How can I work out longitude and latitude through my telescope?

Question

We purchased a Celestron Astromaster 90EQ Refractor Telescope and a Celestron Powerseeker Accessory Kit about four years ago but have not used it much for many reasons. As such my husband and I are complete beginners and was hoping for some advice please?

My Dad passed away during the lockdown and we have had a star named after him. It's a "UK" based star and we will be sent longitude and latitude co-ordinates enabling us to search for it.

On Christmas day we are hoping to use the telescope, with our children, to point out my Dad/Grandad in the sky. However, my husband has now said he thinks you have to buy an accessory or something to do this and the telescope and accessory pack we have does not have the necessary equipment ?.

Can anyone advise how you can do this please and, if we need to purchase an accessory, recommendations?

Thank you very much for any help in advance. Sue Davis

Answer 1

I used to have this exact telescope. It took a lot of practise, but I was eventually able to reliably find most targets I was after. I used this scope for about 2 years learning my way around the night sky before moving on to another scope and mount. You should practise finding bright targets before moving on to dimmer ones, just to get used to the scope. However, you can use the setting circles on the mount to help you too. The setting circles are the 2 silver disks with all the numbers on the head of the mount. The Declination one is just underneath where the telescope is fitted (upper red circle in the picture). The Right Ascension is on the other rotational point of the mount head (lower red circle in the picture)

First, you need to reliably polar align the scope, which will make nailing down other objects easier. This may take some time so for a "roundabout" method, you can just point the mount towards Polaris and it'll be good enough to keep objects centered when adjusting the RA knob, but I'll still go through the "drift" method for a more reliable alignment.

Drift aligning on a manual EQ mount can take a while, but it starts with a rough polar alignment by eye. Align the mount with Polaris as best you can. Now, move the telescope and find a bright star to the south. Center the star in your eyepiece then get the highest power eyepiece you have (will probably be the 9mm one in your accessory kit) and move the star so it is sitting nearly top center of the eyepiece. Wait 2 minutes or so, then move the RA knob slowly to bring the star back into view. If the star has drifted up, then your alignment is too far west. Give it a small adjustment to the east. If it drifts down, you are too far east. Adjust it westwards. Repeat until you have minimal drift.

Next, find a bright star in the east. Use the same method of centering a star then moving it to the top of the eyepiece. If this start drifts up, your latitude setting is too high, so move it down slightly. If it drifts down, your latitude setting is too low, so lift it up slightly. Repeat till minimal drift and you have a pretty good polar alignment!

Now to actually find a target!

Find yourself a starting star, which is the brightest star in the nearby area of your eventual target. Center it in the eyepiece and look up the co-ordinates on Google or any astronomy app you may have. Adjust the setting circles so that the 'pointers' point to the corresponding values in the RA and DEC axis. Do another quick check that the star is centered in the eyepiece and the setting circles are correct. Now find the co-ordinates of your target. Loosen the declination adjustment on your mount and move the telescope s that the pointer is pointing at the declination of your target. tighten the clutch. Now loosen the RA and move the scope to the correct RA co-ordinate. Tighten the clutch once there to secure the scope. Using a low power eyepiece (your 20-25mm one that came with the scope will likely be the lowest power), have a look through the scope and your target should be somewhere in the FOV.

It should be noted that this is isn't a 100% reliable method, and the setting circles do have markings very close together so accuracy can be difficult, which is why it is best to use a low power eyepiece to find your target, but it should get you very close. It may be best to practise by starting on a bright star and using this method to find another bright star. Once you get the method, you'll start getting more accurate and speedy with it.

I hope this helps.

Answer 2

You should be fine without any additional purchase - but finding that star might be hard.

Coordinates of stars are usually given in equatorial coordinates, that is in right ascension and declination - a coordinate system which is independent of observer location, in which stars are fixed; in that the polar star is (nearly) at one of the poles at +90° declination.

So, if you were given the coordinates in that coordinate system, you can find that star. How easy that is, depends on both, your equipment, your skill to use that equipment, and, of course, on how bright that star is.

The first thing to do, would be to start Stellarium (it's open-source, free to download and use) and have a look at the given coordinates, where to find the star and to see what other things are in the vicinity so that I can judge when to observe, and how to find it (if it is not one of the brightest stars).

