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P.S.??An alternative?to consider is to get a shorter FL with a wide field. The magnification will be greater but the corrected angular FOV will be about the same as the Panoptic 41 Panoptic 41.? I like wide?FOV EPs in the 12-24 mm range.? But beware of overly short EP FL because the optimal eye distance?(relief) may be short and overly critical.

There are a few problems with trying to use a large aperture for visual wide field, primarily exit pupil and the extent of the corrected field.

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Exit pupil is the diameter of the parallelized light exiting the EP and trying to enter your eye.? If the?exit pupil is larger than your eye's iris then most of the light will fail to make it thru.? Furthermore, if the scope is obstructed (as SCT is by the secondary) then you will experience unpleasant?shadow effects?that are extremely sensitive to exact eye placement.? So unless you are imaging or using an intensifier (for live viewing) then there is a strict limit on the FL and magnification that can be used with the scope.

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Exit pupil = EP_FL / f-ratio

dark adapted eye iris diam = approx. 8mm (varies somewhat by individual)

magnification = scope_FL / EP-Fl

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So the?longest EP FL usable with that scope is about?80mm?for a minimum magnification of 35x.

Thus?all?the EPs you list are OK and you could get a lower magnification (via longer FL EP) if you wanted.

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However, magnification is only part of the story, especially for expensive very wide field EPs.?If the EP's true FOV exceeds the scope's corrected field then the perimeter of the view will be poor (e.g. excessive coma, astigmatism, defocus, etc.).? The Edge is?corrected for?FOV somewhere near 30mm(?).?The math gets a bit more complicated but a simplification is:

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linear FOV = L / fl (where L is the angular FOV in radians and fl is the optic focal length)

so for linear FOV = 30mm with fl = 2794mm:

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angular FOV = 30/2794 = 0.011 radians = 0.6 deg (larger than the moon but not by much)

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finally, the formula for converting EP apparent FOV to angular FOV is:

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angular_FOV = apparent_FOV / magnification

or

apparent_FOV ?= angular_FOV * magnification

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So if you choose a 40mm EP (e.g. Panoptic 41) then:

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Magnification = 70x

Exit pupil = 4mm (plenty good enough)

Corrected angular FOV = 0.6 deg

Maximum useful apparent FOV = 42 deg

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The Panoptic 41 Panoptic 41 has apparent FOV = 68 deg, thus it is overkill and the periphery quality will be poor.? However, your eye’s periphery is not so good anyway and you might like the “space walk” experience even if the edges are not really in focus.? But you could save some money by getting a more modest EP and not loose much in the way of actual quality.

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Stan

All,

I think that there are many situations where non-ideal viewing conditions limit the effectiveness of upper end eyepieces especially for 67 year old eyes?That being said I do have three Tele?Vue Ethos for my C-11. For wide?field viewing I really like the Orion q70 38mm. At only $99 it's a great bargain.

regards,

Ron K.

Since no one has replied I'll put in 2 cents worth:

The Edge has a fairly flat and well corrected field,?similar to a?quality refractor. You want an EP that does?not correct for coma.? EPs that do well on good refractors should also work well with an Edge.?

I?generally favor a TeleVue EP (unless?the?specifications suggest correction for Newt or traditional SCT).?? But I don't look thru my scopes all that much anymore (mostly do imaging).

Stan

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that is dead?(expired) link.?

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I've never used that scope or reducer so I can't say but I would expect the linear imaging circle (as measured in mm)?to stay about the same (with increased angular FOV).?

Guide stars need not be in focus because the centriod of an out-of-focus star is stable. Out-of-focus guide stars have poorer S/N?but that can be at least partially compensated by binning the guide camera 3x3.

Stan

Despite variable seeing and clouds I captured one image under decent conditions:

Brian

Stan -

You're saying my image circle will get smaller, not larger?

?Stan, the reason I'm asking is because the image circle does not fully illuminate the OAG prism on my QSI683. Will the focal reducer cast a larger image circle and give me a better image on my guide scope? It's nearly impossible to find a guide star now.

P.S. reducer power is multiplicative.? So a 0.7x reducer?changes 42 mm FOV to 42x0.7 = 29mm

A?non-correcting reducer (e.g. AP)?essentially shrinks?the image scale and?the imaging circle?also shrinks.?

A reducer/corrector formulated for the specific scope (e.g. Celestron HD reducer for HD SCT)?enlarges the angular FOV of the imaging circle, though?the linear imaging imaging circle (as measured in mm) may not be enlarged.

All reducers?degrade potential angular resolution within the imaging circle.?With a good quality reducer that degradation is usually negligible for most DS imaging (unless?undersampled).?One should never use a reducer for hi-res imaging (e.g. planetary).

Stan