Thursday, November 5, 2015

Raspberry Pi and astronomy

This time I selected a topic a bit different from usual. After all the blog is about experiments and not only home automation, with RPi...

Since I was a child I've always loved astronomy. I own a small telescope and I took several photos with film cameras, but now I can go a step further thanks to my RPi.

A Raspberry Pi is compact, needs low power and has a nice high definition camera. It seems almost perfect for a small and cheap astronomy setup, so I gave it a try.

To keep this setup useful everywhere I decided to make the RPi a wi-fi hotspot. This way I can connect to it even far from home, in places where a network is not available.

This first thing to do was the PiCamera telescope adapter. Fortunately someone already designed it and if you need it you can find it on Thingiverse.
I modified it a bit for my needs, but it wasn't really necessary. Here a photo of the printed adapter:

In the photo you can also see the wi-fi dongle. For this project I used a RPi model A as I do not really need anything more powerful (and that model was the only one unused at home)...
The case was also 3D printed by me.

The RPi configuration is quite simple. I set up the hotspot, then I installed mjpg-streamer and that's all!

To power it I used a 10000mAh powerbank I have at home and to use the system I just plug the usb power, connect using ssh to start the streamer and then use my tablet to see the video stream.

Of course mjpg is not the best for astronomy as it's a lossy format, but to take a look at the moon and the biggest planets it's good enough. For different purposes (high-res planetary photos, deep sky, etc.) I could change the configuration and save the raw frames to get the best quality.

For now I'm quite satisfied of this setup, even if it's far from being perfect!

When using it I found some problem focusing the image. The PiCamera sensor is small and also the smallest vibration of the telescope will shake the whole image, so it's difficult to focus properly.
For this reason I decided to motorize the focusing knob. This way it should be much more stable.

Here you can see the RPi mounted on the telescope:

In the last photo you can see a small servo already mounted on the left focusing knob. Soon I will test it.

I guess you wish to see some result...

As I wrote, the focus was problematic, so the photos of the moon are not the best I could achieve with this setup, but they are nice anyway. I will retry with the motorized focus to see how better they could be.

In the future I wish to make it much more useful by adding some futher feature like autostarting the streaming (this is quite easy) so I do not need to use ssh, or give the option to get a raw image, or even saving the mjpg to an usb memory (here I would need at least a RPi model B of course). Another nice feature could be a programmed sequence of photos, so they could be stacked later.

Using Raspberry Pi for astronomy is quite promising, at the point that someone is also developing a 3D printed telescope fully based on a RPi. Not bad for a $40 computer!

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