Jones-Bird 2014 overhaul

Cleaning

Spider assembly

The alignment of the spider assembly is the most critical adjustment for achieving perfect optical performance from this scope. The reason behind this is the spider assembly is responsible for positioning the correction optics and diagonal parallel and centered in the principle ray coming from the primary mirror. The correction optics consists of two, air spaced lens elements. These elements are critical in correcting the spherical mirror, color correction and amplification of the final image. When the axial alignment is off, the resulting image in this REFLECTING telescope appears the same as the poor image seen in an air spaced doublet refractor that is axially misaligned. While this misalignment is not as visible or detrimental  in long focus refractors, the error is amplified many times due to the optical arrangement in this design. Put simply, the slightest error in axial alignment creates major aberrations in the final image. Bills' refurbishment has gone a long way into restoring the ease of realignment of the spider.

The spider assembly is retained by four hex head screws and four corresponding nuts. No disassembly of the spider vanes should be needed. The bolts serve to allow positioning adjustments of the spider in longitudinal and axial positions. Once aligned the inside nuts are used to lockdown the spider in the aligned position. 

Until a more thorough alignment procedure can be written, the following guidance will have to suffice:

• 1. Focuser alignment (A focuser alignment procedure will be need. That will go here)

  2. Spider alignment

  3. Loosen the locknuts and run then towards the diagonal assembly.

  4. The hex head screws should be finger tight and just firm in tension.

  5. Insert a laser collimator into the focuser and observe the position of the beam at the primary end of the scope. The beam should be centered in the hole in the mirror on the plate behind the mirror. Of note are the three holes in the plate. The laser spot should be centered between these three holes. The spot can be moved by gently but firmly adjusting the mirror vanes forwards or backwards. This can be done in a "push-pull" motion one vane at a time. This consists of placing one hand on the primary side of a vane at the tube body and the other hand on the outside of the vane. Firmly grasp the vane with both hands and use very slight differential pressure of thumbs and fingers to move the vane forwards or backwards. When the spot is centered, the retainer screws on each vane should be fairly well centered in their slots. Lock the spider in by tightening the lockdown screws.

  6. Diagonal alignment

  7. Loosen but do NOT remove the three capscrews at the aperture end of the diagonal assembly.

  8. Rotating the plate rotates the diagonal. Center the diagonal normally within the focuser tube.

  9. Mirror collimation

  10. Primary mirror collimation is achieved by adjusting three large socket head cap screws behind the mirror cell mounting plate. They are visible through one of the ventilation holes in the mounting plate. These screws behave in the same manner as a normal reflecting telescope mirror cell. WARNING: When reassembled, these crews were adjusted to their midpoint range. If the focuser and spider have been adjusted properly then no more than 3/5 of a turn to these screws will be needed to achieve perfect collimation. Do not make more than one turn in collimation adjustment. If you need to go more than one turn, return to the original position and determine what is causing so much adjustment needs. There is no stop to these screws so it is possible for them to drop out of the cell if adjusted to far out. If this happens then full disassembly of the mirror cell will be required.

Mirror cell and holder

Reinstalled, July 2014