K-7 HDR mode shot of a scope

jogiba · 06-01-2011, 12:45 PM

Originally posted by jimr-pdx

Thanks - I feel more on-thread with the Pentax eyepieces

Man, I thought that I had some serious astro-investments.. dual Ethi? Wow!

The 40mm Pentax XW with 46.5mm fieldstop has the widest FOV of any eyepiece that I know of and works great in my slow scopes like my 102mm F9 APO that gives it 22x , 4.5mm exit pupil and 2.9 deg TFOV.

RonHendriks1966 · 06-01-2011, 01:33 PM

Originally posted by jogiba

Effective Aperture: f/12.5 with 80mm and Pentax PF-CA35 K-Mount DSLR Camera Adapter or about F6.3 without.

My Celestron 100mm ED spotting scope has a faster 540mm F5.4 or 1080mm F10.8 w/Pentax PF-CA35 K-Mount DSLR Camera Adapter :

Wow the difference is only 1/3 stop but both need a sunny day.

This compares with a Sigma 500mm lens and 2x TC.

Nothing else that is more lightstrong?

jogiba · 06-01-2011, 01:50 PM

Originally posted by RonHendriks1966

Wow the difference is only 1/3 stop but both need a sunny day.

This compares with a Sigma 500mm lens and 2x TC.

Nothing else that is more lightstrong?

The 500mm Sigma zooms are F6.3 and F12.6 with 2x TC so they are about the the same as the Pentax PF80-ED .
600mm F5 :

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06-01-2011, 12:45 PM	#16
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491 Original Poster	Originally posted by jimr-pdx Thanks - I feel more on-thread with the Pentax eyepieces Man, I thought that I had some serious astro-investments.. dual Ethi? Wow! The 40mm Pentax XW with 46.5mm fieldstop has the widest FOV of any eyepiece that I know of and works great in my slow scopes like my 102mm F9 APO that gives it 22x , 4.5mm exit pupil and 2.9 deg TFOV.

06-01-2011, 01:33 PM	#17
RonHendriks1966 Banned Join Date: Jan 2009 Photos: Gallery Posts: 9,675	Originally posted by jogiba Effective Aperture: f/12.5 with 80mm and Pentax PF-CA35 K-Mount DSLR Camera Adapter or about F6.3 without. My Celestron 100mm ED spotting scope has a faster 540mm F5.4 or 1080mm F10.8 w/Pentax PF-CA35 K-Mount DSLR Camera Adapter : Wow the difference is only 1/3 stop but both need a sunny day. This compares with a Sigma 500mm lens and 2x TC. Nothing else that is more lightstrong?