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Antares' 2" 0.5x focal reducer screws on to any accessory (such as eyepieces, camera adapters, etc.) that accepts standard 2" threaded filters and provides a nominal reduction of 0.5x. Use of this focal reducer effectively halves the focal ratio of your telescope, resulting in a wider field of view and significantly shortened exposure times for astrophotography. For example, use of this reducer will convert an f/10 telescope into an f/5 scope.
The 2-element reducer features fully multi-coated optics in a black-anodized aluminum filter cell. This focal reducer will work well for visual use too when coupled with the right kind of eyepieces and telescopes (it is not recommended for very fast scopes or very wide angle eyepieces for visual applications). However, it does not have external 2" female threads so you cannot screw/stack additional 2" filters on to this reducer.
The actual reduction will vary a little over or under 0.5x
depending on exactly where the focal reducer is placed in the optical
path. The focal length specification of this reducer is 158mm. Hence, the "working distance" of this specific reducer is 79mm, i.e., this reducer will provide a reduction of 0.5x when the center of its lens assembly is placed 79mm from the focal plane of the eyepiece or imaging device. Move the focal reducer closer to the eyepiece/camera and its reduction factor will increase. Move it away and the reduction provided will decrease.
By using additional spacers or extension tubes (sold separately), you can vary the amount of reduction you obtain with this reducer as follows:
Extra Spacer Length |
Nominal Reduction Provided |
0" / 0mm |
0.50x |
0.25" / 6.4mm |
0.46x |
0.5" / 12.7mm |
0.42x |
0.75" / 19.1mm |
0.38x |
1" / 25.4mm |
0.34x |
Note that the use of any optical element like barlows and focal reducers changes the focus point of your telescope, requiring additional in-focus or out-focus travel. The exact amount of focus travel required will depend on the optics and mechanics of your specific set-up (telescope, diagonal (if used), barlow/reducer, and eyepiece). Hence, be aware that you may not be able to reach focus with all eyepieces or in all configurations with a given barlow/reducer. In our tests, when screwed into an eyepiece, this focal reducer required approximately Xmm of additional in-focus travel which is significant for refractors and Newtonian reflector telescopes.
Total length (including external thread) = 13mm (0.83"); Total length (excluding external thread) = 10mm (0.63"); Weight = 2.1 oz.; Made in Canada.
Copyright Notice:
This description was developed by Agena
AstroProducts. It was NOT provided by the supplier/manufacturer of this
product. Please do not copy for personal or commercial use.
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