Quote:

---

I would say it's a f/15 and build to that focal length. By the way you can put those lights from LA to good use. You can get a good feel for the spherical correction of the lens by looking at a Mercury street-light as far away as possible. Use a green eyepiece filter and ronchi grating with at least 100 lpi. The mercury line at 546nm with be isolated by the green filter and that is were your lens should be corrected it show no spherical abberation so with three ronchi lines showing they should be nice and straight.

- Dave

---

Now that's a slick trick Dave.

Too bad I don't have any street lights close by...

No...that's a good thing.

Rob