2.5" Field Flattener for Refractors

This is a 1.0x flattener designed to provide a corrected field for sensors up to 24mm x 36mm and designed to operate with refractors from 480mm focal length and upwards.

The corrector has a very flexible design with the telescope side providing an M63 thread making direct connection to any of the telescopes we offer that feature a 2.5" focuser. The corrector is then made up of 3 parts, the corrector itself, a red spacing ring and an M63 to M48 adapter.

When used with refractor telescopes from 700mm focal length, the back focus distance from the corrector is 85mm. When fitted with the red spacing ring and the M48 adapter, this becomes a very convenient 55mm. This allows for direct connection to DSLR's with mount adapter rings or many of the QHY CMOS camera packages which are designed to also provide a fixing option to M48 at this common back focus distance.

In addition to refractor telescopes, these back focus distances also apply to use with an RC telescope from 10" such as the GSO RC10.

For shorter focal length refractor telescopes, the back focus changes as follows;

600-700mm - add 5mm back focus

500-600mm - add 10mm back focus

Naturally at the crossover points, some experimentation with back focus position may be needed to find the optimum performance, particularly if using a larger sensor.