completely lost

[FeelLikeANumber]

I just started taking an astronomy class and soon realized I know absolutely nothing about any of this. Now only a few weeks into it I feel like im already falling behind. Here are a couple questions given to us on a handout from last week that honestly make no sense to me and hopefully somebody can explain the ways of figuring these things out so that they make sense.

What is the Right Ascension and Declination of Polaris? Betelgeuse? Full moon on June 21st? My answers were Polaris - 90 degrees. Betelgeuse 6 hours 8 degrees. And couldnt figure out the last one, mainly because im not sure i quite get the concept.

Another question: Estimate the date when we see the Sun In Libra? Full Moon in Libra? for these i'm completely lost on where the sun even is or how to calculate when it would line up with the constellation, same for the moon.

Another question: Where on earth can the full moon be observed exactly on the horizon at midnight? Im lost on this one as well.

I've looked in the book, ive tried searches online and no luck. You people are my last hope. Any input would be helpful, maybe if theres a good website with diagrams and pics.

[barkis]

Those questions are not what I would call easy, especially for a newcomer to the world of Astronomy.

The Ra and Declination questions are simply the coordinates of the stars and planets, and all the object in the night sky.

RA, or Right Ascension, is the position of a star/planet Moon, as it moves across the sky from East to West. The movement of course, is due to the Earth revolving on it's axis.

The Ra of stars, galaxies, clusters, etc. are more or less fixed, ie, their RA stays fixed for all intents and purposes. The reason is, they are so far away, any movement the do have, is so minute, as to be imperceptible. Although, some do change sufficiently to warrant

re doing their coordinates every Epoch, an Epoch being 50 years.

RA, is measured in Hours, Minutes and seconds. Declination is measured in Degrees, Minutes and seconds. 60 secs in a Minute, and 60 minutes in an Hour, Declination is the elevation of a star etc. in the sky. The planets and the moon, have motion because they orbit the sun, the same as the earth does. Because they move in elliptical orbits around the sun, their RA and Declination changes on a daily basis, some by a larger amount than others, because of the various distance from the sun. The moons coordinates change the quickest, because it is so near us, and orbits the sun together with the earth, but the moon also orbits the earth.

Neptune and Uranus are so distant from the sun, their coordinates change very very slowly.

That should give you something to digest for now.

It may all seem difficult, but don't give up, you will begin to understand it believe me.

The Celestial equator is 0 degrees,

so any object above the Celestial Equator is a Positive + and any below it is a Negative -

The Polaris Coordinates are.. RA= 02 : 31 : 50.5 (h:m:s Declination= +89 : 15 : 51 (deg:m:s)

Betelguese is at RA 05h 55m 10s Dec +07d 24m 25s

I think you would be At the North Pole to see the moon on the horizon at Midnight

The sun can be in any Zodiacal Constellation throughout a year, depending on the month.

More like an Astrological question. Look at a Horoscope chart

A full Moon is always directly opposite the sun in the sky, so the moon will be in the constellation 180 degrees round from the sun. Or 12 hours later. so you can work it out for Libra

Ron.

[david o]

Hi there FeelLikeANumber, welcome to SGL .

It is daunting at first, but with a bit of persistence it will become a lot clearer.

Honest !

I found this book very helpful:The Backyard Astronomer's Guide. There is a section that explains most of this in a straightforward way. And with lots of simple diagrams too. Other chapters cover topics that every beginner will come across sooner or later.

It'll cost £21 new from Amazon, but maybe you'll find it cheaper on fleabay, or even in the For Sale section of this very forum.

You'll find everyone on here is willing to help us newbies, so don't worry about asking questions. It gets repeated often that the only stupid questions are the ones you don't ask!

Hope you enjoy your journey into astronomy .

[themos]

Where on earth can the full moon be observed exactly on the horizon at midnight? Im lost on this one as well.

The full moon is opposite the sun (by definition). So the sun must be on the horizon, too. But it's midnight so the sun is at its lowest point, which means that it won't set at all. This only happens within the polar circles of the Earth.

[Brunty12345]

well i might be taking up an astronoy course, so i think i could learn a thing or 2 from this thread because none of them questions made much sense to me haha

[Brunty12345]

and just to add on that, is there any good websites to bulk up our astronomy knowledge??

[david o]

Yes...

SGL of course !

[dark knight]

Hi and a warm welcome to SGL, the free planetarium software Stellarium would also prove a worthy source of information, especially for celestial coordinates.

Stellarium

[yeti monster]

Wikapedia is full of astronomical information and references, just use their search facility. as with any researching it takes time and patience. Keep notes and add any links to your browser favorites.

[Thomas]

The answers given by Barkis regarding Polaris and Betelguese are accurate. In response to the other questions I can tell you the following: The full Moon on June 21st has R A of 18 Hours and declination of 23.5 plus or minus 5 degrees South. the Sun is in Libra between 25th October and 18th November. The full Moon is in Libra between approximately 25th April and 18th May. Astrological charts would be unlikely to accurately answer these points, since astrologers either do not understand, or else disregard, the effects of precession. The full Moon can appear on the horizon at midnight, as stated by Themos, within the polar circles, but also up to 5 degrees outwith the circles. The 5 degrees in these answers is the amount by which the Lunar orbit is inclined to the ecliptic. I hope this is useful to you.

[The Warthog]

Think of the star map as if it were a map of the world. RA then is the longitude, and declination is the latitude. The earth rotates under this map, but the coordinates of the star map are fixed.

So, you can look up the RA and declination of any star, in many places. Its RA is 02h 32m, and its declination is 89º 16' (approx.) I got that from Wikipedia. Betelgeuse, which I was freezing my eyes looking at a few minutes ago, is RA 05h 55m, and declination +7º 24'.

