EyeOpener setup for CCD imaging

In general, the EyeOpener will simply attach Meade's Microfocuser to the scope backplate.  When using the EyeOpener there is no loss in backfocus distance.  And since vignetting can be a problem with all but the smallest CCD chips, some camera makers actually recommend use of an EyeOpener.

 I've been  imaging since 2007, working my way sequentially from a Meade DSI-2c to a DSI-III with added cooling to an SBIG ST-8XME.  The Meade cameras helped me to climb the steep imaging learning curve while taking  "pretty pictures"  Since I'd failed to achieve acceptable astrometry quality with Meade's DSI-III, I made the conversion to SBIG's ST-8XME  - complete with CFW-9 and AO-8.  

When using the SBIG filter wheel and the adaptive optics unit I could not achieve focus when using an f/6.3 focal reducer.  And to approach the Nyquist ideal of 2 arc-seconds per pixel coverage I needed a focal reducer. 

This is my current observatory setup: 

An EyeOpener is screwed onto the backplate of the 14", and Meade's microfocuser is attached to the EyeOpener.

An Agos modified older Meade f/6.3 focal reducer (one with a 250mm focal length) is positioned completely inside Meade's microfocuser. 

The female thread on the SBIG AO-8 adaptive optics unit engages the male thread of the Agos modified focal reducer. Since any filter significantly reduces light throughput, and since my objective is to achieve maximum sensitivity for astrometry, the SBIG filter wheel was set aside.  And the SBIG ST-8XME camera is attached directly to the AO-8.  (There's some tape around the edges as there was some light leakage.)

With the EyeOpener in place vignetting is minimal.  The off axis CCD guide chip in the camera is brightly illuminated. 

Spacing between the focal reducer and the camera chip surface has been adjusted to achieve an effective focal ratio of f/5.87 - which brings the setup very close to Nyquist's optimal 2 arc-second pixel coverage with 2X2 binning.  To date the above setup has gone as deep as 20.7 magnitude.

Note that the camera has been inverted to allow the optical tube to get within 17 of celestial north.  The LX200GPS upper declination travel limit has been set to 72.  While this sounds large, it's actually a very tiny piece of sky that's uncovered and it's never been a problem.

The setup without the focal reducer and filter wheel would look exactly the same as shown when at prime focus except it would be f/10.  Internally, the Agos modified focal reducer would be replaced by a male T-thread to 2-inch tube adapter section between the AO and the Microfocuser.  And at prime focus, the filter wheel could be added to the optical train.

Wishing Star Observatory carries the Harvard/Smithsonian Minor Planet Center designation I15

 

Technical note regarding the AO-8: Even with the modified focal reducer, the optical train will not reach focus with both filter wheel and adaptive optics in place.  But at prime focus everything can be used.  The 14" has been upgraded with Buck's Gears.  And with a PEC of 10 arc-seconds, pinpoint images are achieved even at the native 3550 mm focal length.

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