Wxg, treating the 38mm baffle diameter as the limiting field stop, the max fov without vignetting of C8 at F6.3 will be: 38/1280*57.3 = 1.7 degrees. You can achieve this using a 30mm 70 degree EP (e.g. 30mm XW).
Using a focal reducer with most 2" EPs (30mm UWA, 35mm Pan, 40mm MK-70, etc) will result in vignetting.
2" Eyepieces
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weixing
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Hi,
Err... I think you cannot apply the formula (True field of view = eyepiece field stop diameter ÷ telescope focal length x 57.3) in this case. This is because the field stop (the 38mm baffle) is before the focal reducer... the focal length is still 2030mm and it'll be limited by the 38mm baffle before the focal reducer. You can only apply this formula if the field stop is after the focal reducer which is not in this case.
Hmm... base on the formula, the maximum field of view for C8 is 1.07 degree if the C8's baffle is 38mm.
Have a nice day.
Err... I think you cannot apply the formula (True field of view = eyepiece field stop diameter ÷ telescope focal length x 57.3) in this case. This is because the field stop (the 38mm baffle) is before the focal reducer... the focal length is still 2030mm and it'll be limited by the 38mm baffle before the focal reducer. You can only apply this formula if the field stop is after the focal reducer which is not in this case.
Hmm... base on the formula, the maximum field of view for C8 is 1.07 degree if the C8's baffle is 38mm.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
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Canopus Lim
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I would not recommend connecting the focal reducer and then a wide angle 2 inch eyepiece. The views not only will face vignetting issue, the main issue is the optics will be compromised; I have tried it with my 35mm Panoptic and focal reducer on my C5. By placing a focal reducer, the telescope will not perform as what it was designed because it is already adding some more optical elements to the path and hence the optics may become worse unless you are talking about a really high quality focal reducer that does not introduce ITS OWN optical problems to the system; furthermore, there will be alignment issues when connecting the focal reducer and diagonal.
All optics have their own optical aberrations (optical errors); there is NONE which does not have. It is just controlled to a certain amount so that it would not be either obvious to the eye or to an imaging camera etc. Unless you are talking about a perfect system with perfect manufacturing and perfect design, yes the focal reducer and the telescope somehow can match perfectly and it would thus give a better view but I do not think it is the case. The last point is the focal reducer does not have the most top notch coatings and hence adding it would rob some more contrast of the whole telescope system.
If using a wideangle 70 degree 2 inch eyepiece, just connect it to the SCT and it will suffice and the vignetting will be less than when connected to the focal reducer, and the stars will be sharper and the contrast will be better. Less lenses, better performance unless we are talking about really well designed and fabricated parts. That is the reason why I use my 2 inch eyepieces without connecting a focal reducer. Also, the other point is I can use it at f/10 which would give a smaller exit pupil (better for my astigmatic eye) and it would also allow the eyepieces to perform better due to its slow focal ratio. Last but not least, at f/10 the collimation accuracy is not as severe as at f/6.3.
Just my 2 cents.
All optics have their own optical aberrations (optical errors); there is NONE which does not have. It is just controlled to a certain amount so that it would not be either obvious to the eye or to an imaging camera etc. Unless you are talking about a perfect system with perfect manufacturing and perfect design, yes the focal reducer and the telescope somehow can match perfectly and it would thus give a better view but I do not think it is the case. The last point is the focal reducer does not have the most top notch coatings and hence adding it would rob some more contrast of the whole telescope system.
If using a wideangle 70 degree 2 inch eyepiece, just connect it to the SCT and it will suffice and the vignetting will be less than when connected to the focal reducer, and the stars will be sharper and the contrast will be better. Less lenses, better performance unless we are talking about really well designed and fabricated parts. That is the reason why I use my 2 inch eyepieces without connecting a focal reducer. Also, the other point is I can use it at f/10 which would give a smaller exit pupil (better for my astigmatic eye) and it would also allow the eyepieces to perform better due to its slow focal ratio. Last but not least, at f/10 the collimation accuracy is not as severe as at f/6.3.
Just my 2 cents.
AstroDuck
