Focal Reducer

[kon1966]

Hi, I have a meade f3.3 reducer for a SCT. I can set it to F5 by using the spacer. By setting it to a higher F ratio and not to 3.3 can I use it for visual or do I need to buy the F6.3.

In process of buying my new SCT and cannot test myself.

Regards
Kon

[Terry B]

They are not designed for visual use. Why would you want to use it visually?
Just use a longer eyepiece for the same result without as much aberation from the extra optics.

[kon1966]

I want to use the F3.3 for astrophotography and at in the instructions it does say not for visual use. I thought that by using the spacer to set to f5 that it could be used. On a sct, for me, I find F10 too dim except for planetary viewing. I intend to by a reducer at 6.3 for normal visual astronomy and use my 3.3 when taking photos. That is when I get my sct.

Regards
Kon

[Merlin66]

The x0.33 reducer was specifically designed for the early Meade Pictor camera, with a webcam sized chip.
IMHO I haven't seen it being able to be used with larger modern CCD cameras.

[Terry B]

The f ratio has very little effect visually. The brightness of the image to the eye is affected by the light collecting area ie the diameter of the scope. A focal reducer will make the angular size of an extended object smaller for a given eyepiece and hence make it appear brighter as the light is more concentrated. The same effect is had by using a longer focal length eyepiece but the eyepiece is probably going to have better contrast than the focal reducer as it will have less optical surfaces than the eyepiece/focal reducer combination.
As Ken stated, the 0.33 reducer is only for very little CCD chips and introduces lots of aberations to the image. They are of very limited use with modern camera. Maybe useful if you are experimenting with a webcam as the imaging camera.

Cheers
Terry