Erecting an SCT

OneOfOne (Trevor) · #1 20-12-2007, 03:00 PM

I was wondering if there is an erecting eyepiece or prism that will create an upright image for an SCT with a diagonal. I think the image is upside down and reflected left to right?

browndog (Ian) · #2 20-12-2007, 04:20 PM

Hi OneOfOne - I think that you will find that the image orientation of an SCT will change depending on the accessory being used.

When using a star diagonal the image will be right side up, but reversed left to right. If inserting the eyepiece directly into the visual back (without diagonal) the image will be inverted.
(taken from my Celestron SCT user-manual).

Gama · #3 24-12-2007, 06:08 PM

Yes, buy yourself an erecting prism.

Go here for one https://www.bintelshop.com.au/Product.aspx?ID=6338 .

Theo

OneOfOne (Trevor) · #4 26-12-2007, 10:33 AM

I'll look into that (sorry, couldn't resist the pun!)

OneOfOne (Trevor) · #5 28-12-2007, 01:09 PM

The link is basically for a 45 degree diagonal, which I happened to have one lying around. I bought it a couple of years ago to try something with the Newt, but I didn't have enough "in focus".

I just put it in the scope and swung it around to a pipe on the neighbours roof, and low and behold it was right side up and right way around. There must be a difference in the light path for a 45 compared to a 90 which results in the correct view. The quality isn't the same as my 90, but hey I only paid $60 and I will only use it rarely...like on the neighbours

Gama · #6 29-12-2007, 09:10 PM

Its not just a 45 deg. diagonal. Its an erecting Prism, not a 45 deg diagonal. Theo.

OneOfOne (Trevor) · #7 30-12-2007, 07:13 PM

When I bought mine, I didn't ask for anything specific...just a 45 degree, there was nothing special on the box, and the guys at Andrews didn't mention anything about it being an erecting prism. So is there a difference between them, or are all 45's erecting? Does the light through a 45 get two reflections, and hence makes it right way? Hmm...

Gama · #8 03-01-2008, 08:48 PM

Sorry for the late reply, but a right angle 90 deg setup works different when its used in a 45 deg position.
Rather than a long description, go here http://www.olympusmicro.com/primer/j...sms/index.html and look how it works. Just wait for the java to load and rotate the prism around to see how light is bent.

Theo.

OneOfOne (Trevor) · #9 04-01-2008, 09:16 AM

Interesting how the same block of glass has totally different effects on the light depending on the orientation...

Gama · #10 04-01-2008, 09:26 PM

The same could be said once a wedding ring goes on a womens hand !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Metamorphiasm occurs, wedding rings must contain high levels of Gamma Rays.

Theo.