GSO's new 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. It also has additional 2" female threads so you can screw/stack additional 2" filters on to this reducer. 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).
- Total length (including external thread) = 21mm (0.83")
- Total length (excluding external thread) = 16mm (0.63")
- Clear Aperture = 37.4mm (1.47")
- Weight = 2.4 oz.
- Made in Taiwan.
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 exact focal length specification of this reducer has not been provided by the manufacturer, but we estimate it to be approximately 105-107mm. Hence, the "working distance" of this specific reducer is estimated to be 53mm, i.e., this reducer will provide a reduction of 0.5x when the center of its lens assembly is placed 53mm 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
0.25" / 6.4mm
0.5" / 12.7mm
0.75" / 19.1mm
1" / 25.4mm
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 22mm of additional in-focus travel which is significant for refractors and Newtonian reflector telescopes.
Feb 22, 2019
Eye OpeningPros: Cons: Comments:
I bought this 2" Focal reducer to give me more options when operating my camera for DSO imaging. I have not had a chance to use it yet because of the clouds, rain and cold temps up here in New England. It will give me F/5 straight up using my C8 or I can couple it with the Meade F/.63 reducer to give me F/3.7 on my C8 or use it with my AT60ED refractor to give me F/3. So I have a lot of plans for this reducer, only time and weather will tell when I get to use it.
This review was provided courtesy of AgenaAstro.comDec 24, 2016
Great focal reducerPros: Cons: Comments:
I bought this to use with the Lunt 152mm (semi-) APO refractor, along with narrow FOV cameras. What I found is that as long as you stay within the FOV for which the scope is designed, the focal reducer works well. It allows me to use cameras with small sensors and still get a reasonable FOV. It will not convert this scope to an f/3.5 refractor that will work with TV and other wide-field eyepieces--you get coma and other effects at the outer edge of the field. But it works great for my intended purpose of photos and photo-observation with astro cameras having small sensors.
This review was provided courtesy of AgenaAstro.comJan 24, 2016
2" focal reducerPros:
Quality Lenses,Easy to Use,Accurate,Strong ConstructionCons: Comments:
If you are looking to reduce the focal length of a 2" eyepiece this is what you are looking for. Threads directly on the bottom and does a great job of reducing magnification and increasing field of view.
This review was provided courtesy of AgenaAstro.comDec 27, 2015
Works much better than I expected for visual use 2 inch sizePros:
Accurate,Easy to Use,Quality LensesCons: Comments:
This works much better than I expected ....it works much better than much more expensive things I've tried ..... I was trying to get low-power eyepieces for my Intes Alter 6P.... it's an f/15 scope.... I bought a vixen LVW 42 mm which was a disaster.... when I tried this GSO reducer lens screwed onto the bottom of some of my 2 inch eyepieces I was simply amazed .... in fact some of my eyepieces have even better contrast.... my ES 100
This review was provided courtesy of AgenaAstro.comJul 7, 2015
Good low cost reducer lensPros:
Quality Lenses,Strong ConstructionCons: Comments:
I can image the entire moon or sun (with solar filter) when I use this reducer in my 1000mm focal length telescope. I get about 60x magnification with my neximage 5. You will need to adjust the imager plane carefully to get the best focus. I adjusted mine by using a sheet of wax paper on a distant terrestrial target during daylight to get the optimum setback distance. A one half inch length 2" spacer ring places the lens perfectly.
This review was provided courtesy of AgenaAstro.com
gazer New Member
- Skill Level
- Time with Product
Dec 6, 2013
- User Notes:
- Review by sepi1961 of Vnersborg Sweden.
A good focal reducerPros:
Strong Construction,Quality Lenses,Easy to Use,Lightweight,CompactCons:
Prerequsition is that your telescope accepts 2" accessories. This will work well in Schmidt-Cassegrain and Maksutov-Cassegrain systems.
For 2" eyepieces, you can use the reducer directly for models with max. field stop diameter of approx. 40mm. Bigger eyepieces will show vignetting.
This review was provided courtesy of AgenaAstro.comMay 1, 2010
Inexpensive - But not cheapPros:
Compact,Strong Construction,Quality LensesCons:
Works great, especally for lunar pics. Going to get a 1.25in. for my ETX. Takes one lin k(and about 1in) out of attachment chain. ie. less stress-easier balance. No problems with focal length (behind a 2in. focuser). Great acc.!!
This review was provided courtesy of AgenaAstro.comSort by