Covers on

The photos on this page depict the 160 Field Flattener since we did not have a photo of the 175 version at the time this webpage was written. Please note that the mechanical parts are the same except the length of the extension and the engraving on the retaining ring. The optics, however, were designed specifically for the 175 StarFire.

The 175 f/8.3 Prime Focus Field Flattener is made specifically for the 175 f/8 StarFire EDF with its 4" focuser. The effective speed of the 175EDF will be f/8.3 with this accessory.

Correction is essentially diffraction-limited over a 76 mm (3") circle, encompassing 3.0 degrees of sky. Stars will be pinpoint into the extreme corners of the field.

Required for optimal performance:

• The distance from the field flattener to the focal plane is critical and must be maintained +/- 2.5 mm. If you remove the extension piece, the distance is 114.9 mm (4.5") from rear of housing to the focal plane; plenty of room for rotators, filter wheels, etc.
  
  The distance must be the OPTICAL distance - NOT the mechanical distance. Please be sure that you have accounted for the indexing effects of your filters, sensor cover slips and any other glass in the light path. Please review the document "175 & 160 CCD Field Flattener Spacing Requirements" for more information.
  
  Astro-Physics produces several adapters (listed below). These adapters, when used with their respective cameras, provide perfect spacing. The special adapters for the STL cameras ensure minimal vignetting of the corners of the format (vignetting is unavoidable in these cameras due to the limitations of the filter size). Adapters for other cameras can be custom ordered from PreciseParts.

Included:
The 175 CCD Field Flattener comes with beautifully machined anodized aluminum covers: protection befitting the fine optics.