Glenn wrote: > Brooke Clarke wrote: > >> I'm interested in automatically measuring the earth's period by looking >> close to straight up with a fixed telescope. >> >> > > This sounds like an interesting project. I've been looking for something > to do with the Meade 4455D telescope I just got. (D=114m F=910, f/8) > Doing a fixed mount at a know location shouldn't be a problem. I've also > got an untested Hamamatsu E717-07 photomultiplier tube. Please let me > know how it goes. > > cheers, > glenn > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Glenn
The aperture of your Newtonian telescope is a little too small for this application especially in the daytime. You need to use an IR filter to block most of the Rayleigh scattered sunlight. You will also need to have good baffling and use a Lyot stop to block straylight. With an aluminium tube focus will not be stable as the temperature changes. If you have a plate glass mirror then a steel tube will give a much better match to the mirrors focal length temperature coefficient. Shading the telescope tube and mirror from direct sunlight is also essential to avoid heating the tube and creating large tube currents which will severely degrade the images. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts