Curvature, Tip/Tilt, and Collimation all within acceptable limits and produced round stars
across the entire FOV in the test image below using the Celestron focal reducer. |
Frames used for analysis. FWHM and Aspect values are very good and
indicate the optics should produce good images when
atmospheric seeing is good. *NOTE:
the SBIG AO-8 adaptive optics typically will cause the FWHM values to be
better,
with tighter stars than without the AO-8, due to the first-order
atmospheric seeing correction that the AO-8 provides. From
previous
testing, I would expect the above FWHM values to grow to around 2.5-2.7
arc-sec in good seeing without the AO-8.
The AO-8 is a very integral component of getting a C14 OTA to perform well and I highly recommend
adaptive optics be used
on OTA's with similar focal lengths. *NOTE: for these tests, the jet
stream was directly over the region which degraded seeing
conditions somewhat. The above numbers would likely have been
slightly better without the jet stream effects on seeing. |
Field curvature value of 28.1% with Celestron focal reducer in
use. Acceptable numbers for a typical Celestron SCT.
Wade Van Arsdale
Little Rock, AR., USA
January 19th, 2009
|
The result: Stars are very acceptably round throughout the entire
FOV, even at the corners and edges, indicating the optics are in good
collimation and the OTA is performing well. The test frame is a
sigma combine of the above listed eight frames with dark frames applies
along with gradient removal, histogram stretching and one light of Unsharp
Mask in Photoshop. |
