I just purchased a slightly used Takashashi TSA-120 from a well-known over-the-counter retail and mail order telescope emporium in my area. I mounted it on my Tak EM-200 mount.
First light - for me - came Saturday nite at my favorite high-altitude star party site. The optics are superb. No complaint there. The mount is solid and tracks smoothly. No complaint there. But, whoa, that Tak Micro-Edge focuser has a problem.
It focuses much like the older Celestron and Meade SCTs. As the image is fine-focused in and out to achieve sharpest focus, the image shifts laterally back and forth in the field of view. The higher the magnification, the greater the shift. At 180X, Saturn was moving back and forth about 2 or 3 times its own diameter as I was trying to bracket sharpest focus. Any idea(s) what the problem could be? Thanks for your help.
If the image is shifting as you rock the focus knob back and forth? the draw tube is loose in the focuser! To confirm this just slightly tighten the focuse lock knob on the top of the focuser until you feel some resistance when adjusting focus. If that fixes your issue? Then the next step is to adjust the pre-tension on the drawtube. To adjust pre- tension do the following:
1. Remove the pinion cover on the bottom of the scope by loosening and removing the flat chrome screw.
2. Loosen the two phillips head screws for the pinion shaft until you feel some play but can still adjust the drawtube.
( Why loosen the pinion shaft? the pre- tension screws on the top of the focuser press the drawtube down and you don't want that downward pressure to bind against the pinion shaft).
3. allong the top of the focuser are three 1.5mm allen head screws , they are set in a clear sealer that looks like clear nail polish. Use a small drop of acetone ( nail polish remover ) on each screw until it turns then:
4. adjust the three screws starting with the center one while you move the draw tube in and out untill you are happy with the smooth movement and feel that you have removed any play in the drawtube.
5. adjust the two pinion screws for smooth movement and no backlash.
6. replace the pinion cover
Done, note the three pre- tension screws should harden up as the acetone drys, if not a drop of clear nail polish will lock them in place again.
Edited by tomcody, 04 August 2014 - 12:24 PM.