Field Corrector for Newtonians and D=50mm field diameter

 

Description

The corrector was designed for the larger format CCD-camera (especially with one eye on the new SBIG series) to cover a larger field than possible with a 2” corrector. It should be clear, that 2”, with a clear aperture of maybe 40mm, cannot cover a field of 40mm with an f/4 light cone. Therefore, a 3” barrel was chosen to cover field diameters of up to 50mm with low vignetting. The backfocus is large enough (appr. 59mm) to use most known CCD-Cameras with filter wheels. The corrector ends with a flange with 6xM3 Threads on D=68.5mm. Adapters can be ordered for several cameras. Please note, that the corrector does not use cheap 3xBK7 glasses like other correctors and it does not increase the focal length ! Expensive glasses have been chosen, to minimize the corrector length, minimize the spot-size but maximize the back-focus for easy use of filterwheels.

Examples

The corrector can be used between f/3.5 and f/5.5. The corrector has been optimized for a field diameter of max. 50mm. In the below examples you can see the performance and vignetting (assuming that you use a large enough secondary mirror) for different examples. The box-size of the spotdiagrams is 0.02mm (20 microns). The wavelengthrange for the calculation of the spots have been from 400nm to 700nm. Spots and vignetting are shown for a D=44mm field

300mm f/4 Spotsizes

300mm f/4 Vignetting

400mm f/3.5 Spotsizes

400mm f/3.5 Vignetting

400mm f/5 Spotsizes

400mm f/5 Vignetting

as can be seen from the calculations, the same corrector can be used on a large range of Newtonian mirrors from 250mm to 1m diameter. Spotsize is very small, concentrating 80% in 1 Pixel even for cameras with small pixel size.

Drawing and Distances

 

 

LayoutWynne 



 

 

 

 

 

 

 

 

 

 

 

 


Please note the following distances for different mirrors:

A=Distance from Flange to Focus

B=Distance from Flange to primary mirror vertex (middle of the reflecting surface)

Diameter

Focal length

Focal Ratio

B

A

300

1200

4

1158.4

58.6

400

1400

3.5

1357.9

59.1

400

1600

4

1557.5

59.4

400

1800

4.5

1757.2

59.7

400

2000

5

1957.1

59.9

600

2400

4

2356.6

60.3

 

Price:

please contact

ASA Astrosysteme GmbH

Galgenau 19

A-4212 Neumarkt

Austria

 

german http://www.astrosysteme.at/de/korrektoren.html

 

englisch http://www.astrosysteme.at/eng/correctors.html

 

They also sell great ready-to-go telescopes that use these correctors !