| 1. How do I find a constellation when looking at the night sky? |
| 2. Why 15° degrees for the default declination? |
| 3. Why are image downloads fixed at 1600x1600 pixels? |
| 4. Why doesn´t clicking on a chart image do anything? |
| 5. How do I navigate the atlas? |
| 6. How come I can´t see something in the sky on the month it says its visible? |
| 7. Where do I look for something that´s visible before dawn or after dusk? |
| 8. How can I tell if something in the sky is circumpolar? |
| 9. How do I find the celestial poles in the sky? |
| 10. Where is the center of the Milky Way? |
| 11. Why is the Milky Way all pixelated into little squares? |
| 12. Why can´t I print charts in landscape mode? |
| 13. How do I turn off the stars in the charts? |
| 14. How do I enter a date and time for the planets? |
| 15. How do I enter my viewing location? |
| 16. How do I read my horoscope for a particular day? |
| 17. What did the sky look like when I was born? |
| 18. How do I pronounce the name of a star or a constellation? |
| 19. Is Betelgeuse really pronounced "beetle-juice"? |
| 20. How come some constellations don´t look like what they´re named? |
| 21. What are constellation borders for? |
| 22. Is the Serpens constellation one or two constellations? |
| 23. Why are there two stars named Al Thalimain? |
| 24. Where´s the constellation named Argo? |
| 25. How do I find the HR number of a star on the chart? |
| 26. Where do I lookup a star´s spectral type? |
| 27. Why do some multiple stars have so many components? |
| 28. What do I need to travel to the nearest star? |
| 29. How come I never see any IC objects in my telescope? |
| 30. How do I look at the constellation the sun is in? |
| 31. What´s the difference between the historically-corrected and the revised NGC catalogs? |
| 32. How do I make my own SDSS astro gallery? |
| 33. Isn´t the arc-sec/inch value different for different parts of a chart? |
| 34. What´s the J2000 equinox? |
| 35. What´s an epoch? |
| 36. If the declination is the same as my geographic latitude why is the right ascension different? |
| 37. Who named the constellations? |
| 38. Is it true I can name my own star in the sky? |
| 39. Can I make up my own constellation stick figures? |
| 40. Can I put images from The Night Sky Atlas on my website? |
| 41. What´s a view twist and a viewing angle? |
| 42. How come there´s fewer stars in the same view field I see in my telescope? |
| 43. What´s the round logo image supposed to be? |
| 44. How do I change the colors of stuff in a chart? |
| 45. How come my favorite constellation is under the wrong month? |
| 46. Why aren´t the planets on any charts? |
| 47. How do I enter coordinates in degrees, minutes, and seconds? |
| 48. How come there´s more NGC objects labeled in the SDSS index images than shown in The Night Sky Atlas? |
| 49. What if I find an error in The Night Sky Atlas? |
| 50. Who started and maintains The Night Sky Atlas? |
| 51. Is there a printed version of this atlas I can buy at my bookstore? |
| 52. Who is Gill Couto? |
| 53. What will the next version of this atlas have in it? |
| 54. Is this website copyrighted? |
| 55. Is the web address shown on the images/printouts a copyright notice? |
| 56. Do I own the images I download? |
| 57. Why aren´t there any ads on any pages? |
| 58. How and when did The Night Sky Atlas get started? |
| 59. How do I make a single image covering the entire sky? |
| 60. Can I get a T-shirt with my favorite constellation on it? |
| 61. Why do the constellations disappear from the night sky for a few months? |
| 62. How are the PDF and PNG download filenames generated? |
| 63. The Milky Way appears to be displaced in a few places, is it? |
| 64. Is there a limit to the number of charts or images I can download? |
| 65. What kind of hardware and software is this atlas running? |
| 66. Why is The Night Sky Atlas on the rgbstore.com domain and what is it? |
| 67. Can I browse The Night Sky Atlas on my mobile device? |
| 68. How do I get the location of the planets in my local time? |
| 69. Is there a way to get the rise and set times of the planets? |
| 70. What holidays are shown on the desktop calendars? |
| 1. How do I find a constellation when looking at the night sky? |
| First locate the Earth´s pole that is above your horizon, that would be the North celestial pole (NCP) if you´re in the Northern hemisphere, or the South celestial pole (SCP) if you´re in the Southern hemisphere. Then you just need to orient the stars around the pole to match the current local time and the day of the year, then gradually identify stars and constellations further away from the pole, easy! |
| 2. Why 15° degrees for the default declination? |
