Astrophotography setups used to be incredibly complex, but the currently available components significantly simplify their organization and maintenance. However, this does not mean they are without flaws and do not present challenges – quite the contrary. A key issue is the communication between the components of an astroimaging setup, as all elements must exchange information for the system to function correctly. This process is typically coordinated by managing software (such as MaxIm DL, N.I.N.A., or Sequence Generator Pro, among others), and connections between components are predominantly established using USB cables. Unfortunately, this is not an optimal solution, and the average user has limited options in this regard. USB receptacles and plugs rarely feature any locking mechanisms. Most standard USB plugs exhibit considerable instability within the socket. Furthermore, smaller USB sockets (mini and micro types) are characterized by very small connecting pins. Adding to these challenges is the USB protocol itself, which, despite its rapid evolution, is sometimes implemented by manufacturers in a manner inconsistent with the prevailing standards.
Communication between astrophotography system components involves two steps. First, fulfill all requirements to establish the communication process—connecting and powering devices, configuring connection parameters, etc. Once communication starts, ensure it remains uninterrupted. This blog entry is dedicated to this second part – keeping the communication working during the astroimaging session.
There are three possible kinds of reasons why communication may break.
- Software issues – the software problem may occur in any piece of software. In the device driver, in the operating system, in the acquisition software, in the software not related to our setup but working in the background.
- Hardware issues – electric. Such as ground loops in the setup or a poor-quality power supply that does not provide stable power.
- Hardware issues – mechanic. Like poor-quality cables and plugs and messy cable management.
Let’s discuss each of these in the following sections.
Software issues
Suggested Revision: “Data must traverse several communication layers to travel from sender to receiver. If you consider the usual astronomy mount or filter wheel – both these devices contain the processor that is sending and receiving the commands to work. These commands are usually via a serial port to a COM to USB adapter connected to the computer. The first piece of software in the chain is the virtual COM port driver. Then, the data comes to the actual device driver – in the Windows system, it will be the ASCOM driver in most cases. ASCOM platform may work locally or remotely, so the data eventually comes to the acquisition software. And the operating system is controlling the process all the time.
Here is a list of the most common communication problems caused by software.
Virtual COM port drivers must be downloaded from the manufacturer’s site and installed properly. The driver that Windows proposes by default usually works but may not be the most recent or the fully tested version.
Device drivers (ASCOM and system drivers) are different topics. The best approach is to have the version that works for us. Camera or mount drivers are updated quite often, but these updates are usually not related to the model we have or do not make any difference. If the device works correctly and we do not miss anything, let’s not touch it.
It also happens sometimes that the device driver or acquisition software does not work correctly after updating to the latest version. Sometimes it requires some adjustments in the configuration. But sometimes it is not possible to fix it and we need to be prepared to uninstall this version and install back the one we used previously. Do not do that before the session, when the clear night starts – unless you are ready to collect no data this night!
Pending Windows update installation or pending restart after the update installation can also cause some problems with communication. I am not sure why it is the issue, but already noted several times that after the pending restart, all things come back to normal and work fine. Some astrophotography amateurs use setups that are not connected to the internet and do not update the system at all. They only update the selected software once a bug is fixed or some feature is added.
And remember – do a system backup before any driver or application update.
Hardware electrical issues
Other communication issues are caused by electrical hardware issues. These are sometimes hard to identify. The most common problems of this type are:
- ground loops – read more here
- Poor-quality power supplies
- Electromagnetic Interferences (EMI)
- voltage drops
Ground loops are present in many astrophotography setups, but they can be harmless and do not cause any issues. Till the moment we will replace one component or one cable and all of a sudden the communication starts to break. We started to expect that the replaced cable or camera would be broken, but the root cause was a ground loop. More about the ground loops and fighting them is said in the linked entry, but the general rule is to keep cables short and good-quality and to power digital and analog setup parts with separate power supplies.
Poor-quality power supplies should be avoided at all costs. It does not make sense to skimp on a PSU for a setup worth several thousand dollars. PSU must be good quality, grounded and fully isolated. It basically means it cannot be cheap.
