Chriske

Collimation of the primary mirror is a classic push-pull system. Secondary mirror is a completely other system. There was not enough room for a push-pull so came up with something completely different. I've actually used the classical push-pull principal, but in completely different way. This is the scope with it's top cover on. Top cover removed and the scope tilted to see inside the collimation part. All collimation holes, side by side. Seen from the other side. The red parts is mounted in the big telescope unit and rotates in only one direction. It is secured with one push-pull set of bolts In the lower right drawing you see two parts. At the far right in the 'assembly2 drawing' you'll see somewhat smaller hole. That hole allows the blue part to rotate just a little bit. The rotation in the drawing is strongly exaggerated of course. The rotation of that blue part is done with the two push-pull bolts at the far left. That central hole there has noting to do with that last collimation. For that last collimation I only needed one set of push-pull now that I come to think of it. The difference between the classical collimation system is that I tune in only 2 directions instead of three. And again I could remove on set of holes in the blue part.

As a matter of fact, many years ago it used to be standard procedure during telescopemaking course at our local club. There are many things to consider using flexed mirrors. The procedure has to be performed ab-so-lu-te-ly perfect. There no room for error. After a while we abandoned the procedure because some course members were to sloppy during the gluing procedure. But there's a reason why you should not do this. When a flexed mirror need a new coating, all companies will refuse that mirror. Reason : they will not put your mirror with a neoprene disk glued on it's back in their coater.

Made a small telescope for our youngsters. At the moment it's only a 'paper version', Just started printing the parts. It is a 75mm f/20, So basically to watch the Moon and maybe a few planets. The pole is 25mm thick aluminium. Main issue was to make this little thing as cheap as possible. The mirror I made for this scope was a 250mm f/6 spherical. After final polishing I used a 75mm diamond coring bit to drill out 7 smaller mirrors. I chose this f/value because it has a rather good spotdiagram. The central spot fits exactly in the airydisk(somewhat smaller in fact, not absolutely perfect), but good enough imo. The focuser is of own design. There's no focusing knob. Focusing will be done by pushing the eyepiece barrel very slowly up or down. While moving up or down I need to rotate that barrel very slowly to have a smooth action. I did something similar in the past and it works very well. To tune the scope the very first time you need to lay the scope on a flat surface. All three parts do have a plane at the side. Pushing the scope firmly to the flat surface you need to fasten these three parts(mirror holder, bearing part and the focusing unit) to the main pole. Next you need to collimate the optics. This is the plane at the primary mirror holder. Focusing unit and secondary mirror combined in one part. To hold the eyepiece barrel in place there's a spring involved Focusing unit, friction between the unit and focusing barrel should hold the eyepiece in place. Cost to print this focuser : 0.36€ Scope seen from the business end ...

Shortly I'll start posting about two projects..

Next project has just started...😉

let's try again...

??

As JamesF already said, under a cover it gets rather hot. But in the open and backing sun white PLA will do the job. I have lost of stuff printed in white PLA, and for many years now there's no degradation at all. And no, these parts are not in the shade at all. most of them are even all day long in the backing sun...! Once more I'll post a few pictures of a test I performed years ago. Tested PLA, ABS, nGen. Put it even during a heatwave all year long in the sun with a load of one kg. Started in March (if I'm not mistaken) These 6" rings are hollow. The perimeters are just 0.8(!)mm thick. Started with 0.5kg a few weeks later I filled the bottles so now 1kg. midsummer ...and a few months later... And the winner is white PLA. As you can see it is also a bit deformed. But after it was released from its load it (almost) got back to its original shape. The others did not. Needles to say, what if I had used white ABS or nGen...? Who would have won.....?? Point is I wanted to test white PLA in the sun.

I was curious so put it on a scale, result : 11.5kg, optics not included yet. And another thing, the alt bearings run on felt, works very well.

