Small but long focal

[dugun]

Hello there,
I am planing to build a small 60-80 mm, long focal about f/15 refractor. Can you make such a lens for my project ? Sometimes special, single productions cost much much more than serial production. So I will need also a rough quote to see if building such a telescope is worth.

Sorry for my english

Regards
Demir

[Ales - iStar Optical]

Hello Demir,
the smallest achromatic doublet we produce is 100mm of clear aperture (104mm lens diameter). I do not plan on producing a smaller doublets. iStar Optical specializes in producing large lenses only and we do not have market for a small doublets. Also, there are plenty of Chinese mass produced small doublets and triplets and we don't want to compete with those.
To produce one single lens is extremely expensive, only the molds cost around 850 dollars, single lens in approx. 80mm aperture would be additional 800 USD minimum. If you add design cost and overhead cost you will land at around 2200 dollar mark. This is a very rough estimate but I doubt that anyone else can design and produce such lens for less. In your case, I would seriously consider a good 100mm F12 for 279 dollars. Talk to people who own them, you can not go wrong with these doublets at this price. Please follow up on this with Mike Harden. He will give you a current stock situation, shipment cost, etc..
best regards,
Ales

[dugun]

Thanks Ales, I'll think about 100mm
Regards
Demir

[jimcurry]

Demir:
I purchased the Istar 4" f/12 when they were first released and built a telescope. Absolutely superb lens. Ales says they're finished to L6 and they are! Our club optician looked thru my scope and exclaimed that it was as perfect as an achromat could be. "Like it was turned on a lathe."

Kind regards,
Jim