| The default declination value is chosen such that it results in a chart that varies the most from day to day, which means it must be close to the equator. It should also end in ´5´ so that the RA grid labels appear as legible as possible. 15° just fits right in, any larger and the view gets too close to the NCP and tends to vary less than at the equator every month. |
| 3. Why are image downloads fixed at 1600x1600 pixels? |
| That´s the largest image size produced by The Night Sky Atlas and yields the most legible images. To download at other sizes, just set your image width and height then save the image on the screen. |
| 4. Why doesn´t clicking on a chart image do anything? |
| There is no feature like that on this version of The Night Sky Atlas. All functions are controlled by the HTML form values and by CGI options in the address line. |
| 5. How do I navigate the atlas? |
| Either by entering the relevant values in the HTML form boxes or by using the viewer page shortcuts below a chart image. |
| 6. How come I can´t see something in the sky on the month it says its visible? |
| Because of your geographic distance from the Earth´s equator. The visibility info applies to when a chart´s right ascension is visible, except that in reality it also depends on what latitude on Earth you´re looking at the sky from. Viewing the sky from the Northern hemisphere leaves part of the Southern sky invisible and vice-versa. All objects over the equator are always visible from either hemisphere. |
| 7. Where do I look for something that´s visible before dawn or after dusk? |
| Objects visible just before dawn will appear rising to the East just before sunrise. Similarly, objects visible after dusk will appear in the sky following the sunset as they set shortly after to the West. |
| 8. How can I tell if something in the sky is circumpolar? |
| By comparing two values: your geographic latitude and an object´s declination on a chart. In the northern hemisphere, when an object´s declination > 90° - your latitude, it will circle the NCP and never set. It´s the same for the southern hemisphere if you use positive values. |
| 9. How do I find the celestial poles in the sky? |
| Locate where geographic North is from your location in the Northern hemisphere, then go up from the horizon by exactly your latitude. That point is the NCP, similarly for the SCP |
| 10. Where is the center of the Milky Way? |
| The exact location has been a long-standing mystery because it is not viewable in visible light. In recent decades, it has been detected by radio telescopes to be a location now called Sagittarius A where a massive black hole exists. |
| 11. Why is the Milky Way all pixelated into little squares? |
| The Milky Way is made from a map of an all-sky Milky Way image with a resolution of 1200x200 pixels. That´s not very high when zooming in a small portion of it and the pixels become very large. |
| 12. Why can´t I print charts in landscape mode? |
| This version of The Night Sky Atlas is very simplified and has very few printing options. |
| 13. How do I turn off the stars in the charts? |
| That´s often needed when overlaying chart images on photos and must currently be done during the image composition. The option wasn´t provided so that stars would never disappear which is what most viewers would want to always see. |
| 14. How do I enter a date and time for the planets? |
| All positions for solar system bodies are precomputed into a large table for each day of the year. It´s not possible to specify a specific date and time. That can be achieved by interpolating between the two nearest dates to the date you´re looking for. |
| 15. How do I enter my viewing location? |
| That´s a feature found in planetarium software that often recreates a view of the sky for a particular observer. The Night Sky Atlas has a different purpose of merely mapping the whole sky. Your viewing location determines what you can see at a particular time and date, but The Night Sky Atlas shows what´s in the sky whether it´s visible or not at any time. |
| 16. How do I read my horoscope for a particular day? |
| Astrology is a very interesting field from which astronomy was born before scientific methods were applied to understanding the universe. Horoscopes remained a part of astrology and don´t have a serious place in astronomy sciences. The Night Sky Atlas provides information from scientific astronomy data and not from astrology, so there are no horoscopes in it. |
| 17. What did the sky look like when I was born? |
| It looked just the same as it looks today, except that the more you know about, the more meaning everything has when you look at it. The stars move very little in less than 100 years, only solar system objects move around in that time frame, and the celestial poles were just a fraction of a degree off from today. |
