Optical Systems and Equipment... (Dave Erickson)

Optical Systems and Equipment...

Revision title: Star testing a C11 on a large collimator optical bench

I have designed, constructed, and tested a lot of optical systems over the years:
I thought it would be interesting to post an example of the significant advantage CCD imaging has brought to amateur astronomy. The image on the left is from 1975 taken with a home made 5" F/4 Wright Schmidt, guided with an an off axis 5" F/8 home made Schmidt Cassegrain. This is a manually guided 1.5 hour exposure using 103aF film and an R60 filter, a home made glass filter the HAlpha filter of the day.

It was one of the first amateur images published by the Astronomical Society of the Pacific in their Mercury Magazine as an example of how amateur images rivaled those of professionals. Not a good image by today's standards...

The one on the right is a first light 60min HAlpha image taken with a home made 8" F/2.6 catadioptric, taken 30 years later in 2005 using an SBIG STL11000m self guided camera.

I think the difference speaks for its self.

While I miss the romance of the darkroom and wet chemistry there is no comparison in the image quality and capability available to amateurs today.

The image on the left is "dry mounted" on acid free matboard. The yellowing is from age having been printed and mounted in 1975 some 45 years ago...

B: I added a photo of the imaging setup used. I made the system back in 1972. It won several awards at RTMC in 1973, and 1975... Fork mount made from walnut and oak, with an 8" Byers drive, off axis mechanics for the guide scope, home made drive controller. A work of passion that lead to a career in optics.

C: An image from a couple of decades ago, of acceptance testing a Single Point Diamond Turning Machine at the Moore Nanotech facility in Keen NH.

D: Testing a C11 on a 12" Off axis collimator in the lab at Zygo Costa Mesa Facility. This system has a 12" off-axis parabolic mirror and (2) 20" diameter fold flats to direct the beam into the test area. As part of the installation of this collimator, I made a deal to test all of the 20" flats and select the best two for this instruemnt. The final collimator had a 10th wave 12" diameter beam running dead parallel to the nodal slide bench. The C11 is respectable at 1/4 wave over the 11" aperture.

Happy Imaging... Dave

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Title: (DYI) Wright Schmidt Astrograph with Schmidt Cass Guider

Description: This is a Wright Schmidt Astrograph. The primary mirror is an oblate spheroid F/3.6 100% undercorrected. A Schmidt corrector with 2X the correction sits near the prime focus. A secondary flat mirror folds the image out of the tube. I made this system over a 3 year period completing it in the early 1970's. The Schmidt cassegrain is an F/8 off axis "VISUAL" guider.

The astrograph used a Leica focal slider for roll film Kodak 103a-F. I would hand roll film for an evenings imaging, usualy 2-3 objects-images. The film I would process in D19 developer and print with an enlarger.

The Fork mount is made from Walnut and Oak. There is an 8" Byers clock drive driven using a homemade drive controller that ran on 12 volts. The AC frequency was increased and decreased for correctios of RA. There is a separate drive for both electric and manual corrections of declination.

The entire telescope including optics was made in a modest garage shop.

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Title: Acceptance Testing a Diamond Turning Machine in 2006

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Title: Star testing a C11 on a large collimator optical bench

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