Never Enough Spacetime


Tales of an astronomer trapped in a programmer's body.


NexStar SE Telescope, Meet Raspberry Pi

This being my first post, I'll give some brief background. For my birthday, my girlfriend bought me a telescope that I could hook up to my computer. My eyes lit up when I imagined the possibilies. This first post will detail my configuration and how I got the hardware to come together so I can use a Raspberry PI for astrophotography.

Celestron NexStar 4SE Telescope

This is a Maksutov-Cassegrain telescope which, in short, means it has a large focal length for it's size. It has a handset that allows me to move the GoTo mount, align the telescope, and find objects in the sky.

My favorite part of this scope is the RS232 serial port. This gives me the ability to interact with the scope remotely.

Raspberry Pi Model B

I won't go into a great deal of detail here, as there are plenty of places to find more information about this on the internet. This is my small "computer" that I'm going to affix to the rear camera port of the telescope, and attach to the RS232 serial port. I'm running Raspbian on the Pi, but the flavor shouldn't matter really.

I should note that I also have the camera module, which is purchased separately.

My goals for the Pi are:

  • Provide a live video stream from the rear camera port
  • Take still photos of objects in the sky
  • Provide TCP socket server for remote control
  • Interact with the telescope via its RS232 serial port

Make Them Play Nice Together

I did quite a bit of research to figure out how to attach the Raspberry Pi to the NexStar 4SE. To save everyone a good bit of time, I'll detail the pieces and even link to them! This part is pretty important for astrophotography, because we want the camera sensor to line up perfectly with the beam of light from the telescope.

Proto Armour for Raspberry Pi/Camera

This is the cornerstone of the whole operation, and it couldn't have worked better. The Proto Armour is a case for the Raspberry Pi, and this particular version has a small hole and an inner mount to which the Camera Module can be attached.

The nice folks at MobileApp Systems allowed me to try their evaluation version of their CS-lens adapter for the Proto Armour case. To make this work with the telescope, you need to unscrew the lens from the Camera Module to expose only the sensor!

You can pick up these case products from MobileApp Systems

Celestron T-Adapter for NexStar 4SE Telescopes

If you want to attach anything to your NexStar telescope, you'll need the T-Adapter. The T-thread is the most common connector for cameras, microscopes, and telescopes.

I picked mine up from Hayneedle.

Opticstar C/CS to T-thread Adapter

Here's how we bridge the CS adapter to the T-Adapter. Another adapter... the CS to T-Thread adapter. Believe it or not, with three adapters, the alignment works out perfectly. Imagine the look on my face when I got the camera to focus for the first time!

You can get one of these from Adorama Camera

USB to RS-232 DB9 Serial Adapter

In order for the Raspberry Pi to talk to the telescope, you'll need a USB to Serial Adapter. The chipset on the adapter is important, so you'll want to make sure you get the right one.

This is the adapter I picked up from Amazon

Power Tank or Portable Battery

So, as you can imagine, you can't take this anywhere without a power source. Celestron sells a Power Tank which looks pretty cool, but I already had a portable battery sitting around. This powers my Raspberry Pi and the NexStar GoTo mount:

Black and Decker 500 Watt AC/DC Portable Power Station

Pics or It Didn't Happen!

Ok, here's a pic of everything put together:

NexStar 4SE and Raspberry Pi

And a close up in case you didn't believe me:

Proto Armour CS Mount to T-Tread Adapter

Stay tuned for way more cool stuff like:

  • Setting up a live video stream
  • My TCP socket server, StellarSocks
  • My Android NexStarGPS app
  • Pictures from the Camera Module