Astronomy automation 101

A beginners introduction to the different terms and principles of amateur astronomy automation. We look at ASCOM and INDI and the differences in their usuage and capabilities.

There are two main software interfaces that most astronomers use to interface with their equipment to leverage astronomy automation. ASCOM has been around and developed for 20 years whereas INDI is much newer but rapidly gaining adoption. They both have their place in your automation arsenal so let’s take a look at both and compare their subtle differences…

ASCOM

ASCOM stands for AStronomy Common Object Model and for many years required the .net framework to be installed for its use. It was originally designed for Window machines only but since 2019 work continues on the ASCOM “Alpaca” platform which is set to potentially replace ASCOM in the future as it will be platform independent allowing its cross platform use on Mac’s and Linux operating systems etc.

ASCOM only works for the synchronous control of local devices – i.e. direct control. The future of Alpaca should mean ASCOM updates to provide asynchronous indirect communication like INDI does.

For an ASCOM primer see this You Tube video from Dylan O’Donnell

INDI

Indi stands for Instrument Neutral Distributed Interface, a complex name but what does this mean? Well as the name suggests, it is a system neutral set of protocols that allow communication between software and hardware. INDI drivers support full astronomy automation including mounts, cameras, focusers, filter wheels and auxiliary equipment including domes and weather stations and more – see here.

INDI is asynchronous, it provides a framework that decouples low level hardware drivers from high-level front-end clients. That is, clients that use the device drivers are completely unaware of the device capabilities. INDI is neutral, the protocol does not care what the system running it is written in, if it can talk to it, it will… There are currently 22 clients that can use INDI – see this link here.

INDI versus ASCOM

Which one to use for astronomy automation? Well I often use both for different approaches and software. They both have pro’s and cons which I will detail later but for complete automation, currently INDI gets my vote in combination with the software and equipment I wish to use.

I will illustrate by example…

I Polar Align my mount using ASCOM connected to my PC via USB using the IOptron IPolar (CEM60 mount) and their desktop windows application – its quick and easy but requires I have a laptop available.

I fully automate my mount, camera’s, focuser, plate solve, guide using a Raspberry Pi 4 running the Astroberry platform and using Kstars / Ekos. I use Wifi to connect using VNC viewer to remote in.

If I want to use software such as Stellarium and APT to automate imaging via my Laptop (USB) or SharpCap to run an EEA session, then its ASCOM.

ASCOM

ASCOM drivers produced by most hardware vendors.

ASCOM interfaced by most software clients.

Free to download and use, open source, active development.

Alpaca requires (Windows only) “ASCOM remote” to allow Wi-Fi/IP based access;

ASCOM as it stands is more USB focused for synchronous connection;

Alpaca requires device and non-windows software providers to incorporate it for access to non-windows platforms;

INDI

Free to download and use, open source, active development;

Cross platform, client agnostic;

Distributed Control – client server architecture, devices local or remote transparently;

Can fully automate imaging sessions;

RPi / Arduino system images available (e.g. Astroberry & Stellarmate);

Can be complex to setup depending on route taken;

INDI can lacks drivers (or driver features) – you need to check first;

There is less INDI compatible client software than ASCOM currently

Conclusions

For automation, I currently now prefer INDI. The user group and support seems good but future support is never guaranteed. When I used to use a laptop outside then it was always ASCOM, but I now remote into a Raspberry Pi which handles everything including image storage on Astroberry – this has led to increased sleep and a happier wife!

This is a personal choice and I am sure many of you will disagree, KStars is not to everyones liking but once you get it set up well, its really fun if you are techie like me. If you are more of a hands on kind of astrophotographer (like Trevor from Astrobackyard) then you well might stick with ASCOM.

Its great we have the choice! Feel free to add your comments below…

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