I thought it might be helpful for new users trying to understand what INDI, along with Kstars/Ekos, is.
Comments/corrections/questions are welcome.
UPDATED 8/27/20
DISCLAIMER: I am a fellow a user. I have ZERO, zilch, nada, NO affiliation with the brilliant and hardworking developers of Stellarmate, Astroberry, INDI, Kstars/Ekos. These are my personal experiences and opinions. YMV.
What is INDI, Kstars and Ekos and why would I want to use this software?
INDI is essentially a hardware "driver server" that is run on a Mac or Linux computer. It works together with a program called Ekos that controls all your AP gear. Ekos is a "client" astrophotography module within the Kstars planetarium program. Together, they make up a powerful trio of software that was written to work seamlessly in unison, typically via a standard home WiFi network and is VERY easy to get running. Ekos can be run on the server computer too (the Raspberry Pi) and does not require it to be networked in order to use it.
INDI server is the heart of the system. Many/most people run INDI on a tiny Raspberry Pi computer that is running the Linux operating system. You can buy a complete hardware/software package that's ready to plug-in and run, called Stellarmate and for $229 it's a GREAT way to go and a super value. For people a little more experienced with computers, or Linux in particular, you can buy the Stellarmate OS for $49 or download the free Astroberry package and install it on your own PI. Both Stellarmate OS and Astroberry are complete, ready to run software packages - no Linux experience necessary and include all the software you need for a Raspberry Pi computer.
The INDI server computer, with its hardware drivers (which you select from a list, specific to your astrophotography hardware) is then controlled by client software -which as mentioned above, is called Ekos. Ekos runs on Mac, Linux or Windows PCs. Ekos is a sophisticated "astrophotography control module" built into and is an integral part of the very robust and powerful (and FREE) Kstars planetarium program.
Ekos does all the heavy lifting and it is STRONGLY recommended to run it on a separate computer (laptop or workstation). Which is where the networking comes in: A Raspberry Pi runs INDI server, running all the drivers for your AP and "serving" them to Ekos. Ekos is typically run on a more powerful (than a Pi) remotely networked PC. Ekos is where you set up your AP session: target, plate solving, tracking, focusing, and of course imaging - and MUCH more. If you have the hardware, Ekos can probably run it. Ekos (which again, is built into the Kstars planetarium program) is the nerve center controlling all your gear.
Example Set-up
In my case, I have a 4GB Raspberry Pi 4 computer that is running the INDI server software. INDI server is "serving" drivers I chose from the INDI hardware menu list for my specific gear. I then have a Windows 10 PC that is running Kstars/Ekos. Both computers are networked together via a router.
Stability of the Stellarmate system has been a persistent problem for me. After months of experimenting, I've come to believe the core software is quite solid and stable (but there are problems with some device drivers (the developers are typically quick to respond to bugs they can duplicate)). I believe the primary stability problem is the WiFi from the Raspberry Pi: it has no external antenna and has a weak signal, prone to interference. My solution is a dedicated (for my astro rig) Netgear home network router.
I connect the Raspberry Pi to the router using a gigabit Ethernet cable. FYI: My Pi is mounted beneath my scope, the router sits on a shelf on my tripod. With good cable management, this has not created any problems for me. Then I connect to the router from my Win10 laptop using WiFi which is a MUCH stronger wireless signal. In Ekos, when setting up a new equipment profile, I input the IP address of the Raspberry Pi (Stellarmate box) and it connects to INDI server on the Pi and Ekos controls ALL my astrophotography hardware via my Win 10 laptop. For the most part, your entire imaging session is controlled in Ekos. Using this networking configuration has proven (so-far) to be very stable and MUCH faster too - I download to the laptop, 18MB image files from my ASI533MC Pro camera in less than two seconds! Using a router is just one way to fix the WiFi problem. I chose it because I wanted the uber-relaiability gigabit Ethernet provides. Others include a USB WiFi antenna or networking adapter plugged into the Pi, a home network booster, Mesh system, etc..
About INDI
INDI server is a breeze to use and is controlled by a super user-friendly app called Web Manager and is installed automatically with Stellarmate. It's mostly a drop-down menu listing all the hardware drivers supported by INDI - it's an impressive list that covers probably 99% of the most common and even some not-so-common gear, both high-end and low-end, and it's growing all the time. You simply "check" each piece of your gear on the list, save it as an "equipment profile" and start the server. That's it. You can also choose to have the INDI server (Web Manager) automatically start when you turn on the Rpi and you'll rarely need to directly log into the INDI server Web Manager again.
