AstroPi3 Part 01 - Raspberry Pi 3 as guiding computer

astronajar Tutorials 25 January 2020 Hits: 2903

AstroPi3 Part 1 - Raspberry Pi 3 as a autoguider computer
AstroPi3 Part 2 - Creating the Installation Image
AstroPi3 Part 3 - Installing Ubuntu Mate
AstroPi3 Part 4 - Installing AstroPI3
AstroPi3 Part 5 - PhD2 Configuration
AstroPi3 Part 6 - DSLR/Guide Camera Setup and Control
AstroPi3 Part 7 - Raspberry Control with Tablet/Cell
AstroPi3 Appendix A - Index of Possible Problems, Causes and Solutions

Introduction

In this series of articles you will find a complete guide on how to install a Rasperry PI mini computer as an assistant in the autoguiding and DSLR camera control, being able to control it directly with a cell phone or any device that can connect to a wifi network.

We're going to use as software components Ubuntu Mate linux and the use of AstroPi3, which is not a system itself but a script or series of instructions that will automate the installation process of opensource applications used in astronomt/astrofotography such as KStars, Ekos and PhD2, in addition to installing extra components such as VNC to control our raspberry remotely.

Clarification: These articles are oriented to people with experience in astrophotography but with basic knowledge of software installation; it is possible that computer experts might find the tutorial a bit tedious as the texts try to be simple and detailed.

Everything is explained to make an installation from scratch, yet you can skip stages if you already know how to do it.

Motivation

In 2018 I was able to make significant progress in learning astrophotography, and after having managed to take pictures with a telescope, the next logical step was to achieve long exposure shots and for that it was necessary to start with auto-guiding.

I had two options:
1) Use an autoguide with a computer, which is connected to an auxiliary camera that is installed in a guiding telescope, and guide using the PHD software.

2) Buy a stand-alone guiding device such as the celestron NextGuide which is also installed on the guiding telescope but does not need an external computer, since the guiding system is integrated in the same device.

I didn't like the idea of carrying a computer for the following reasons: it's an extra burden but the main reason is the power consumption. It is already complicated to use moderate voltage batteries for the cameras and mounts, then for a computer it is more complicated, and it get more complicated if you do not have access to electrical installations in the observation site. However, this solution may be the "cheapest" given the wide range of prices on the market for special self-guiding cameras, and the fact that they are very accessible.

The second option looked good to consider, but it is much more expensive than the first one: equipment like the latest SBIG autoguider does not go below US $ 1,195 and alternatives like the Lacerta MGEN II no bajan de EU $ 550, in addition to the fact that they are not very common in the market.

So I decided on a more or less intermediate solution: I found out that it was possible to use a Raspberry as a guide controller. This has many advantages because this small computer can be operated with a simple lithium battery pack, which are very cheap and have a long life. Also the price of these computers is very accessible, since they come prefabricated with the minimum indispensable hardware, which for the guiding, is enough. Let's add to this that they are very compact and super light to transport, unlike a laptop.

In fact, Raspberries are the basic hardware used by models such as the ZWO ASIair or the el Stellar Mate. The only difference is in the software that those devices use: we will use Linux with the PHD and KSarts/Ekos installed, and they bring their own software that is more adapted for the mortals, and that can be a disadvantage for us. The advantage, on the other hand, is the price: this setup will be much cheaper for us than those brand name devices, and it still uses the same hardware.

Given the complications I had for the installation of this equipment, I have created this step-by-step guide so that anyone else can install it.

Choosing the Raspberry model

For this setup, the model used is the following:
-Raspberry Pi 3
It is crucial and extremely important to choose the right model, otherwise the operating system installation will not work. I originally bought one of the latest models, the Raspberry Pi 3b+ and spent a whole week trying to find out why the operating system wouldn't boot up for installation.

At the time of writing this article, this model was the one that worked with Ubuntu Mate versions 16.04.2 for Raspberry and Astroberry, without any problems.

As for the kit, I recommend buying the LANDZO Raspberry pi 3 Completed Kits, as it includes everything to get started:
- Case (ZWO ASIair style)
- Raspberry Pi 3
- Eliminator
- 16 GB micro SD card (important)
- Extra: heat sinks

Note: The only serious problem I had with this kit is that the SD card came defective, and I had to buy a more known brand like the SanDisk.