Looking through a telescope is a bit like looking through a straw, unless you know exactly what its pointing at then it can be really difficult to know what you’re seeing. Just pointing a telescope randomly at the sky will result in seeing a bunch of stars. Unfortunately stars look about the same and it can be hard to find a reference point. This is essentially the problem the first time you look through a telescope. It’s a bit easier to start with something like the Moon, which being super bright is very easy to spot and get in the eyepiece. This is the challenge, actually getting what you want and to look at in the eyepiece. Converting the information in star maps and handy apps on your phone can be rather tricky. If you’ve purchased a computerised mount then you still have to line it up so the telescope knows where it’s pointing. From there it’s pretty easy as the telescope’s mount will do all of the tricky work is locating things to look at. For those of us without an automated mount then you have to do the hard work in finding stuff and pointing the telescope in the right direction.
I have a small amount of experience flying aeroplanes and before a pilot straps in and starts boring holes in the sky they check that the aeroplane is airworthy and safe to fly. Handling an expensive and heavy telescope can be both dangerous to your head and pocket so I think it’s worth having a pre-flight check list for astronomy as well, especially if it’s the first time you’ve used the telescope. The system in using a telescope can be usefully thought of as having three parts, the telescope (or optical tube assembly), the mount and the accessorises (eyepieces and cameras etc). Important areas to check are moving parts, joins between parts, optical covers and fastening mechanisms.
So the first thing to do is have a good look at your telescope during the day as it is a good idea to become familiar with it when you can see it. I’ll assume you’ve managed to assemble the mount and the telescope is safely mounted. Make sure the mount is secure and the legs are locked in place. For a dobsonian mount, make sure it’s on a firm and flat piece of ground. Then you check all of the bolts and lugs holding the telescope on the mount, as if it falls off it can hurt – both physically and mentally. For setups with weights you need to make sure it is balanced so when you release the axis brakes the telescope won’t rapidly move out of control. Check the telescope has free movement in every direction and you know how to lock it in a particular position. Get used to the feel of moving the telescope left and right and up and down. For EQ type mounts ensure you know where the main axis of the mount is, as this is the axis that must line up with the celestial poles. For dobs that doesn’t matter. The picture below is one of the Sydney Observatory telescopes, all ready and mounted for some solar astronomy.
The next bit is to check where all of the covers are and how to take them off and put them back. One of the most common mistakes for the newbie astronomer is simply not removing the cover. It’s worth thinking about where you will put them when you take them off too, so you don’t lose them. There will normally be a tube cover on the end of the telescope as well as a small cover on the focuser, these all stop dust getting on the optics so don’t lose them. Most telescopes also have a finder scope which will need the dust covers taken off as well, or else you won’t be able to see through it and lineup on the celestial objects you want to see.
Now it’s time to familiarise yourself with how the telescope actually works. Like most things with a telescope, you’re better off learning how it works and getting familiar with it when it’s light rather than trying to work it out in the dark. So first up, have a look at the focuser and ensure it has free movement and notice how much travel there is. The position of the focuser, to have a view in focus, will depend on the telescope and the eyepiece you’ve got. Some focuses have a fine tuning control which can be very useful for getting the view as fine as possible. It’s worth looking at how your eyepieces slot into the focuser too. You don’t want to be figuring this out in the dark and risk dropping one. Check how the eyepiece is secured how much travel there is so you know what it feels like.
Now you want to look through the telescope to make sure you know how to focus it and get a nice clear picture in the field of view. Again it’s best to do this during the day. What you need to do now is lineup the finder scope with the main telescope. To do this you find something prominent in the distance like a towel or a tree or a rock, or something that’s a couple of kilometres away, and you adjust the finder scope so that the main object is in both the telescope and finder scope. A finder scope is basically a tiny telescope so it will need to be focused and can be adjusted where is pointing usually buy a few little screws. Once you’re happy with where the finder scope is pointing then lock it in place.
now is the complex question of collimation. For a reflecting telescope this is where you line up the mirrors (see above picture) so the light is going in the right direction to the eyepiece and into your eye. Collimating a telescope is a whole topic on its own. Now that your telescope is ready and lined up and you know how to remove all of the dust covers and you know how it moves, you are ready to take it outside and start viewing the night sky.