Swizerlan Would it be possible to incorporate ASTAP sensor tilt analysis into asi air plus to assist with correcting tilt and collimation?
If you want a turn key solution, you can use the tool in PixInSight.
You can do it manually on a budget by looking at the star sizes (HFD, FWHM, etc) at different locations of the frame. Many programs have tools to display star sizes. Even ASIAIR has a star size tool.
For a frame that has no tilt and no field curvature, all stars in the frame will have identical (to within 10% or 15%) star sizes. With field curvature, the star sizes at the corners will be larger than the star size near the center (i.e., same way as you adjust backfocus of a reducer). With decentered optics, the lowest star size will not be at the center of the frame.
With tilt, one of two corners will have larger star sizes that the remaining corners.
You can do better by using a Bahtinov mask and inspecting the focus of a star near the center, and compare with focus of the stars near the four corners. This method not only tells you there is a tilt, the Bahtinov mask will tell you the direction of the tilt (i.e., which direction it is off focus).
Unfortunately, star analysis will need a steady, clear night. The best way to adjust tilt (and very accurately) is to reflect a green laster pointer (any bright monochromatic light source would do) off your camera's sensor. Google for "cloudy nights sensor tilt green laser," and you will find lots of resources. (I use an OAG in the reversed direction to mount my laser, with the laser installed in place of the guide camera, and with the beam emitting from the prism towards the camera.)
If you really plan on adjusting the tilt of the sensor inside the camera, I also recommend getting one of ZWO's camera rings to mount the camera so you can have a steady platform to adjust the internal tilt.
But my real recommendation is to let someone with proper tools to do that kind of adjustment. Just adjust tilt with the tilt plate.
Chen
