Hi all,
<tl;dr>
When I look through an eyepiece and refractor with or without diagonal, not only will the produced image suffer from a reflective impurity on the mirror surface, those missing 6-10% lambda, but also from the flattening, dimension-substracting effect a flat mirror has on
rays in a bundle of rays in relation to each other.
</tl;dr>
Still pondering this thread
http://www.iceinspace.com.au/forum/s...d.php?t=172903 . Mental4astro says that there are eyepieces designed specifically for the convex image a refractor produces and also eyepiece designs for concave images from a newt's primary mirror.
I'm on my own quest of starting my first eye piece collection for f4.9 achromat plus TS-Bino with 1.6x barlow, and I’m doing a bit of general “getting the hang of optics and perception”. Without any previous knowledge other than reading the occasional forum post here on IIS. Mental4astro's and Wavyton's for example
The mirror mystery is my first obstacle. What does a flat polished mirror like a refractor’s diagonal or a newt’s secondary do to the convex or concave curvature of the entering image ray bundle?
Does the mirror murder that curvature? Does the mirror murder the eyepiece design?
I read on wikipedia: one incoming light ray reflects off the mirror surface in the same angle as its impact angle.
Okay. Hm. Why is it then, when I hold a ping pong ball in front of the mirror and look at the mirror surface, what I see is not a 3d ball but a flat image? It’s only my brain knowing it’s actually a sphere and not a mere circle. But what I see as reflection IS a flat circle. Correct?
So my train of thought goes like this:
when the bundle of light rays from a curved object reflect off a mirror surface, the distance or time difference between ray 1 from the edge of the ball [further away from mirror surface] and ray 2 from the middle of the ball [closer to mirror surface], this difference is lost during reflection. Hence the loss of depth perception. A 3d object becomes a 2d image.
This would mean, a mirror's effect on an image can't be discussed looking at one single light ray. It's the rays in a bundle in relation to each other which produce a sphere or a flat circle.
In this thought direction it then follows that the 3D curvature, convex or concave, (not the image of an object but its curved representation produced by scope design) is lost when being reflected off a secondary or a diagonal. Like Wiki says, the individual rays ARE reflected at the same angle. But the produced image is not mirroring the convex nature of the image. Like the pingpong ball is no longer a sphere but a circle, the convex curved image from the refractor becomes a flat 2D round circle or maybe shaped slightly elongated, I don't know.
So what enters the eyepiece and comes out of it at our eyeball MUST differ from the image we would see through an eyepiece if there were no diagonal in between.
If this is true, then even with a super top-of-the-shelf reflective diagonal mirror, the generated image rays bundle would still be blunted and flattened when they enter and traverse the lens construction of an eyepiece.
Meaning: an eyepiece working for a refractor’s convex image curvature, would be surprised by the flattened, 2D, non-convex ray bundle coming off the mirror. The eyepiece would still attempt its eyepiece magic, being designed for refractor's convex curvature, but in a mirror-falsified work place, the produced image at the eye ball won't match the quality of the image intended by they eyepiece designer.
The reflective quality of 95% lambda or whatyamaycallit silver or dielectic mirror surface is not the only limitation of a flat mirror in an optical path.
The way I am thinking, being a mirror in the first place is a more prominent limitation.
Let’s forget about the newt’s secondary mirror for the moment because I see no way of testing or verifying without a secondary.
But when I look through an eyepiece and refractor with or without diagonal, not only will the produced image suffer from a reflective impurity on the mirror surface, those missing 6-10% lambda, but also from the flattening, dimension-substraction effect a flat mirror has on rays in a bundle of rays in relation to each other.
? Is that so?
This question is not directly related to my actual quest of eyepiece purchase. But it's an open question in my head which hinders progress in decision making.
Thank you so much for any input!
Annette