Focal reducers are used to reduce the focal length of the telescope, which - while reducing the magnification - increases the field-of-view (FOV) so that more of the sky (and deep space objects, "DSO") can be captured in one image. At the same time, they reduce the F# of the scope (focal length/diameter), which increases the "speed" of imaging to similar signal-to-noise ratio (S/N). Although this is somewhat controversial - ref: Stan Moore's "F# Myth", most astro-imagers are interested in "pretty pictures", and for this purpose faster scopes (smaller F#s) certainly help. Finally, focal reducers also can serve the function of field flatteners - i.e., they can reduce the curvature at the CCD plane, thereby enabling better focus (and less distortions, such as coma) at the edges of the field; this is especially important these days, with large CCD chip cameras becoming available at lower prices.

I will mention, however - and may add to this web page when there is time - that correcting distortions of scopes depend critically on the type of scope you are correcting, and the scope for which the field flattener was designed. For example, the Meade focal reducers will flatten the field of the older LX series scopes, but may not be appropriate for the newer ACF scopes; similarily with the Celestron HD scopes - which are already better corrected than the original scopes. Further testing is necessary (which we have not seen from anyone) to determine the effect of many of these focal reducers on the newer scopes. At the same time, companies like Optec are designing and releasing newer version focal reducers, which are design specifically for the newer scopes. I haven't tried any of these, yet.

Meade f/6.3 Focal Reducer

This is the most common focal reducer used with the LX200 series scopes. It provides a 0.63x focal length or, in other words, changes the original f/10 system to an f/6.3 system, which is 2.5x "faster" than the original scope. I have used this with the LX200R (ACF) version, and results were OK, but I was less critical at that time, and have not gone back to look more closely at the results.

Meade f/3.3 Focal Reducer

The Meade f/3.3 focal reducer turns the f/10 system into an f/3.3 system - thereby making it 10x faster than the original optics. The focal length is reduced to 1/3 (so the approx. 3000mm FL of the 12" LX200 would become 1000mm). This seems like a fun addition to the LX200 scope ... EXCEPT, with the larger CCD chips now available (even the 15x15 mm chip of the ST-4000XCM), there is just too much distortion created by this focal reducer, and the field will not cover any of the mid-size or larger chips. Therefore, I have not found this device useful for my purposes; however, it could be a great help for someone with one of the original LX200 scopes, who only has a small-chip camera (e.g., Meade DSI Pro II) - as this will significantly increase the field-of-view of the system, allowing capture of larger objects, and making it much easier to find objects with the small CCD chip.

Optec NextGen 0.5x Focal Reducer

The Optec NextGen focal reducer was the latest version of their FRs until recently; they have now started introducing focal reducers designed specifically for the better-corrected catadioptric scopes, such as the Meade LX200ACF and Celestron HD series. I tried using this focal reducer when I first received it, but had the spacing (to the CCD image plane) wrong, and did not get good results. I plan to re-try using this focal reducer, carefully setting the distance from the CCD, in the near future. As it is a 0.5x model, it will provide even larger FOV than the Meade 0.63x, but not as wide - or with as much distortion - as the Meade 0.33x version.

I have spoken with Optec (Jeff Dickerson provides absolutely great customer service!), and have found that I will probably not be able to use this focal reducer if I am using the AO-L adaptive optics accessory - as the AO extends the distance to the focal plane (CCD chip), and is out-of-range for the design of the reducer. So, I will need to disassemble the STL-11000 and AO-L, and just use the camera when using the focal reducer. The NextGen focal reducer has the proper dovetail to fit directly onto the telescope side of the Pyxis rotator (the other side fitting into the TCF-S focuser); this should provide proper spacing to the CCD as long as the Pyxis is connected directly to the STL camera (via the bolt-on nosepiece with Optec dovetail that fits into the Pyxis rotator).

William Optics FF/FR 0.8x v.III

The William Optics FF/FR is a combination field flattener and 0.8x focal reducer for their refractors in the 80-100mm FL range. I tried using this with my Megrez 90, and had OK results but - again - probably did not have the spacing to the CCD set correctly, so never achieved measurably flatter fields. Now that I have sold the Megrez 90, I will be selling this FF/FR. It is extremely high quality, incorporating a camera rotator, and a nosepiece that allows insertion into a typical 2" focuser. I'm sure if this were adjusted properly, it would provide excellent widefield views with the Megrez; the original focal length of 610mm would be reduced to about 490mm, and the F# would also be decreased, for about 40% faster photographic "speed".