SaratogaSkies Jim Solomon's Astropics


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ED80 Focal Reducer Shootout

This page compares several focal reducers for use with the Orion ED80 600mm f/7.5 refractor:

  1. William Optics 2" APO 0.8x Flattener
  2. TeleVue #TRF-2008, 0.8x Reducer/Flatener for TV-85 and TV-76
  3. Celestron Reducer/Corrector f 6.3 (0.63x) for SCTs

Note: The data for the William Optics and TeleVue reducers was collected by Alan Smallbone and posted to the Orion_ED Yahoo Group and his web site.

Note: The data for the Celestron reducer was collected by me, Jim Solomon. I used the two halves of the Orion #05269 (Prime Focus Camera Adapter for 2" Focusers) to adapt the Celestron reducer to an upgraded 2" visual back on the ED80 (namely, the FAS2 from ScopeStuff). This results in a spacing from the camera side of the reducer, to the camera side of the T-adpater, of 18mm.

[Update 11/13/05] I've added my own data for the ED80 plus the TeleVue 0.8x Reducer. My results for this combination are essentially identical to Alan's results.

[Update 12/7/05] I've added my own data for the ED80 plus William Optics 0.8x Reducer. My results for this combination are also identical to Alan's results.

I assembled Alan's and my own data on these pages to allow quick switching among the four-corner-plus-center, full-resolution crops. Click on one of the links below depending on your monitor's resolution and your bandwidth. Then move your mouse among the labels to display the respective images taken with those reducers.

Note: the mouseover effect requires JavaScript to be enabled.


In this data set, it's pretty clear to me that the William Optics reducer is the best match to the ED80 of the reducers tested. However, it's important to note that the spacing between the focal reducer and the imaging plane is very critical for the performance of these reducers. In particular, other astrophotographers appear to have gotten better results with the 0.63x reducers from Celestron and Meade by varying this distance. More data is needed to draw any meaningful conclusions.