase contrast by avoiding interference from the spider viens - but on the flip-side - resolution goes down with decreasing aperture. Benefits outweigh costs?

Hi Mark,
During the times of particularily bad seeing, a scope with a larger aperture can see through multiply cells of air, these cells have differing temperatures and have different refractive indexes (so I read somewhere), this means you'll end up with an inferior image. A scope with a smaller aperture isnt physically wide enoughn to be seeing through 2 or more cells, so it sees through only one cell and could have a better image, this is why masking down a scope can sometimes work, it captures less bad seeing then a bigger aperture scope,
All the same, I have to say that I've rarely seen this work. The bigger scopes generally show more.
When I got the 20", I fully expected the seeing to dramatically reduce the quality of the planetary views, I expected it to be inferior to the 12", you read so many stories on the web. BUT, I'm not exagerating that the 20" has given me some of thee best planetary views I've ever seen, it absolutely floors the 12" every time.
I read somewhere that some of the faith in stepping down big scopes for planetary views came from experiences with big dobs in the 1980s, scopes that were eventually shown to have bad optics (by modern standards) where stepping them down locked out bad areas on the mirrors.