Reduces exposure time and gives a larger, flatter field with various refractors.

The camera-facing rear thread on the Planostar unit is T2 (M42) male, which allows the use of the Starwave DSLR Adapter for Canon/Nikon, and various T2 spacers for use with Altair and other CMOS cameras.

Spacing from rear flat shoulder of the PlanoStar to the camera sensor plane varies, and one can use the Altair Astro T2 variable spacer system to fine-tune the optimum distance for their particular chip and filter setup.

Recommended Starwave v3 0.8x Reducer Spacing:
Telescope model:    Sensor to reducer rear flange spacing (mm):    Focal Length with & (without) reducer (mm):
Starwave 80ED-R    63    448 (560)
Starwave 102ED-R    61    572 (715)
Starwave 110ED    61.5    616 (770)

Why should I use a field flattener/reducer with my refractor?

A field flattener / reducer performs 3 main functions:

• Flattens the field: All refractor lens systems show some natural field curvature which, while not relevant for visual observation, can be visible in images. A field flattener creates a flatter photographic field than the existing lens system alone, improving the quality of star-shapes at the field edges.
• Reduces magnification: An 0.8x reducer gives and 0.8x reduction in magnification, showing a wider area in the image, so you can include a larger object in the field of view on your camera sensor.
• Reduces exposure times: Additionally, the focal ratio of the telescope is also reduced, and that in turn reduces exposure times. For example, with an 0.8x reducer, an F7 scope exposing an image at 100 seconds becomes a "faster" F5.6 scope, allowing an equivalent exposure time of 64 seconds, all else being equal.