Modular Altitude Azimuth Telescope Mount

I have a really good supply of known good quality casting alloy. I work at a company developing pumps, and the housings are 0.5" thick 15lb virgin A356 castings. After a couple of prototypes and revisions we have accumulated a bunch of NFG housings.

A casters paradise.

 

I use only car wheels. Should be close to A356. It is still always a little gummy and coarse when I machine it.
Robert

 

I made a temporary bracket to adapt the 1/4-20 thread on my so-so spotting scope to the mount. I also added an aluminum handle for now, until I work out the fine motion controls.


I took it out last night to look at the crescent moon. The mount does have a little sticktion when looking through the scope, It's difficult to make smooth adjustments smaller than 1/5 moon diameter (0.1°). Other than that the mount is solid, tapping on the mount has little effect on the image. The spotting scope on the other hand uses a flimsy cantilevered plastic foot for mounting so it was shaky non the less.

I used a digi-scoping bracket to take a picture with my phone.


Not great, chromatic aberration aside. Touching the phone to trigger also shakes the scope. I need to find a timed burst feature, or someone needs to come up with a clap-on trigger app using the phones microphone, that would be nice.

I bought a 127mm Maksutov cassegrain from the astro-frourm's classifieds, so I just need to make a telescope clamp before it arrives and that should at least remedy the shaky scope interface.

Any way, I think I will play around with surface preparations to try and reduce the stick slip. Because of the geometry of the groove I'm pretty much stuck with the special bearing material I am using.

I have some self adhesive HDPE I can play with, but I might roll that into a rev2. I plan to redesign using easier to acquire materials and components and hopefully open source the design.


-Corey

 

Good to know.
Thanks!

 

If you had a samsung, you can say "SHOOT" to it and it takes the photo. FWIW, the S8 camera blows away the iphone... Not sure about the new iphone. I forgot about the remote switches on selfie sticks. Thats a good idea.

But that is a pretty damn nice photo of the moon considering you did it with a PHONE!

 

The biggest improvement I have seen is with solutional heat treating and artificial aging, trying to achieve T6. I made a thread on that years ago. I age all my castings before machining. I did not see where Corey did any aging or heat treatment yet the machined surface looks great, at least in these pics.
Robert

 

I am not claiming to have gotten perfect T6 temper. I do not have a salt bath. I used an electric furnace to hold a casting at about 900-950 deg and then artificially aged it. I forget the exact temps and times. Bottom line was that it significantly improved machining compared to controls of the same alloy that were either untreated or just artificially aged.
And I agree that extrusion will machine better, but as you say we are talking about relative improvement. They guy on AA who cast the motorcycle cylinders heat treated them in an electric oven with good results.
Robert

 

I don't want to hijack this thread further. If you are saying that if one does not achieve a perfect T6 temper there is no improvement in machineability I would dispute that. I have no doubt the setup you describe would produce excellent results and I would love to see you pursue it.
This guy did oven treating and thought it was beneficial as well:
http://www.alloyavenue.com/vb/showthread.php?11802-Air-cooled-2-cycle-motorcycle-racing-cylinder.

Robert

 

This is very interesting. Your post made me research telescope building. I have been reading about it all week. You've got me tossing around the notion that it would be interesting to make a telescope in the future. Hopefully a 22 incher so I can see some good views but I'd want to take photos through it so I'd need to figure out the tracking part of it.

The mirror aluminizing process is interesting.

 

There is a great full length telescope making documentary on YouTube with John Dobson himself.
There is also a great ATM section on the Cloudynights forum(I have a sister thread there).

22" is a big commitment, most people dip their toes in with a 6-8" mirror grinding kit. It is always recommended to try and find and join a local club if you can. Most clubs will offer mirror grinding classes with a guru, and you'll get to meet a lot of knowledgeable people, and look through a lot of different types and sizes of scopes.


Check out "equatorial platforms" for getting a larger dob to track for basic imaging.

 

Will do thanks. Already watched that documentary, it was good. A lot of good advice in there, except of course, where to buy the glass blanks from...

I figure if I'm going to spend hundreds of bucks of supplies and many hours of elbow grease grinding a mirror by hand it might as well be a big assed one that I won't want to upgrade again. I've found that you can pretty much get any project done right if you spend enough time doing it. Most of my projects take the better part of a year or more to finish so the time it takes to do doesn't matter that much to me.

Still need to look into where to get the mirror aluminized since I don't know if I want t build the apparatus and go through all the testing and mistakes I am sure there are in getting a good finish.

Also need to figure out if I want to do this project at all, especially since I'm most interested in the photography aspect of it rather than the viewing part of it. The tracking gear probably isn't something I can DIY myself since I'm sure there are electronics involved.

 

If imaging is you main interest, most experienced astrophotographers on the forums and Reddit recommend stating with something small. Most recommend a 80-100mm refactor, on a heavy duty computerized German equatorial mount. When you are imaging aperture does not really matter since the camera integrates light over time. What does matter is the focal length of the telescope, the bigger it is the more magnification it will have, and the more shaky the view will be, so the mount has to be over designed, which gets expensive fast. Most people recommend starting with less than 600mm focal length.

Take your time and read up. Astrophotography is very tricky, some people that startinto it get fed up and leave the hobby; occasionally you will see whole setups for sale on the used market.

It is always recommended to start visually and learn the sky first, before adding the complexity of imaging. Binoculars and a free skymaps.com chart are a great way to start, that's how I started.

 

Some food for thought Zap, I am heading in this direction with a solid concrete mount in the back yard a long term plan...

https://makezine.com/2015/09/11/star-trackers-for-night-sky-photos/

 

I received the 127mm Mak. It seems like a nice solid scope.

It has 1/4-20 threaded holes in it's dovetail, so I temporarily mounted it to the same Jerry rigged spotting scope bracket just to test out the optics. I think the size and proportions look good on the mount, 5 inch aperture on 5 inch friction discs.




Tested it out on the moon for comparison against the spotting scope; no comparison. (Using the same digiscoping phone bracket)





Because of its longer focal length, I can push the magnification much higher.

This morning, for the first time ever, I was able to pack a small telescope in my car on my way to work and do a little observing before dawn. I got a good view of Jupiter's belts and its moons that I would not have otherwise had. I think I am going like this little scope.

As far as the motion of the mount, the extra magnification exacerbates the stiction issues. I am planing on applying UHMW-PE tape to the flat friction plate so the Rulon J rides on it instead of the aluminum. I might also try UHWM on UHWM, diferent coatings, and different textures.

In the coming weeks I am going to try and make some progress on the fine motion control. if I can get it working the stiction should have less of an impact.