Opticstar - AG-131C CoolAir Auto Guider Camera

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The Opticstar AG-131C COOLAIR auto-guiding system includes everything you need to auto-guide any telescope with an ST-4 compatible port (this includes the vast majority of telescope mounts).

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Product Description

Opticstar AG-131C CoolAir Auto Guider Camera



  • Complete guiding solution for telescopes
  • For all mounts with a Guide Port (ST-4)
  • For all ASCOM compliant mounts
  • Also supports most non-ASCOM mounts
  • Max frame rate: 22 @ full res (WDM mode).
  • Max exposure time: 10 seconds (native mode).
  • Ideal for Planetary imaging
  • Air-Cooled with internal fan
  • Resolution: 1280 x 1024
  • Binning: 1x1, 2x2, 4x4
  • Region of Interest (ROI): USB 2.0 Powered
    • 640x480
    • 320x240
  • Computer controlled
  • Contents:
    • 1.3mp Monochrome video camera
    • Computer-to-mount interface box
    • All cables
  • Bundled Software (max. 10s exposure):
    • Opticstar View (up to 220 FPS)
    • etAMCAP (up to 220 FPS)
    • PHD Guiding
    • Nebulosity Lite
    • Plug-in for MaxIm DL
    • Plug-in for AstroArt
  • Computer Requirements:
    • Microsoft Windows (32-bit & 64-bit) XP/Vista/7/8
    • USB 2.0 port



The Opticstar AG-131C COOLAIR auto-guiding system includes everything you need to auto-guide any telescope with an ST-4 compatible port (this includes the vast majority of telescope mounts). A complete list of compatible mounts is included on this page. The AG-131C COOLAIR system includes the Shoestring GPUSB connectivity kit that interfaces the computer (USB 2.0 port) with the telescope mount (ST-4 port). All necessary cables are included.

The auto-guider system includes the Opticstar PL-131C COOLAIR colour video camera that connects to your computer's USB 2.0 port. For auto-guiding, the camera is software controlled by PHD Guiding that is included in the package. The telescope is also controlled by PHD Guiding. It is possible to use alternative auto-guiding software such as Guidemaster that is also included. There is also support for AstroArt and MaxIm DL. Both of these software packages can be used for auto-guiding and/or imaging. Plug-ins are included for both of them. Nebulosity Lite is also bundled with the AG-131C COOLAIR and it supports 2x2 binning, stacking and much more. Nebulosity Lite is well suited for image capture, lapse photography and basic image processing including frame stacking.

The maximum exposure time in PHD Guiding, Nebulosity, AstroArt and MaxIm DL is 10 seconds (in native mode). If maximum frame rates are required (22 F.P.S. at 1280x1024) then the camera can be used in Windows DirectShow/WDM mode.


Opticstar PL-131C COOLAIR Video Camera

The camera is very easy to use and provides a quality, low noise affordable solution for viewing or capturing high quality digital video from the telescope and recording it to your computer at a maximum 1.3 mega-pixel resolution. In order to purchase just the camera without the auto-guider accessories please visit the Opticstar PL-131C COOLAIR camera page.

The PL-131C COOLAIR is high-speed, a high-resolution 1.3 mega-pixel colour camera that is sensitive and can be used to capture images of the planets, Sun and Moon.  There is no infra-red (IR) filter in order to substantially increase sensitivity across the spectrum and the camera is thus well suited as a guider. The camera is cased in a robust metal body and can be connected to any telescope with a standard 1.25" drawtube.

A PC with a USB2.0 port running Windows XP/Vista/7/8 is required. The PL-131C COOLAIR is powered by the USB port and therefore no power supply unit is required. The camera will operate at a maximum true resolution of 1280x1024 but lower resolutions of 1024x768, 640x480, 320x240 are also supported.



In order to auto-guide with the AG-131C COOLAIR auto-guider system you will also need:

  • A telescope with an ST-4 (guide) port.
  • PC or laptop computer running Windows XP/Vista/7/8.


With the Guidemaster software provided, the computer can control your telescope mount and direct it's motion. Many telescopes come with a six pin port that looks like a phone jack. This is called an RJ-12 connector.

Typically, a hand controller is plugged into the ST-4 port. However with the AG-131C COOLAIR you can plug its RJ-12 cable to the hand controller which itself is connected to the mount. Depending on you telescope, you might have to plug the RJ-12 cable directly to the mount.

Either way, Guidemaster on your computer will control the telescope based on the image that it receives from the Opticstar PL-131C COOLAIR video camera (part of the AG-131C COOLAIR system).

The AG-131C COOLAIR system includes the Shoestring GPUSB interface box and needs a USB connection to your computer. If you do not want to plug it to a USB port, it is possible to replace the GPUSB interface box with a Parallel Port version, please see below.