| 18. How do I pronounce the name of a star or a constellation? |
| Correct pronounciations of constellations and star have varied over the times. Different names have been given to the same objects by different cultures in the past. There´s a nice list of pronounciations at USC ISI which may be useful, and another at Sierra College. |
| 19. Is Betelgeuse really pronounced "beetle-juice"? |
| No, it´s pronounced "bet-ell-jooz", particularly when it´s the distinguished brightest star of the most famous constellation of all time, Orion. |
| 20. How come some constellations don´t look like what they´re named? |
| Only a few constellations look like what they´re named because they were named at a time when imagination and storytelling were the dominant focus of the peoples who named them thousands of years ago. Some were named after seasonal events like floods and plantation times and not actual objects. See Ian Ridpath´s Star Tales for some fascinating constellation history. |
| 21. What are constellation borders for? |
| The 88 constellation borders in the sky are the equivalent of continents on the face of the Earth. They are 89 regions (Serpens is split in two regions) of the sky neatly bordered around their traditional figures such that any object in the sky can be located in exactly one constellation. Borders were established by international agreement in 1930. |
| 22. Is the Serpens constellation one or two constellations? |
| It´s a single constellation that is split into two parts, Serpens Caput the snake´s head, and Serpens Cauda the snake´s tail, being held by the serpent wrestler Ophiucus. |
| 23. Why are there two stars named Al Thalimain? |
| The two stars named Al Thalimain refer in Arabic to the two ostriches in the constellation of Aquila, one on the star Iota Aquilae and the other on the star Lambda Aquilae. Al Thalimain refers to both stars together, but each star is labeled individually with the same name. |
| 24. Where´s the constellation named Argo? |
| Argo was an ancient constellation that has been split into three smaller constellations: Vela, Puppis, and Carina. |
| 25. How do I find the HR number of a star on the chart? |
| The data tables for principal stars and multiple star list most notable stars in The Bright Star Catalog (BSC). Choosing a constellation in any of these data tables lists selected stars from the catalog, though not all HR stars are shown in the atlas. |
| 26. Where do I lookup a star´s spectral type? |
| With the HR number, all the data for any star as collected when the catalog was created, can be found the SIMBAD online database. |
| 27. Why do some multiple stars have so many components? |
| Most star components cannot be seen visually, they have been found by indirect means with very precise measurements. The actual component count can be considerably larger than what can be seen optically. |
| 28. What do I need to travel to the nearest star? |
| The only thing you need to travel to the nearest star is a reliable means of transportation that can safely travel the great distances to the nearest stars. The duration of the trip would have to shorter than your lifetime. You might also have to invent it yourself. |
| 29. How come I never see any IC objects in my telescope? |
| There are several IC objects that are visible even in small telescopes. However, most deep space objects (DSOs) listed in the IC are smaller and dimmer than those in the NGC. It´s the DSOs in the IC that are more difficult to see than most DSOs in the NGC. |
| 30. How do I look at the constellation the sun is in? |
| Looking at the sun is dangerous and should only be done with special filters. It´s only possible to see stars near the sun either during a total solar eclipse, or from outside the Earth´s atmosphere with an occulting disk. There is an orbiting satellite named SOHO that continuously monitors the sun. You can see background stars behind the sun in current images. |
| 31. What´s the difference between the historically-corrected and the revised NGC catalogs? |
| The original NGC was created in 1888 when very little was known about the universe and astronomy equipment had much less precision than today. Many astronomers have since corrected some of the data in the NGC with newer technology and knowledge, and two of these catalogs have become very popular. Some major differences are that the revised version separates some objects originally unknown to be made of smaller individual objects, by adding letters to the NGC number. The HCNGC does not introduce new object entries, but extends the NGC with details of when, who, and with what equipment the objects were found. Both list more precise positions and in the J2000 equinox. |
