Moravian instruments, Inc., source: https://www.gxccd.com/art?id=715&lang=409, printed: 26.09.2023 1:26:08

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New version of the C1 camera with Trigger input and GPS module
 GPS satellite signal receivers provide location information and also very precise (sub-microsecond) timing information. Integration of the GPS receiver with an astronomical camera thus allows very precise timing of exposures. Geographic location data, also available to the control software through specific commands, is an added bonus. The GPS receiver module port on the new C1 cameras is identical to the port of the C5 cameras, so both camera lines use the same receiver modules. What's more, the new C1 cameras also contain trigger input port, which allows external devices to determine start of exposures. This functionality can be used for precise exposure timing from external signal source and/or for synchronized exposures of multiple cameras etc.

Original version of the C1 camera and a new version with attached GPS receiver module with external antenna

Original version of the C1 camera and a new version with attached GPS receiver module with external antenna

C1 and C1 “T” cameras

Because majority of C1 usage scenarios (astronomical photography, variable star research, etc.) do not utilize the benefits of the sub-microsecond exposure timing or external exposure triggering, and both the GPS module interface and hardware trigger port increase the price of the C1 camera, the original variants of the C1 cameras without these ports are still available. The new variants with trigger port and the ability to attach an optional GPS receiver are marked with letter “T”.

Back side of the original version of the C1 camera with the USB, Power and EWF connectors

Back side of the original version of the C1 camera with the USB, Power and EWF connectors

Back side of the new T version of the C1 camera with the USB, Power, EWF and Trigger connectors. GPS port cover is visible on the left side

Back side of the new “T” version of the C1 camera with the USB, Power, EWF and Trigger connectors. GPS port cover is visible on the left side

GPS receiver module

New version of the C1 cameras can be equipped with an optional GPS receiver module, which allows very precise timing of the exposure times. Geographic location data are also available to the control software through specific commands.

There are three variants of available modules:

  • GPS module with integrated antenna, compatible with GPS and GLONASS satellites.

  • GPS module with external antenna, compatible with GPS and GLONASS satellites.

  • GPS module with external antenna, compatible with GPS, GLONASS, Galileo and BeiDou satellites.

GPS modules can be attached to the port on the side of the C1 camera head. If the camera is not equipped with the GPS module, the GPS port is covered with a flat black cap.

GPS receiver module with integrated antenna

The module cover is made from orange plastic to indicate the presence of RF antenna, which needs unobstructed view of the sky to successfully acquire signal from GPS satellites.

If the camera is located in the observatory dome, especially if the dome is covered by copper or other metallic sheets, GPS receiver may not be able to capture signal from GPS satellites. Also, if the camera is located on the telescope back side, so the camera back side points mostly to the ground, GPS signal reception can be compromised.

The GPS receiver with integrated antenna also can be unable to capture signal from enough satellites when the USB3 connection is used. Please note this issue is not specific to the C1 camera, but it affects any GPS receiver or other RF devices, operating in a close proximity to a USB3 line. Using of USB2 cable solves this problem, but at the expense of slower image download. If the USB3 connection is used, usage of the GPS module with external antenna may be necessary.

GPS receiver modules with external antenna

The variant of GPS module with external antenna is attached to the camera head the same way like the version with internal antenna. The module cover is black as it does not need any special positioning. The cover is thinner, but there is a connector for the GPS antenna on it. Note the module can work only if the antenna is connected.

GPS antenna is shipped with this variant of the GPS module. Antenna cable is 3m long and the antenna is equipped with a magnet, allowing it to be attached to any ferromagnetic surface.

The C1 camera with the attached GPS receiver module with external antenna

The C1 camera with the attached GPS receiver module with external antenna

GPS receiver module handling

Please note if the GPS module is to be added later, the camera must be sent to manufacturer. Just connecting the GPS module to available port is not enough, it is also necessary to reconfigure the camera firmware.

GPS module is handled through camera command set. Its main purpose is to provide very precise timing of the exposure times with better than μs precision (the GPS module provides time pulses with 30ns tolerance). Geographic location data are also available to the control software through specific commands.

The GPS tab in the SIPS camera control tool window shows information about GPS receiver state

The GPS tab in the SIPS camera control tool window shows information about GPS receiver state

The GPS module needs to locate at last 5 satellites to provide exposure timing information. Geographic data are available if only 3 satellites are visible, but especially the mean sea level precision suffers if less than 4 satellites are used.