Equipment Review (preliminary)

It is said that fixed focal length eyepieces are superior to zoom eyepieces of equal design. This may no longer be exactly true.

Inherent to zoom eyepieces of its focal range, the Baader Hyperion 8-24mm Mark IV is not parfocal and changes the apparent field of view. The wide, almost 70° field at 8mm is extremely pleasing. Zooming is absolutely smooth with tangible click-stops which are basically incorporated for bino viewers. Likewise inserted into a diagonal of a telescope it tactilely informs the current focal length in the dark (without need for swapping eyepieces).

Of course, with a barlow lens a second set of magnifications can be obtained, however the assembly will grow tall. The form factor will be much lower with a barlow lens only (without extender piece) screwed to the zoom eyepiece. In this event, the barlow lens will be closer to the eyepiece in that the barlow factor can drop to 1.5x to 1.6x which is fine.

Tested with a Ø71mm/FL=450mm quadruplet FPL53 APO, there was virtually no comatic and chromatic abberation, sharp across the range of magnification. The view through is rich of contrast and detail. The Trapezium stars were clearly resolved at all magnifications from 18x to 56x (90x with barlow lens). At 18mm the Baader can compete with an 18mm fixed eyepiece from Explore Scientific, though way not in terms of FOV. The same impression was felt with a Ø60mm/FL=360mm doublet FPL53 APO (without flattener). The sweet spot ranges between 12mm and 16mm for contrast and FOV.

When mounted on a F5 Newtonian without coma corrector the zoom eyepiece requires slight refocusing for the circumference when the center of the moon is pin-point. However, this is the same with a 12mm fixed eyepiece, in that this is not an attribute of the Baader Zoom, but of the reflector's parabolic main mirror.

The specified FOVs are actually a little narrower than specified, but very few eyepieces will come out to the exact FOV advertised. The zoom function is a great assistant for scope alignment. A nice gesture is the included holster for belts and tripod legs. There is no need for a 2-inch adapter for focal lengths under 24mm, but if a 1.25" diagonal is not at hand this can be a "live saver".

If this Baader zoom eyepiece is purchased for the purpose of replacing low-cost bundled eyepieces, the feel is like having a new telescope. A direct comparison with Explore Scientific, Panoptic, Pentax, Nagler, etc. fixed focal length eyepieces is found in forums but technically inappropriate.

 

 

Pros

• Optically: generous eye relief, notably high contrast, virtually edge-coma free, absense of glare, no blackouts or beaning.
• Mechanically: solidly built, smooth zoom action, light weight (290gr), slim form factor (Ø55mm) and finish.

Cons

• AFOV's are a little smaller than specified.
• Click stops have a very soft tactile response.

Conclusion

In particular for occasional observers, travellers and group events the Baader Hyperion 8-24mm Mark IV is a smart choice, reducing parts count and bill of materials. If a wide field is not a must, this single eyepiece can replace 5 fixed-focal-length eyepieces, with only little sacrifice in optical performance, mosty regarding field of view. Budget-wise a winner in any case.