Equatorial Sky Guide

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Equatorial Sky Guide

Post by starfinder »

I was thinking the other day what would be visible at Mersing this month, since I can't quite remember everything from past experiences.

I then realised that from the equatorial regions, which Singapore is in, what can be seen at any particular date is generally speaking, those areas of the sky which are NOT obscured by the glare of the Sun. This is because we are not "blocked" by the body of the Earth as observers in far northern and far southern latitudes are, and so the Sun is the only factor.

I therefore thought of divising a sky guide which would be suitable for use in the equatorial regions. This would readily and quickly show what is and what is not visible.

After much thinking about the matter, I drew up the attached Equatorial Sky Guide. (Copyright asserted)

The main chart is a mercator projection of the celestial sphere, from -70 to +70 degrees declination. It was generated from a planetarium software. I think mercator projections are only good up to about 70 degrees, and in any event, the extreme ends don't contain many important objects of interest and these regions are low in the horizon for us.

I then wrote in the names of key bright stars and some prominent asterisms and clusters.

The main features of the Guide are the rows of bars at the top and bottom of the main chart.

With this, one can quickly tell what is not visible in a particular month, and therefore, what is visible (i.e. the remaining).

For example, for this month (March), we can see from the Grey bar and the ecliptic line that the Sun is now in Aquarius, and areas of the celestial sphere from about 21hrs to about 0 hrs 30 mins Right Ascension are not visible due to the Sun's glare, e.g. Pegasus, Cepheus, Aquarius itself, Tucana and Capriconus.

(I estimated these areas by running the planetarium program with the normal projection and setting the times of sunrise and then sunset.)

Therefore, those areas outside of the Grey Bar for the month of March are visible during the course of a night, i.e. the remaining [20] or so hours of right ascension.

Next, the top row shows which areas of the celestial sphere (right ascension hours) will culminate at midnight. So for example, for March, we can immediately see that Leo culminates at midnight. It also means that Leo rises in the East at dusk, and is up all night long (i.e. similar to an Opposition).

There are also features giving rough directions where to look for a constellation, and which constellations are setting at Sunset and which are rising at Dawn in any given month.

This is a detailed prototype, and I might need to refine it for accuracy. I avoided using the colour red since this chart would sometimes presumably be viewed at the field at night with a red torch.

I think it also helps us amateur astronomers understand the workings of the celestial sphere better, and this would be a very good educational tool for basic concepts.

Most importantly, with this, one can quickly see on one sheet of paper what constellations are and are not visible during any month in a year.

What do you guys think? For example, does anyone see any major flaw in the design/concept of this guide, etc.?
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Last edited by starfinder on Wed Mar 07, 2007 12:29 pm, edited 1 time in total.

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Post by jennifer1611991 »

I'm printing it out :)

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Post by starfinder »

jennifer1611991 wrote:I'm printing it out :)
Hey, this is still a prototype. I am hoping for some views on the accuracy and validity of the chart's overall design concept. So far it seems ok to me. Also, I might want to add a few more details, and refine the width and positioning of the Grey bars, etc.

I think this Guide is our equatorial version of the planispheres that are used for northern and southern latitudes. The advantage of this Guide is that the whole celestial sphere (from -70 to +70 declination) can be seen at one glance. The downside compared to planispheres is that it does not immediately show e.g. whether an object is which is located near the celestial equator (i.e. near declination "0", e.g. Orion) is at the East or West. This information has to be derived by looking at the guide bar(s) at the top (I will add some more bars at the top).

Another advantage is that this Guide also tells the user what to expect to be coming up next over the Eastern horizon during the night, and an all-night observation session can be planned out properly. In fact, a year's observations can be roughly planned out with the Guide.

Now, if only I had this bought (if available) or done up years ago....

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Post by rlow »

This would work. I have been using my own equatorial star map like this for more than 20 years. :)
Richard Low

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Post by starfinder »

I have completed drawing up the Equatorial Sky Guide. New time bars have been added, the Grey Bars have been tidied, two polar maps have been included as well, plus other wordings added.

I have also tested the chart's time bars against a planetarium program, and it seems to be accurate.

Once again, this guide is for use in equatorial regions. The times stated in the Guide are valid for Singapore and Peninsula Malaysia.

Click here for a large version of the Guide on the Singastro Wiki website:
[link edited to newer version]
http://www.singastro.org/web/mediawiki/ ... ressed.jpg

I suggest that it be printed on an A4-size paper, in landscape mode, and preferably in colour.

Immediately below is a small preview version of the guide.

Comments on the guide, positive and negative, are most welcome!
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Last edited by starfinder on Sun Mar 11, 2007 5:07 pm, edited 1 time in total.

