Re: Barlow et chromatisme
Posted: Thu Sep 24, 2020 7:27 pm
Hi Tom,
Yes sorry, my calculations have gone awry somewhere. I should have said 2.4 arcsec for the ALPY and the standard 23um slit (can you get a 35um slit?) and 1.8 for the LHIRES and 35um slit. There is a resolution penalty going to 35/50 though of course.
Unless they have updated it the open aperture of the LHIRES 200mm fl doublet is f8 but the ingoing and return beams are at a slight angle and the return beam is dispersed so I think there must be some vignetting at f8, though perhaps it is minor.
Cheers
Robin
Yes sorry, my calculations have gone awry somewhere. I should have said 2.4 arcsec for the ALPY and the standard 23um slit (can you get a 35um slit?) and 1.8 for the LHIRES and 35um slit. There is a resolution penalty going to 35/50 though of course.
Unless they have updated it the open aperture of the LHIRES 200mm fl doublet is f8 but the ingoing and return beams are at a slight angle and the return beam is dispersed so I think there must be some vignetting at f8, though perhaps it is minor.
Cheers
Robin