Chriske

From now on we will be adding parts every other day or so, depending how fast we can 'deliver'. Next a crane will be added. There was non we know but we thought it would be fun to go this way. Especially for the many children visiting our local observatory.

Hey thanks for printing...!! Cura does a rather good job with it. Far netter then the PrusaSlicer.

In such a case I print the man upside down, to avoid using support. Because of the very delicate parts(fingers) these parts break while removing the support. I add a small disk, 1mm high to secure it's head firmly to the buildplate. Afterwards I cut it off and file to smooth the helmet. While printing its head is embedded in that small disk. skirt 30x1.stl

In case someone wants to try and slice with his Slicer.... Scaled-Arbeiter_5.stl

My son has a PrusaMini and wants to print these workers I mentioned higher up in this thread. When slicing he gets a very strange result, the Prusa Slicer decapitates the figures(not all). Even after a repair in the P-Slicer itself. Slic3r does the same job perfectly. What's wrong here...?

A stalling stepper when using a barndoor tracker..? You do have serious problem. There are in fact no forces involved at all in a regular barndoor tracker. You have a mechanical problem or the current on the stepper is far to low. Or you need a bigger stepper.

Nope not at all, the 'polaraxis' is tucked away nicely between these two sheets of plywood. You need two printed parts(that's what I do) and a few angled blocks. The polaraxis is set at 51° and the (gliding) blocks at the opposite site are cut at 39°(in my case) But you living in or near London it would not differ that much from mine I suppose. Look at the drawings higher up and you'll notice a few holes in both sheets of plywood. These holes are there to allow passage to both blocks at the upper and lower sheet of plywood. This is not necessary of course. The only reason I made it this way is the challenge involved to make this EQ platform as low as possible, 65mm in my case. It is indeed a ridiculous low platform, I know, but I like a challenge from time to time..:-) If I were you I'd make it like the Boxmount I made for my Kutter Bino a few years back. Far more easy to construct. This page explains it all...

Nope there's no Decl axis involved. Just RA. But now that you mention it, maybe a good idea in case the polar axis is not correctly aligned and small corrections are needed. A second axis would be overkill imo. Just a polar-axis correction should suffice. Anyway a second axis would not correct Decl errors. Yes it would but only when observing at culmination point. But observing more East or South there's no way you can compensate for Decl errors. A device could be added at the rocker of the Dob itself...just maybe. Now that I come to think of it, how do regular-equatorial-platform users correct Decl errors while taking pictures. For years now I used this Boxmount, never had any issues with it because I exclusively used to observe visually . But now, planning to use it for astrophotography, it's a complete different problem. Sven's solution is absolutely perfect to track in RA, but what if (small)corrections are needed in Decl....? Think with us...🤔

Thanks... Another project were Sven is involved...

and now...?

A dual axis platform...? Explain please...

Launchplatform installed, spots included and first parts of the LUT. From now on every other day we will install more parts. To make things easy during assembly I installed a hinge at the bottom of the LUT. So when adding parts we tilt LUT to horizontal position and reposition afterwards. When LUT is complete we will secure it with a thick bolt to the launchplatform. The lower-frontpart of LUT is removed to make room for the tilting of LUT. When all is done that frontpart will be re-installed to make it complete again. The elevator part is not complete. Now it is 'just' 2.5m high. Meanwhile SaturnV is busy 'growing' on my printerplatforms...😃

The most important part in a tracker this accurate is the quality of the threaded rod. A standard threaded rod out of a 'normal' hardware shop is a no-go. Even with a integrated PEC system it would not be feasible imo. These threaded rods are good enough to track the stars if you don't mind the objects floating up and down constantly in the FOV. As my little lathe can't handle thread cutting I will use the threaded rods very often use in 3D printers for the Z-axis. They're available with different pitch. From 2 to 8mm if I'm not mistaken. The 2mm pitch would be the best choice. If I'd have a lathe capable of cutting threads I'd go for that option. These would be the perfect choice. My point : using 'everyday' threads in combination with Sven's software-solution would be a waste of time. Lead screw with T8 brass nut should do the job nicely.

