Now that the ISON hoopla has dissipated, it’s time to get back to astronomy again!
Finally got my new gear together and am in the process of preparing to start imaging again! I sold my observatory and old newtonian parts for an Astrotech carbon fiber 10″ Ritchey (see the equipment page) and Moonlite DRO stepper focuser. I am going to try my hand at full automation eventually so this is the first step! So far things look good! The focuser interfaces with FocusMax for those who have used that program. Autofocusing measures a parameter called Half Flux Diameter.A measurement that is an improvement on the older Full-Width Half Maximum measurement, invented by Larry Weber and Steve Brady. The half-flux diameter is the diameter in pixels that contains half the energy in a star image. In other words, if you add up the ADU (analog digital units- which you can usually read off in your camera program) values (less the background) inside the diameter, and outside the diameter, you will get the same number. This measurement gives a very similar answer to FWHM, but it is much more robust in the presence of seeing and noise, and can handle images that are so out-of-focus that they look like “donuts”. The Half-Flux Diameter also varies linearly with focus position, except very close to best focus. This makes reliable autofocus possible. You can see the V-curve generated by the program which plots the points inside and outside of focus to determine the optimal focus position and the star image resulting from my first autofocus run! I would say not bad for below average seeing! Still using my old SBIG ST8XME…for now
Moonlite is a fantastic focuser manufacturer with excellent reliability and customer service. Prices are competitive. Ron Newman is one of the co-owners whom I have known for years and his passion for creating innovative precision focusing equipment is unrivaled.