Collimated Beam Projector

A "Collimated Beam Projector" is an instrument to produce a collimated beam of photons of a known spectrum.  These devices are useful for measuring a telescopes throughput for astronomical point sources, since they arrive at the telescope as collimated wavefronts. 

The Stubbs group has worked on several iterations of these instruments, and we continue to refine our method.  

Here is a descriptive paper on the first generation of CBP, written by Michael Coughlin, a former Stubbs group graduate student:

https://www.michaelwcoughlin.com/publication/coughlin-cbp-2016/

May 2021 version

Richey-Chretein version has better configuration than the Newtonian one. Focus sits behind the primary. 
Omegon ProRC154. $600 from Amazon, https://www.amazon.com/Omegon-Ritchey-Chretien-Pro-154-1370/dp/B073J2R76Q 

Weight is 17 lb, Celestron spec is 25 lb. 

RC optical configuration, hyperbolic primary

Mounting rails are 44mm VIxen standard, this ought to work with Celestron Evolution NexStar mount, without adapters

focuser is 2" diameter and also reducing sleeve. 

focus extension tubes are 2 x 25 mm and 1 x 50mm. 

focal length is 1370, pupil is 154 mm, so f/8.8

one arcsec subtends 4.86E-6 * 1370mm = 6.6 microns. A ten micron pinhole maps to 1.5 arcsec.

also comes in 203/1624 and 254/2000 versions

back focal length from end of tube is 240mm, or about 9.4 inches !

They say an APS-C sensor get diffraction limited stars across the full field, for their 254/2000 version. Those sensors are 25 x 16.7 mm. So the corner is at a field angle of 15mm/2000mm = 25 arcmin.

Manual: 53809_1_10_11_Omegon_Fulltube_en-GB_Instruction_Manual_REV_A.pdf

So we need to have adapters from 2-inch or 1.25 inch amateur eyepiece mount to Thor labs aperture slide. Slower f-number makes focus more forgiving. 

T-mount is 42x0.75 metric threads.