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which direction......????


petermartin5
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No chance to use my new scope due to weather so I have been readind various books, mags on astronony. Please forgive my very basic question!!

I know that the earth turns counter clockwise ( i.e.west to east) so that the constellations appear to move from east to west.

But what about the planets? As they orbit the sun ( just like the earth) is their path across the sky also from east to west?

Please excuse my lack of knowledge ( I am determined to get there!) but even basic books dont always give basic answers!.

Oh secondly, on some star charts it looks like constellations SOUTH of the celestial equator are visible to us? Am I right?

Thanks, Pete

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One of the things my Astronomy professor said, yea these 38 years ago, that has stayed with me, is that "everything rotates eastward." So, the Earth rotates, and revolves, eastward, the Moon revolves around the Earth in the same direction, and rotates eastward, and so does everything else.

There is a technical exception to this: as the Earth passes an outer planet, the outer planet appears to turn around and go backwards against the backdrop of stars as it is passed by the Earth. It is, however, still moving eastward. All the outer planets exhibit this illusion, less so the farther away they are.

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Technically, Uranus is upside down. (I'm not joking, OK?) It is considered to have a tilt of 97 degrees, which produces the impression that it is rotating backwards. Venus, with an axial inclination of 177 degrees, is almost completely upside down. Still it is considered to be rotating eastward, in an upside-down orientation.

Mercury has a day that is 29 days longer than its year. I'm pretty sure that the terminator on Mercury would have to move eastward, but its rotation is still eastward. Pluto also has an axial inclination of more than 90 degrees, and therefore appears to be rotating the wrong way.

Certainly, everything revolves eastward.

Retrograde motion must have driven the ancients crazy.

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Now there are 2 exceptions to the rule. Which are Venus and Neptune. Which rotate the opposite way to the other planets. So we have kind of a hiduldy piguldy mix. :lol:

So we kinda have a Retro Retrograde. :?

You've lost me, and it doesn't take much, whats wrong with just admiring them through the eyepiece, do I have to understand their movements to??.... :shock:

Yeah, I just take a look at the star chart if I haven't been paying attention lately, but generally I just know which is which without regard to retrograde or forward motions.

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Pete,

I think you are asking about the path of the planets over the course of 1 night. Surely they all move east to west. The only thing that doesn't is shooting stars and aeroplanes.

Over the course of the year the position of the stars moves the other way - west to east except for the retrograde rotations of planets. Gallileo used the occasional retrograde path of mars to determine that the planets including earth must must be rotating around the sun.

Am I talking rubbish. Are there really retrograde paths over the course of a single night.

Martin

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Hi Martin, yes I am talking about the movement of the planets over the course of the night, not their rotational spin. So they move east to west?

Still confused re. stars though. Thought that the constellations appear to gradually move east to west, as seen from earth?

pete

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Pete,

They move east to west like the sun and the planets over the course of the night as the earth rotates on it's axis. They rotate west to east over the course of the year as the earth rotates around the sun.

The planets rotate east to west overnight but can have irregular movements over the course of the year due to the movements of the orbiting earth and and planets in relation to each other.

Martin

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I suppose you could measure the change in the position of a planet in a single night, but it is so slight that a driven mount will not lose the planet overnight. I think. Intuitively, Mars should change by up to half a degree in a night, less when it is in retrograde motion, but it seems to have been in Aries for a long time. The moon moves obviously towards the east by an average of about 12 degrees a day. The motions of Jupiter and the outer planets are very small.

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over the course of a night the retrograde movement of a planet would be like a millipede moving very slowly along a train going at 120mph in the opposite direction!

Martin

I'm interested to hear how you get on with your new scope Pete

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HI Martin, thanks to you and everyone else who took the time to reply. There seems to be a great bunch of people on this site. As a newcomer sometimes I need to ask what some feel maybe basic questions and its nice to know that noone is going to " take the mickey"!

Re. my scope, my wife ( bless her!) bought me the " famous" Lidl 70mm refractor. As astro. scopes go I know its small-- but its a start. If I can only get " a glimpse" of say Saturn or Jupiter with some small detail I will be happy. I am realistic about what I will be able to see but so far the viewing here has been hopeless.

Maybe in the future if things progress I will think about getting a bigger scope.

Cheers, Pete

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Pete

Everyone at some point has to ask questions, even those of us that know a thing or two (or at least, pretend!!!).

I think the general consensus was that your scope is a good starting point. You should be able to see enough to whet your appetite, but not having spent a fortune if you decide astronomy is not for you.

As for asking questions,keep at it!!! Everyone has to ask at some point and it's the role of the more experienced to pass on that knowledge.

Really looking forward to hearing your 'first light' report and how you get on :lol:

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Re. my scope, my wife ( bless her!) bought me the " famous" Lidl 70mm refractor. As astro. scopes go I know its small-- but its a start.

I am new to this hobby as well and have seen some exciting thing on my 30year old Prinz 60mm refractor including great views of Saturn - once I got used to things either looking very small or very dim and sometimes both. I am now looking to move on and have borrowed a friends Lidl 70mm. It has a great mount which includes setting circles so it should provide good practice polar aligning and star finding. I have bought some decent eye pieces and a barlow for it since I will still be able to use these when I get my new scope (whatever that is going to be). The supplied eye pieces don't look up to much and the 1.5x erecting lens looks pretty useless.

Good luck when the clouds finally clear.

Martin

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