Baader Hyperion quality w/rings, removing negative

Anyone have direct experience with the quality of the Baader Hyperion eyepieces when using the "Finetuning Rings/FTR" or when removing the nose piece/negative group? The use of these features changes the focal lengths and are advertised as advantages and used as selling points, but I wonder if there is a degradation of image quality. Also, when using the rings there is a longer optical train. Does this reduce the image brightness?

Thanks in advance for any and all responses.

Oddog

Tom: Just a few general comments.

- Probably the most important thing to know when discussing eyepieces is the focal ratio of the telescope that it will be used with. As the telescope's focal ratio becomes faster, the angle of the cone of light entering the eyepiece becomes steeper which makes it more difficult for the eyepiece to cleanly achieve focus off-axis.

If one is dealing with an F/12 telescope, almost any eyepiece will provide reasonably sharp stars right to the edge of the field of view. On the other hand, if one is looking through an F/4 telescope, there are very few eyepiece which can provide sharp off-axis stars.

One tool the designer has to help is placing a negative section in front of the main element group. In the simplest form, this is putting a barlow in the optical train, to the main eyepiece, the negative front section makes the telescope appear to be slower, with a 2x front section, the rear would see an F/8 light cone rather than an F/4 and this cleans things up...

So in your situation, the question of removing the front section negative section would most likely depend upon the focal ratio of the scope you would be using it in.

- The Hyperisons are reputed to be nearly identical to the Orion Stratus eyepieces. These eyepieces offer big eye lens with a very comfortable eye relief and a generous field of view but in my experience, their off-axis performance is not satifying even in a relatively slow focal ratio telescope. The outer 25%-30% of the field of view is poorly focused with addition light/less contrast. Simply put, they are reasonable eyepieces for the money but do not offer the sort of sharp off axis stars and evenly illuminated field of view one would see with a Nagler.

- Image brightness... The eye is relatively insensitive to image brightness, one does not see single digit percentage changes. What changes image brightness is the magnification, this is inherent, when one increases the magnification the same amount of light is spread out over a larger area so it is dimmer. The image brightness is measured by the exit pupil size and is related to it's area.

So, if one increases the magnification by a factor of 2 the exit pupil will be cut in two and the image will be one quarter as bright.

This means that when playing with the Hyperion rings, you will see changes in image brightness but the cause is simply the result of changing the magnification.

Hope this is of some help.

Best wishes to all, hope you had a fine day yesterday and may your new year fulfill all that it promises..

Jon Isaacs