There is a handle present somewhat hidden in the bearing unit. To reinforce that handle I inserted two threaded rods. It's not the first bino I ever made, it's my fifth. But this actually the first one I used lenses instead of mirrors. There's no reason why it will not work. And btw, a set of 20" mirrors for my next bino is almost finished, only final polishing and figuring to do..😉 This 152mm bino is not yet finished. As I said before there was not enough time. As an active member in our observatory I had too many other project running for our open door. This weekend is our open door and I want to take it along with me, even without optics, pity...😟 Next week I'll add all optics. I'll report back when 'first light' has been done.

Finished...!

In an earlier post I forgot to mention I also added dualspeed focusers. But I think most of you will already have noticed...😉

Thank you for these kind words...

Meanwhile I got company from a few friends. These two guys, Peter and Michel, are joining the 'Modelling club' at our observatory. This is what we did last weekend. LUT is now almost completely finished.

A last modification... a one hour job to transform it into a blue version.

Thanks for the kind words...😃 Nobody would ever expected to be able to make such a bino at home, for that kind of money. It all has to do with these 3D printers. I said it before there almost no limit with what you can do with these things. Best invention ever imo these 3D printers...

Nearly done. Only optics to add, but I will not have enough time to mount and tune before next weekend(our annual open door)... pity... IPD unit works perfect. Did not use linear bearings to move the two IPD parts. This time I've counted on the smooth action between PLA and polished brass rods.

I will use a boxmount(also own design) It's a bit like a barndoor mount, only much bigger and very solid. I'll add a stepper to do the tracking. The stepper's electronic is designed by my friend Henri. The mount is capable of tracking for 2 hours before I have to reset it again, but it'll do for simple stargazing. I know it's not a perfect solution, but now I have a Dob mount on top of a equatorial mount. Very easy to build and most of al very fast setup for a quick observing session. During work in our garden I installed two piers for that bino to mount on. One pier, the concrete one, is still drying and the second pier is an old tree cut of to the correct height. Each pier will contain three M16 SS threaded rods.

PID setscrews(left and right handed thread) and its holder.

Still at it, all parts printed, busy assembling. These have to hold on a bit longer, black paint still wet... This is a dummy to test all the actions before I proceeded making the final two units. These units serve as focuser and IPD adjuster at the same time. And on top of it contains the secondary(last) mirror.

Cement has the tendency to crack if it is not reinforced btw, especially used with a MoM. Cement does not withstand the high pressure I sometimes use.

I always use dental plaster to make a tiled tool.

A few years back we made 3 MoM's. Two that can handle 20" mirror and a third one capable of grinding a 10" mirror. We built the two larger machines in my workshop. They’re standing side by side and together with my best friend Marc we grinded lots of mirrors with it. That small machine we made it to install it in Marc's garage, so when he was at home he could continue working with his small MoM at home. We installed peristaltic pumps to automate these large MoM's. Every grit has it's own pump system. Feed speed of the slurry is done by electronics. The containers continuously mix the slurry to keep it homogeneous. The MoM's can be left alone for a longer time as there is a safety built in. When the containers are near empty the machines do stop automatically. The electronics part of MoM's project was made by Guy. Sadly enough he left our ATM-group. Anyway, only grit #120 was done manually because the peristaltic pumps couldn’t handle that larger grit. The reason for these two MoM's was simple. We didn’t want to spend to many hours grinding on a mirror. We started grinding early '80 and made 'a few' mirrors/telescopes. So we decided to work on more complex systems like for example a Schupmann telescope. But first we wanted to build a Stevick-Paul. A Gregorian telescope was already finished and awaits a coating session... Again, long grinding and polishing sessions are out of the question, finishing a say 10" mirror took us about 3 days. We prefer to spend more time on building/tuning the scopes itself, and obeserving of coarse. While grinding we only use 3 grits btw and do not clean in between them. Only for polishing we do clean of coarse. Sadly enough my best friend Marc passed away jan'20.(I knew the man for almost 40 years). And since then I didn’t touch the MoM's at all. Only a few weeks back now I'm thinking of restarting using my MoM. But first I need to remove that second one. That will be a very difficult task...

I have two larger MoM's in my workshop(up to 20") Most probably I would not build a MoM anymore if I'd start all over again. I would go for a fixed post grinder. Very easy to build. This site has lots of info about such fixed post grinding machines.