China can do for APM long focuse doublet Apos

to continue the Apo discussion where the question came up, can a visuel doublet Apo for lower price be made , I contact a chinese maker whom I trust and got in reply, yes we can do it up to 7" with FPL 51.

Due low quantity and higher shipping cost they would be a little more expensive then other chinese apos

If we give them our Zemax design they would quote it.

So how many people want a F/10 or better F/12 doublet visuel apo for low price in the 5" , 6" and 7" range ?

comments are welcome

thanks
Markus

A 7" f/12 would definately get a 2nd look from me....... While I love my 8" F/9 Achro I think I would give up an inch of apature for the enhanced performance of an f/12 doublet APO.

Markus Ludes said:

to continue the Apo discussion where the question came up, can a visuel doublet Apo for lower price be made , I contact a chinese maker whom I trust and got in reply, yes we can do it up to 7" with FPL 51.

Due low quantity and higher shipping cost they would be a little more expensive then other chinese apos

If we give them our Zemax design they would quote it.

So how many people want a F/10 or better F/12 doublet visuel apo for low price in the 5" , 6" and 7" range ?

comments are welcome

thanks
Markus

So how many people want a F/10 or better F/12 doublet visuel apo for low price in the 5" , 6" and 7" range ?

I think 7" F/12 with good wavefront would be very interesting,
maybe 6" too. At 5" there are already several good options at
good prices, so not so interesting.

For me F/12 with better color correction would be much more desirable
than F/10. I know makers have been afraid of long tubes and slow F-ratio,
but I see this as a "classic" planetary visual scope.

Can you post some multi-color spot plots with Airy disk size marked?
That would help the discussion.

HI Markus,

I was holding out for an 8" F/10 for visual but a 7" F/10 to F/12 would be of interest to me as well.

LArry

I would be interested in a 7" F/10. Estimated cost?

Keith

Based on experiences with a 5" f/9 ED doublet, that scope is getting too long and cumbersome for my taste.
A larger aperture, slower f-ratio ED doublet is tempting... but not for this user.

I own and use an 8" f/13 doublet, a classic instrument and certainly my favorite of all my scopes. Swinging a big refractor under the skies is a great pleasure. Mine is mounted in "dob" fashion and works more smoothly than when mounted on an Eg mount.

A few years ago, I was communicating with a China optical company for a 14" doublet with my specifications. Price was right but with each communication the priced changed untill it was no longer affordable and there was no end in sight for price increases.

I also have a 5" f/12 D&G OTA which gives fabulous images and would use it much more if the 8" was not in competition.

So, sign me up for a 14 incher............. :-)

Markus,
I would be very interested in such a scope, a 7" f/12, for permanent mounting, obviously. You welcomed comments, I hope negative and not very well informed comments are okay too!

I am dubious about a doublet that big from this glass. I fear that the elements would be so thick and strongly curved that the lens would be hard to make, hard to center in the mounting, heavy, and hard to cool. Combined with spherochromatic effects and other aberrations resulting from strong curvature, the expense of such a lens might not be justified compared to an achromat, for visual use. Secondary spectrum isn't everything.

So, yes, with those reservations.
Thanks,
Ron

6 inch F/10 doublet APO - yes, I'd be interested.

7 inch F/10 - maybe.

7 inch F/12 - maybe...might make a decent folded refractor.

Kwang

What's a low price?