Posts Made By: Jason Lane

Very nice, Peter.

-Jason

Awesome Marcin! And it's the first time you ever looked at Saturn? What a great start!

Cheers,
Jason

Antares W70 25mm
UO 12.5 mm HD Ortho
Vixen Orthoscopic 9mm

These are used on Vixen VC200L (8" f/9) and also my 8" f/5.875 Dob (my first ATM project).

-Jason

Keep in mind that with shorter focal ratios, focusing is more difficult and harder to maintain.

-Jason

Nice shot, Pete. It's a keeper!

-Jason

What they are basically talking about (but don't know if they realize) is a Diffractive Optical Element (DOE). The Fresnel is simply an early example of a DOE. Diffractive Optics have gotten pretty common these last few years, finding widespread use in the disposable camera industry and also in the infrared where the wavelengths are longer and the tolerances aren't as critical. The primary use is for additional color correction, but that isn't to say it could be used by itself as an objective.

The main issue with DOE is light scatter off of the diffractive surface. The other problem is that they must be diamond turned, which can be costly for one-off systems (or even for production systems).

-Jason

Lots of custom shops out there that will do prototype designs like this. Choose one that has the ability to coat optics as well, to help keep costs down. Expect to spend, for something like this, anywhere in the $100 to $1K range, and likely towards the middle-to-higher end and a lead-time from a week to a month. You'll want to look for small to middle-sized shops. Like you said, Edmunds is too big to concern itself with small fish (they've no-bid requests for 2-dozen custom parts before..don't know how they make money that's for sure). Just be sure that you've fully specified your design. That is, fully dimensioned including tolerances, surface finishes, clear apertures, etc. You'll want to see how tolerances affect the design. That is, tweak the radius of curvatures, thickness, etc., to see how it affects performance. If the design is too sensitive or if the tolerances need to be too tight, any shop you choose will either (a) charge you an arm and a leg, or (b) say they can't or won't make the parts. And, if you don't fully spec out the design (a mechanical drawing is preferable), they may not touch it either and/or you may not get what you wanted.

Something to keep in mind. Hope it helps,
Jason

Doing something because "everybody else does it" shouldn't be a valid reason.

Instant gratification isn't for everyone. In addition, digital cameras cannot match film for Field of View...especially in the medium and large format. Of course, you can always mosaic a set of digital images. Also, a scanned 35mm frame can provide 100+MB of lossless data which would reveal much more information than a 4-5 MB JPG.

It's also as well to ask why people still sketch what they see at the eyepiece.

Some folks, like myself, work with digital imaging on a daily, professional basis. As in the design and testing of imaging systems in an R&D type setting. I'm not saying I don't enjoy what I do for a living, but using film for astrophotography provides a break away from the routine. No computers required! I also have a heck of a lot of Technical Pan Film stored away to use up, since I wasn't able to try it when it was still being manufactured. That means I'll be developing it myself, and never having used a darkroom when it was the "in" thing means I am fascinated by the process. As far as Tech Pan is concerned, nothing digital can yet touch it for resolution. Pixels are just not that small yet.

Choosing to use chemistry rather than electricity to capture photons doesn't make the process wrong or anachronistic. I've heard that teenagers who are able to work in a darkroom at their school (ie yearbook staff or chemistry class, etc.) say that, having grown up with computers and digital equipment from the time they were born, it is actually pretty cool and refreshing to get to work with film and chemicals. I can understand completely where they are coming from.

So basically, "Because film is cool."

-Jason

That's pretty good, Pete. I've always found globulars to be the toughest to photograph for some reason. Everything has to be perfect, including the exposure length, to get them "just right".

-Jason

Very nice, Wei-Hao. I love the wide field view

-Jason