Back focus Lhires & Alpy

[Paul Luckas]

Hi all,

I'm after a sanity check on the backfocus (distance from mounting plate to slit) of the Lhires and Alpy (full config) respectively.

I've found a reference on-line for the Lhires that shows a distance of 68.5 mm from the outside face of the mounting plate to the slit.

For the Alpy, I presume the distance is ~47mm - consisting of 30mm for the calibration module, plus 17 mm (half the thickness of the 34mm guiding module, assuming the slit is positioned approximately half way into the module).

Does this sound about right?

Cheers,

Paul

[Olivier Thizy]

Paul,

the slit is actually aligned with the edge of the Alpy guiding module. So backfocus is 30mm for the calib module + 34mm for the guiding module, ie 64mm total.

Cordialement,
Olivier Thizy