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Post by chrisyeo »

Hi Starfinder,

Beautiful and an excellent job. I have been using a chart like this for many years now, but they are not readily available on the net. It's wonderful that someone can finally design something like this and hopefully allow Singastroians to use it. :) I found the chart intuitive and highly-usable. The gray bars are also unique and a great addition.

As a reference, the chart I am using is attached (for reference only; printing is locked). Another set of equatorial starcharts can be found here: http://www.midnightkite.com/starcharts.html. I have also seen a version being sold by Perseid before.

Here are some comments and suggestions:
1. The map should be much expanded in your full-res version and the words much smaller. Linked starcharts show a good scale.
2. Some constellations are missing - perhaps too faint, but it still might be helpful to represent them.
3. There could be say, a three hour overlap on the left and right so that constellation identification can be easier.
4. You can consider adding some objects of interest. Perhaps Singastro will like to consider voting for the best 50 objects visible in our sky?

Sure would be beautiful if someone could add in the creative-commons constellation artwork used in Stellarium and eventually print it out poster size!
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Last edited by chrisyeo on Sun Mar 11, 2007 1:10 pm, edited 1 time in total.

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Post by alvinsclee »

Put your name in the charts designed by you and get printers to produce copies of it in A4, A3 or even A1 and A0 size. Laminated, they can look quite professional. Then, have Joo Beng of Astrobargains to help you market them to the regional equatorial countries.

As I said before, I have always believed in the potential of Singastro. This will be good collaborative effort for the benefit of the community.

And, I would like to book some autographed copies now... :)

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Post by starfinder »

Hi Chris, Alvin, Richard,

Many thanks for your comments and suggestions.

Regarding printing and lamination, my intention is to let this be available to everyone to download off the Singastro Wiki website and print it for their own use. I think A4 size is handy to bring out to the field for observations. Also, I think the resolution is not high enough for anything much larger, maybe A3 size is possible.

However, if anyone wishes to market it (not sure if they would!, but a good idea nonetheless), they would need to do it with permission, etc (hence the assertion of copyright).

For myself, I have printed it out on cream coloured cardboard paper, and then placed it in a U-shaped clear plastic folder with punch-holes at the side. I got this from a stationery shop for 50 cents. Below is a photograph of it.

Regarding the constellations, I have carefully checked just now. The main chart lists 82 constellations, and the remaining 6 are found in the polar charts. However, the names "Libra" and "Circinus" were half-lost in the side-edges, so I have done some hand-touching up to the chart and shifted the names. I overlooked this earlier.

As for the sides and overlapping, perhaps I shall add in a 2-3 hour overlap on each side of the main chart in some revised future version. However, I had already selected the display output as it is for the main chart (i.e. starting from 15 hours at the right), as this places the main groupings of the constellations together. Therefore, Centaurus, Crux, Carina, Vela and Puppis are together at bottom left. Ursa Major, Virgo and Leo are at middle-to-top left. And Scorpius and Sagittarius are at bottom right. The main split is between Bootes at leftside and Hercules at right.

Regarding adding more detail, I did not want to put in too many objects since this chart is meant to be printed for use in the field and for general reference and observation planning. The resolution is not quite high enough for too many names, and that may clutter the chart too. I had written in the names of the major bright stars, as well as some key objects like the Pleaides, the Summer Trangle, the LMC/SMC, the False Cross, the Teapot, and M31.

Perhaps if I could get a higher resolution for the chart could more objects be added in.

Finally, I hate to say this but I have discovered that there was an err... error... in the south polar chart. I had written in the 6hr and 12hr mark at the wrong place, and so also put the LMC at the wrong place. I have since corrected it and uploaded the corrected version to the Singastro Wiki (version 11.3.2007). The link in my earlier post above has been edited to link to this new one. Apologies! [BTW, not to worry about the main chart. Since it was computer-generated, the R.A. and Declination numbers (and constellation names) are all correct. Only for the polar charts did I hand-write in these numbers.]

The new link once again is:
http://www.singastro.org/web/mediawiki/ ... ressed.jpg

One last mention again. I think the Grey Bars at the bottom are quite unique, at least for Singapore. Now I fully understand myself what we can and cannot see throughout the year!
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Post by Clifford60 »

I downloaded the 10/3 version and increased the resolution to 200 pixels/inch and then break the chart into 4 different pcs, print it and tape them together to approx A2, its OK. A bit long-sighted, so need bigger printout. haha

Thanks Gavin for all the hard work.

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Post by acc »

Great work! :)
We do it in the dark...
Portaball 12.5"
Takahashi Mewlon 210
William Optics 110ED
...and all night long!

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