Posts Made By: Jason Lane

Never heard of it. Why not use PayPal and have peace of mind?

-Jason

Hi Alan,

The problem is that the data you're wanting is data that the optical engineer would generate for an ideal system. This wouldn't be realistic. Manufacturing and mechanical tolerances means a real telescope will perform ever-so-slightly less than his ideal design data would show (not by a lot, but enough to upset the nit-pickers who would be expecting the performance to be *exactly* the same as the data shows). The designer would be setting himself up for a lot of grief if he shared that kind of data. I'd bet this type of thing is what changed Zambuto's mind about releasing analysis data with his mirrors. Oh, and there's also the chance of other designers figuring out his prescription (which wouldn't be good for business).

As an optical engineer, I share the ideal design performance with maybe the optician in the shop, the other engineers working with the optics who understand it's ideal, and my team lead. Anybody outside that circle and even within after I've done tolerance analysis, I stress the design tolerances and the performance to be expected with a real system. While by no means am I trying to hide anything, I know there is such a thing as sharing too much information...I don't want the important aspects (both good and bad) of the designs to be lost in a myriad of details that really only matter to myself, the optician who will be making the optics, and the mechanical engineer who will be designing the lens mounts. I definitely don't want to give them ideal performance data and have them expect ideal performance out of a real system. It's not good for your career to promise more than you can deliver.

Cheers,
Jason

Floyd do you have a link that talks about this laser test, or can you explain how it works? Never heard of it before.

-Jason

Hi Paul,

I live out in the desert as well. I found a soft brush per Dr. Clay's ASO cleaning method to be ideal. Check out this link:

http://www.arksky.org/asoclean.htm

Under the "Preparation to Cleaning" section, he goes into detail about what the ideal brush is for cleaning off dust. I think Oceanside Photo & Telescope also sells a kit which includes a brush that fits this criteria.

Cheers,
Jason

Second,

View of Owens Peak from front door of our home.
November 2006
Olympus OM-1 on tripod
Zuiko 200mm f/4 operating at f/8, 15 minute exposure.
Kodak E200 Color Slide Film

Check out Olympus OM-1 (OM-1N or MD) or Nikon F2. These two seem to be the most popular for astrophotography.. the Olympus (what I use) is lightweight and the focusing screen can be changed out for a brighter one. The prism on the Nikon can be removed, allowing the focusing screen to be viewed directly with a magnifier (easier to focus).

The key point is to get a camera with a mechanical shutter so you don't drain the batteries. Luckily, all-mechanical film cameras are very cheap these days. Check the classifieds here or check ebay.

Cheers,
Jason

Epson's (as well as Canon's) line of scanners starting with the 4870 have been giving superb results. You should read the review available at this link:

http://www.photo-i.co.uk/Reviews/interactive/Epson%20V700/page_1.htm

Hope this helps,
Jason

The correct spelling is parfocal.

I've always believed that to make eyepieces parfocal, the distance from the aperture stop in the eyepiece to the mounting flange must be the same.

The mounting flange is the shoulder or step that keeps the eyepiece from sliding farther into the eyepiece holder. Where the shiny 1 1/2" or 2" diameter part stops.

The aperture stop sets the apparent field of view, so it's location must coincide with the image plane formed by the telescope.

The aperture stop is a metal disc usually found in front of the lenses (i.e. farthest away from the eye), so it'd be easy enough to measure the distance between this and the flange on two parfocal eyepieces and see if they are the same.

-Jason

This shot is the view to the south.

Cheers,
Jason

Positive vs. antagonistic. Posting a negative viewpoint to begin a discussion is fine (reference the last time you visited). Mocking the film forum for lack of activity serves no useful purpose and won't be tolerated. Start a discussion, don't start arguments. That's my call and it has nothing to do with the first amendment.

-Jason