User manual SBIG AO-L

[. . . ] At the 45 degree angle the mirror is used at it foreshortens to only 35 mm. It also had an issue with image rotation at large deflections which becomes serious for large CCDs, but is not a problem for the smaller CCDs of the ST series. For these reasons SBIG has designed a new Adaptive Optic device for high speed beam steering called the AO-L (Active Optic ­ Large Format). It does not have the range and speed of the old AO-7, but can cover the larger CCDs. [. . . ] The total overhead in the software for an AO-L move is 45 milliseconds. If, for example, you are taking 50 millisecond exposures with an optimized focal length (3 pixel Full Width Half Maximum stars), the total cycle time is 45 + 50 + 28 ms, or 123 ms (8 updates per second). The AO-7 advantage is that a move of any length is 20 milliseconds, but the exposure and overhead times were similar. Based on our experience and knowledge, AO-L and AO-7 rates help only slightly with reducing ground layer atmospheric turbulence, but are quite effective in reducing guide errors and wind buffeting. AO-L Installation: The AO-L is designed to be bolted directly to the nosepiece mounting plate on the front of your STL camera. The motor portion of the AO-L hangs over the top edge of the camera. The steps to attaching the AO-L are as follows: 1) Very important: Make sure the AO-L is unpowered so if a screw falls into it you do not get an electrical short. 2) Remove the top plate of the AO-L by removing the 6 screws that hold it down. 3) Remove the pieces of neoprene or foam that were inserted between the window paddle and the top plate during shipment. Save these in case the unit ever needs to be returned to SBIG. They cage the window paddle, keeping it from flying around when the shippers throw the boxes from truck to truck, and being damaged. 4) Using the 4 screws provided, attach the housing of the AO-L to the camera nosepiece mounting plate, which is 2. 75 inches (7 cm) on a side. You can do this without removing the window paddle. Be VERY careful not to let the screws fall into the camera. If they do fall in, shake them out carefully or remove the camera chamber front plate to reach them so as to not scratch the optical surfaces within the camera. You do not need to remove the camera nosepiece front plate. If you do, be very careful to keep any shim washers found under it in the same position so as to maintain the squareness of the CCD to the optical axis. 6) Plug the cable from the AO-L into the I2C-AUX port on the STL. Download the latest drivers from SBIG and install them. At the time of this writing CCDOPS is the only image acquisition program that supports the AO-L but we expect CCDSOFT and Maxim will follow shortly. [. . . ] Vibration: the AO-L does vibrate substantially in exercise mode, with an easily felt buzz. This is not a problem for the much shorter moves typical of actual operation, and when mounted to a substantial telescope. Use with ST-Series cameras: SBIG will soon offer an adapter so the AO-L can be used with the ST- series cameras that have USB capability Removal of Paddle: the paddle containing the window can easily be removed if necessary by unhooking one end of the spring and pulling it off the pivot point. The pivot point is a spherical ball with a snap fit. [. . . ]