MOBILE ASTROPHOTOGRAPHY WITH INDI, KSTARS AND EKOS RUNNING ALL INSIDE A RASPBERRY PI 2
What are we talking about?
For astrophotography that requires auto-guiding a computer is compulsory. Thanks to INDI, you can detach computer and devices and control everything remotely using a Raspberry Pi. There is a detailed tutorial about that setting here (). 
If you go outside, far from shelter, a notebook is used to control devices (main camera, guider, focuser ...), guide, solve field, etc. An interesting option for improving the mobility of the equipment is substitute the computer for a Raspberry Pi 2. That is, using the Pi not only to run INDI server, but to run kstars/ekos too.
This article details the use of a Raspberry Pi 2 as "astronomical" computer. You can use other ARM devices, but using the Raspberry Pi makes life easier thanks to a great community behind it. In the Pi we run kstars/ekos and INDI and we control it wirelessly from our phone.
Why is it useful?
Apart from being "cool", does it make sense? I see these advantages:
• Inexpensive. If you already have a tablet or mobile phone with a big screen, the cost is around 50-60 euros. And the Pi has many other uses.
• Control from mobile or tablet wirelessly. For me, to be inside the car in a freezing winter night is a compelling reason. If you haven’t experienced a freezing and windy night, at 2000 meters altitude and hooked to the laptop because it refuses to guide might not think the same ...
• No computer. Big point here. Not only because the cost, but because the risk. Moisture…
• Less "stuff" to transport. In addition to the laptop, save transport a table, a chair, a box to isolate moisture, a giant battery to feed the computer... The Pi fits in the palm of a hand and weighs about 50 grams ;)
• Power consumption. The difference between power consumption of a notebook and a single-board is huge. We can go with much less battery capacity. So less height again…
• Compact. With the Pi attached in a suitable place, there aren’t many cables hanging. When there is people "hanging around" you avoid much trouble.
Check if your devices are listed here (http://indilib.org/devices.html) before continuing.
But, can a Pi handle it all?
Yes, it can. I became amaze by how smooth it runs. Thanks to ubuntu-MATE for Pi2 and kstars/ekos being available for it.
So let’s try 
Assuming you already have equipment for astrophotography, you should add to it:
• Raspberry Pi 2. Older ones will not do. 
• Micro SD> 4 GB. I use a 32 GB to have enough spare room. 4 GB is the minimum. 8 GB is sufficient, but there will be no room for many astrometry.net indexes (field solving) or for a big catalog of stars (USNO NOMAD alone needs 2 GB).
• Mobile phone or tablet. Big screen. No matter the power. I use a 6.2-inch mobile phone .
• USB wifi dongle. Mine is a Edimax EW-7811Un. It works fine. It is small and recommended for the Pi.
• Cables to power from battery.
• A powered USB Hub. You might not need it, but chances are you will not realize you needed it. 
• For the installation process, a monitor or TV with HDMI input, an HDMI cable, a USB mouse, a USB keyboard, a micro SD to SD adapter to write the micro SD from the computer and micro USB charger (your phone one is ok).
You may get everything easily under 60 euros. Except for the phone ;) I bet you already have one.
Installation and Configuration
You need a software to burn disk images to the micro SD. I use Win32diskimager. It's free and easy to use.
1. Download the image of Ubuntu-Mate for Raspberry Pi 2. (https://ubuntu-mate.org/raspberry-pi/), write it to the micro SD.
2. Installation of the system. Connect the Pi to a monitor with a keyboard, mouse, USB wifi, SD card and power it on (any micro USB mobile phone charger will do). Follow the installation steps.
4. Change the size of the file system to use the full capacity of your card. By default only have available 4 GB.
sudo fdisk /dev/mmcblk0
Delete the second partition (d, 2), then re-create it using the defaults (n, p, 2, enter, enter), then write and exit (w). Reboot the system (sudo reboot), then:
sudo resize2fs /dev/mmcblk0p2

5. If you have wifi available, configure access from the icon in the upper right corner. And once you're connected, update the system by typing "sudo apt-get update" and "sudo apt-get upgrade". 
7. The resolution of the graphics system is automatically adapted to your screen. And it has a black border, to make sure everything goes into screen. When booting the Pi without being connected to a screen, it will use a default low resolution that is not suitable for ekos. So we will force it to always start with a specific resolution and without black border. To do this, edit the file /boot/config.txt. Add or uncomment these lines:
disable_overscan=1 
hdmi_force_hotplug=1
hdmi_group=1
hdmi_mode=16
This will force a resolution of full HD. Check (http://elinux.org/RPiconfig) to adapt it to your preferences.
8. INDI. Install INDI (http://indilib.org/):
sudo apt-add-repository ppa: mutlaqja / ppp
sudo apt-get install indi-full
9. Install kstars. It will take a while.
sudo apt-get install kstars
10. To solve astrometry.net field installed as follows:
sudo apt-add-repository ppa: mutlaqja / astrometry.net
sudo apt-get install astrometry.net
Now we download the appropriate index files for your setup, following the instructions http://astrometry.net/doc/readme.html and downloading files from http://data.astrometry.net/debian/. We can do it with Firefox in the Pi, which is installed and works very well, although sometimes a little slow. Quite normal, provided it is a micro-computer.
cd Downloads (or the place you downloaded them)
sudo dpkg -i astrometry-data - *. deb
It is important that we ensure that the file /etc/astrometry.cfg points to the correct path where index have been installed. In my case the indices are in /usr/share/astrometry, so I modified /etc/astrometry.cfg, the line that says "add_path /urs/share" with "add_path /usr/share/astrometry".
11. Now we need to see the desktop of the Pi from the mobile phone / tablet. One option is the following (http://www.megaleecher.net/Raspberry_Pi_VNC_Setup): 
sudo apt-get install x11vnc
x11vnc -storepasswd (and set your VNC access password)
Now, we need to make X11VNC server start with LXDE, to do that use following commands at terminal.
cd .config
mkdir autostart
cd autostart
nano x11vnc.desktop

Now paste following:

[Desktop Entry]
Encoding=UTF-8
Type=Application
Name=X11VNC
Exec=x11vnc -forever -usepw -display :0 -ultrafilexfer
StartupNotify=false
Terminal=false
Hidden=false

Save the above file by using - Ctrl-X, Y,
This will auto start our VNC server every time.
Then install a VNC client in your phone. There are many. In android I use, among others, DesktopVNC.
12. To reach the Pi from your phone. The quickest and easiest option is to create wifi hotspot from your phone. And set the Pi to automatically connect to that network when available. Your phone hotspot app will tell you when the Pi is connect and its IP number. Connect the VNC client app from your phone to that number.
Done. I hope you find it useful.
Improvements
Should you require a large catalog of stars, you can use the USNO Catalog (100 million)
• Download Catalog of http://download.kde.org/apps/kstars/USNO-NOMAD-1e8-1.0.tar.gz USNO (Care> 1.4 GB before unpacking).
• Unzip to /usr/share/kde4/apps/kstars
My experience has not been good. It works, but kstars gets slow.

Another possible improvement is to use the version of kstars / ekos kstars-bleeding, including the latest development version. There are several new interesting utilities. Although not stable:
sudo apt-get install kstars-bleeding
In case you have a QHY5 camera, chances are it will not run. There are many versions that the driver does not directly recognize but you can "tell" the Pi to recognize them. And there is a link error in the installation of the latest version. You can see what to do in (http://www.indilib.org/forum/ccds-dslrs/741-qhy-driver-problem-wrong-libqhy-so-version.html?start=6).