Hi mental
I will try borrowing some eyepieces from the club members at the next gathering to see if I can get a better image.
Thanks for all the info.
Quote:
Originally Posted by mental4astro
Expanding on astro744...
What eyepiece were you using?
One thing that is next to never mentioned about eyepieces is that they DO NOT PERFORM THE SAME IN ALL TELESCOPES!
Telescopes produce a focused image that is not flat. The shape of this 'plane' depends entirely on the optical system. Newtonians produce a concave shaped focal plane. Maks & SCTs a convex shape. Refractors also convex. Then, add to the mix the focal ratio & the radius of the focal length of the scope (yes !), and the ultimate focal plane is one heck of a fruit salad!
Eyepieces too respond best to certain focal planes than others. Manufacturers won't mention this as it could mean to some people that their products are "faulty" when this is not the case.
If the scope & eyepiece are not an optical match, you can get a terrible image, or change the ease of use (less eye relief or more critical eye placement), or see other aberrations such as chromatic aberration or astigmatism, even field flatness.
Even within a model range of eyepieces performance can vary greatly between scope designs.
Big brands are also no garrantee of optical match.
Best thing is to give some examples: Baader Hyperion eyepieces are excellent in SCTs, but very poor in Newtonians. Nothing wrong with Hyperions - I love them in my C8, but no good in my Newts. Only the 5mm Hyperion is good in Newts & SCTs, which is why the 5mm is the only Hyperion in my kit. If you only have an SCT, all the Hyperions will be great.
Pentax XW eyepieces. Many people believe these are the best eyepieces in the world. They are very bloody good. BUT, depends on the scope you use them in. The 14mm is excellent in Maks, but requires a coma corrector to improve them significantly in Newts. The 10mm is exquisite in Newts, but in an SCT, eye placement is really, really fine, which is ok if you are just observing, but for me with my sketching & constant back and forth to the eyepiece, it is a significant drawback.
AFC does not change the shape of the focal plane. The image you see is still due to the optical mismatch between the scope and eyepiece you are using.
Mental.
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