Eyepiece FOV images in a 127mm Mak

[Louis D]

I took a bunch of images of the field of view (FOV) through many of my eyepieces in my 127mm f/12 Mak for comparison against those I took through my AT72ED f/6 refractor.  I haven't had the time to pull together comparison groups for all of them as I did for the images taken with my AT72ED.  However, I did pull together one for the 29mm-30mm group since it shows how much marginal/terrible eyepieces can improve in a slow telescope.  It also shows how spherical aberration of the exit pupil (SAEP or kidney-beaning) becomes more obvious as black donuts.  It also shows chromatic aberration of the exit pupil (CAEP or ring-of-fire) as a rainbow effect.  Last, it shows that really good eyepieces become razor sharp.

The above images were taken with the high resolution Samsung Galaxy 7 camera at f/1.7.  The edge images were taken by pointing the camera straight at the field stop for best sharpness.

The above "full width" images were taken with the lower resolution LG G5 super wide angle camera at f/2.4 so center and edge can be seen in a single image.  Notice how this camera's smaller aperture is more sensitive to SAEP and CAEP than the Samsung's camera.

The above image is from my original group of FOV images taken through the AT72ED which is an f/6 telescope.  I included it for ease of comparison.  I did not include a "full width" image for the APM UFF when I composited this image since its entire image fit within the Samsung camera's FOV.  By comparison, notice how much the Rini, Kasai, and Agena eyepieces improve by going from f/6 to f/12.  The ES-82 shows CAEP at f/12 and is sharper while the APM UFF shows some SAEP and has incredible edge sharpness at f/12.

The slower Mak seems to show any inherent eyepiece SAEP or CAEP more obviously than the faster refractor.

The Mak images all show greater image scale due to its 1540mm focal length versus the AT72ED's 430mm FL.  Both sets of images were taken from the same distance, to within a few inches.

I will try to add more comparison images to this thread as my time allows it.  Each one takes over an hour to edit and composite.

[RT65CB-SWL]

Great follow up article @Louis D 

Thank you for taking the time to put this and the previous article together.

[Louis D]

Here's the 32mm to 42mm 127 Mak group, minus the military surplus eyepiece that I forgot to include when taking the images:

Here's the original group image through the AT72ED at F/6:

It's pretty clear that everything improved quite a bit going from f/6 to f/12.  However, the AFOV of some eyepieces, especially the Rini MPL 38mm and Rini Erfle 42mm, changed somewhat.  Since neither has a defined field stop, this doesn't surprise me all that much.

Edited November 25, 2020 by Louis D