Newtonian erecting prims, any good?

[emadmoussa]

Do they actually work? Do they have a barlow effect or add additional coma?

[Cornelius Varley]

Probably a bad idea altogether. More glass etc . The erecting prisms I've seen also increase the magnification by 1.5x

[emadmoussa]

Prisms - not prims..sorry!

[emadmoussa]

Probably a bad idea altogether. More glass etc . The erecting prisms I've seen also increase the magnification by 1.5x

Humm...more magnification...not good!!

[michael.h.f.wilkinson]

I have a proper erecting (Amici) prism for my frac, and that is OK, until you get to about 100x. You also get odd out of focus effects on stars, but for wide field and nature viewing they are great. For Newtonians, they would not reach focus, so some magnification needs to be added, which is not a good idea.

[emadmoussa]

Perhaps I can stand upside down...

[cotterless45]

Why would you be wanting to see stuff the right way up in a Newt ?

Certainly standing on your head would do the trick !

Nick.

[YKSE]

Perhaps I can stand upside down...

I actually prefer the view in a newt than through a diagonal.  In newt, it's naturally rotated 180 degrees, you can still easy follow the star chart, while the mirrorred- view through a diagonal really needs extra work to figure out.

[emadmoussa]

The confusing bit is trying to match what you see in the erected finder scope and the scope eyepiece...

[YKSE]

The confusing bit is trying to match what you see in the erected finder scope and the scope eyepiece...

Yes, you're right about that. t,erefore I prefer RACI finder, so that I can follow the star chart with ease.

[michael.h.f.wilkinson]

I have no difficulties with it by now. The RACI finder is used with the star chart, and I print separate stellarium or AAVSO charts with "diagonal orientation" for view through the scope. I even use the non-RACI 6x30 finder intermixed with the lot from time to time. You get used to it after a while (OK, 18 year with the C8, 3 or so since the addition of the RACI finder)

[Peter Drew]

If you used a pentaprism in your finder you could have a 90 degree offset and still have the same orientation as the Newtonian. 

[Laurie61]

I wonder what would happen if you replaced the secondary with a prism of some type ? I assume it would have to be made oval rather than oblong, if the recent comparison of diagonal's and prism's is an indication of performance a planetary newt may benefit.

Although that test was on dialectic diagonals not std aluminised surfaces ?   

http://stargazerslounge.com/topic/211695-diagonals-prism-vs-dielectric-vs-aluminum-vs-silver/

[John]

I wonder what would happen if you replaced the secondary with a prism of some type ? I assume it would have to be made oval rather than oblong, if the recent comparison of diagonal's and prism's is an indication of performance a planetary newt may benefit.

Although that test was on dialectic diagonals not std aluminised surfaces ?   

http://stargazerslounge.com/topic/211695-diagonals-prism-vs-dielectric-vs-aluminum-vs-silver/

I've seen DIY newtonians that use diagonal prisms rather than a mirror. One complication could be the light path through a prism which I think is longer than that of a mirror diagonal. 

[Moonshane]

The confusing bit is trying to match what you see in the erected finder scope and the scope eyepiece...

not really - map the right way up for the finder and map the wrong way up for the eyepiece?

[emadmoussa]

not really - map the right way up for the finder and map the wrong way up for the eyepiece?

You say that..but have You met my brain?! It's fitted the refractor way: D

[michael.h.f.wilkinson]

You say that..but have You met my brain?! It's fitted the refractor way: D

So clearly you need a brain refit

[emadmoussa]

So clearly you need a brain refit

Apparently I do... I was thinking a spare one in my sock as well...