How can I work out longitude and latitude through my telescope? 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 &quot;UK&quot; 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
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 &quot;roundabout&quot; 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 &quot;drift&quot; 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 settign 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.