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View Full Version here: : Downsizing to a 1.25 diagonal on 6" SCT


KG8
23-12-2017, 07:56 AM
Here is one you won't hear every day, I recently sold off some heavy visual observing kit and bought a star discovery mount for a C6 I kept. the object is ease of setup in the backyard etc. Purely for visual obs both astro and terrestrial.

The new alt/asm mount payload is rated at 5kg but with the the C6 @ 4.5kg and a 2" WO focuser and diagonal I have already exceeded this. I don't need to use 2" EP's so I figure I can get away with just the visual back and a decent 1.25" diagonal.

Is anyone using a 1.25 on a 6" SCT? What are your impressions? I ask this because a google search pulls up some conflicting opinion, usually based the long optical path and about flatness of diagonal mirrors etc. I'm in Brisbane, on the South Side BTW.

thanks for any input.

Merlin66
23-12-2017, 11:31 AM
Don't believe all you read....
The 1.25" mirror diagonal is almost a standard fitting on SCT's up to 10"
Re Long optical path...rubbish! The SCT to function at it's design f10 needs about 125mm backfocus - plenty room for a diagonal.

dannat
23-12-2017, 12:03 PM
yep do the quality 1.25" diagonal, grab a 40mm plossl & you wont look back. I have a taka prism but any quality prism or mirror diagonal one will be fine

AEAJR
24-12-2017, 10:37 AM
If you look at the Celestron line most of the 6" and 8" OTA or GoTo bundles come with 1.25".

KG8
24-12-2017, 11:26 AM
Yep it looks like 'm in the market for a WO or a teleview 1.25"

Merlin66
24-12-2017, 12:27 PM
Save some money.... A GSO or similar will do a good job in your f10 system.

bigjoe
24-12-2017, 12:48 PM
+1 for Prism diagonals Dan.. at long F ratios..I see more clear planetary detail...esp Maks and SCTs.
bigjoe.

KG8
25-12-2017, 05:39 PM
What brand and version are you using?
Weight is important in my current system so i have been looking at this one
https://www.astronomics.com/takahashi-1-25-inch-prism-diagonal_p3349.aspx
It weighs in at only 85 grams, nearly half the competition's weight. I'm just not sure if it's a good match for a slow scope like the C6 since it's obviously designed for refractors?

Wilso
25-12-2017, 07:07 PM
+1 on the Tak 1.25" diagonal
Light weight, excellent optics and twist lock
I got mine from a wanted ad. (like new)
I was reading on the Baader planetarium site a couple of weeks back and they don't recommend prism diagonals for fast scopes but didn't say how fast!


Cheers

KG8
25-12-2017, 09:02 PM
prisms can also experience chromatic aberrations at higher mags