| 32. How do I make my own SDSS astro gallery? |
| The Sloan Digital Sky Survey (SDSS) has made considerable effort to share it´s images and data with the general public. The SDSS team went as far as providing many useful online tools for users on their website. It´s not everyday you get a chance to go to a website and grab images from a 2.5 meter telescope that would otherwise cost you many millions of dollars to put in your own backyard. The index images on this website provide a way to locate the larger objects in the SDSS survery area of the sky. This direct link to M86 and its surroundings is a good start. |
| 33. Isn´t the arc-sec/inch value different for different parts of a chart? |
| The linear scale of any chart is exact only for the chart center, where the chart coordinates are specified. Because charts are projections of a spherical surface, some distortion results towards the edges of a chart. Charts that cover larger areas have correspondingly larger errors towards the edges. |
| 34. What´s the J2000 equinox? |
| It is a reference frame for the equatorial coordinates where the right ascension and the declination are defined to be exactly zero. Since the frame of reference moves in a complete circle every 25,750 years, it is fixed to a convenient year, the year 2000 in this case. The J2000 equinox reference is being replaced by newer position references that are independent of solar planetary orbits. A visual reference frame called ICRS, based on selected Milky Way stars, and ICRF which is based on extragalactic radio sources. |
| 35. What´s an epoch? |
| An epoch is a reference time used to mark when an object´s position is determined of the moving positional frame of reference, the equinox. The movement is known as precession of the equinoxes. |
| 36. If the declination is the same as my geographic latitude why is the right ascension different? |
| The right ascension is fixed to the line of equinoxes on the orbital plane of the Earth. It doesn´t rotate with the Earth once a day and is different from a longitude value on Earth. The two are related though as a function of time of day and day of year by Kepler´s Laws. |
| 37. Who named the constellations? |
| The earliest civilizations were the first to associate the constellations with significant figures of their days and named them accordingly. Later civilizations carried on some original names, renamed others, and when the southern sky was discovered even newer constellations were named. It´s unlikely that complete records for constellation names can be found. |
| 38. Is it true I can name my own star in the sky? |
| Not really, if you did it wouldn´t be recognized by the IAU, see their page on Star Names details. |
| 39. Can I make up my own constellation stick figures? |
| The constellation stick figures simply associate the principal stars of a constellation with the figure a constellation is named after. Different authors use different stick figures in their charts, so the answer isn´t "no". The stick figures for The Night Sky Atlas have been chosen from the Hayden Planetarium of the American Museum of Natural History in New York City, in an attempt to abide with a well-known planetarium. |
| 40. Can I put images from The Night Sky Atlas on my website? |
| Of course, preferably with a link back to the chart that it was created from. |
| 41. What´s a view twist and a viewing angle? |
| The view twist is a rotation of the image around its center. The viewing angle is better known as the field of view (FOV) which is the angle formed by two diagonally-opposite corners of an image and the observer. |
| 42. How come there´s fewer stars in the same view field I see in my telescope? |
| The Night Sky Atlas uses The Bright Star Catalog for the database, which includes all the stars visible to the naked eye, with only a few exceptions. It is smaller than most star catalogs and is perfect for fast rendering of chart images on a live web server. As a result, it contains less stars than can be seen with a telescope or binoculars. |
| 43. What´s the round logo image supposed to be? |
| It represents the whole celstial sphere that can be viewed in The Night Sky Atlas. It´s an attempt to be an all-encompassing image of what this website represents. |
| 44. How do I change the colors of stuff in a chart? |
| That can be done in a paint program after downloading a chart image. This version of The Night Sky Atlas has no color options. |
| 45. How come my favorite constellation is under the wrong month? |