As your telescope is a solid beginner telescope, but not one of the super-duper fancy, many-€€€€€, easy-to-use auto-goto telescope which you just setup, you will have to practise to setup the telescope to have your axis align to the Earth axis and then steer it to coordinates you want. The quality of alignment is quickly checked if you can follow a star near the celestial equator by just turning the right ascension wheel.

For faint stars the usual procedure is to start with a bright star, and then using a star map of where you want to go (e.g. looking at a laptop screen, running Stellarium), and then star-hopping to ever fainter stars until you end-up where you want to be. This needs practise though... comparing the patterns of what you see through the scope with what you see on your star chart.

For a real beginner IMHO the best advice is: get some experienced observer from your local amateur observatory or organisation and teach you hands-on with your equipment. They often are quite happy to help - we regularily invite people with such requests sent to us to bring their equipment so that we can jointly go through it and observe with it. The 2nd best only is using some of the tutorials on setting-up a telescope.

Only invest in other astronomical equipment if you find you like and fancy observing with your telescope - and you want more of that, just easier and "better".

Answer 3

I second @planetmaker's excellent answer. If the pandemic prevents having an expert come to help, then I recommend trying a few practice nights. Look for a few sights that are easy to find, and beautiful to behold.

As a practice run, I recommend finding (in the telescope, for December 2020, early evening, Northern hemisphere):

• mars (red, you can see it before any other stars come out),
• betelgeuse (smaller than mars, but big and red, next to orion's belt),
• rigel (blue, next to orion's belt),
• vega (brightest star other than mars, but sets around 8 or 9pm), and
• the moon (especially beautiful towards Dec 25th)

These are all "very easy", but I was surprised how difficult it can be to simply find the moon in a telescope, even when it is quite clearly visible. Around Dec 25 the moon should be positively breathtaking; it won't be visible in the early night for a week or so (Dec 16th it starts rising in the early evening again).

If you go out now (Dec 9th to Dec 15th or so), then the first "stars" you can see, even before the sun sets will be planets: the red dot is Mars, the bright dot with another fainter dot near it is Jupiter and Saturn. If you look at Jupiter through the telescope you will likely see 3 or 4 bright but tiny dots near it -- the moons of Jupiter. If you look at Saturn you will either see an egg shape (different from the roundness of Jupiter) or the rings themselves. Jupiter and Saturn will be nearer the horizon, so any clouds in the distance will obscure them. Mars will be high in the sky (so easier to see), but its features are harder to see.

By the time you've enjoyed those planets, all the other stars will be coming out. The brightest will be Vega, though it will set around 8 or 9pm. Almost as bright will be Betelgeuse and Rigel, both near Orion's belt. There are many beautiful things near there.

Especially, Dec 11th through 14th (this weekend) keep an eye out for shooting stars. There is likely to be one every minute or so.

From Dec 16th to to Dec 25th the moon will be visible in the early evening/night and is truly breathtaking. If you haven't already practiced a bit, you might even be surprised at how hard it is to find the moon in the telescope. It is an excellent target to practice choosing the right eyepiece for what you want to see.

Once you check Stellarium / a star chart for the general section of the sky, you can select a nearby, major landmark (roughly, the "first" hop of your star hopping) and you may find that view quite moving.

Answer 4

and welcome to Astronomy Stack Exchange.

I’m very sorry to inform you that whatever star you “had named after” your late father is not recognized by the International Astronomical Union—nor by any other legit astronomy organization. Basically all these star-buying and star-naming things are scams. On the other hand, I don’t think you need a star to remind you of the person your father was, and I offer you my most sincere condolences.

The coordinates you are supposed to receive may not be the real coordinates of the star that will be shown on the photograph. I heard of one such case—actually, there was not even a star at the location specified!

Should you obtain real coordinates (for that star or any other), the simplest way to use them would be using graduated circles that most telescopes have. One of them needs to be calibrated, though, and it’s rather difficult to explain just like that. Another option would be to point a star of known coordinates and just go from there, comparing the difference in position and moving the telescope by the same amount.

Again, sorry for your loss, and sorry too for having to break you the bad news that you were the victim of a scam.

Clear skies!