In brief:
- Astrograph with quartz glass optics
- Modified Dall-Kirkham design with fully corrected image field
- Prepared for Delta T heater (Hedrick focuser and EFA kit sold separately)
This variant of the CDK20 offers an additional 48.3 mm backfocus and an additional 497 mm focal length compared to the CDK20. PlaneWave Dall–Kirkham telescope DK 508/3454 CDK20 Astrograph
The CDK optical design
The PlaneWave CDK layout is an optical design based on the classic Cassegrain design by Dall-Kirkham.
It was developed to accommodate the ever-increasing size of chips in digital and CCD cameras. With many other mirror optics, you quickly see off-axis aberrations such as coma and/or astigmatism; in addition, many systems suffer from image field curvature, which causes the images of stars to become increasingly blurred as they move away from the optical axis.
The image field is free of coma and astigmatism. In addition, the image field plane is absolutely flat and level across this diameter, so that stars are rendered equally sharp in the focal plane across the entire field.
The CDK design offers a perfect solution to the problems mentioned above with the best price-performance ratio and moderate delivery times.
It consists of:
- an elliptically curved primary mirror
- a spherical secondary mirror
- and a 2-lens field corrector
All three optical elements are perfectly matched to achieve the incredible image quality. The image quality is largely dependent on the seeing conditions at the installation site.
The quartz glass (fused silica) used is a synthetic amorphous quartz glass of the highest purity and one of the most transparent glasses available. Due to its purity, the optical and thermal properties of quartz glass are superior to other types of glass. Its transmission and homogeneity exceed those of crystalline quartz and avoid the problems of temperature instability that crystalline quartz glasses suffer from.
Fused silica has a thermal expansion coefficient six times lower than that of borosilicate glass (Pyrex). It therefore retains its shape with a very high degree of accuracy when it cools. This results in consistent optical performance and an unchanged focal point during temperature changes.
Scope of delivery:
- Telescope with prism rail
- Built-in heating elements to prevent condensation - The heating elements on the primary and secondary mirrors require the separately available Delta-T controller for PlaneWave telescopes with pre-installed wiring for the heating
- Cover to protect the primary mirror and the inside of the optical tube
- Cover for the secondary mirror
- Flash drive with software and instructions for collimation and primary-secondary mirror alignment
- Tool kit
- 12V AC adaptors
