<p>NOTE: Information on question and comments has been changing a lot, so please beware that some parts of the answer may be related to previous versions of the question.</p>

<p><strong>Short answer:</strong></p>

<p>This is a question to check if you know the sky. Once you can identify constellations and planets on the sky, the answer on the map is quite obvious.</p>

<p><strong>Long answer:</strong></p>

<p>To answer this question you need to be familiar with the northern hemisphere sky. If you don't know it, you would need a properly labelled map to answer the question.</p>

<p>Suggested steps:</p>

<ul>
<li><p>Assuming that the map just represents the visible portion of sky and the horizon is printed in it, first step would be to look for Polaris. The point of the horizon which is closest to Polaris is the North. The South is in the opposite edge of the map. To locate East and West, place the map with South lower and then East is at left and West is at right - just opposite as they would be in a map of Earth, but this is a map of Sky.</p></li>
<li><p>I think it would be easier to identify constellations before planets. The easier constellations are likely to be the circumpolar ones (those that we can always see in the northern hemisphere).</p></li>
<li><p>To find the planets, you should find the Ecliptic by looking at zodiacal constellations and then check for points that don't belong to those constellations. Of course, to do that you need to know the constellations. A helpful piece of information is that at 00:47 local time, the Sun, Mercury and Venus can't be seen. If the map shows the planets visible with naked eye, Mars, Jupiter and Saturn may be there in addition to the Moon.</p></li>
</ul>

<hr>

<p><strong>Edit: addition about 1st step (finding north)</strong></p>

<p>Your map is drawn inside of a circle. That circle represents the horizon, and Polaris is not in the centre of the map. Therefore, there is a point in the horizon that is the closest point to Polaris. That point is the north.</p>

<p>All this just comes from the fact that Polaris is always in the north. If you look at Polaris in the sky, you are facing north - just as if you look at the Sun at noon, you are facing south.</p>

<p>To better understand this, I suggest taking a sky map and a compass, going outside and trying to find Polaris tonight in the actual sky - tonight or the next available starry night.</p>

<hr>

<p><strong>Edit: finding Polaris</strong></p>

<p>To find a constellation or a given star, you need to know the constellations or compare your map of the actual sky with a labelled star map. The question is not very different to (for example) "find Ireland in a blank world map": either you know the world and where Ireland is, or you have a labelled map to compare. Star maps aren't that different from geographical maps. In Earth maps you know where you are by looking at geographical features, and in sky you know where you are by looking at stars positions. To find Polaris, look for Ursa Minor; finding Ursa Major or Casiopea may help, too.</p>

<hr>

<p><strong>Addition after the map was included in the question:</strong></p>

<p>North is in the right side of the map. Polaris is the dot halfway from the center and the right side.</p>

<p>The easiest clue to find Polaris is the conspicuous Ursa Major in the center of the map. As others have suggested, two stars of the Ursa Major point to Polaris. Furthermore, some stars from Ursa Minor are easy to spot over Polaris.</p>

