Friday, February 16, 2007

Celestron C5, C6, C8, C9.25 baffle size

Belows figures are collected from the Internet via Google search, I didn't measure myself and thus the figures might not be accurate, just for further reference:-

C5 - 25mm
C6 - 27mm
C8 - 38mm
C9.25 - 48mm but it's restricted by SCT port size which is ~45mm

So, it's pretty pointless to use 2" visual back with a C5 or C6? However, mechanical advantage with beefier 2" visual back will keep me using one with my C5.

I did this searching originally wanted to give myself a reason to upgrade to a C6, after downgrading from a C8 to a C5, but now, I simply won't.

I shall check by myself to see if my 40mm Pentax SMC XL can deliver more actual field of view than my 20mm Japanese Widescan Type III. If it couldn't my Pentax would be only useful for my tiny Borg 45ED II, but in any case, I won't sell my Pentax since I truely love this eyepiece, very comfortable, extremely high constrast, second to none color fidelity and sharp to edge.


mr.hopkins said...

I am a novice using a C5 spotter with its stock eyepiece. I do not like the "pinhole" sized dot or view presented to my eye. Please recommend a wider-angle eyepiece that presents a much larger image. An image that is easier for my eye to find.

Oldfield said...

First of all, do you mean that you can see the shadow of the secondary in the view?

Or you want an eyepiece which is easier to look through? Like easier eye positioning, or longer eye relief, etc?

Finally, do you intend to use it during day time?

mr.hopkins said...

Yes, easier eye positioning and longer eye relief for my wife's glasses. Day & night....harbor scope/birder by day...simple telescope at night....

mr.hopkins said...

I also would consider adopting a 2" back if a 2" eyepiece would help...

Oldfield said...

My 13mm Tele Vue Nagler Type 6 works great, and if you want even wider true field, go for a longer focal length version. I have a 20mm Japanese Widescan Type III which works very well, too.

Too low power is not recommended for day light observation for you can see the shadow of the secondary.