Upside down?

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Upside down?

Postby Premacy10 » Mon Mar 28, 2016 7:42 pm

Hi all

Only my second post and second month of being a telescope owner.

I haveJust managed collimation on my skywatcher 130 Newtonian telescope and feel it went well , just a quick and I imagine to the experienced astronomer a proper derrrr question.

When I was sorting my red dot finder I picked out a chimney about 300 metres away and the view it gave me was upside down . Is this correct?

After collimation I was looking forward to tonight but I'm currently sitting inside watching a hail storm.

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Re: Upside down?

Postby Gfamily2 » Mon Mar 28, 2016 10:11 pm

Yes, in general, astronomical telescopes produce inverted images. However, if you use a diagonal, the image will be flipped again to produce an upright (though reversed left-right) image.

Diagonals are not generally used on Newtonians - but are commonly used on SCTs and often used on Refractors.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: Upside down?

Postby Aratus » Tue Mar 29, 2016 3:22 pm

That's a good observation, Tony, and it isn't immeadiately obvious why the image is upside down. Basically these telescopes brings all the light entering it to a focus. It then spreads out again but all the rays of light have now crossed over. It is at that point that the image is grabbed by the eyepiece. The whole image is therefore turned upside down, like turning your TV upside down! :) In fact an astronomical telescope is a 'normal' telescope. A terrestrial telescope, binoculars etc have to insert extra lenses or prisms to turn the image the way we see it with the eye. This makes the image dimmer, so we don't bother to do that.

As Gfamily2 says, adding mirrored diagonals confuses things even further. This time the left and right are put back the 'original' way but it is still upside down! It is possible using a camera with a particular telescope to see the image the same way as the eye. In fact I have 3 different maps of the moon for each possible combination! 'Normal', 'upside down' and 'North/South only flipped' :?

Fortunately with your Newtonian, you only have to get used to moving the telescope the opposite way. Don't worry, it is something you very quickly learn to do.

Let's hope the weather gets better soon. :)
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Upside down?

Postby Premacy10 » Wed Mar 30, 2016 11:51 pm

Thank you both for your replies,I'm still learning and enjoying every minute.

Regards tony
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