CC BY-SA 3.0
2017-12-24T10:43:30.220Z
And how do I know where North is? On the map, Polaris is just a small dot. As you know, there are many other stars brighter than that. Also how do I know that at 00:47, at a random time, a random place those planets can't be seen?
Alex S
CC BY-SA 3.0
2017-12-24T10:55:36.950Z
Your map is drawn inside of a circle, isn't it? That circle represents the horizon, and Polaris is not in the centre of the map. Therefore, there is a point in the horizon that is the closest point to Polaris. That point is the north.
Pere
CC BY-SA 3.0
2017-12-24T11:16:10.347Z
And how do I find Polaris? There are other stars or planets which are brighter than Polaris. I get your point. Since the latitude is about $45^\circ$ N, it should be somewhere in the middle between the center which is the zenith, and the North. But the problem is that I don't know in what direction is this North point
Alex S
CC BY-SA 3.0
2017-12-24T11:32:22.437Z
You need to know the constellations or compare your map of the actual sky with a labelled star map. The question is not very different to (for example) "find Ireland in a blank world map": either you know the world and  where Ireland is, or you have a labelled map to compare. The sky maps aren't that different from geographical maps. In Earth maps you know where you are by looking at geographical features, and in sky you know where you are by looking at stars position. To find Polaris, look for  Ursa Minor; finding Ursa Major or Casiopea may help, too.
Pere
CC BY-SA 3.0
2017-12-24T19:51:30.847Z
I don't think you understand that the North on the map I am given is not necessarily on the top of the map! It could be also on the bottom of the map, which you would normally have associated with South, the map can be rotated anyhow!
Alex S
CC BY-SA 3.0
2017-12-25T10:15:05.483Z
The north may be anywhere in the map, but Polaris is always in the north, among the circumpolar constellations - just as in an Earth map the north pole is always between Canada, Russia, Greenland and Spitzbergen.
Pere
CC BY-SA 3.0
2017-12-25T12:59:55.933Z
How could you not understand what I am saying? You don't know where North is on the printed map! Fo find Polaris, you need to know where North is. You can't just say: here, this dot is Polaris, therefore here is the North point. Becase in the first place you don't know that the dot is Polaris! There are brighter stars than Polaris and fainter stars than Polaris. On the map might be hundreds of stars. Look on the website skymaponline.net, you will see a compass near  the map. Rotate and you will see that all stars move with respect to that rotation.
Alex S
CC BY-SA 3.0
2017-12-25T16:34:56.153Z
You need first to learn the map: a real map, with all stars labelled. Not thousands of stars, but you need to learn a handful of constellations and stars. Then you will be able to look at your unlabelled map and tell which dot is Polaris. When you know which dot is Polaris, you can know where is north.
Pere
CC BY-SA 3.0
2017-12-25T16:36:41.297Z
In fact my first addition to the answer is just that: how to find Polaris without knowing where is north. If you don't know constellations, you need to compare the given map with a properly labelled star map. That is, you need to compare the pattern of dots in your map with the constellations in a star map.
Pere
CC BY-SA 3.0
2017-12-26T02:07:52.720Z
@AlexS I would recommend you edit the question and add all relevant information *there*. Describe the map clearly. If it's a circle, say it's a circle. Explain what is or is not present, contrasting to what we normally imagine when we hear "star map'. If there are no cardinal points, nor RA/Dec lines, nor star names, describe *all of that within the text of the question itself*. If you don't constrain your question as completely as possible, you can't expect a constrained answer.
uhoh
CC BY-SA 3.0
2017-12-26T18:44:12.797Z
With your idea, it would be now interesting to find Polaris on the map. Let's see where your North is on this map, according to you. You kept arguing with me about that
Alex S
CC BY-SA 3.0
2017-12-26T23:39:29.957Z
Thanks! Although I still didn't understand how did you figure it out
Alex S
CC BY-SA 3.0
2017-12-27T00:06:07.783Z
Please start by taking a star map and comparing the pattern of stars. For example, look at the stars in Ursa Major and Ursa Minor in [this piece of map](http://www.skymaponline.net/view.aspx?r=844&x=601&y=820&lat=4762&long=-12233&time=20171227000128&rotation=90&w=960&h=500&gmtoffset=60&loc=Seattle,%20United%20States&id=a5fea7270) and compare them with the dots on your map to identify both constellations.
Pere
CC BY-SA 3.0
2017-12-24T00:54:54.230Z
2017-12-26T20:20:07.357Z
2017-12-26T20:20:07.357Z
Pere
<p>Interesting question :).  To find polaris, find Ursa Major, then use the pointer stars (the two in the bowl of the big dipper furthest away from the "handle" part) and use those to find Ursa Minor/Polaris. [Edit - since you're at around 45 degrees latitude, Polaris is going to be somewhere on a circle centred on the middle of the map with radius going about  halfway to the horizon, which gives you a cross check].
That gives you two constellations. The W shape of Casseopeia is also circumpolar - roughly the same distance opposite polaris from the big dipper star where the "bowl" joins the "handle". That's three. Depending on the time of year, you should be able to find at least two more easily recognisable constellations - Orion and Leo are easy to remember, as are Lyra and Delphinus and Sagitta.</p>

