There are a lot of bits and pieces of information out there that you have to piece together yourself to figure out how all of this stuff works together. As soon as you figure out how one piece works, there’s another piece of the puzzle. Hopefully I can put this into perspective and outline all the pieces.
Think about the PC controlling everything as the brain, the mount as the heart, and the OTA and camera as the eyes. This is meant for a general overview. There will be more in-depth pages on each of these controls and I’ll link them here as I write them. Take a look at this quick process breakdown, and then below, a layout of my setup.
- Planetarium software talks to the mount to slew to a target.
- Plate-solving software uses the imaging camera and imaging software to center the target in the imaging camera’s field of view.
- Guiding software send commands to the mount to keep a star in the same spot based on images provided by your guide camera.
- Imaging software allows you to create an imaging plan and set image settings to for your camera.
- ASCOM Driver software pulls all of it together.
My background is in IT, and is highly process-driven, so I created this flowchart to help myself understand how everything is working together. Visualizing it like this helped me to write a setup checklist and eliminate mistakes in my setup. There are more subtleties and connections used that aren’t listed here, but there are only so many lines you can draw before it gets way too confusing.
Think of the flowchart breakdown this way:
- Yellow = the eyes and imaging components of the setup
- Blue = Mount and it’s software controls
- Green = a crossover of imaging and controls specific for Astrotortilla since it uses both aspects to center an object
- Orange = the brain – the main control laptop
- Purple = intermediaries and extras. They are not absolutely necessary to image, but help a lot
My PC runs the following software simultaneously to control all the pieces:
- Stellarium Scope
- Allows Stellarium to use the POTH ASCOM driver
- Planetarium Software to view the night sky and move without the clunky handset
- POTH hand controller
- Allows you to make small adjustments using the PC as you would with the hand controller
- Guiding and alignment
- Backyard EOS
- Plate solving/object centering
- This is a free luxury with two PCs (or phone/tablet) that I use to remotely control the PC at the Telescope from the warmth of my family room, or even away from home.
That’s a lot of work for the brain. Let’s take a look at how the brain interacts with all of these pieces to get them to work together.
The thing that makes all of this possible is the ASCOM standard drivers for PCs. Most mounts today are ASCOM compatible, and descriptions on product sites will let you know if they are. With the use of the POTH (Plain Old Telescope Handset) Hub you can connect all of the control software simultaneously using virtual COM ports. You can use device specific ASCOM drivers to connect directly to the mount, but you will be restricted to running one piece of control software at a time. Using POTH hub, each piece of software connects to to the hub, and the hub connects to your mount using the device specific driver.
You can use the object database programmed into your hand controller to slew the scope to objects, but I don’t see the point of that if you’re already using a PC to control guiding. Stellarium and Stellarium Scope are free pieces of software that allow you to point the scope using a visual reference. Stellarium sends commands to the mount through the handset telling it where to point. Stellarium can control your mount without Stellarium Scope, but Stellarium Scope is necessary if you plan on using the POTH hub.
PHD2 (Push Here Dummy) has two purposes. The first used in a setup is Drift Alignment. Through a process of determining guiding errors, you adjust the Azimuth and Altitude adjustments on your mount to get the alignment dead-on. This will allow for longer exposures with fewer thrown away. The second, and primary purpose of the software is to send pulse commands to your mount to keep the guiding right on target, based on the star image provided by your guide camera. This software can be used in a basic setup (Push Here Dummy) or an advanced setup with subtle changes to increase guiding accuracy. I’ve recently tapped into more of the advanced settings and have been able to increase my guiding accuracy significantly, usually to a total error of under 1 arc second. For example, I imaged for 10 hours and only had to throw out 4 captures due to tracking errors.
Astrotortilla puts your image in the center of the FOV. For a mount GOTO as inaccurate as mine, Astrotortilla is essential. Astrotortilla takes an image using your imaging software (BackyardEOS in my case) and imaging camera. With that image, it then uses a database specific to your field of view to determine where your scope is pointing, and where it needs to be. After calculating the error, Astrotortilla sends commands to the mount to slew to the object. It repeats this process to get the object centered within one arc-minute. This software can be very confusing, and all of the setup information I’ve seen out there is over-complicated and makes things more confusing. This is a very useful piece of software, but it can be extremely frustrating if it’s not setup properly.
BackyardEOS allows you to create an imaging plan and gives you a bit of a set it and forget it method to imaging. Obviously it interacts with the imaging camera, but also has the capability to communicate with your mount by porting to PHD2 for dithering (a process to reduce noise that moves each image a couple pixels).
Lastly, Teamviewer is a free remote control software that I use to control the PC connected to the scope. Living in Chicago, where it’s either 95, or -5 and rarely in-between, I can image more often and for longer from inside the house.