The principle of operation:
A common method of shifting an image for AO purposes is to use a ‘tip-tilt’ mirror to reflect 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. Starlight Xpress USB Adaptive Optics device is more convenient and optically shorter. 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.
The AO element is a Multi-coated AR bloomed plane-parallel optical window with a thickness of 13mm and a diameter of 60mm. 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 0.075mm per 1 degree of tilt. The maximum image deviation is therefore approximately +/- 0.15mm in both the X and Y planes.
Image of M57 planetary nebula recorded with Celestron C11 telescope at f/10 (2800mm focal length): to the left with the adaptive optics switched off (using mount guiding only), to the right with the adaptive optics switched on and operating at 3 updates per second.
▪ Image tracking and stabilisation using a high speed tip-tilt optical window.
▪ Fast tracking speed of 5mS per increment.
▪ Overcomes rapid gear errors to stabilise even difficult mounts.
▪ Mount control output for correcting large drive errors while maintaining AO stabilisation.
▪ Image shift factor independent of optical system or camera back-focus spacing.
▪ Off-axis guider assembly (optional) for use with an SXV guide camera.
▪ May be used to image stabilise many other makes and types of camera, given suitable control software.
▪ Clear aperture of 60mm for up to 35mm full-frame size chips.
▪ Short optical length - 74mm with OAG, 44mm without (add 6mm if front end adaptor is used).
▪ Very low light loss (~2%) from the multicoated optics.
▪ Filter threads for adding 48mm 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 - 50mA quiescent current.
▪ Compact and lightweight - only 132mm in diameter x 32mm long - less than 700 grams load on the ‘scope.
The perfect combination:
Unlike other solutions, Starlight Xpress USB adaptive optics can be used with any imaging camera. However, it requires the use of an off-axis guider and a Starlight Xpress guide camera (such as the sensitive Lodestar X2 we recommend for this application). Adaptive optics are often used with medium-long focal length telescopes in long exposure astrophotography and often these telescopes require you to place the imaging camera at a precise distance from its integrated corrector, if present (for example the integrated flattener or reducer of Celestron EdgeHD telescopes needs 105mm distance). So you also need to pay attention to the thickness of the entire system consisting of
adaptive optics + off-axis guider + possible filter wheel + imaging camera
Starlight Xpress has a special low-profile off-axis guider that is fixed directly on its adaptive optics and also on special low-profile Starlight Xpress motorized filter wheel. This will prevent any bending and the entire group of accessories (adaptive optics + off-axis + filter wheel) has a thickness of only 78mm. This design also allows for the Lodestar X2 guide camera be close to parafocality with the imaging room (if this has an approximately 15-20mm backfocus).
Starlight Xpress USB Adaptive Optics - scope of delivery:
• Starlight Xpress USB Adaptive Optics
• AC Mains Adapter
• USB cable
• Guider Cable
• T-Thread Female Adapter - (Telescope Side)
• SCT-Thread Female Adapter - (Telescope Side)
• T-Thread Male Adapter - (Camera Side)
• M72-Thread Male Adapter - (Camera Side)
• CD-ROM - Manual