Thanks Sven for joining in...!!!

Some tests have been performed if I recall correctly at CN forum years ago. These test were done side by side comparing two different spiders. There was no mentioning of loss of contrast at all. In our workshop we did the same test only a few years ago. During telescopemaking course exactly same telescope different spiders. No loss of contrast, Maybe there was some but not visible. To be clear all telescopes are identical. I asked course(I always do) members to switched mirrors every 10 minutes or so. They end up with exactly the same mirror/scope. So that is why we could compare these different spiders without any doubt at all.

Well first of all whether you would go for curved vanes depends. Installing classical vanes you end up with spikes in the field of view around bright stars. Diffraction you know. 4 spiders -->>four spikes in case of three spiders you end up with six spikes around stars. To get rid of these spikes you need to install curved spiders. To be completely correct. The diffraction of these curved spiders is not gone at all. It's diffraction is spread evenly all over the field of view, invisible of course. You need to bend these spiders correctly to achieve the correct result. Many curved spiders out there have the wrong curve, even commercial spiders. There's also another way to get rid of these spikes. The very old ATM-I book of Albert Ingalls also deals with this issue. He does mention a strange pattern is glued on top of the spiders. There's even a drawing of these patterns in his book. Never tried it. On the other hand many amateurs do love these spikes around bright stars, so up to you...😉

From time to time I do drink a beer, preferably a Belgian Leffe. It is a bitter/sweet beer. Anyway, I need to compensate (in my case that would be) for 875g (about 2 lbs) for both glass and bottle...😳 I was just curious....🤭

A fellow observer asked me to repair the alt-bearings of his 10" dob. The glue between the wooden bearings and Formica layers gave up after almost 40 years of intense use. I said : no, I will not repair them, I'll make you a brand new set instead. I started drawing and while at it was thinking of making these bearings multi-purpose. This is what I came up with. At the observers(eyepiece) side there are some holes in his new bearings, capable of storing 4 eyepieces. At the opposite side of his dob there's that second bearing with just one 8mm hole. Well in that hole I'll put a smooth rod + a couple of ball bearings. Hanging on these bearings, actually on top of these bearings, I will install him a platform on which he can put some refreshment, say a beer or so😋. To compensate for that beer sitting on top of that axis I'll add a counterweight at the lower side of the central axis. So where ever he's pointing his scope in the sky, ball bearings and counterweight will take care not spilling the goodies out of his glass of beer... These 250mm diameter bearings will be 3D-printed. They're 35mm thick. More images to come...

You could consider curved spiders.

I'll ask Sven whether it is do-able for a real barndoor capable of tracking one hour or even more. I mean, my Boxmount only tracks for about 20 minutes. For my goal it is more then enough as I explained higher up in this thread. So the differences in speed between centre position and highest/lowest point are very small. I suppose it will work for longer tracking, it's only a matter of extrapolating I guess.

Not yet, but I'll try it alongside with a cycloidal gearbox, that too looks promising.

Change of concept.... Because the mount has no constant speed over it's racking length I'll try another approach. The stepper will rotate very accurately at the same speed, but because the mount has a straight threaded driving rod it will not track the stars at the correct speed along the length of it's treaded rod. As a matter of fact it has the same tracking problem as the well known barn-door trackers. A friend of mine(electronics guru) said he could solve that problem. After some calculation he sent me a sketch to upload in my arduino in which he programmed the stepper's speed variations along the 20 minutes of tracking. I'm very happy with this solution. Needless to say this solution could be adapted for any 'barn-door-isch' mount.

In case it does not work, due to the heavy weight, you also could try a collapsible focuser. There's zero play and can hold a massive weight without sagging down. The only disadvantage is it's rather massiveness. But it does the job perfectly.

The list of parts and projects I've printed so far (during the 10 years I own printers) is long, very long. I can't even begin to tell how many things I've printed so far.. In my opinion every 3Dprinter owner should start learning drawing his own parts. Drawing your own parts, the possibilities are endless ....