IStar Objectives, pathway to large diametre long Fl

[glend (Glen)]

As a builder of an iStar refractor, I still look in at their website now and then. They are one of the few objective builders left for potential scope builders to go to for quality optics. They offer APO, R30 Antiastigmatic, and Achromat products in large diametre, adjustable cells. Some of these Achro objectives, at the longer focal lengths, like f15, have no CA to be concerned about. The 220mm diametre f15 objective, for $3400 USD, seems like a bargain, provided you have the swing room to host a 3300mm focal length scope. Weight won't be a concern at 6.14kg for the cell. Link is here:

https://www.istar-optical.com/achromatic.html

For those who remember my iStar build thread, it's still here in the archives if your interested, and good with Advanced Search.

Have fun.

[JA]

Hi Glen,

It's an interesting prospect building a larger optic and thanks for the link. I recall one being advertised here by one of our members in the classifieds .....

I Star 180

Best
JA

[anj026]

I remember your iStar build thread Glen and I agree these are nice lenses and make a fun project. My own experience was with the 5" f12 R30 lens and a couple of 5" f5.5 lenses. I also made a couple of Scopes with D&G lenses.

Telescope Express also has some lenses available for ATM builds.

https://www.teleskop-express.de/en/t...-1000-mm-14406

https://www.teleskop-express.de/en/t...-1800-mm-14413

https://www.teleskop-express.de/en/t...-in-cell-10290

[glend (Glen)]

Anj, thanks for those TS objective links. It's good to see your still interested. While those objectives are interesting, the focal lengths are just too short, the CA would drive me crazy. Alas my observatory dimensions will not allow me the swing room for a large diametre f15ish objective, I am happy enough with what I have.

That said, everyone interested enough to read this thread, should give it a go. Building a refractor is very rewarding, well until you try to sell it.