<p>To find north, draw a line through Polaris from the center of the map. Where that hits the horizon is North. Going the opposite way is South. Rotate the map so North is at the top and West is to the right, East to the left (remember you're looking up at the Sky, so they're reversed from a normal looking-down-at-the-ground map). </p>

<p>For circumpolar stars, it depends on the map projection used. If it's using a planisphere projection, then you can draw a circle centered on the polaris and just touching the horizon (But in that case, I don't think the horizon is going to be a circle unless there's something special about 45 degrees).</p>

<p>For the celestial equator, you want a circle 90 degrees out centred on Polaris (again, assuming a planisphere projection). That goes through the northernmost star in Orions belt, if orion is visible. Otherwise, at 45 degrees latitude, it's two thirds of the way from Polaris to the horizon on your north-south line. (North to Polaris is 45 degrees, Polaris to south is 135 degrees (45 to zenith then 45 to equator then 45 to horizon). </p>

<p>For the planets (Mars, Jupiter, and Saturn) either remember roughly where jupiter and saturn are (since the date is close to the present), or order by magnitude. (Mercury and Venus are ruled out since as inner planets they're closer to the sun, and near midnight they're on the the other side of the earth and not visible).</p>

<p>If the map isn't using a planisphere style projection (where circles of equal declination map to circles centred on polaris on the map) then trying to draw the celestial equator and circumpolar stars needs a much better memory for how the declination lines fit with the constellations, since they won't be circular on the map</p>

CC BY-SA 3.0
2017-12-25T14:15:49.917Z
2017-12-27T00:29:09.683Z
2017-12-27T00:29:09.683Z
JerryTheC
<p>I think the previous hints were already quite extensive, so I'll comment on the planets.<br>
You should know that Venus and Mercury can't be visible at midnight (which is not a random time for those planets, think why!).<br>
The total number of possibly visible planets in the whole solar system is 5. If you're taking an Olympiad on the topic then I'd assume you had an introductory class into astronomy at least, then it should be clear why it's 5.  </p>

<p>You have been given the information that there are 3 planets visible. So from 5-2=3 you know which planets that must be. Then the only thing you have to do is to order them according to magnitude to assign them their Names.</p>

CC BY-SA 3.0
2017-12-24T19:41:19.610Z
I have not been given the information that there are 3 visible planets.
Alex S
CC BY-SA 3.0
2017-12-24T19:41:46.260Z
Where have I ever said that?
Alex S
CC BY-SA 3.0
2017-12-24T20:04:50.983Z
@AlexS: Ah, I've misread. That was question 3 of your part. Then I guess you'll have to estimate from the magnitudes, if they're given.
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-12-24T20:34:47.703Z
You are also not given the magnitudes
Alex S
CC BY-SA 3.0
2017-12-24T11:50:06.857Z
2017-12-24T11:50:06.857Z
AtmosphericPrisonEscape
<p>Assume you are given a star map that doesn't have the name of the stars on it. You know the latitude, longitude of the observer and the local time (year, month, day, local time). How could I proceed to find the stars, planets?</p>

<p><a href="https://i.sstatic.net/MZw1j.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/MZw1j.jpg" alt="enter image description here"></a></p>

<p>Notes: This requirement is given by a problem with the photo shown above. You cannot go outside, nor use other resources. 
The stellar map represents the sky of a city ($44^\circ 26'$ N, $26^\circ 06'$ E, local time 00:47, date 04.03.2016).</p>

<ol>
<li>Mark on the map the cardinal points</li>
<li>Identify on the map the planets from the solar system</li>
<li>Identify Polaris</li>
<li>Identy the circumpolarity zone. Identify at least 2 constellations outside the zone</li>
<li>Find the galactic equator and the ecliptic</li>
</ol>

