Terrestrial observing with reflector

chris.au · #1 19-01-2011, 09:30 PM

Hi All,

Just wanted to ask, can a reflector telescope like the Meade XL series 12'' or 14'' also be used as a terrestrial observer (long distances)?

I am only starting out and have limited knowledge regarding scopes and optics, any advice will be greatly appreciated.

Thank you,
Chris.

that_guy (Tony) · #2 19-01-2011, 09:52 PM

well, all i know is its a pain to look anywhere other than up with a newtonian, cant speak for SCT or MCT... small apperture Maks are used in terrestrials so it should be doable for SCT as well :\ someone who owns one might be more of a help haha

cheers
tony

cookie8 (Vincent) · #3 19-01-2011, 10:21 PM

Hi Chris
Welcome to the forum.

Well The Meade LX series are Schmidt-Cassegrains(SCT), not reflectors.
Reflectors also known as Newtonians are hopeless for terrestrial use because images are upside down.
I think images of SCT are the right way up but left to right but not 100% sure because I have never used one.

mental4astro (Alexander) · #4 19-01-2011, 10:54 PM

The Schmit-Cassegrain telescope can most certainly be used for terrestrial viewing. The right-angle diagonal it comes standard with has the image right way up, but left to right.

You can get a 45deg diagonal for terrestrial viewing. These give a 100% correct image orientation.

I've got an SCT & I use a 45deg diagonal for this purpose,

.

Mind you, with a 12" or 14" SCT, you'd be able to make out the bird-poop that's on top of the tallest building. These scopes provide an enourmous amount of magnification, even at their lowest power. A 35mm eyepiece in a 14" SCT (f/10 ?) will give you 101X magnification - way too much to make it a practical terrestrial scope as its field of view is also very, very small.

My 5" SCT gives me 35X with a 35mm eyepiece- at this magnification, I still need to have a light touch when shifting the position of the scope. But then again, the quality of the image it provides is extraordinary! Just about count the eyelashes on a roo at 500m.

Oh, and

&

to IIS, Chris.

Mental.

astro744 · #5 20-01-2011, 06:48 AM

Quote:

Originally Posted by cookie8

Hi Chris
Welcome to the forum.

Well The Meade LX series are Schmidt-Cassegrains(SCT), not reflectors.
Reflectors also known as Newtonians are hopeless for terrestrial use because images are upside down.
I think images of SCT are the right way up but left to right but not 100% sure because I have never used one.

Actually SCT's are reflectors with a cassegrain focus (hole in primary mirror through which optical path travels). An ACT also has a thin lens at the front acting as a correcting plate (Schmidt element) that also hold the convex secondary mirror.

Any odd number of reflections produces reversed images. A Newtoniam reflector has two reflective survaces so the image is NOT reversed but may be upside down (depending on how you turn your head and if your looking from the side).

An SCT with no diagonal (straight through viewing) has two reflective surfaces so the image is NOT reversed but may be upside down (and usually is if your standing behind the 'scope looking forward with the 'scope horizontal).

An SCT with star diagonal has three reflective surfaces so the image is reversed but not upside down if looking horizontal standing behind the telescope not at the side, (again it depends on how you tilt your head).

The most important thing to remember is that reversed images cannot be correlated with star maps whereas upsidedown images can.

chris.au · #6 20-01-2011, 07:02 PM

That's excellent, thank you very much for the informative replies!

Geoff45 (Geoff) · #7 24-01-2011, 02:22 PM

A newt on an altaz mount is fine for terrestrial as long as it's not too big and cumbersome. Use the tube with the eyepiece vertical and train your brain to ignore the image orientation.
Geoff

ZeroID (Brent) · #8 25-01-2011, 09:59 AM

I once aimed my 10" DOB at the Skytower in Auckland from top of a local small volcano from where I was viewing one night. Distance was about 12 kilometers. I could easily see the diners in the restaurant. But they were upside down.
I never got to see Andromeda though which is what I was looking for. Too much cloud on the horizon.

mswhin63 (Malcolm) · #9 25-01-2011, 12:45 PM

If you have a camera at least you can flip it:

http://www.iceinspace.com.au/forum/s...56&postcount=1

M110 (Andrew) · #10 27-01-2011, 09:17 PM

Could you a diagonal to achieve the right way up view?

that_guy (Tony) · #11 27-01-2011, 09:56 PM

Quote:

Originally Posted by mswhin63

If you have a camera at least you can flip it:

http://www.iceinspace.com.au/forum/s...56&postcount=1

Broken link

mswhin63 (Malcolm) · #12 28-01-2011, 04:19 AM

Sorry http://www.waelect.com.au/mswhin63/M...l/index.html#3

cookie8 (Vincent) · #13 11-02-2011, 03:24 PM

May I ask a silly question?
Why are telescopes (Spyglass) used by pirates the right way up and not flipped?

astro744 · #14 11-02-2011, 04:01 PM

Quote:

Originally Posted by cookie8

May I ask a silly question?
Why are telescopes (Spyglass) used by pirates the right way up and not flipped?

Typically Galilean design with convex front lens and concave rear lens. Search the web for Galilean Telescope and you'll find lots of info.