Thanks Christian and Francois.
Christian,
Shortly after I joined the ARAS group I posted a description of my setup with photos here:
http://www.spectro-aras.com/forum/viewt ... ?f=8&t=811
The important details are:
Telescope:
311cm home built corrected f9.8 Dall Kirkham with a 45mm dia. diffraction limited field.
Spectrograph:
- classical home built designed for low resolution
- f6.6 focal reducer built in to spectrograph mount
- 23 um slit (an APLY slit) gives 2.3 arcsec width after the f6.6 reducer. Reducer delivers an image circle of 1 arcsec from 400 to 750 nm.
- collimator - Edmund spherical mirror with 101.6 mm fl (203.2 mm radius)
- gratings - Edmund 25x25 mm, 600 and 1200 lpm and an Optometrics 25x50 mm 1800lpm
- collimator to camera angle - 38 degrees
- camera - 85 mm f1.8 Nikon lens (internal focus). Better than average resolution - got lucky!
- imager - QSI583 (5.4 um pixels)
Calibration source:
- Relco lamp behind a frosted aperture and motor driven into beam so as to illuminate the spectrograph identically to the telescope.
Weight of the spectrograph with the reducer guide and calibration assembly but without the imagers is 1.5 Kg
Originally I had some flexure problems that resulted in small orientation dependent wavelength shifts but these were
tracked down to flexure of the front face of the QSI 583 and movement at the camera lens mount. Both were solved.
With the 1800 lpm grating I have pushed this classical design to the limit. The 0.63 anamorphic factor results in a 14 um slit image on the CCD.
Focus is thus critical and I had to change the imager mounting to allow a precise tilt to be dialed in for each grating rotation.
I now have a table of tilts versus grating rotation that enables me to set this up quickly.
Tim