CC BY-SA 3.0
2017-12-23T22:51:38.477Z
What coordinates don't you know? You can find the stars by going outside and looking up, but you don't need a map to do that. Please clarify.
James K
CC BY-SA 3.0
2017-12-24T00:58:01.150Z
Those 3 questions should be in the question rather than a comment.
Pere
CC BY-SA 3.0
2017-12-26T02:03:02.587Z
@AlexS the comment above is correct. Comments can be used to help to clarify issues with questions, but they might be deleted at some point in the future. All clarifications should be made to the original post above by editing it. Thanks!
uhoh
CC BY-SA 3.0
2017-12-26T17:32:26.683Z
@AlexS Bravo! Looks much nicer after you've added all of the additional information; *thanks!*
uhoh
CC BY-SA 3.0
2017-12-26T18:24:55.100Z
Now we have the problem. If you want, I have more similar problems. I could send you some of those
Alex S
<star><night-sky>
Star map - finding stars
Alex S
# Star map - finding stars

(Asked by: username_0 on 2017-12-23)

Assume you are given a star map that doesn't have the name of the stars on it. You know the latitude, longitude of the observer and the local time (year, month, day, local time). How could I proceed to find the stars, planets?

[![enter image description here](https://i.sstatic.net/MZw1j.jpg)](https://i.sstatic.net/MZw1j.jpg)

Notes: This requirement is given by a problem with the photo shown above. You cannot go outside, nor use other resources.
The stellar map represents the sky of a city ($44^\circ 26'$ N, $26^\circ 06'$ E, local time 00:47, date 04.03.2016).

1. Mark on the map the cardinal points
2. Identify on the map the planets from the solar system
3. Identify Polaris
4. Identy the circumpolarity zone. Identify at least 2 constellations outside the zone
5. Find the galactic equator and the ecliptic

**Tags:** star, night-sky
> **Comments:**
> **username_1**: What coordinates don't you know? You can find the stars by going outside and looking up, but you don't need a map to do that. Please clarify.  
> **username_2**: Those 3 questions should be in the question rather than a comment.  
> **username_3**: @AlexS the comment above is correct. Comments can be used to help to clarify issues with questions, but they might be deleted at some point in the future. All clarifications should be made to the original post above by editing it. Thanks!  
> **username_3**: @AlexS Bravo! Looks much nicer after you've added all of the additional information; *thanks!*  
> **username_0**: Now we have the problem. If you want, I have more similar problems. I could send you some of those  

---

## 3 answers

### Answer by username_2 on 2017-12-24. Score: 4

NOTE: Information on question and comments has been changing a lot, so please beware that some parts of the answer may be related to previous versions of the question.

**Short answer:**

This is a question to check if you know the sky. Once you can identify constellations and planets on the sky, the answer on the map is quite obvious.

**Long answer:**

To answer this question you need to be familiar with the northern hemisphere sky. If you don't know it, you would need a properly labelled map to answer the question.

Suggested steps:

* Assuming that the map just represents the visible portion of sky and the horizon is printed in it, first step would be to look for Polaris. The point of the horizon which is closest to Polaris is the North. The South is in the opposite edge of the map. To locate East and West, place the map with South lower and then East is at left and West is at right - just opposite as they would be in a map of Earth, but this is a map of Sky.
* I think it would be easier to identify constellations before planets. The easier constellations are likely to be the circumpolar ones (those that we can always see in the northern hemisphere).
* To find the planets, you should find the Ecliptic by looking at zodiacal constellations and then check for points that don't belong to those constellations. Of course, to do that you need to know the constellations. A helpful piece of information is that at 00:47 local time, the Sun, Mercury and Venus can't be seen. If the map shows the planets visible with naked eye, Mars, Jupiter and Saturn may be there in addition to the Moon.

