Ok so what mirrors are you using for that telescope?
My kid would be all over this! She just has a cheap amazon telescope right now! I see several pair mentioned.
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I was looking at this DIY goto scope awhile back, but a lot more cost than this one to start with.
The Micro Scope | a Miniture GOTO Telescope. : 42 Steps (with Pictures) - Instructables
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Running a raspi-cam on the telescope is great! Especially with the new hq cam. Being able to show on several screens is great - but the best feature is being able to keep the telescope steady! My telescope performs lousy when adjusting and changing the directions - while looking through the ocular. Adjusting the aim while looking on a separate screen is super convenient.
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This is 114 mm diameter and 900 mm focal length with a 25 mm secondary. Mine is from Amazon for just under $40 but I think the other sellers would be equivalent.
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This is great! Now Iām going down another rabbit hole 
. I have a Meade beginner telescope that I used a lot in college. Iāve been kicking around the idea of building a GOTO mount for it for several years. Looks like it might be doable with an OnStep controller.
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What are the practical limits for sizing?
Just for fun, I tried a 203mm / 1280FL with a 50mm secondary.
The spider isnāt a full assembly at that scaling.
I may need to try making one of these.
Hmm yep it looks like a ābugā where I hadnāt considered that as a combination. In particular such a large secondary. Fundamentally there should be no limit as long as the focal ratio isnāt super short. Give me a minute and I can fix it.
Ok, I think I fixed it.
Since itās in the middle of judging, Iām reluctant to change the files on Printables, but I made the change on github. Iāll update Printables once the judging is finished.
Note that the 203 mm / 1280 mm focal ratio should probably be using a parabolic mirror and not a spherical one. My understanding is encoded in this chart for which sizes can achieve ideal sharpness with a spherical mirror:
Also note that you will need a printer that is at least 31 mm larger than your primary mirror, so for a 203 mm primary mirror a 220 mm print bed is not sufficient.
Thank you! Iāll grab this off of gitub and look at it some more.
The Taz can do 300x270, and while Iām waiting to build the next repeat I have refurbed a rigidbot big, which can do 300x400.
I also typoād the FL of the mirror set Iām considering, which is 1820, not 1280. Still on the short end but might be workable.
I changed the spar_w setting on the spider in core_parts.scad to be double as it looks fairly flimsy when at the resulting 228mm tube outside diameter.
I set it to:
spar_w = 1.6;
Iāll try printing one of the resulting spiders and see if it looks workable.
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Jamie, change them now on Printables - if they havenāt checked yours out then it will be correct when they do - AND make a note of the change in the text!
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Iāve just checked out the results and sorry you didnāt get a shout out, particularly since the winner was ā¦
a Telescope! 
Could you let us know out of curiosity, the differences between that one and yours? Iām not saying āyou were robbedā or anything like that. (I donāt know), but Iād just like to know a bit more about that one (which looks to be more complicated) compared to yours.
Thanks
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I have mixed feelings and I learned a lot personally from the results of the contest, which is a subject for another day.
The other telescope is what motivated me to submit one of my own. I had a design with an 80 mm mirror that I had made a few years ago but there was a lot wrong with it, so I wanted to redo it basically from the beginning.
Both should be easy enough to build. I believe mine is very easy to source the parts and build, but from the looks of it, the other one is by no means difficult.
The optical quality should be about equally good since the mirrors are what provide the clarity. I think mine should be better for daytime terrestrial viewing because the tube blocks out stray light from the environment, but they would be equally good for astronomy at night if your surroundings are dark.
On mine, the arms for the spider have a very thin cross section and they are large in the axial direction, whereas the other one has slightly fatter arms. This might make a difference in the amount of diffraction but I have not tried to measure it.
My design does not have a good mount. A camera tripod is really awful unless you have a large field of view (large image sensor or long eyepiece) and you are aiming for something huge like the moon. For higher power observing you need a Dobsonian mount or fancy equatorial. I have a sorta half-ass solution for that. Iām not sure about the mount for the other telescope. That is an area where some complexity and non-printable parts are probably necessary. The mount is very important and with my design you would be mostly on your own to develop or adapt something. I think maybe a structure made from conduit and 3d printed joints could be a good solution for those without woodworking tools.
Another big difference area is the focus mechanism and the means for adding eyepieces or other viewing mechanisms like cameras. I donāt fully understand how the threaded mount on the other telescope accommodates anything other than 1.25" eyepieces but it looks like it does have a focus mechanism.
My design offers only a 1.25" boss and then you can mount different viewing accessories to that. One of the accessories is an eyepiece holder but it doesnāt have a fine focus adjustment. I think I could adapt the threaded mount from the other design to fit onto mine, and then my telescope can benefit from the focus adjustment and any other viewing mechanism that is created for the other telescope.
From a user perspective those are the things that are most significant.
Mounting a digital SLR with a large sensor was a priority for me because there will be a total solar eclipse in Dallas in a couple years. Most things you can take your time and stitch pictures together, but for an eclipse you need to get the whole thing in the field of view at once, so you need a big sensor.
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Your design is Parametric as well, with source scripts shared. Thatās pretty neat, and probably underappreciated by most folks that stumble onto the Printables model.
Fwiw, I nudged/nagged Dr D Floās channel, his huge printer would be awesome to make this project, providing he can source large mirror/lens I guess.
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I really like this design. I wasnāt sure what provisions there are for collimation, as the AWB onesky that I have has three screws on the mirror for that purpose.
The fact that this design- like so much of your stuff- is parametric and open source is really awesome.
Maybe when I get around to making one, I can work on some of the things that would be interesting to me- a better mount as you describe, provisions for mounting a guidescope, and the collimation mentioned above.
Really awesome work, Jamie!
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On my design the rings that clamp onto the back and the front, for the primary and secondary, can be partially tightened and then nudged to adjust the alignment of the mirrors, so no extra mechanism is needed. It is possible to use screws to do the nudging; there is a provision for three screw holes for that and I did try it, but I found it easier to just do it by hand with a little tappy-tap-tap.
A more traditional design uses rigid mounts and then an additional mechanism for alignment is necessary. As a wise person once said, the best part is no part.
There are several design aspects that I am very happy with, and being parametric is one of them, but not all of them are necessarily meaningful to the average end user. There is an aesthetic aspect to a minimal alignment design for example, which I am pleased with, but the traditional alignment method is still doable and to the end user itās not that big a benefit. Parametric almost becomes a downside because OpenSCAD is an extra barrier for a certain percentage of potential users.
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Thanks for the detailed reply. I hope you are not too permanently disappointed! Competitions donāt always have my preferred results, and I am always mystified as to what the judges missed about my perfect entry. 
I will come back and try to get my head around those little things in the future. I have an old camera tripod and access to others which I hope will work.
I have this on my list of things to do some time in the way distant future - Iām quite invested in photography so see this as āanother lensā with a lot of interesting potential.
Iām not sure - it is a barrier for me but I think I could make it work if I really had to - or if I had to make a change I would contact the designer and ask for a different file.
Having said that I have lots of parametric models (in Onshape, which needs a free account) and most people seem to simply scale them in their slicers, which is not giving the result I intended, but they seem happy enough.
Another contestā¦
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All the best!
I must admit Iām missing that part of my āhomeā life while Iām away - solving problems I didnāt know I had!
The current contest is āMechanical Marvelsā @vicious1 - why havenāt you entered the LR3 yet?
Serously, thereās nothing there so far thatās remotely as inspiring!
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