| Visibility info applies to the center of a chart image, while constellations span many degrees in the sky. A single point of a constellation is chosen to determine visibility. It´s possible that this point can lie in an adjacent month. It´s not exact but it gives a very good idea when a chart is actually visible. |
| 46. Why aren´t the planets on any charts? |
| Being an atlas and not a planetarium forces the exlusion of any time and location dependencies. Inclusion of any orbiting bodies in the atlas would tie its charts to a specific date and divert from the original determination to merely map the night sky for any date and time. |
| 47. How do I enter coordinates in degrees, minutes, and seconds? |
| The current HTML form only recognizes equatorial coordinates in decimal hours (nn.nnn) for right ascension and decimal degrees (+/-nn.nnn) for declination. It just maintains everything consistent with little room for errors. |
| 48. How come there´s more NGC objects labeled in the SDSS index images than shown in The Night Sky Atlas? |
| The NGC objects shown in The Night Sky Atlas are limited to the brightest 4 in each constellation in order to somewhat distribute them throughout the sky. This restriction was removed in creating the SDSS index images to locate all NGC objects within the SDSS survey area. |
| 49. What if I find an error in The Night Sky Atlas? |
| It would be good to let the author know about it. Some star data varies with time and it´s normal to find minor changes. Some discrepancies are just too big, like the magnitude for HR 5958 of 2.0 where the newer value in the same star as HIP 78322 is 10, so it was removed from this atlas since it´s not visible to the naked eye. |
| 50. Who started and maintains The Night Sky Atlas? |
| A computer engineer with a long-time interest in many aspects of astronomy known to others as Gill Couto. The idea started when I realized I had gained enough knowledge of astronomy to write a chart-making program. It was then one more step to place it on a web server on the internet to share with others who may want to locate anything in the sky. |
| 51. Is there a printed version of this atlas I can buy at my bookstore? |
| None at all, The Night Sky Atlas was not meant to go to print. It creates PDF files suitable for printing high-quality charts of the night sky but it´s not likely they´ll find their way to any bookstore. |
| 52. Who is Gill Couto? |
| Not an astronomer, not a map-maker, just an amateur with spare time and some leftover skills from an engineering education. Courses in mathematics and physics made it easy to make the programs running on this webserver to produce the atlas charts. |
| 53. What will the next version of this atlas have in it? |
| It will certainly be a subscription service since it will be providing advanced features like extensive object catalogs with complete data fields. Work on it advances as free time allows, among other ongoing tasks, so no promises will be made. Some content will continue to be added to this atlas version, particularly a calendar page, and possibly planet icons on the zodiac page, and an updated star catalog will certainly happen sometime. |
| 54. Is this website copyrighted? |
| In legal terms all content is copyrighted by its author, even if there´s no copyright notice. You have permission from the author to use content from this website as you would like as long as you display the web address, but the author always holds the legal copyright. The legalities can get very intricate, the author has simplified it to the fullest for you. |
| 55. Is the web address shown on the images/printouts a copyright notice? |
| No, the copyright notice is legally implied by the author´s original creation. The web address required to be displayed by the author is merely the terms of permission for your use of the content. |
| 56. Do I own the images I download? |
| Ownership of copies of downloaded content never changes the ownership by the original author. You simply have permission by the author to use your copies accoring to the terms which are simply to display the website address in all copies. |
| 57. Why aren´t there any ads on any pages? |
| Ads by Google were tested for a short period and left only on the search results page. It was determined that ads closely tied to Astronomy would be a much better choice. At this point there´s no intention of placing ads. |
| 58. How and when did The Night Sky Atlas get started? |
| It got started after some failed attempts at finding software for conveniently placing common sky object labels on astrophotos. That was towards the end of 2007, and it led to testing ways of easily labeling photos of the night sky. After a few months, with a few more features, the results started looking like a complete atlas and it was made into a website as such. The name "The Night Sky Atlas" was found to be unused by anything else and so it was named. |