---

**Edit: addition about 1st step (finding north)**

Your map is drawn inside of a circle. That circle represents the horizon, and Polaris is not in the centre of the map. Therefore, there is a point in the horizon that is the closest point to Polaris. That point is the north.

All this just comes from the fact that Polaris is always in the north. If you look at Polaris in the sky, you are facing north - just as if you look at the Sun at noon, you are facing south.

To better understand this, I suggest taking a sky map and a compass, going outside and trying to find Polaris tonight in the actual sky - tonight or the next available starry night.

---

**Edit: finding Polaris**

To find a constellation or a given star, you need to know the constellations or compare your map of the actual sky with a labelled star map. The question is not very different to (for example) "find Ireland in a blank world map": either you know the world and where Ireland is, or you have a labelled map to compare. Star maps aren't that different from geographical maps. In Earth maps you know where you are by looking at geographical features, and in sky you know where you are by looking at stars positions. To find Polaris, look for Ursa Minor; finding Ursa Major or Casiopea may help, too.

---

**Addition after the map was included in the question:**

North is in the right side of the map. Polaris is the dot halfway from the center and the right side.

The easiest clue to find Polaris is the conspicuous Ursa Major in the center of the map. As others have suggested, two stars of the Ursa Major point to Polaris. Furthermore, some stars from Ursa Minor are easy to spot over Polaris.

> **Comments:**
> **username_0**: And how do I know where North is? On the map, Polaris is just a small dot. As you know, there are many other stars brighter than that. Also how do I know that at 00:47, at a random time, a random place those planets can't be seen?  
> **username_2**: Your map is drawn inside of a circle, isn't it? That circle represents the horizon, and Polaris is not in the centre of the map. Therefore, there is a point in the horizon that is the closest point to Polaris. That point is the north.  
> **username_0**: And how do I find Polaris? There are other stars or planets which are brighter than Polaris. I get your point. Since the latitude is about $45^\circ$ N, it should be somewhere in the middle between the center which is the zenith, and the North. But the problem is that I don't know in what direction is this North point  
> **username_2**: You need to know the constellations or compare your map of the actual sky with a labelled star map. The question is not very different to (for example) "find Ireland in a blank world map": either you know the world and  where Ireland is, or you have a labelled map to compare. The sky maps aren't that different from geographical maps. In Earth maps you know where you are by looking at geographical features, and in sky you know where you are by looking at stars position. To find Polaris, look for  Ursa Minor; finding Ursa Major or Casiopea may help, too.  
> **username_0**: I don't think you understand that the North on the map I am given is not necessarily on the top of the map! It could be also on the bottom of the map, which you would normally have associated with South, the map can be rotated anyhow!  
> **username_2**: The north may be anywhere in the map, but Polaris is always in the north, among the circumpolar constellations - just as in an Earth map the north pole is always between Canada, Russia, Greenland and Spitzbergen.  
> **username_0**: How could you not understand what I am saying? You don't know where North is on the printed map! Fo find Polaris, you need to know where North is. You can't just say: here, this dot is Polaris, therefore here is the North point. Becase in the first place you don't know that the dot is Polaris! There are brighter stars than Polaris and fainter stars than Polaris. On the map might be hundreds of stars. Look on the website skymaponline.net, you will see a compass near  the map. Rotate and you will see that all stars move with respect to that rotation.  
> **username_2**: You need first to learn the map: a real map, with all stars labelled. Not thousands of stars, but you need to learn a handful of constellations and stars. Then you will be able to look at your unlabelled map and tell which dot is Polaris. When you know which dot is Polaris, you can know where is north.  
> **username_2**: In fact my first addition to the answer is just that: how to find Polaris without knowing where is north. If you don't know constellations, you need to compare the given map with a properly labelled star map. That is, you need to compare the pattern of dots in your map with the constellations in a star map.  
> **username_3**: @AlexS I would recommend you edit the question and add all relevant information *there*. Describe the map clearly. If it's a circle, say it's a circle. Explain what is or is not present, contrasting to what we normally imagine when we hear "star map'. If there are no cardinal points, nor RA/Dec lines, nor star names, describe *all of that within the text of the question itself*. If you don't constrain your question as completely as possible, you can't expect a constrained answer.  
> **username_0**: With your idea, it would be now interesting to find Polaris on the map. Let's see where your North is on this map, according to you. You kept arguing with me about that  
> **username_0**: Thanks! Although I still didn't understand how did you figure it out  
> **username_2**: Please start by taking a star map and comparing the pattern of stars. For example, look at the stars in Ursa Major and Ursa Minor in [this piece of map](http://www.skymaponline.net/view.aspx?r=844&x=601&y=820&lat=4762&long=-12233&time=20171227000128&rotation=90&w=960&h=500&gmtoffset=60&loc=Seattle,%20United%20States&id=a5fea7270) and compare them with the dots on your map to identify both constellations.  

