Newtonian Terrestrial Orientation

[richyrich_one]

Hi

This is probably a stupid question but here goes...

Just collected my 10" dob and I was setting up the finder scope . During daylight I found a distant object with the OTA and then adjusted the finder scope so it lined up.

All good but I noticed that the view from the eyepiece of the OTA was not upside down as I expected but seemed to be turned a further 45 degrees maybe.

Is this correct? I have been trying to get my head around why it would be but can't fathom it.

I know in space there is no up so it doesn't really matter I guess but just wanted to make sure all is right with it.

Rich

[RT65CB-SWL]

Hi Rich,

Perfectly normal. You can purchase an image erecting prism for use terristrial veiwing, but I am unsure whether they are suitable for newtonian reflectors. Welcome to SGL.

[richyrich_one]

Hi Rich,

Perfectly normal. You can purchase an image erecting prism for use terristrial veiwing, but I am unsure whether they are suitable for newtonian reflectors. Welcome to SGL.

Thanks Philip

But please excuse my ignorance, but an errecting prism would effectively rotate the view 180 deg, but that would still make it off by the "extra" 45 deg that I am seeing.

Or am I missing something?

[RT65CB-SWL]

Excuse my ignorance too, but the more 'glass' you add to the light path, less photons reach human eyeball Mk1.

I have just found this: http://www.365astronomy.com/image-rectifier-or-erecting-prism-for-newtonian-telescopes-p-1889.html Is this what you are looking for? The 'normal' 45º prisms are normally used with catodioprics (ie Maksutov & SCT) and refractors.

[ronin]

The "extra" 45 degrees or so will be the angle at which the eyepiece is to the horizontal or vertical. You will be looking in at about 45 degrees.

You get inversions and this extra bit thrown in.

[richyrich_one]

I am not looking for an errecting prism but thanks for the link

Can someone explain why the view I am seeing is NOT just upside down, ie turned 180 deg as I woulod have expected, but turned a little bit further (or less) , say 225 deg (or 135 deg)?

[richyrich_one]

The "extra" 45 degrees or so will be the angle at which the eyepiece is to the horizontal or vertical. You will be looking in at about 45 degrees.

You get inversions and this extra bit thrown in.

Sorry you replied as I was typing...Thank you for putting my mind at rest.

[Owmuchonomy]

Yes, because your focus see is probably at 45 deg to the plane of you scope. If you orientate your scope so that your focusser/EP is perpendicular to the ground it should look as you expect.

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[Owmuchonomy]

Yes, because your focus see is probably at 45 deg to the plane of you scope. If you orientate your scope so that your focusser/EP is perpendicular to the ground it should look as you expect.

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Blooming spell check! Focusser not focus see!

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