Many members have noticed that their new 12"LB won't come into focus using the supplied Meade QX 26mm EP, even when the focuser is fully extended. They find themselves retracting the EP from the focuser itself until focus is achieved. What results is the EP precariously hanging out of the focuser instead of being firmly held in place by the brass compression ring. It appears that the optical path is to short using the supplied EP.
The crayford style focuser has two knobs on the underside. The one closest to the observer is the traction adjustment. This controls the level of grip and traction applied to the focuser barrel.
The second knob which is closest to the telescope tube is the locking control. It is used to lock the barrel into possition after focus is found ie. When using imaging units.
TIP 1
If the locking control is lossend to about half it's travel, the focuser barrel can be extended another +/-8mm, thus lengthening the optical path. This was pointed out by fellow IIS member
astronut.
Another issue that recent owners of the 12"LB have raised is the soft collimation compression springs under the primary mirror. The need to upgrade these was also pointed out by IIS member
astronut. I have discovered that the following technique is very helpful, not only to compensate for the soft springs but also to help bring the supplied QX 26mm EP into focus.
TIP 2
First loosen the three collimation locking knobs all the way (Thay are the ones that protrude the most from under the scope and are also smaller in diameter). You can even take them all the way out if you like. Next contract the three collimation screws all the way so that the compression springs are fully compressed. When a compression spring is compressed, it gives more resistance, thus a soft spring becomes a little firmer. The other advantage of this exersize is the optical path has been lengthend again by about +/-10mm, helping to bring the supplied EP into focus.All that's left to do is collimate using two screws (you only need two to do this) and tighten the three locking screws.
Summary
Depending on where the collimation screws were set before, you may now have gained as much as 18mm in the optical path when the focuser is fully extended. This should be more that enought to bring the supplied QX 26mm EP into focus.
Lightbridge Focus Quick Fix x2
