Question re. BYE Focus Metrics

[Seldom]

I focused on Caph last night,  At the center of the frame the focus metric ranged around 4.1 +/- 0.2.  At the left edge of the frame it read 3.7 +/- 0.2,  At the right edge of the frame it read 4.5 +/- 0.2.  My scope is an NP101is with imaging rings.  My camera is a 60Da.

 

Questions:

1) Is BYE 3.1 accurate enough to calibrate my focus in the manner described?  The measurements were repeatable.

2) Is this measurement spread sufficient to be a concern in my images?  The scope permits adjustments to the focal plane.

3) Any suggestions on how to determine if the error is in the scope or the camera?  My guess would be to rotate the camera and see if the measurements stayed at the same location on the frame (error in camera), or moved (error in scope).

[admin]

This is probably due to field curvature.  Just guessing.

 

The focus metric in BYE are pretty accurate.... but seeing will impact the metric greatly

 

Regards,

[Seldom]

Thanks, Guylain.

Does the focus metric include the entire FOV?  I noticed that the lowest number was on the left of the FOV, but that I couldn't get the focus number at the center of the FOV to get as low as the one on the left.

Also, shouldn't field curvature be roughly symmetrical around the center of the censor?  This curvature would be centered on one of the edges.

[admin]

Thanks, Guylain.

Does the focus metric include the entire FOV?  I noticed that the lowest number was on the left of the FOV, but that I couldn't get the focus number at the center of the FOV to get as low as the one on the left.

Also, shouldn't field curvature be roughly symmetrical around the center of the censor?  This curvature would be centered on one of the edges.

 

No, the focus metric data is taken form the smaller zoom box in the lower right corner... just below the bell shape star graph.