We currently live in a world full of electromagnetic signals. Even if we transfer our astroimaging setup to the middle of the desert, we will bring EMI with us. In theory, all consumer devices should both generate a controlled amount of EMI and also be resistant to the EMI from the outside. The fact is that many devices are not measured and certified at all, and there are significant sources of EMI in the astroimaging setup. The most obvious are all components powered with PWM (pulse width modulated) square signal – dew heating tapes, Peltier cooled cameras. Generated EMI may interfere with and disturb communication over long and poor-quality data cables, so it is always worth keeping USB cables short and double-shielded if possible. Flat USB cables are fancy and flexible but, quite often, do not provide efficient shielding from external EMI.
Last but not least are the voltage drops. Voltage drops are also the root cause of the ground loop problems, but they can also be a direct problem. Let us imagine a perfect power supply that outputs 12V all the time. Then we have a 2m cable to our power splitter with nice 5.5mm diameter DC receptacles and then another 1.5m of thinner cable that powers the camera. Each cable and connector introduces some resistance to the circuit, and the resistance multiplied by the current drawn causes a voltage difference. If the connector is dirty or low quality, it may introduce 0.1 ohm resistance. Plus, 2.5m of thin cable may introduce another 0.2 ohms. It does not look like a large value, but three connectors with 2.5m cable give us 0.55 ohms. Now, when the camera cools at 100%, it may drain up to 3A (large cameras even 5A), and that means 0.55 * 3 = 1.65V drop. So, even if we have a perfect 12V PSU, the camera will be powered with only 10.35V! This underscores the importance of using short, thick power cables and maintaining clean connectors – various connector-cleaning products are available. Furthermore, utilizing an adjustable PSU and setting the output voltage to 13-13.5V can be beneficial. Most cameras, mounts, etc., can tolerate this slightly elevated voltage (though manual verification is essential beforehand), and this adjustment can partially compensate for voltage drops.
Hardware mechanical issues
It is also worth writing a few sentences about cable management. There are a few important aspects of cable management in astrophotography setups:
- Some parts in the setup are moving/rotating against each other. If we connect the cable between the moving parts we must consider somehow fixing them, so they will not pop out of the connector or wobble inside during the movements. But we need also to consider the whole extent of the movement (it is usually valid for mounts and rotators) when organizing cables, so the cable location and length will not limit the movement.
- Cables should be of good quality. USB cables should be at least single-shielded, preferably double-shielded. The power cable should be short and with a large enough cross-section area to limit voltage drops. Connectors should be of good quality. Current above 4-5A should not be transferred with a simple DC 5.5mm receptacle. Both power and data connectors should be kept clean with dedicated cleaning agents (Kontakt S, for example)
- Connectors in the devices should not be pointed upwards, because the dew that is condensing over the night is collected in the up-facing surfaces and may get into the connectors and cause immediate issues, but also can cause corrosion in the longer term. Unused receptacles should be covered with caps, so the dew will not condense inside, and also insects will not build nests there.
- It is usually a good idea to lead cables together and wrapped; however, in some cases, leading the PWM signal cables (dew heating tapes) next to USB signal cables may cause interferences and communication issues. Then the cable organization must be revised.
Resolving problems
If we have a working setup, then once we need to change something, it is always a good idea to change one thing at a time. One cable, one camera, one power supply, one driver, etc. Then, if something stops working, it is relatively easy to find the root cause.
If we, for some reason, change several parts or have a new setup and we are not able to make it work, then the good approach is to test it in isolation.
First, we take a single component – camera, mount, or anything else- connect it to the power supply and computer, and test if the connection works. If not, then try with different cable, different power supply and different computer. If it does not work with two different computers, then most probably the device is broken. We may also try another version of driver – the most recent one, or maybe the older one if the latest is not working.
If a single component is working, then we add another one to our growing setup and also test. Like a camera with the mount – connect to computer, to acquisition software and start some artificial session with missing devices connected as simulators.
This way, step by step, we add more and more devices, we add a USB hub if we use, and we add a power splitter, till the moment our tested setup looks exactly the same as the one we use in the night. This process is somehow time-consuming, but usually, it is possible to resolve the problem completely.