Networking Ekos to INDI
Connecting Ekos to INDI is also a breeze: you simply give the Ekos equipment manager your INDI server's network name or IP address and it'll automatically find it and connect up to it and all the drivers you selected in your profile. Easy to get connected, yes. Easy to keep up reliably, eh, maybe, maybe not. The WiFi networking on the RPi is in my opinion the Achilles heal of the entire system. The built-in WiFi on the RPi is just not reliable enough for our application (see my example set-up above, for my solution). Also, sometimes you need to tweak some equipment profile settings for the AP hardware drivers to connect or function correctly. Plan to do some trial and error here, but by-and-large, the default driver settings work pretty well for most pieces of AP gear. Once you get it sorted out, I have found it to be rock solid, before then however, it can be a bit finicky. As I mentioned above, you CAN run INDI and Kstars/Ekos together on the same computer to avoid networking altogether, but you may experience performance issues, especially if that computer is a Pi. Most people run INDI on a Pi and connect to it via their network to Kstars/Ekos running on a laptop or workstation (PC or MAC).
About Ekos
Ekos is the brains of the system and while configuring and using INDI is a breeze, Ekos itself is a different animal. While Ekos IS user friendly, it also has a rather steep learning curve. This is in-part because of it's sophistication and vast number of powerful features and also in-part due to somewhat dis-jointed documentation leaving new users to learn by trial and error for the more advanced features. There is however, an excellent set of written and video tutorials that will easily get new users up and running using standard "must have" features with a minimum of fuss. Hopefully in time, a full-blown user-manual detailing every feature will be written (being a volunteer group, I suspect they'd LOVE to have an experienced technical writer volunteer - hint hint anyone out there!) Power users can get their fix on, with an astounding array of capabilities - although most are not needed to take excellent photos for the rest of us normal folk. A session scheduler is also included in Ekos (I told you this software is powerful!) and you can pre set-up your night, then walk away and Ekos will do the rest, based upon what you configured it to do. BTW: INDI, Kstars/Ekos is particularly well suited for remote observatory control.
The Future of AP?
While I'd call running your astrophotography rig on a tiny SBC (Single Board Computer) like the Raspberry Pi with INDI server networked to a workstation or laptop running Kstars/Ekos client somewhat "experimental" at this stage, it has actually become a powerful and capable platform featuring one of, if not THE longest list of compatible AP gear currently available! In the last year or so, INDI, along with Kstars/Ekos has taken tremendous strides to become an ever more mature client/server AP solution that when used with a tiny SBC, many see may be the future of astrophotography.
Benefits
Benefits include MUCH lower power requirements, VERY low cost of entry: a SUPER-INEXPENSIVE computer the size a a deck of playing cards that weighs only a few ounces, no more tethering an expensive and heavy laptop with cables to trip over, sorter, lighter, and easier to manage cables, and a COMPLETE, extremely powerful and inexpensive or even free software package instead of buying and running simultaneously, numerous (and sometimes expensive) programs that don't always play well together and as a result are not always stable.
All Rainbows and Unicorns? Not quite
The biggest con at this point is simply learning how to use it with your particular gear and configuring the system to work its best for your rig (true for any system), but for many that is also part of the fun! I believe the software (currently SM 1.5.3 and Kstars 3.4.3) is stable. I've traced the problems I've experienced (mostly dropping connections, freezing up, or AP gear features that won't work) to either my mistake in equipment profile configuration settings, Ekos options settings, or poor WiFi from the Rpi.
I've been working with INDI, Kstars/Ekos on and off for about two years now and continue to be ever-more impressed with it. Mind you, it's not all rainbows and unicorns. I admit to getting off to a rather bumpy start - mostly due to me being in a rush and expecting "Push Here Dummy" software simplicity. (Which BTW, PHD II is included and works within Ekos, or you can choose to use Ekos' native tracker.) I've spent many an evening learning, reading/watching all I can, tweaking settings here and there and experimenting with different networking configurations. If you enjoy configuring and tweaking, you'll enjoy working with Stellarmate. If you're looking for plug-and-play, this is probably not the system for you. As for necessary computer experience, I'd rate it a 2.5 to 3 out of 5, with 5 being a guru. Linux experience is NOT needed and intermediate computer users should have no problems they can't resolve with some persistence and experimentation. Networking experience is, I'd say required, but you certainly don't need to be an IT expert.
Know that HELP IS AVAILABLE - RIGHT HERE - THIS IS THE PLACE - JUST ASK!!
Bare in mind this is essentially experimental/prototype software at this stage. Don't think of it as a commercial package, but more like an experimentation kit you can buy.
There ARE bugs in the system (say it isn't so!) and you may run into some problems. (Yep, you likely will.) And, like anything worthwhile, you'll have to put you time in. However, I've found this forum to be SUPER friendly and extremely helpful when I have had problems. Many of the problems I've experienced have been configuration errors on my part - part of the learning curve - and for me, that's all part of the fun of this wonderful hobby! The Rpi's weak WiFi being the other serious but easily fixed problem. For me, INDI, Kstars/Ekos is an adventure in building the future of AP. Never stop learning! Are you ready to rock?