8.10.20

8.10.2020 New focuser in the post.

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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.


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