January 21, 2013

New Sky Shed POD MAX

Category: Astronomy — Tags: , , – vincechan @ 10:40 am

Development of the new Sky Shed PodMax – a much larger version of the SkyPOD observatory. Imagine the size of the telescope you could fit in there!!!


New Skypod MAX – 12′ in diameter


August 4, 2012

Rapid Prototyping a laser collimator

Category: Astronomy — Tags: , , – vincechan @ 10:49 pm

One of the most important aspects of keeping a telescope operating in peak condition is to make sure that the mirrors are properly collimated.  One of the easiest methods of aligning your telescope mirrors is to use a laser collimator.  These can be quite easily made using a regular laser pointer purchased at any dollar store.  If you have a lathe, you can turn one easily out of aluminum or wood, as seen here: http://vincechanblog.ca/laser/laser.html

An alternative method is to use a rapid prototyping machine.  In this case, I needed a new collimator for a “pen” style laser pointer.   In this design, the build was in two stages, the bottom half (4 hour build):

Bottom build on Makerbot Cupcake

An the top half (10 hour build time):

Top portion which holds the laser pen

Here are the final parts, before being glued together.  I did lightly sand the bottom build to ensure it would fit into the telescope draw tube.  The bottom build was designed to be 10 thou’ oversize.


Two halves before gluing

Here is the final finished laser collimator, painted black.   The laser is held with two sets of 3 set screws (#8-23).  A 1/4″ screw press on the  on/off button on the laser pointer.

Finished collimator



July 12, 2012

Dob in a POD

Category: Astronomy — Tags: , , , , – vincechan @ 3:27 pm

Seems like not a lot of people have Dobsonian telescopes in their POD observatory.    Given the 4′ high walls, the POD does limit what you can see from a Dob on the horizon.  However, as I live in Toronto, my horizon is fairly blocked off by trees and houses anyways.

To get the most out of my limited views, my Dob is mounted on a dolly.  Basically, its just a piece of 3/4″ plywood with some 3″ castor wheels screwed to the bottom:

Dob dolly on a rope


Dob dolly side view


DSC – Digital Setting Circles with Sky Safari and Arduino

Category: Astronomy — Tags: , , , , , – vincechan @ 1:57 pm

OK, I’ve always been a visual observer, and have resisted jumping on the GOTO telescope bandwagon.  Part of the fun of astronomy was always using charts and star hopping to find a new deep sky object.   How else would one learn the night sky?

However, I must admit, having the power of a star atlas in something as small as your iPod is a real luxury.  And having that connected to your telescope makes things real easy, maybe too easy, but that will be a debate for another day…..

DSC on iPod using skywire


Here are the major components of the project:

  1. iPod or iPad with Sky Safari plus or pro
  2. Sky Safari skywire – goes between you iPod Touch to an RS232 port
  3. Quadrature Encoders – I used a pair of capacitive types CUI-AMT102
  4. Arduino – microcontroller
  5. Max232 – a microchip that converts a RS232 signal to TTL signal

Sky Safari plus or pro – this is an astronomy program that runs on your iPod or similar device.  It’s a pretty full fledged astronomy software package, considering what used to cost $100′s on a PC.  To use this as an interface, you need to use cable that hooks up to your iPod, sold by Sky Safari as the “sky wire”.  Basically, this sends out a RS232 serial signal to your telescope or device.   You need to set Sky Safari in the “Settings” menu, telescope setup to Scope Type:  Basic Encoder System, and under Mount Type: Alt-Azimuth Fork.  Also, in that menu, set the “Encoder Steps Per Revolution” to +4096 for both axis, and set “Get Automatically” to OFF.

Quadrature Encoders – the versions that I use are capacitive types, they are much cheaper than optical encoders.   The encoders are CUI-AMT102-V kit, order from Digikey: 102-1307-ND  Luckily, the pin outs on the encoders are 0.1″ pitch, so any 5-pin straight plug would fit.  On my Dobsonian telescope, the azimuth encoder was mounted to the center bolt of my rocker.

Azimuth encoder in Dob rocker box

Azimuth encoder close up of mounting

The altitude encoder is mounted at the center of rotation of the Dob’s rocker arms.  The required the fabrication of a tangent plate to hold the encoder stationary, relative to the rocker box.  I just happen to make mine out of “plexi” glass, as shown below:

Altitude encoder mounting

To interface between the encoders and the iPod-skywire cable, I used an Arduino micro-controller.  Initially, I tried to read the encoder pulses without interrupts, but that resulted in loosing steps if I moved the telescope too fast.  A relative  new encoder library for Arduino/Teensy was posted by PJRC, and can be downloaded here: http://www.pjrc.com/teensy/td_libs_Encoder.html  You’ll need to install the ‘encoder’ directory to your Arduino library on your computer.   If you are new to Arduino, they can be purchased from many suppliers: http://www.makercanada.ca/  You can download the IDE fro Arduino for free here: http://arduino.cc/

As the skywire cable requires a RS232 serial signal, you need to shift the signal using a MAX232 chip.  They can be purchased relatively cheaply either from shops listed in http://www.makercanada.ca/ or from Digikey #296-6940-5-ND.  I power the MAX323 with 5V pin from the Arduino.  The Arduino is powered with a 9V battery.   Here’s a picture of the prototype circuit:

DSC circuit in lozenges box

Eventually, I’ll find a better mounting box… ha ha.  Here’s the schematic of the circuit:

encoder schematic

Here is the source code for Arduino:

sky_safari_encoder_interrupt  – note: you’ll need to change the extension to .pde or .ino


July 10, 2012

Arduino – Sky Safari digital setting circles

Category: Astronomy — Tags: , , – vincechan @ 9:40 am

Working on making an Arduino digital setting circle interface to Sky Safari on my iPod.  Had it working last year, but was loosing steps if I move , the telescope too fast.   Re-wrote the code to use the two interrupts on the Arduino, waiting for a clear night to test it out.