---

### Answer by username_4 on 2017-12-25. Score: 2

Interesting question :). To find polaris, find Ursa Major, then use the pointer stars (the two in the bowl of the big dipper furthest away from the "handle" part) and use those to find Ursa Minor/Polaris. [Edit - since you're at around 45 degrees latitude, Polaris is going to be somewhere on a circle centred on the middle of the map with radius going about halfway to the horizon, which gives you a cross check].
That gives you two constellations. The W shape of Casseopeia is also circumpolar - roughly the same distance opposite polaris from the big dipper star where the "bowl" joins the "handle". That's three. Depending on the time of year, you should be able to find at least two more easily recognisable constellations - Orion and Leo are easy to remember, as are Lyra and Delphinus and Sagitta.

To find north, draw a line through Polaris from the center of the map. Where that hits the horizon is North. Going the opposite way is South. Rotate the map so North is at the top and West is to the right, East to the left (remember you're looking up at the Sky, so they're reversed from a normal looking-down-at-the-ground map).

For circumpolar stars, it depends on the map projection used. If it's using a planisphere projection, then you can draw a circle centered on the polaris and just touching the horizon (But in that case, I don't think the horizon is going to be a circle unless there's something special about 45 degrees).

For the celestial equator, you want a circle 90 degrees out centred on Polaris (again, assuming a planisphere projection). That goes through the northernmost star in Orions belt, if orion is visible. Otherwise, at 45 degrees latitude, it's two thirds of the way from Polaris to the horizon on your north-south line. (North to Polaris is 45 degrees, Polaris to south is 135 degrees (45 to zenith then 45 to equator then 45 to horizon).

For the planets (Mars, Jupiter, and Saturn) either remember roughly where jupiter and saturn are (since the date is close to the present), or order by magnitude. (Mercury and Venus are ruled out since as inner planets they're closer to the sun, and near midnight they're on the the other side of the earth and not visible).

If the map isn't using a planisphere style projection (where circles of equal declination map to circles centred on polaris on the map) then trying to draw the celestial equator and circumpolar stars needs a much better memory for how the declination lines fit with the constellations, since they won't be circular on the map


---

### Answer by username_5 on 2017-12-24. Score: 1

I think the previous hints were already quite extensive, so I'll comment on the planets.  
You should know that Venus and Mercury can't be visible at midnight (which is not a random time for those planets, think why!).  
The total number of possibly visible planets in the whole solar system is 5. If you're taking an Olympiad on the topic then I'd assume you had an introductory class into astronomy at least, then it should be clear why it's 5.

You have been given the information that there are 3 planets visible. So from 5-2=3 you know which planets that must be. Then the only thing you have to do is to order them according to magnitude to assign them their Names.

> **Comments:**
> **username_0**: I have not been given the information that there are 3 visible planets.  
> **username_0**: Where have I ever said that?  
> **username_5**: @AlexS: Ah, I've misread. That was question 3 of your part. Then I guess you'll have to estimate from the magnitudes, if they're given.  
> **username_0**: You are also not given the magnitudes  

---

