Pyrex Glass in the Skywatcher 250 Dobsonian

[Optical Dob]

Does anyone know why Skywatcher decided to put pyrex glass in just the 10inch dobs? I understand that it helps with changing temperatures and reduces cool down times and that it will be a bit stronger. I've also seen that it ensures high quality images. This bit I'm not to sure about.

Why did they not put it in the 12 14 and 16 inch ones as well.

[Tinker1947]

Does anyone know why Skywatcher decided to put pyrex glass in just the 10inch dobs? I understand that it helps with changing temperatures and reduces cool down times and that it will be a bit stronger. I've also seen that it ensures high quality images. This bit I'm not to sure about.

Why did they not put it in the 12 14 and 16 inch ones as well.

So what went in the 12, 14, 16" if it wasn't Pyrex....

[neil phillips]

I would be interested in this too

[John]

This question gets asked quite frequently on here but I've never seen a clear explanation other than, thats just how it is

If Pyrex was used on the other aperture scopes then I'd expect Skywatcher to note it as they do for the 250PX. But they don't so I guess we have to assume that other glass is used.

[neil phillips]

I wonder if that other glass is thermally inferior ?

[John]

My (limited) understanding is that Pyrex, and other glass with similar properties, maintain their figure slightly better while cooling. Once cooled though that "edge" disappears and performance is governed by the quality of the figuring and coating.

I don't think Pyrex is intrinsically "better" in terms of ultimate optical performance.

[neil phillips]

My (limited) understanding is that Pyrex, and other glass with similar properties, maintain their figure slightly better while cooling. Once cooled though that "edge" disappears and performance is governed by the quality of the figuring and coating.

I don't think Pyrex is intrinsically "better" in terms of ultimate optical performance.

There could still be a edge with pyrex then, there has been occassions were i have started imaging before fully cooled. ( quite a few actually ) I also wonder if pyrex copes better with falling temps, were the optics cant catch up quick enough ? Kind of irrelevant, if i wanted to use the 12" though. But the Orion would likely be better on those nights. if the glass is more thermally stable, i think they use suprax.

[Optical Dob]

Thanks for all your replies. It was more out of curiosity than anything else.

[Peter Drew]

113/4" diameter used to be the largest commonly available Pyrex blank, it could be that 10" is now the case.

[ronin]

This came up a while back:-

S&T

[RikM]

I have seen 200px scopes advertised by European suppliers, not on the UK though.