dannybgoode

The full clean, collimate and test is £100. RVO have a full clean room now so saves sending it away for a test

As you are a Mac user do you have a separate monitor. If you have get a Mac Mini M1 and that will be massively faster than what you have now and is a cost effective upgrade (as these things go). I prefer to work locally so this would be my route to faster processing

It's not terrible stuff in mine however it's far from the best and it's very gloomy and sticky. Will report back on any improvements

Wasn't it down to a mis-calibrated measuring tool? Think the thing they used to measure the curve was reading wrong. Luckily it was very accurately and consistently reading wrong hence it was the most accurate mistake ever manufactured! A smoothness of 10nm over 2.4m is impressive! And of course the blanks for both the PerkinElmer and Kodak blanks were produced by Corning. Nearly everyone who has ever owned a modern mobile phone will have stroked and fondled Corning glass

This is precisely what happened with Hubble's mirror. There is a misconception that the mirror was badly ground somehow when in fact it was essentially as perfectly smooth as they could make it given the constraints of the technology but was the wrong curve. Indeed it was because it was so perfectly wrong (it that makes sense!) that they could make the corrector lens.

Nice. Yes I saw the For Sale post for yours and it is an original Thomas Back CNC also with the outrageously engineered focuser. Lovely thing to use Mine isn’t going anywhere!

A pair would be very nice. You could set them up as the most outrageous pair of binoculars going Aye, getting the full Zygo test and a clean and collimate has been well worth it. Just need some clear nights now...

Mine is the early Thomas Back CNC one and they weigh a fair bit more than later ones, mainly due to a focuser that would survive a nuclear blast.

I found this on that very subject from Thomas himself: --- Strehl ratio is defined as the illumination at the center of the Airy disk for an aberrated system expressed as a fraction of the corresponding illumination for a perfect system (i.e., 1.00). It is not calculated by P-V, but by the RMS value. As my friend Valery Deryuzhin of ARIES INSTRUMENTS Co. is fond of saying, if a drop of dew forms on your lens, what is the P-V of the systems now? And would you see any performance difference? No, because very small localized errors have no affect on overall performance. As we sample a few thousand discrete points over 100% of the aperture, in a three element, six surface lens, the P-V measures relatively low as compared to smaller sampling or knife edge tests. It is the RMS wavefront measurement that really defines the quality of the optic, and thus the Strehl ratio. As{*filter*} Suiter says, an optic with a Strehl ratio of .88 to 1.0 is "excellent to perfect." Zeiss' standard for its highly regarded APQ triplet apo objectives were .95 or better. We agree, and a lens with a Strehl of .972 is certainly a planetary lens. Thomas Back TMB Optical ---

Nice. I'd want one with an LZOZ cell though. Although in any event my buying the 105/650 nearly led to divorce. A purchase like that would seal the deal 🤣

I have one of my dream scopes in my TMB 105/650 LZOZ. A bit like @John a good part of my interest in this scope is the background and mine is a Thomas Back built one as opposed to a later APM one and I enjoy the history that goes with that. Plus it's just a joy to look through and use. That huge, massively over-engineered focuser, enormous CNC rings, the choice of Kruppax for the tube and of course that LZOZ objective can. A commercial failure because nothing but the best would do. A total no compromise approach. The only downside to it is weight. Nearly 10kg for a 105/650! Until I got this scope though a frac had been of limited appeal but now I can't see me spending serious money on anything else and a 130 Tak of some description or a longer 4" is highly tempting. Of course if a 130 TMB came up... Maybe a Mewlon as well if I were going to have something spendy with a mirror.

The focal length of the scope divided by the focal length of the eyepiece. So a 650mm FL scope with a 10mm eyepiece will give you a 65x magnification. The max theoretical magnification of the scope as a whole is 2x the aperture in mm - so a scope with a 105mm aperture will have a theoretical maximum magnification of 210. In reality this figure may be lower or in some case much higher though.

Couldn't watch. This is was all done in their clean room. They just took some pics to share

@Space Hopper - in the meantime have some outright objective porn. This is my scope on the testbench...

I will always indulge in pictures :). Will get it out and take some snaps. I am not far from Hillsborough football ground in Sheffield with a patio facing a row of houses, each with huge security lights etc so as well as just the general city light I also have localised light pollution also. Still, I get some images and now the scope is back to its best, I have finally fully completed everything I need to get things set up quickly each time etc I am hoping to do more work.

Absolutely however as I don't have the original report I was keen to have one just for interest really. Given my Bortle 100000000000 skies and pretty much permanent cloud cover the figures are indeed meaningless ! Plus it got cleaned and collimated also and the objective is now looking really good. @John Specifically the red generated by a helium-neon laser (I looked that up BTW, I am no laser expert).

@John - RVO test at 632.8nm ...

I don't but will ask the guys...

The guys thought it looked good for sure. Just that little peak right at the very edge ruining the P-V . I never had the original certificate and Markus couldn't track it down for my cell so now RVO have the Zygo thought I may as well see what the numbers are :). Could the test rigs be a little more accurate these days than when the optics were first tested perhaps?

Very nice. Am finally getting round to having my 105/650 all ready for some proper imaging. I have had a bit of a play but for one reason or another not spent serious time with it yet which is criminal really...

Thought this may be of interest to some. Took my scope into the fine chaps at Rother Valley Optics the other day just for them to give it a quick once over as I've been paranoid about lens fungus. They assured me it was fine which was great news and since I was there I left it to make use of their Zygo test service as well as I was interested to see how it measures. This is an original Thomas Back built scope and is my baby and I am ultra paranoid about anything happening to her! And here is the report - looks a really nice optic :). They also gave the cell a good clean and then recollimated it as well. Overall a first class service and well worth the money And of course my scope is now ready for me to get down and actually start doing some imaging and observing....

First snag hit. Yes the RA locking nut is a pig. I have found this though - looks the right size so ordered. When I reassemble I will not quite tighten it as much and then bent nose pliers should do the trick but it ain't shifting with a locknut tool. Sealey SMC22 Motorcycle Swingarm Lock Nut Socket 4-Pin 50mm | McCormick Tools

The ones that are pretty firmly embedded in the actual casing,,,

Ha - I am not. I suspect with the right tool it would be fairly straightforward but then of course there is getting them back in again as well. May well need a bearing press to do that...

Not yet! You just need the right tool or to be able to at least fudge the right tool. I’ll have a rummage later for something to use. The grease doesn’t come until Friday so taking my time with this one