Posts Made By: Thomas Dey

Hi, Rolando. Impressive! Wonderful performance and great data reduction and reporting format. We had done some satellite characterizations that required rock-solid stability (absolute) for months and years. Our test-set had to fit on a 5x10 Newport table, collect data continuously and be able to self-recover from hiccoughs, without blowing the initial set points. Required drift-limit of the test article(s) was 0.1 arc-sec. Our test set had a noise floor of a few mili-arc-sec, (long term!)... fine for the job. Anyway, I'm STILL trying to strobe the Crab Pulsar! Your Fourier Analysis (Especially the Power Spectrum) is what I will use to try to sift the Crab's rotational rate from the anticipated gross noise. Your drive characterizations have the same feel. Like the Neutron Star is a giant gear as big as a big city... spinning at around 30 Hz! Tom

There's are other ways to assess a seller on high $$$ items: Just Talk to him on the phone. If he readily knows obtuse things about the item and astronomy, that is a +++. Does his phone # ID when he calls you? Does his house appear on Google Maps, with his name on the Tax Roles? Now-a-days ALL that stuff is easy to access. Sometimes great deals on big items are family selling off assets of the astronomer ~RIP~ Tom, still kickin' Tom

I sold my 29-inch for $6K, but I built it myself, although it had mostly Astrosystems parts and fresh, enhanced coatings. I also included a brand new $2500 enclosed 6x12 trailer for half-price. You might want to advertise high and reduce the price until it sells? Tom

Interesting conversation! I grew up before and through the ~Dobsonian Revolution~, my Newtonian visual scopes progression: 3" f/10, 4.25" f/10, 6" f/12.5, 6" f/6.1, 12" f/6, 13.1" f/4.5, 17.5" f/4.5, 29" f/4.5 and now 36" f/3.75 [yeah, the dreaded, love/hate Aperture Fever Syndrome]. One VERY significant additional pleasure-affective parametric, that improves with faster scopes, rarely in the conversation, is AVAILABLE VISUAL FIELD: The driving boundary condition for that is the now-standard/ubiquitous two-inch focuser, and, hence nearly ALL ~premium~ eyepieces limited to about 90% of that 2-inches aka 46mm [allowing 0.1 in around the edge for housing and vignetting!] Evidence the TeleVue published Field Stop sizes > 55 Plossl has 46mm, 41 Panoptic has 46mm, 31 Nagler has 42mm, 21 Ethos has 36.2mm. Of these four (increasingly sophisticated) gems, only the last two can handle the ultra-fast cones feeding them from our big/fast Dobs. The ParaCorr T2 increases the telescope's f/# (and focal length) by 15%, and, not coincidentally, has a clear aperture of 45mm. TeleVue rates its performance down to an f/3 feed (amplifying it to f/3.45). The referenced 31 Nagler, mated to a f/3 scope with ParaCorr, yields a 9.0mm exit pupil... FAR too big for anyone's eye! The referenced 21 Ethos generates a 6.1mm pupil, possibly fitting a young, healthy adult. Hmmm... All of this bloviating leads to This Conclusion: For the most ~truly available~ visual field, allowed by existing premium eyepieces and coma correctors... a middle-aged avocational astronomer should not go much below an f/4 scope. NEVERTHELESS we Can and Do use "too long EFL" eyepieces. I tried the 31mm Nagler on my 29-inch, f/4.5 Dob, to ~see more of~ the Andromeda Galaxy. This gave a 6.9mm pupil, significantly over-filling my 70-year-old eye. BUT, the view was wonderful! My eye was clipping the scope down to 25 inches. I hope this stuff makes sense, I tend to get quantitative... retired scientist, can't help myself... PS I measured the axial throughput of the ParaCorr: red 96.4%, green 94.7%, blue 92.5%. ~Fin~ Tom

Nice. Looks like the format is long and skinny... and OLD! Only one precision micrometer knob. Maybe it was used to measure spectra?! Cool! Tom

I like it! There's no one right way, ~processing~ just determines what is brought out. Nearly all chips comprise "antiblooming" now-a-days AKA suppress electrons overflowing downstream by about 1000x. Before that, most bright stars turned into long streaks! And we lived with it... Tom

Hint #1: The fringes were intended to be quadratic frequency with radius, ref phase zero at the center dot. Tom

Hint #2: If the radial fringe density goes as 1/r, what is the shape of the surface?

More pictures; the 36 surrogate is coming great! This shows it all assembled, cept for the 1/4-inch round plate glass "bathroom" mirror faceplate, which is being made now. I have just come in from disassembling it and sanding all the parts for stain and seal next. Notice that there are four stems inside to ballast with barbell weights to achieve 130 lb and CG same place as the real mirror. I will make a crate this week and send the entire thing out to support building of the scope. Tom

Nother picture. BTW this is a corner of my home shop, upstairs in the barn, nice 20x30 ft area where I make stuff. Tom