SBIG brought adaptive optics (AO) technology to amateur astrophotography to assist guiding, by "wiggling" an optic several times a second, and only "bumping" the mount when there is a significant deviation. It is in essence a "fast" guider.
Adaptive optics can reduce the size of stars, measured as FWHM (full-width at half-maximum intensity), by 0.5 arcseconds or more, depending upon the seeing conditions. This becomes significant at longer focal lengths for high resolution astrophotography.
SBIG AO technology was designed for use with their internal guide CCD contained inside the imaging camera. A major disadvantage is AO guiding through filters. Finding a bright guide star without AO optics with the internal guide CCD is often times a challenge. Finding one behind H-a, OIII or SII narrowband filters is even more problemmatic. AO guiding makes that even more challenging or impractical with AO frequencies of 5-20 Hz smearing out the star flux.
The MOAG-A now provides you with the opportunity to guide in front of your filters, potentially increasing signals over RGB filters by a factor of 3 and over an H-a filter by a factor of >100.
The left figure below shows the MOAG-A placed between the SBIG STL and AOL. Light comes from the telescope from the left, passes through the transparent AOL moving optic, through the MOAG-A and into the STL camera. Some of that light is diverted with a pick-off optic and sent up to the STL-Remote guide head in the MOAG-A. in this way, the benefits of AO technology can be used with unfiltered light. Brighter guide stars allow higher frequencies to be used for AO guiding.
The AOL screws into the MOAG-A as it would into the STL. The MOAG-A includes an adaptor with 2" male threads that screw into the STL nose plate. This adaptor has a dovetail groove that fits into the MOAG-A body, and is tightened down against a flat flange with 4 set screws. In this way, the AOL/MOAG can be rotated to the vertical position (relative to the imaging CCD) and locked into place, as shown below .
A variety of adaptors can then be used to connect the assembly to the telescope. As shown below, an STL-to-APmale adaptor screws into the AO-L and into a 2.7" AP extension tube at the back of a 12.5" RCOS RC telescope using 2.7" AP tubes
The MOAG takes up 2" of backfocus and the STL adaptor takes up another 3/8".
This image shows active AOL tracking of a very bright guide star, Scheat, in Pegasus with the MOAG-A on the 12.5" RC shown above. MaximDL v 4.55 was used. A track time of 0.1s was used, resulting in a guide rate of 6.9 Hz..
Click on image to enlarge.
A 1 minute image taken with a green Astrodon filter using this AOL guiding configuration resulted in a FWHM of ~1.8 arcseconds that night. Without the AO, the seeing was >2.3 arcseconds.
The MOAG in many cases makes narrowband AO imaging possible. The image of M33 below show a 10 min (uncalibrated) exposure using the STL11000M and a 6 nm Astrodon H-a filter guided with the MOAG-A and AOL on a magnitude 8.1 guide star. The guide exposure was 0.2s and the guide rate was 4.3 Hz (click on image to enlarge).
Once the location of the guide star is mapped, data acquisition programs can potentially find guide stars automatically. The following screen capture from Software Bisque's TheSky v6 shows the location of the guide star used for the above H-a image of M33 with the MOAG-A. It is near the center at the bottom with the red circular target.