| 59. How do I make a single image covering the entire sky? |
| The kind of spherical projection needed for that is not used by this atlas. That would result in extreme geometric distortions and a lot of effort has been made to minimize such distortions. The best way to get full sky coverage is with 6 views: one of each pole and four equatorial views, all at viewing angles of about 135°. |
| 60. Can I get a T-shirt with my favorite constellation on it? |
| You could try to get a PDF chart onto a t-shirt or onto anything else like coffee mugs or even a nice telescope paint job. That´s entirely up to you, this website makes it possible to create the exact chart you need for something like that. |
| 61. Why do the constellations disappear from the night sky for a few months? |
| They disappear when the sun is located in the RA near them, making it impossible to see the stars near the Sun. Each day the Sun travels by about one degree in the sky, that´s about a 4 minute change in right ascension. The sky within about 18° to the East and West is occupied by each sunrise and sunset respectively. That´s about 36°, or over 2 hours in RA, that are hidden by the bright sun, or under 2 months time in a full year. You´d have to see down to both the E and W horizons to catch a star that disappears into the sun after sunset then rises a month or later again before sunrise. |
| 62. How are the PDF and PNG download filenames generated? |
| The automatically-generated filenames like NightSkyAtlas-20081018184907.pdf are created with a timestamp to keep from overwriting previously-downloaded charts and images. The numbers are YYYYMMDDHHmmss and are a simple way to keep filenames unique and in sorted order by download date on your computer. |
| 63. The Milky Way appears to be displaced in a few places, is it? |
| Alignment of the Milky Way to the star positions is as close as possible, though close inspection will reveal a few areas off from their alignment with some stars. The Milky Way is intended to produce a visual effect and it´s mapping to the celestial sphere is not as precise as that of all other items shown. |
| 64. Is there a limit to the number of charts or images I can download? |
| The only limit is as much as the webserver can produce which is quite high at many GB per day. There are no other limits to worry about under normal usage conditions. The server automatically slows down when too many requests are made in a short period of time. |
| 65. What kind of hardware and software is this atlas running? |
| The web server has quad Intel(R) Xeon(R) CPUs at 1.60GHz with 8GB DRAM, with 4 FPUs for parallel math computations, all under SMP Linux. The atlas software is custom written by the author in Java and JSP. Several other custom-written tools are also used to process the star and space object catalogs. |
| 66. Why is The Night Sky Atlas on the rgbstore.com domain and what is it? |
| RGBstore.com is the author´s domain for a previous photo archive website. The name was chosen after working with color image data, from the "RGB" color channels for Red, Green, and Blue. The Night Sky Atlas was added as on the skyatlas.rgbstore.com subdomain only because the web server was already setup at the time the subdomain was added. If The Night Sky Atlas becomes more popular, it will be placed on its own domain with an apropriate name for it. |
| 67. Can I browse The Night Sky Atlas on my mobile device? |
| That´s certainly possible by linking directly to images the exact size of your mobile device via the skyatlas.jsp page. That´s the PNG and PDF image/chart view generator. Feel free to create your own page with image links of the correct height and width for yours or any device. |
| 68. How do I get the location of the planets in my local time? |
| All times in the planets page are for UT and interpolation is currently required to obtain exact local times. Keep in mind that negative timezones like -4 through -7 for the US refer to the day previous to the day listed for 0 UT. |
| 69. Is there a way to get the rise and set times of the planets? |
| Rise and set times for the Moon, Sun, and planets will be available in the next version of The Night Sky Atlas along with other data. That´s in the works but not yet available. |
| 70. What holidays are shown on the desktop calendars? |
| All U.S. public holidays on the days they are observed, the holidays are: New Year’s Day, Martin Luther King, Jr.´s birthday, Washington’s Birthday, Memorial Day, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving Day, and Christmas Day. |
