M13 imaging example with CGE mount and C11 at f/11
This is the result of an evening of testing MetaGuide on a CGE mount. Here are details of the setup:
- CGE mount with C11 and Taurus off-axis guider
- Guided with MetaGuide and a Toucam Pro, using a star adjacent to M13
- PEC NOT enabled - all corrections handled by MetaGuide
- CGE mount polar aligned with built-in polar alignment procedure - one iteration. In fact, mount was leveled using only its bubble level, and the polar alignment was only adjusted in azimuth, and only roughly, by hand and without wrenches
- Processing done in Iris, and stacking done using 1-star alignment, with no field rotation
- Results are limited by coma at the edge of the cluster, since M13 was off-center due to a poor guide star choice. Field rotation does not appear to be an issue for this image, and could be reduced by stacking with rotation if desired.
Stack of thirteen 4-minute MetaGuided images on a CGE mount with C11 at f/11. Sigma stack with coefficient 2.0 in Iris. Flats, darks, offsets applied - but no rotation and no deconvolution. RGB balance set in Iris, then levels applied in Photoshop. Approximate fwhm of stars in center of main image frame is 2.5".
Single 4-minute frame straight out of camera in jpg format, with levels applied in PhotoShop and then reduced in size. M13 is offset in frame due to non-optimal guide star selection. Vignetting on left is due to obstruction in the Taurus off-axis guider.
Visualization of star motion across full frame between first and last 4-minute image, 66 minutes apart. Field rotation is evident, but much of it is translation that can be removed with a 1-star align prior to stack.
As above, but after subtracting the translation of the central star. The effective rotation about the central star is evident, but the magnitude of the shift is well under one arc-second. Depending on the size of the cropped final image, and the fwhm of the exterior stars, the effect of this rotation on the final image may be minimal.