Max FOV in C8 and C6R

jermng · Post by **jermng** » Mon Jan 22, 2007 4:05 pm

Hi, does anyone know what the Max TFOV is in a C8 with f/6.3 FR and what the Max TFOV is in a C6R?

Thanks

Post by **weixing** » Mon Jan 22, 2007 4:15 pm

Hi,

Hi, does anyone know what the Max TFOV is in a C8 with f/6.3 FR and what the Max TFOV is in a C6R?

Not quite sure about C8, but I think maximum should not more than 1.5 degree. You should be able to hit around 2.1 degree with C6R using 2" 55mm plossl or 41mm Panoptic.

Have a nice day.

jermng · Post by **jermng** » Mon Jan 22, 2007 5:23 pm

Will there be vignetting if I use a 30mm 70° EP on a C8 w/ 0.63 reducer?

Post by **weixing** » Mon Jan 22, 2007 5:52 pm

Hi,

Will there be vignetting if I use a 30mm 70° EP on a C8 w/ 0.63 reducer?

I'm not quite sure whether will there be any vignetting, but I try before a Pentax 28 XL on C5 with FR. I didn't check for vignetting because I "xian" already when I saw quite serious coma in the FoV.

Anyway, IMHO if you are 2" eyepiece, you'll be better off without FR... the FR + 2" eyepiece may give a larger FoV, but the coma may be very serious.

Have a nice day.

rlow · Post by **rlow** » Mon Jan 22, 2007 10:14 pm

For C8, the max TFOV is about 1.3 deg with a 2" 40mm EP with 70 deg AFOV (without reducer). A 2" 30mm 70 deg AFOV gives a slightly smaller TFOV than the 40mm.

Canopus Lim · Post by **Canopus Lim** » Mon Jan 22, 2007 10:47 pm

It would be better to use 2 inch eyepieces to achieve the widest field for the C8. Try not to use the focal reducer as it would only make the image worse visually since you are adding more optical elements. Also, by operating at f/10, you can use simpler eyepieces and your good eyepieces will perform even better.