This is the first telescope that I have ever owned. In fact, this is the first telescope that I have ever "looked" through (not counting images from Hubble, and yes I'm not actually even looking through this one either). Anyhow, I don't know what I'm doing... So much so that it took me a good 15 minutes to even find the Moon with this telescope. I have no spotting scope, I was just sighting along the barrel and I had trouble.

The problems boiled down to:

- Vibration / Stability - The whole setup shook while moving it by hand, not because it was unstable, by just because my hand vibrates enough to cause problems. Also I had difficulty focusing because that would move or jiggle the whole thing. In reality I am going to have a hard time making a rigid telescope out of paper.
- Positional Resolution / Repeat-ability - It was very difficult to move the telescope in only one axis or be sure that I was "scooting" it just a little bit and not to much to overshoot my target.
- Inexperience - I didn't know what I was doing or even how large my view of the moon would be

A little homework was in order... First, I've been using this site: in-the-sky.org to find the size of the objects that I was interesting in seeing. On the first day 11 - Dec My telescope was giving me a field of view of about a third of the Moon which was 1770 arc-seconds in size. So my field of view (FOV) is in the neighborhood of 600 arc-seconds. I'm using the 8MP Raspberry PI Camera v2 (native res of 3280 X 2464). Rather than do actual math, I figures that I start with some napkin math. I'm going to consider the my horizontal as equal to the 600 arc-second FOV and just round down a little so 3000 / 600 = somewhere 5 pixels per Arc Second.

Next, I went back to in-the-sky.org and found the sizes of some other things that I wanted to see:

| ArcSeconds | Pixels |

| Min | Min | Min | Min |

Mars | 24 | 3 | 120 | 15 |

Saturn | 18 | 15 | 90 | 75 |

Jupiter | 44 | 30 | 220 | 150 |

So a day is 23:56:04 or 86,164 seconds to turn a total of 1,296,000 arc seconds in a circle or, 15 arc seconds per second. Thus, during a one-second exposure Saturn would move 15 pixels (1/5 of its size). That would be a pretty blurry image!

I will limited to 1/30 of second exposures if I want to limit my blurry to sub-pixel size, but that may be pushing the ISO limits of the camera. This will be my first experiment.

It would be better if I could move the telescope to keep up with the earth's rotation (like the big boys do). To do this I would need to be able to generate smooth motion at about 1/120 of a second of earth's rotation (I just made that number up). So 15/120 that give me 0.125 arc seconds "steps" or 10,368,000 steps per revolution.

A quick google search did not turn up any 9.645 * 10^-8 deg stepper motors. I think a little reduction is going to be in order. Likely 1/120 of an arc-second is probably an exaggeration of what I will likely need so to give myself a fighting chance, I'm going to aim for a 1 step per arc-second resolution (not to be confused with accuracy).

That works out to a 6480:1 reduction (3,600 arc-seconds per degree * 1.8 degree stepper motor = 6480). You can also think about it as 1,296,000 arc-seconds per revolution / 200 steps per revolution stepper = 6480 reduction.

6,480 is the magic number.

cogs are all 3D Printed. I'll be posting them shortly. I'm still finishing up the reduction box. I'll post the links to the belts right now. I got the threaded rod at my local hardware store.

I'm still in the processes of catching up this project page with all things I have done thus far so more is coming.