All lenses have been returned from the coater.
On a causal inspection of the grating assembly, that has been in storage. I note that some "fluid" has "wicked" from a mount screw hole onto the surface, and travelled along the grooves in the grating surface. It is 3 to 4 mm wide, and travels the whole length of the groove. The cause must have been that one of the tapped holes, still had some mechanical fluid, or cleaning fluid trapped in it.
All optics and mechanical cells assembled.
The collimator went well, and has been tested in simple auto-collimation with a flat mirror, with a simple Ronchi test. This visual test indicates the collimator assembly is very good. The two cameras units proved to be more difficult in assembly (new cushion rings required). Some small mechanical assemblies then need to be completed on shutter units etc.
Then I will be able to test thru the whole system. I plan to evaluate the image quality at the cameras with a eyepiece/microscope, using the focal plane screen as a target.
Grating washed and cleaned.
The Cameras are finally fully assembled. An
optical test shows that all is good.
The material for the cryostat adapters arrived yesterday, and we have just started machining. We have finished the spacer for the new filter and Gabe will install the filter in its cell today.
All the other modules have been installed and aligned, and the three modules will be screwed together today.
we have the PNS system assembled, with images at the camera, from the focal plane mask pattern.
The O III filter was assembled in its cell, with a new thickness spacer. The angle setting plate was tested, to confirm its operation. All performed very well.
Image tests have been done on the assembled system. With gratings in place, and the filter, camera images have been studied with an travelling eyepiece, and a matched microscope. The source was the collimator focal plane mask, illuminated with a bright source and several diffusers. The images look very good.
Image tests also carried out with a plane mirror in place of the grating. This mirror (150 mm diameter) is slightly larger than nominal pupil size, and feeds one camera at a time. Images studied with eyepiece and microscope again. Again we report that the undispersed images look very good.
Currently we are constructing a mount to adapt to the dewar mounting plate, to locate the camera axis. This plate will be used hold the "eyepiece/microscope" on axis. This will be used to confirm that grating mount angles are correct etc, and that the center image of the mask is on the camera axis.
When this is complete, and alignment is confirmred, John Hart will contact Nigel Douglas to enquire what other testing is required. ie if attempts will be made here at MSO to mount a detector on the cameras etc.
There are some "small works" still to be done on the PNS, probably at the next dissassembly.
1. Paint black the ground flat annulus of the small negative lens in the collimator (CL1) (second element from the focal plane mask). The mount flange does not cover this ground flat, and stray light is visible around the ground edge.
2. White fill the angle alignment setting
mark on the filter cell.
3. Drill and ream the alignment pin holes on the
"grating mount plate" to the body. These are the only known "things to do"
left at this time.
Note:
1. If the other two filters are different thickness, then new spacers will be required. There is only one filter cell holder. The thickness needs to be correct to ensure that the "wire" ring holds the filter securely. Changing from one filter to another will be a very delicate operation. The process is not easy or quick.
2. On testing with the gratings in place, and observing the images with the eyepiece, stray light is clearly visible. This comes from one camera seeing out the other camera, via the other grating in what appears to be zero order. Remember that in this test setup, the other camera is un-covered by an enclosed detector package etc, but has its own eyepiece freemounted in space. It does not appear to be in the "target field", but how far it is "off axis" is yet to be measured. This will be followed up later.
3.The concave grating arrangement. There is some small stray light coming from the junction of the two gratings. It is seen in the eyepiece, but again it is off axis to some (as yet unmeasured) extent. It appears to come from the edge of the grating that is not covered by the ruling replication. If this appears to be a problem after further investigation, a strip mask may be required along the junction edge to block this.