Telescope Optics

The optical system in every DFM telescope is custom-created to meet customer specifications. Even the standard optics are held to rigorous DFM Engineering quality standards, as they are an extremely critical element of the DFM Telescope Optics system.

Lens Figuring
DFM technicians take extreme care in the process of grinding, documenting, testing and polishing the product.  Mirrors 26" and larger are manufactured and tested at the DFM Engineering Optical Facility. This ensures incident light is contained within a minimum of 0.6 arc seconds.

DFM concentrates on fast, highly aspheric primary mirrors. Typical mirrors are 1.3-m F/2.3 mirrors for the wide field F/4 telescopes. These mirrors have a surface departure from the best fit sphere of 60 waves. 

Lens Figuring

DFM has also made several field corrector elements which are fourth order (Schmidt) type lenses that are used with the 1.3-m F/4 wide field telescopes. A 3 element field corrector is featured in the  ATLAS Optical Tube Assembly (Asteroid Tracker), also manufactured at DFM.

The DFM Optics Shop uses two large optical flats (0.9-m and 1.6-m), several smaller flats, an interferometer, various test fixtures, and many tools.  The DFM Engineering Team has considerable experience handling large optics typically used in telescopes. A 2 ton variable speed electric hoist and a gantry crane allows for safe and efficient handling of large optics. 

3-Element Field Corrector Diagram

Mirror Polishing
Mirrors larger than 26" are manufactured within the DFM Engineering Optical Facility. The optical shop capabilities have included a variety of large mirror sizes with multiple 51" mirrors adhering to critical customer specifications.

Since the quality of the mirror is directly related to the light gathering power and ability to resolve detail, DFM technicians take extreme care in the process of grinding, polishing, testing, and documenting, the product.

Optics Testing
The optical facility is staffed with expert technicians that deliver large quality optics typically used in telescopes. All primary and secondary mirror finishes are tested at DFM so as to be within the proper range. Finish on the mirrors is typically 80/60 for the primary and 60/40 on the secondary.

Mirror handling systems that are specifically designed to integrate into observatories to safely allow technicians to move, reinstall and collimate the optics are a significant feature of the complete customer satisfaction provided by DFM Engineering.  The mirror handling equipment often consists of hoists, mirror insertion tools, carts, crates, lift tables, slings, and fixtures.

Telescope Optics Custom Features
DFM Engineering delivers the assurance that only experience can provide. Every optical system is custom created to meet customers' specifications and optical requirements. In addition to telescopes, DFM Engineering has produced multiple modern scientific instruments requiring excellent optics, including satellite trackers, beam directors, lidar scanners, and heliostats.

DFM has also created and manufactured the Prime Focus Instrument™ (PFI™).
A PFI™ retrofitted to older telescopes can allow them to be re-purposed to perform wide field astronomy such as multi object photometry, super nova patrol, variable stars, planetary transits, occultations, orbital debris searches, asteroid searches, etc. With a PFI™ the FOV can be increased to 1° or more.

Prime Focus Corrector Diagram