If you're new to astrophotography, this article will explain the different approaches to choosing how to control your rig. If you've been imaging for a while, you've already settled on the approach you prefer. In that case, skim the article for tips related to your setup and learn how the other half lives.
Controller
Every astrophotography rig has a computer of one kind or another controlling the mount, camera, focuser, and the rest of your equipment to capture images. There are basically two approaches to choose from. The traditional computer-based approach is a Windows computer running NINA software. The (arguably simpler) appliance-based approach involves a specially designed computer that is controlled with an app on your phone or tablet. Which you choose depends on your tolerance for complexity and your need for flexibility in choosing the rest of your gear.
Windows Computer Running NINA
NINA uses an interface standard called ASCOM to communicate with virtually any astro device that might be on your pier. As a result, it can be a capable and flexible solution — but it can be challenging to set up. It requires you to remotely manage a Windows PC (often a mini PC riding on the top rail of your scope), as NINA only runs under Windows. But in return you get a system that can do almost anything you ask of it and is very much at home in the remote observatory. You just need a way to access it remotely, which you can do with Remote Desktop or any number of similar apps.
The downside of this approach is that you are responsible for Windows updates, installing drivers, choosing the right PC, solving USB weirdness, and anything else that comes up when working in the Windows ecosystem.
One option if you choose this route is the PrimaLuce Eagle. It starts with a normal Windows PC and adds multiple USB ports, controllable power ports, dew heater ports, and more all in one box. It's more expensive than a mini PC with, say, a Pegasus Astro Powerbox Ultimate, but the Eagle both obviates the need for additional devices and includes observatory-specific features.
Mac Computer Running NINA
This comes as a surprise to most people, but it's possible to run NINA on a Mac using products like Crossover. But unless you have a strong preference for Macs, you're better off using a mini PC.
Appliance-Based Approach
Solutions like ASIAIR, StellarMate Pro, and Stellavita are similar in that they are small Linux computers, usually based on Raspberry Pi architecture. But you don't ever need to know that. They sit on your scope and connect to all the components — camera, mount, filter wheel, focuser, etc. — and you control the device from an app on your phone or tablet.
The computing appliance does all the work; your phone or tablet is just the user interface. While system upgrades are necessary from time to time, they're not usually as disruptive as Windows updates can be and are more under your control.
ZWO ASIAIR
ASIAIR's defining characteristic is that, while it operates using the INDI standard supported by almost all astro products, it has only limited support for non-ZWO hardware. It has a broad selection of mounts and supports popular DSLR cameras, but only ZWO astro cameras. Filter wheels, focusers, guide cameras, and rotators must all be ZWO models. That being said, ZWO has a wide selection of cameras and other devices — you may find yourself ASIAIR-compatible without really trying.
The ASIAIR software runs on iOS or Android and offers several modes for viewing in real time or planning an entire night's worth of targets. Most find it much easier to use than the other options presented here. The ASIAIR is arguably the fastest path from "I just started imaging" to "I am successfully imaging at a remote observatory". Its limitation is flexibility in the hardware it supports. Its power is in its simplicity.
More about using ASIAIR at AstroPeak.
StellarMate Pro
Like the others in this category, the StellarMate Pro is a Linux computer running special software that you can access a few different ways. These include accessing it via its phone/tablet app or using the KStars/Ekos program on your Mac or PC.
Unlike ASIAIR, StellarMate Pro supports a very wide variety of gear from different manufacturers using the INDI interface standard.
The app is not as polished as the ASIAIR app, but it's functional. KStars/Ekos is very powerful, but has a very steep learning curve. Of the "easy to use" appliances for controlling your scope, StellarMate Pro might be the most challenging to master.
StellaVita
The best way to describe StellaVita is "ASIAIR with broader compatibility". It's not limited to any one brand of gear, even though it is made by ToupTek, which sells cameras and other astro hardware.
StellaVita is not as widely used as ASIAIR and the software is still evolving. It should be on your list to consider if you're looking for ASIAIR's ease of use but need it to work with non-ZWO gear.
Choosing a Solution
For most people, the real choice is between NINA and ASIAIR. If you want full control and don't mind complexity and administering a Windows box, you choose NINA. If you want something that "just works", you end up choosing ASIAIR and building the rest of your rig around it from the ZWO catalog.
If you already have non-ZWO gear but like the simple-to-use appliance approach, StellaVita is worth a look. StellarMate can be challenging to learn, but it offers more of the control and configurability that attracts people to NINA without requiring Windows.
Additional Considerations for Remote Operation
If you're using NINA, you're ready for remote. Just use a remote desktop solution to access your PC. If you're using one of the appliance-based solutions, you will likely be connecting to it from an app on your tablet or phone. But there's another option to consider.
Any Mac computer built on Apple Silicon — that is, the M-series or A-series processors (not Intel) — can run selected iPad apps natively. That is, the app believes it's running on an iPad. If you prefer to control your rig from a device with a bigger screen, real keyboard, and a mouse, consider getting a Mac and running its iOS app from there.
You might also benefit from a Mac mini mounted on your pier. You could use remote desktop software to remote into the Mac from your PC or Mac at home. The advantage to this is that it's easy for the Mac on your pier to maintain a solid connection to your ASIAIR, StellarMate Pro, or StellaVita, and it's easy for you to connect to it with one of the many remote desktop solutions.
Having a Mac (or a Windows PC, if you don't already have one running NINA) on your pier also gives you options when it comes to managing files and interacting with other gear directly. For example, if you have an "all sky" camera on your pier, it can be difficult to access if you are using, say, ASIAIR. You have to stop imaging, switch from the imaging camera to the pier camera, see what you wanted to see, then connect the app back to your imaging camera. With a Mac mini on your pier, you can run ASICap from the free ASIStudio app to view images from your (ZWO) pier camera even while your ASIAIR is busy imaging.
So when it comes to choosing a way to control your astrophotography rig at a remote observatory, you need to think about how much control you want to have, what brands of equipment make up your system and whether they're supported by the solution you choose, and how much work you want your control solution to do for you. The fact that your rig will be at a remote observatory doesn't generally play into the decision — all the choices are equally comfortable operating remotely.