I am just wondering what the mirror quality will be like.
As the mirror gets larger and faster it gets logarithmically more difficult to make and specifically to make well. While a very large number of the GSO and Synta mirrors I have seen have been very good they have been smaller aperture and a good bit slower in F-Ratio. A 20"/F4.3 mirror is starting to push the envelope even for a premium mirror maker. It may still be a ways for the mass produced Asian factories to get right. Buyer beware.
Seems other people have asked their Skywatcher suppliers and they don't know about a 20". There might be a misunderstanding somewhere. I so hoped that this was true!
Sure haven't the US distributors only recently admitted to the Tracking motorised Skywatcher dobs. (Or have they even admitted to them yet?)
And yet we've known about them for months from other sources. Twas quite funny reading about them claiming they knew nothing about a new tracking Dob while some of us were looking at the adverts in S&N magazine!!
And like you said. Your SA distributor was very specific about the 2200mm FL wasn't he.
Of course its still just a rumour that hasn't been confirmed from any other source yet but the rumour isn't quite dead in the water yet.
Sure haven't the US distributors only recently admitted to the Tracking motorised Skywatcher dobs. (Or have they even admitted to them yet?)
And yet we've known about them for months from other sources. Twas quite funny reading about them claiming they knew nothing about a new tracking Dob while some of us were looking at the adverts in S&N magazine!!
And like you said. Your SA distributor was very specific about the 2200mm FL wasn't he.
Of course its still just a rumour that hasn't been confirmed from any other source yet but the rumour isn't quite dead in the water yet.
Yes he was, at least to the extend that he said 'If I remember correctly''. It would be nice if the rumour could be confirmed/denied since I definitely don't want to be responsible for leading people on a wild goose chase.
I am just wondering what the mirror quality will be like.
As the mirror gets larger and faster it gets logarithmically more difficult to make and specifically to make well. While a very large number of the GSO and Synta mirrors I have seen have been very good they have been smaller aperture and a good bit slower in F-Ratio. A 20"/F4.3 mirror is starting to push the envelope even for a premium mirror maker. It may still be a ways for the mass produced Asian factories to get right. Buyer beware.
Cheers,
John B
I'd agree with Johns comments here. I wouldn't hold my breath about the quality. At 20", you'd want to be using at least low expansion glass for the mirror substrate.
Mass producing a 20 inch is not that easy. I picked up one of the few 29 inch F4.5 newtonian sets built by Coulter Optical about 25 years ago. It was a beast of a thing and although I got one of the best amateur views of Halley, mounting the thing fair killed me..... but manufacturing it, killed Coulter ;-)
Right now I am saving up for the 12inch Skywatcher dob but when I am older I will buy the 20 inch. I hope it will be retractable. I would get a trailer for it to save the weight problem. I think it should be a goto. We should give design suggestions to Skywatcher.
the same people said they knew nothing about 16"truss dobs
:sc ared:
