7" Achromatic doublet lens ?

[john2233]

Hello,

I noticed that there are no 7" achromatic lenses for sale, why is that ?  I'm looking to build a "compact and light" rich field refractor and searching for a 7" f5.5 - f6.5, I only could find a 7.1" f8 R35 which is to long for rich field and also pricy... and the comet hunter 204-6 which is very big and heavy and it's only sold as an OTA.
I currently own a 5" short refractor and I think that the jump to a 6" won't be that noticeable as a jump to a 7".  A 7" f6 refractor would have a ca ratio of 0.85 which is almost the same as standard synta 6" f5 (0.83), and those 6" f5 really perform on dso.

Thank you.

[Mike]

Hello, nice to hear from you. It's just a matter of economics supply and demand. We try to produce what is called for. It's impossible for us to produce every conceivable aperture and focal length. I would say we could arrange to get you a 204mm F6 lens only. We try to reach the majority by producing a 150mm and a 204mm short focal length. There is currently no design or intention to produce a 180mm F6. Sorry Even trying to meet the needs sometimes fails. An example is the 127mm F5.5 which we thought would go. Nope. I have two or three lenses in stock that are over a year old. Just didn't fly... They would make a nice light wide field scope or binoculars. Even 150mm F6 scopes have been fairly slow. I just sold one a few days ago but that was the first in a while. The 204-6 is the hot product in wide fields as I sold three in the last two weeks and have had several inquiries. If you want to discuss this further please email me direct at [e-mail]

BTW anyone interested in a deal on a 127-5.5?