This is a bit backward, as I should have posted this before the programming part, but hey ho!
This Christmas (2013), my most awesome wife surprised me with a Celestron Travelscope, a small refracting telescope mainly for lunar and planetary observations; which she may be starting to regret! I am now hooked on astronomy and want to see more and start photographing my views too.
This Christmas (2013), my most awesome wife surprised me with a Celestron Travelscope, a small refracting telescope mainly for lunar and planetary observations; which she may be starting to regret! I am now hooked on astronomy and want to see more and start photographing my views too.
The Travelscope is an excellent low powered wide field scope perfect for lunar viewing and some astrophotography. But, the mount does let it down, something my wife had researched and warned me about.
So, I like a challenge and started looking at what mount options are out there - not knowing a single thing about any of them!
I wanted to make the mount more sturdy, primarily and easier for AP. So, after some research it made sense to concentrate my ideas on the Equatorial Mount style as this it is much easier to track object during long exposures with an equatorial mount. A little bit about mounts; I am just a beginner so don't rely on my explanations at all! If you want to know more about the two options Wikipedia actually have some pretty good information:
I wanted to make the mount more sturdy, primarily and easier for AP. So, after some research it made sense to concentrate my ideas on the Equatorial Mount style as this it is much easier to track object during long exposures with an equatorial mount. A little bit about mounts; I am just a beginner so don't rely on my explanations at all! If you want to know more about the two options Wikipedia actually have some pretty good information:
Alt/Azimuth Mount; https://en.wikipedia.org/wiki/Altazimuth_mount
Equatorial Mount (German); https://en.wikipedia.org/wiki/Equatorial_mount
So you can see why I chose the Equatorial design - once set up you just need a 'simple' tracking motor to run at a fixed rate that equals the earth's rotation; 365ยบ/day. How on earth was I going to do this cheaply without effecting the quality (too much) and in a way that I could scale up simply as my new found hobby expanded? ? ? In my day job I have to overcome substantial engineering hurdles while simultaneously answering to my MD with regards to keeping costs to minimum; so I like to think I am pretty good at this - or perhaps I am just good at making people think I've spent less on development worj? Yeah, probably the latter....No, definitely the latter... anyway, this is my money, so I'm going to be a tight fisted Scrooge!!
I had seen some "pipe" based mounts online which seemed to be in the sort of ball park I was thinking about:
Here and Here.
But I really wanted to make something I could scale simply and without access to a lathe or mill (anymore) I decided to look at PVCu plastics, I design with the them on a daily basis, so know the range of fittings well. The goo thing about PVC is that they come with a massive range of solvent weld reducing bushes, many of them coincide nicely with standard bearing housings:
Standard ABEC "609" bearings have an OD of 22mm and a 1/2" reducing bush has an ID of 21.70mm with a + only tolerance, they fit nicely! There are also larger sizes which fit too. My advice would be to get a standard bearing chart and a PVCu pipe OD chart (this is what the reducing bushes mate with and find the size you are after:
A metric bearing chart is here; http://www.bearingworks.com/bearing_sizes/index.php
A PVCu pipe diameter chart can be seen below, these are nominal as they are extrusions and generally the reducer will have a decent tolerance of up to 0-5 - 0.8mm:
I had seen some "pipe" based mounts online which seemed to be in the sort of ball park I was thinking about:
Here and Here.
But I really wanted to make something I could scale simply and without access to a lathe or mill (anymore) I decided to look at PVCu plastics, I design with the them on a daily basis, so know the range of fittings well. The goo thing about PVC is that they come with a massive range of solvent weld reducing bushes, many of them coincide nicely with standard bearing housings:
Standard ABEC "609" bearings have an OD of 22mm and a 1/2" reducing bush has an ID of 21.70mm with a + only tolerance, they fit nicely! There are also larger sizes which fit too. My advice would be to get a standard bearing chart and a PVCu pipe OD chart (this is what the reducing bushes mate with and find the size you are after:
A metric bearing chart is here; http://www.bearingworks.com/bearing_sizes/index.php
A PVCu pipe diameter chart can be seen below, these are nominal as they are extrusions and generally the reducer will have a decent tolerance of up to 0-5 - 0.8mm:
So, I had established that I could use standard bearings and PVCu pipe to make the mount, but how was I going to do it and what parts should I use.
I have drawn up a quick 3D model showing my proposed idea proposed idea, they are very vague at the moment but indicative of my plan, I have chosen to use 1 1/4" fittings with 1/2" reducers running 22mm bearings (10mm bore):
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| The red shows the two main axis, motors are floating in mid air for the time being counter weight not shown. |
Showing the press-fit bearing idea in a bit more detail:
I will try an update this further soon, I have got the parts and have been dummy-ing it all up, I will do another page on the assembly process when I get to it.
PVCu pipe can be brought from lots of places, I have a commercial supply, but Pipestock is good in the UK for small quantities:
If you have any questions feel free to email me, or contact me on Stargazing lounge, where I have started a discussion about the idea:
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