The Starlight Xpress Adaptive Optics Advantage

The Starlight Xpress USB Adaptive Optics (with OAG) device provides an effective method of removing the effects of rapid guiding errors from CCD images. All but the most expensive telescope mounts suffer from rapid gear errors during guiding and such errors are very difficult to correct when the only control method available is to send speed corrections to the drive motors. A device that can adjust the image position by rapidly deviating the optical path, can correct for such errors very quickly and without the associated settling time issues.

A common method of shifting an image for AO purposes is to use a mirror to re-direct the beam through a variable angle. This works well, but deviates the optical path through 90 degrees and takes up a considerable back focal distance. Its motion sensitivity is also affected by the distance between the mirror and the CCD. A straight-through device is more convenient and optically shorter, so the original Starlight Xpress AO unit was designed with this in mind back in 2004.

A secondary advantage of the straight-through design is that it is possible to construct a system that has a well defined optical deviation for a defined input signal. This means that the sensitivity of the system in pixels shift per input step is essentially constant and is independent of the optical system used and the distance between the CCD and AO.

Excellent Optical Clarity

The AO element is a multi-coated AR bloomed plane-parallel optical window with a thickness of 13 mm and a diameter of 60 mm. This element can be tilted by up to approximately +/- 3 degrees.

Converging light from the telescope objective lens or mirror passes through the window on its way to the CCD chip, but is essentially unaffected when the window is perpendicular to the beam. However, when the window is tilted, the converging beam is displaced by an amount which can be defined as approximately 0.075 mm per 1 degree of tilt. The maximum image deviation is therefore approximately +/- 0.15 mm in both the X and Y planes. This corresponds to about +/- 23 pixels on the CCD of an SX-825 camera.

Major Features of the SX Adaptive Optics System

• Image shift factor independent of the optical system or camera back-focus spacing.
• Comes with OAG (Off-Axis Guider)
• STAR2000 guiding compatible.
• May be used to image stabilize many other makes and types of camera, given suitable control software.
• Clear aperture of 60 mm for up to 35 mm full-frame size chips.
• Short optical length: 74 mm with OAG, 44 mm without (add 6 mm if front end adapter is used).
• Very low light loss (~2-percent) from the multi-coated optics.
• Filter threads for adding 48 mm narrow band. IR blocking or pollution rejection filters without affecting the guide camera sensitivity.
• USB controlled.
• Low power consumption. Less than 600 mA at 12v DC when moving, 50 mA quiescent current.
• Compact and lightweight, only 132 mm in diameter x 32 mm long - less than 700 grams load on the telescope.

Trius and AOLF - the Perfect Combination

The Trius range of CCD cameras from Starlight Xpress offers a unique advantage over other imaging cameras. With a built-in USB2.0 hub in the rear of the camera, all of your imaging setup -the SX AO module, Lodestar X2, and the Starlight Xpress USB filter wheel-can all be controlled through the rear of a Starlight Xpress Trius camera. This significantly reduces the number of cables running back to the computer, helping to keep things organized and helps prevent cable drag and cables from being snagged in the dark. Both the Lodestar X2 (the most sensitive dedicated guide camera on the market), and the Starlight Xpress USB filter wheel are powered and driven through the USB so no additional power cables are required.

• Image tracking and stabilization using a high speed tip-tilt optical window
• Comes with OAG (Off-Axis Guider)
• Fast-tracking speed of 5 mS per increment.
• Overcomes rapid gear errors to stabilize even difficult mounts.
• Mount control output for correcting large drive errors while maintaining AO stabilization.