Video Mode V Single Shot Mode

The PL-131C COOLAIR camera operates in two distinct modes. In video mode the camera will show as a DirectShow/WDM device and will produce very fast frame rates with exposures limited to under half a second. This mode is ideal for solar and planetary imaging as well as for 'training' telescope mounts. It can also be used for guiding with less dim stars.

The single shot mode supports longer exposures, in this mode a full frame is only sent to the computer once the exposure has been completed. This mode is ideal for guiding on dimmer targets. It is recommended that guiding exposures of around 1 second are used as this will even out any atmospheric turbulence, reveal fainter stars and improve guiding performance.


Hardware Requirements

The PL-131C CoolAir camera requires a fully featured, full speed USB2.0 port to take advantage of all the camera’s advanced features. Fully featured USB2.0 ports are rare in older laptops and not always present in entry level laptops. PCMCIA/CardBus USB2.0 cards typically do not deliver full USB2.0 speeds and will not work with USB2.0 high resolution video cameras including the PL-131C CoolAir.

To resolve such issues an ExpressCard (with a USB2.0 port) could be used instead of a PCMCIA/CardBus card due to the ExpressCard's superior speed of 2.5Gbit/s (480 Mbit/s through USB 2.0) per slot.

Express type cards use a 34mm slot where PCMCIA/CardBus cards use 54mm slots. An ExpressCard should be connected directly to the computer and not via a PCMCIA/CardBus card.

Please note the ExpressCards will resolve USB related issues assuming that the laptop data bus can support full ExpressCard speeds and is fully implemented.

Computers with slower USB2.0 ports may still be able to capture at full resolution but may be able to only transfer a user selectable area (ROI 640x480 or 320x240) to the computer while sustaining image resolution and high frame rates. This does not have a real effect when imaging planets where video capture should ideally take place at the smallest ROI size possible, typically 320x240 @ 220fps for focal lengths to around 6 meters for planets like Jupiter or Saturn.

Always download and install the latest Windows and Direct X service packs.


Technical Details

The GPUSB guide port interface adapter plugs directly into a USB port on your computer or a USB hub attached to your computer. Using an RJ-12 cable, the adapter connects to the guide port of your telescope mount. This guide port interface uses optocouplers to electrically isolate the computer from the telescope, eliminating a possible source of electrical interference. This interface adapter requires no external power source since it receives its power via the USB cable. More information can be found in the user manual.



Warning About Cables

The use of improperly wired cables with mounts can result in damage to the electronics in the mount, as well as damage to the interface adapter. The importance of using a properly wired cable cannot be stressed enough. It is strongly recommended to use only the cables included in the package.


ASCOM Compatible

Shoestring Astronomy has developed an ASCOM driver for the GPUSB. Using this driver, any autoguide software package that supports the ASCOM standard will work with the GPUSB and hence the Opticstar AG-131C COOLAIR Auto-Guider System. Most telescope mounts are ASCOM compliant. Therefore even if you decide not to use Guidemaster but use an alternative auto-guiding software package, the chances are that it can still be made to work via the ASCOM software platform. Please follow these steps in order:


  1. Download and install the ASCOM platform from the ASCOM website.
  2. Install the Shoestring Astronomy's GPUSB ASCOM Driver for the GPUSB from the link above.



Telescope-Mount Support

Any ASCOM compatible mount with an ST-4 compatible autoguider port should work with AG-131 COOLAIR. Mounts tested so far include:

  • CG5 (requires Shoestring's Guide Port Conversion Kit)
  • EQ3 (requires Shoestring's Guide Port Conversion Kit)
  • EQ5 (requires Shoestring's Guide Port Conversion Kit)
  • EQ6 PRO SkyScan via the hand controller
  • HEQ5 PRO SkyScan via the hand controller
  • Vixen SPHINX
  • Vixen GPDX via SkySensor 2000 (requires Shoestring's SkySensor 2000 converter)
  • Vixen Altux via SkySensor 2000 (requires Shoestring's SkySensor 2000 converter)
  • Losmandy GM-8 or G-11, without the Gemini box.
  • Losmandy GM-8 or G-11, with new-style Gemini box (circular DIN connects to connect motors).
  • Takahashi EM-10 (requires Shoestring's Guide Port Converter for Takahashi mounts)
  • Meade LX-200.
  • Meade LX-90.
  • Celestron Nexstar i-series.
  • Celestron Celestar 8.
  • Celestron Advanced Series GoTo.
  • Celestron CGE.
  • Orion Atlas EQ-G style.
  • Gemini G-41.
  • Astro-Physics AP900 QMD.
  • JMI NGT.
  • Tom O. Equatorial Platform.

With modification, you can also add an ST-4 compatible autoguide port to your EQ style mount.


Name Opticstar - AG-131C CoolAir Auto Guider Camera
Manufacturer Opticstar


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