*
Further to my recent [helical] focusing problems I have ordered a new focuser. This also offers the opportunity to extend the protection filters forwards into the OTA. By supporting them on a TS adapter attached to the inner end of the drawtube. With the male M48 [2" filter thread] provided I can even use my existing 48mm extenders as well.
There are numerous other advantages to having a normal focuser. Its greater weight [over the helical] will help to balance the OTA better. Most refractors are very nose heavy from the weight of the objective lens and cell. I can also add my belt driven DC focus motor for effortless fine tuning from my imaging desk.
Touching
the long OTA at such image scales [typically from 1500mm minimum to
over 3000mm focal length] is a complete disaster. Not just for the short term
vibrations. Nor even temporarily losing the image from the screen. The
mere act of a focusing is utterly pointless unless the image is steady enough to
discern the finest detail. Despite the long focal lengths involved
being in or out of focus is within a very tight margin. Since sharp
focus is so vital the helical focuser was always a cyclic, overshoot and
undershoot exercise. Particularly once the focusing motor was removed.
No comments:
Post a Comment