Filter Thread Mounted 0.6 Focal Reducer

Purchase Focal Reducer

What can it do for you?
What does it look like?
What is the extension tube?
Does it work at night?

Will they work with the Meade ETX-90 - 105 - 125

*** Double Focal Reducer gives F/0.2 reduction ***

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Picture Description

So what does it do for you ?


Check my comparison testing of focal reducer field of view (FOV)

I have now found a reasonable source of new coated lenses to make these focal reducers from. They are a little more expensive than the surplus lenses I was using but the quality and availability is very good. I had to raise the price a little to cover the additional cost.

This is new. Something I wanted and thought you might also. I couldn't stand paying US$130 for a focal reducer lens for my LX-90. After all they are designed for 35mm film guys who want a large flat field. I only have a 1/3" CCD chip. I don't need a large flat field, I just want to get more sky on my chip.


The lens screws into the filter thread on a UWAS-F, UWAL-F and UWAT-F. And you get to see nearly twice as much field and only need half the exposure time.

The lens is a coated doublet. the coating reduces reflections.

Focuser Travel

It needs nearly 30mm (1..2") of in focus travel. (that is wind the focuser inwards). Not a problem on the SCT but check your Newt for in focus travel before you get to excited. With the extender you require about 80mm

See Peter Katreniak's web site for all the details on how this works.
 (Read - Math Details)               TOP

Double Focal Reducer Trial

I don't know if Craig Stark is a brain surgeon or not but he has done some fantastic research on my focal reducer. Craig discussed the theoretical reduction possible and then conducts experiments to determine the actual reduction ratio. And even explains why they differ. Craig also trialled a DOUBLE focal reducer setup. Which gave him a workable f/2 on an LX-90 scope. He also have a very good distortion testing approach pictured at left. Thanks Craig.

Craig Stark, Ph.D.            
Department of Psychological and Brain Sciences

Extending the F-0.6FR away from the CCD give you an even greater focal length reduction. The F-0.3EXT extension tube allows you to get an f/0.3 reduction.

Focuser travel: The Extender tube needs way more focuser in travel. This will only work on a moving mirror SCT scope. Sorry.

 The F-0.3EXT can get long when it all goes together


M31sum387.jpg (14406 bytes)

F-0.6FR Focal Reducer - Results

Images taken by Dr. S.J. Wainwright M31

" Tonight, I tried the focal reducer on my f/5, 80mm refractor with the Mintron video camera (which has a 1/2 inch chip).  With this little scope at least, the focal reducer gave excellent results right to the edge of the field of view."

Dr. S.J. Wainwright


M45sum61.jpg (10360 bytes) Images taken by Dr. S.J. Wainwright M45. Note (Particularly in th elarge picture - click image) star image quality to edge of frame. This was taken with a 1/2" CCD camera which is larger than your normal WebCam 1/3" CCD. Effective focal ration of f/2.8 for both these pictures.

F-0.3EXt - Extension Tube Results

Last night Derek Francis and myself tested the Mogg f=0.66 reducer lens in conjunction with a prototype further reducer extender tube and a short (0.75 inch) Mogg C adapter on a C11 SC (normally at F10). We have not worked out the exact focal reduction. However, the test was to determine whether the stars were acceptable.

The results are presented in the attached image as well as pictures of the camera-reducer-tube-adapter configuration. The picture of the separate components of the focal reduction system also includes a standard Mogg C adapter for comparison.

The stars were good to the edge of the field.

This would seem to be a good, low cost focal reduction system.

Dr. S.J. Wainwright               TOP

  Email me for more details if you are interested