The Full Moon, or the Moon at any phase, could be observed on the horizon in the polar regions when it is at a declination that is on the horizon for that latitude. Seeing that is one more thing on my bucket list.

The other questions are quite difficult. On June 21st, or within a few hours of that date, the sun crosses the celestial equator. If there is a full moon, it should be crossing the celestial equator on the other side of the earth. However, the Moon doesn't travel on the ecliptic, but a bit north or south of it, depending on the part of its orbit that it's in. Nevertheless, my best guess would be that it is at 0º declination, opposite the sun.

The horoscope is an unreliable guide to the position of the sun. Although the sign of Libra is supposed to represent an October birth, the sun is in Libra in late November. This is because the celestial coordinates have changed over the long period since astrology was invented. I got the position of the sun by using a star map, and going through the year until the sun was in Libra. However, the Full Moon should be in Libra six months later, in May.

Hope this helps. Instead of just studying, go outside and look at the stars. You'll get hooked!

[brantuk]

I don't know how to work out the answers to your questions mathematically - but if you want to check your results before handing in then get Stellarium and/or Skyviewcafe. Both are free software and provide positioning info for all cellestial objects past, present, and future. At least you'll have an idea if your calculations are on the right track.

[FeelLikeANumber]

Thank you for all the responses! I was glad so many people took the time to read my post and offer input. I have been playing with the skyview cafe, and stellarium programs for about the last two hours and its been alot of fun as well as helpful to understand why we see things in the sky and other people dont. As well as its helped figure out where to look for things. I've turned on the coordinate maps on the program and developed a little better feel for understanding how those work as well.

I was feeling overwhelmed yesterday at the thought of never being able to understand this astronomy class. Mainly i took the class with the idea of learning some of the basics and maybe one day being able to impress the ladies or friends with a knowledge of whats in the sky, as opposed to only knowing "orion's belt" or "the big dipper." Im sure in due time like many of you said, it can only get easier. Little by little its starting to make sense. I appreciate all the responses and thank all of you for not just replying with sarcastic comments, or laughing at my inability to read a map of the sky. Im sure it wont be long before im stuck on the next concept but i look forward to playing with the computer applications and learning more. You're never done learning.

Thanks,

Scott

[Vega]

I remember starting out here on SGL and everyone is very friendly and helpful. You certainly wont get any sarcastic remarks about inability (Everyone has to start out). You'll find there's plenty of toungue in cheek on here tho LOL. I for one have been doing this malarky for 5 years now and still cant get my head around stuff. Took me 2 years of observing just to recognise half the sky lol

Most of your questions have been answered now so I look forward to your next lot of questions from the course very soon

Cheers

Matt

[LukeSkywatcher]

Another question: Where on earth can the full moon be observed exactly on the horizon at midnight? Im lost on this one as well.

I would have guessed at either the north or south pole during summer months.

Wouldnt the DEC of Polaris depend on the observing location?. I live 53 degrees N. So from where i am if i subtract 53 from 90 = 37.......so from my location Polaris will be @ DEC 37 degrees.

My first though was 90 degrees.

LOL.

[Ptolemy]

Hi there,

Not sure what course you're doing - I do know how you feel though, I did a beginners course last year and it was all a bit overwhelming to start with. It's worth sticking with it - there's loads to learn and once some bits drop into place it'll all start to make some sense.

I did mine with the Open Univesity (Introducing Astronomy Course No. S194). It was brilliant. The quality of the teaching materials, support CD's and online community were excellent. I'd recommend it to anyone who like me is an interested beginner.......even though the Q's are quite hard! The OU course had some similar Q's to the ones you mention and we were given a Planisphere (and Stellarium software as part of the course) which helped answer many of them. If you haven't got one you night find it useful.

Good luck with the rest of the course............as a result of mine I got hooked, even got my other half interested in the subject too - we bought a scope at Xmas and are now having a great time looking at the sky .... .enjoy:)

[The Warthog]

Wouldnt the DEC of Polaris depend on the observing location?. I live 53 degrees N. So from where i am if i subtract 53 from 90 = 37.......so from my location Polaris will be @ DEC 37 degrees.

My first though was 90 degrees.

LOL.

No, the altitude of any star varies with the observing location, but the RA and declination are the same. You may be looking at a star in the western sky from England, while I observe it in the eastern sky from Canada, but it's RA is unchanged. We are both looking at the same part of the star map, from different places on the earth map. The star map moves with the stars.

[LukeSkywatcher]

Thanks Warthog. I'm such a dope. I dont know what made me refer to altitude as Declination.

[The Warthog]

It's so easy to get confuzzed about this stuff. I always have to do some mental gymnastics to remember which way the RA increases.

[Thomas]

I note that two of the answers that I gave in my first post of this thread have been incorrectly contradicted in the following post. "The Warthog," stated that, " On June 21st, or within a few hours of that date, the Sun crosses the celestial equator." This, and the Lunar declination inferred from it are utterly incorrect. On that date, the Sun is 23.5 d North of the equator. The answer that I provided is accurate. Similarly, it is stated that, "the Sun is in Libra in late November." In fact the Sun enters the narrowest part of Scorpius from Libra on about 19th November, then passes into Ophiuchus on approximately 27th November. I hope this eliminates any possible confusion.

[The Warthog]

Oops, my mistake. I was thinking equinox. I bow to your superior intelligence, sir.

[Thomas]

No bowing please, but you can repeat, "Superior intelligence," as often as you like !!

[brantuk]

If its the girls you want to impress - get a laser pointer - the missus got me one for my birthday and regreted it cos it allways pulls a crowd of girls in the pub car park.

As for the sky you can just make up names for stuff - they'll be drunk, none the wiser, and wont remember anyway - but if you marry one of 'em you'll have to start getting accurate or be rumbled lol