Second Light of the Millennium Telescope
More observational notes on astronomical performance
Upper handrail for Newtonian access on the 30" fitted up yesterday afternoon (Sunday 11th); 2nd observing session followed last night between still-retreating clouds, sky-transparency very good in the clear but air churning, seeing execrable and a brisk north wind. 2" eyepieces now usable, so all these observations were made with 30mm wide-angle eyepiece, x157 magnification:
Jupiter - fuzzy, tremulous & crapulent in bad seeing, 4-5 on a 1-5 scale.
Neptune - a pale blue dot.
M2 Aquarii, a fine globular, stupendously bright and very spectacular even at this minimal magnification, a heap of diamond-dust.
Double star Zeta Aquarii well resolved at 2.1 arcsec (about = Neptune's disk) despite the very poor seeing.
Finally an eyeful of Pleiades, which almost required sunglasses (& strong hints of Tempel's nebula).
Together with last Sunday's more precarious 1st-light observations of Jupiter at x235 - 20mm focus 1.25" eyepiece, see Andrew's report - in slightly better seeing, 3-4, and at higher power, therefore a more searching test, these results would seem to settle the following important issues:
Collimation errors are not obviously visible, at least at these low powers (below 8/aperture-inch) and in this very 2nd-rate seeing. However, final fine-collimation has not even been attempted yet.
Optical/figuring, etc. errors are not visible, at least through the seeing-fluff. First signs very encouraging here but see comment above re-collimation. In particular, apart from the 30" spec. itself, this entirely vindicates our £5 ex-military optical flat as Newtonian diagonal, which saved £600 on the cost of the telescope!
Thermal distortion, etc. of main mirror in falling night-time temperatures - absolutely no sign of this so far, despite thickness of the disk.
Mechanical vibrations due to human presence on telescope - not serious, see Andrew's previous report.
Mechanical motions of telescope - vertical/altitude motion very good but there is further work to do on the horizontal/azimuth motion to eliminate pronounced unevenness of rolling friction and stiction.
All of these were major uncertainties whose real-life outcome could not be predicted before they were put to the test of practical field-trial, so all of this is very encouraging: the 30" not only will work but it actually is working. These are very early days, however, and much testing and evaluation, plus further fine-tuning and correction of any problems arising, remains to be done in the coming months. This is going to commence this evening if the weather holds, with Terry coming up from London to do some formal sky-tests on the mirror (so this will not be a general sight-seeing session); given today's soaring barometer, the seeing will almost certainly be much better than on the first two nights.
C.