Upsize collimator diameter in Lhires

[Paul Luckas]

Hi all,

I may have access to the means to fabricate a new collimator assembly for my Lhires in order to retrofit it with a larger diameter lens for use with a 'faster' telescope - as per Lothar Schanne's version some years ago - http://www.astrospectroscopy.eu/Einstei ... sIII_e.htm

Although in practice the gains with my F/7 RC may not be that dramatic, it's something I've been considering for some time. There appears to be plenty of room inside the Lhires carcass for a larger diameter collimator, and the retrofit does not seem to be a particularly complex undertaking with access to suitable fabrication expertise.

I'd be grateful for a sanity check on the idea. Are there other factors to consider with the move to a larger (40mm diameter) f=200 mm lens - grating size, mirror size, unforeseen optical aberrations, etc? In other words, is the mitigation of vignetting the only issue to consider, or are any downsides to be expected from using a larger diameter collimation lens in the current Lhires design?

Many thanks,

Paul