Chriske

The only visible thing we still buy here is wood. Buying a sheet of plywood, 95% we buy is still 1220x2440 mm, that is 8'x4' if I'm not mistaken. Meaning, at a bigger scale lots of wood is lost because nobody works with Imperial sizes at this side of the channel...😁

I think the older guys here must be masters in using fractions. When I was younger, even using metric units, I often would grab the wrong wrench for a certain hex-bolt I needed to fasten. After 'a few' years now I know what wrench to grab for any bolt. Let's say you're working on a project assembled using Imperial hex bolts, different sizes. How do you know what wrench to grab when you took the wrong one in the first place. Another thing, I do have a well equipped workshop. Among the many tools I have, also many drills. The smallest drill is 0.1mm. It goes up by 0.1mm per step, ending at 10mm. After that it continues to go up with 0.5mm per drill. An example drill 5.0mm, next 5.1mm, next 5.2mm, next 5.3.....until 5.9, next 6.0....etc... How do you(did you?) name these set of drills if it were imperial sizes only differ 0.1mm(equivalent)....? I know you have that numerical system, but I'm talking before that system was used. When I was at school we had to learn all about Imperial, The smallest we could measure with our calliper at the time was 1/128". There were even questions during exam about it....😡. At the time we all hated you....🤭 To be clear that was looooong before digital callipers existed.!

Waiting for the scaffold(next week), I'm busy making/finishing the last smaller parts for HST now. - Painting frontcover - Printing ESA logo(almost forgot) - Making a few small counterweights to have HST perfectly balanced. In the future I'm planning to add a small motor to have HST very slowly rotating around a vertical axis. That's why the counterweights. - Finding names to glue on the astronauts arm-patches.

You need to make or buy a secondary far beyond that quality if you stop at 1/4, or you indeed will end up with a light bucket. I'd go for at least 1/8.

yep. To overcome this I use bubble-wrap or a soft carpet under the mirror(flat back) while working on my M-o-M.

Yep, and if I'm not mistaken they're mentioned in the original post higher up. (The picture)

Just kidding...😁

Oh...! Nooooo.....! PINK...!!😳

Following the building instructions from Dave Trott I drew this very basic version. It is basically nothing more then three parts(in the drawing) Hinges are not included in the drawing. But the constraints(to simulate these hinges) are in place. The driven part is the brown one, the bleu surface is where the camera(s) go. Pushing the brown part upward, the blue part has to go with it. Notice that both moving parts do not have the same speed. The difference is very little. But just enough to correct the error that is produced by a 'single arm Barndoor tracker'. In fact the error is no more then 1 arc second (max) during a one hour tracking session, according to this list. After two hours tracking the error gets smaller again. Fully opened the angle between the two moving parts is a little bit wider. Not much but apparently just enough to eliminate tracking errors completely.

How did you guess...😁

Hey thanks for replying so quickly ..! I'm planing to build a type 4, I found a PDF and need to recalculate the distances and speed of the threaded rod. Not planning to build it this way, I'll be printing lots of parts(of course..😁), only a larger version. Point is, looking at the drawing, How do I recalculate distances r, b and c when I want to make it twice as large. heavy-duty-double-arm-barndoor-building-plans.pdf

I'd like to make a type 4 barn-door tracker, only I want it to be a bit larger. How do I proceed, can I simply enlarge all the figures linearly, lets say size x2. And also speed x2..?

We use float and never wait to measure mirrors on the optical bench. How..? We always rinse with water at ambient temp and dry immediately afterward..

As a matter of fact, you've re-invented a fork mount...😉

Could explain this a bit more in an assembly drawing please, not sure I understand, sorry...

I might have come up with a completely 'new' EQ-platform, First need to do some more brainstorming...🤔

Waiting to be finished and installed.

Mind-boggling isn't it..😳 In this case I made the astronaut juuuust a little bit taller, my size actually...😁 Forgot to blacken the inside of HST, sorry...

These rods, I suppose there for strengthening/stabilizing the tube, 4 of them have been added. They run under the grips Also a secondary secondary mirror holder. As a telescopebuilder I (of course...😁) added 4 collimation screws. Wonder if somebody will notice.

Today a few last/minor parts to be mounted on HST before it is 'shipped' to Urania(local observatory) tomorrow. It'll not be hung tomorrow. Scaffold will be delivered only in a fortnight. So meanwhile it'll be parked there on the floor. If I had the room to store it, I'd rather keep it here. But now it's hanging in my van, and I need my van from time to time...😁 I hope all goes well during transport...fingers crossed..!

Nope... Facebook, not for me either, and I don't even sorry for it...😬

I know ...😟

Did exactly the same 35(or so) years ago. In my case I glued the 'sandwich' together with silicone. Resulting in very weird star patterns. That scope was nothing more then a 'light bucket'. Using very low magn. it was doable, but high magnification revealed the true problem. Six fat spikes were visible, and no, not spider diffraction. I had glued 6 thick glass-blocks between two 19mm thick sheets of glass. Strangely enough after a few our the image got better. One of my earlier experiments...😏

One minor issue about our HST project is that I had to built it all on my own. It was suppose to be a two man job. Michel and I did lots of planning, research, lots of drawing together. In the past he never drew, after a CAD-crash-course he's now drawing like the best... Planning to gather, building that thing in my workshop, and then 'C19' comes along and 'kept us all at home'...😳 Pity... dam...!😡

Looking good Marcopolo... You still need to test that focusing knob using gloves...😉 And now you can start thinking on drawing V2 : adding a dual speed focusing knob to the unit...😁