One thing that may not be obvious to new telescope owners is how to focus a telescope. However, it is a very important skill which is easy to learn.
We all know that a telescope gives us a clearer view of the night sky, and we can get a fantastic view of different stars, moons, planets, and various celestial objects. However, you will not get a good view of these if you do not know how to use your focusser to produce a sharp, clear image.
This can be a challenge, especially if you are using an older telescope for which you do not have a guide. This article will simplify the process!
So, if you have a telescope and want to learn how to focus it but have no idea where to start, keep reading!
Step By Step Guide
Of course, before we get onto the actual steps, there are certain things you will need to do, like getting the right telescope for you, knowing where to set it up, and just everything before you want to think about focusing.
Getting to use a telescope for the first time is incredibly exciting, but be careful when setting up and do not do anything that could damage your telescope.
If you are yet to obtain a telescope you may like to see some of our telescope suggestions.
Align The Finder
The first thing you will need to do when you are setting up your telescope is to ensure that you have aligned the finder scope. This is the small tube that should be on the side of your telescope.
The finder scope makes it much easier to point the main telescope to the objects you wish to observe. However, this only works if you have the finder set up correctly. During daylight hours, you can align your finder on objects around you, like a distant building or tree.
But, once you know how to use it, you can use the crosshairs of the finder easily. You can adjust this using screws, and your telescope should hopefully give you the option to lock the settings.
This can be a challenge, but you want to make sure it is done correctly before you move on!
If you wish to read more about setting up a telescope and/or how to adjust the finder scope see How To Use A Telescope.
Set To The Lowest Magnification
One thing that will make focusing your telescope a lot simpler is to make sure to use an eyepiece that will provide the lowest possible magnification.
The easiest way to do this is select the eyepiece with the longest focal length. Check the eypiece’s barrel for the focal length. This number is in millimeters. Our article on eyepieces explains eyepiece magnification.
To know your telescope’s magnification, you want to divide the telescope focal length by your eyepiece. Because of this, you get a higher magnification with an eyepiece that has a shorter focal length.
Set The Finder On The Target
Then, you will want to set your finder scope’s crosshairs on the object you are looking to observe. This is easiest if you look through the finder scope with one and and keep the other eye open and looking towards the target. This sounds a little awkward, but with practice, it is a very effective method of finding your target. I’d recommend practising on bright objects.
This procedure makes this step a lot easier. You want to make sure that you have your crosshairs in the center of, or very close by, whatever you want to look at.
Once you are sure that you have it in the center, you are ready to continue.
Once you are sure it is in place, you will want to ensure that there are no movements or bumps to knock it out of place since this is where you want to keep it. Ensure that both axes of your telescope are locked (you may need to check the manual for your telescope/mount).
Set And Direct The Eyepiece
If the finder is aligned correctly your telescope should hopefully be pointing at the object you will to observe. Your finder scope and telescope should be centered on the same object.
To ensure this, you want to ensure the eyepiece is properly adjusted and locked tightly before you start. As you probably know, you can get eyepieces of varying different focal lengths.
The higher the number of the eyepiece, the lower the magnification power will be.
You will want to start off using an eyepiece of lower power to make it easy to focus and end up with a wide field of view to work with.
These eyepieces will leave you with an image that is both crisp and bright, this makes observing objects with it simple and easy.
The higher the power of the eyepiece, the less detail and the less sharpness you will get with your image.
You should ensure that these higher-power eyepieces are being used for binary star, lunar, or planetary observations.
Remember that if you are changing your eyepiece, you will need to refocus the telescope. This is because different eyepieces have different focus positions, so do not worry if you change the eyepiece and the image has become blurry.
When using the eyepiece, do not put it up against your eye directly. Give yourself at least 15 mm of space, or a little more if you wear glasses.
Set A Sharp Focus
Once you have found that the object is in your telescope’s field of view, you will want to check that you have the best focus by adjusting the focus knob on the side of the telescope.
The photograph on the right is the focus knob on my William Optics FLT 110 refractor. It has two knobs on one side of the tube (on the other side, it is a simple knob). The larger knob provides standard focus adjustment, while the smaller knob allows for finer focus adjustment.
Make sure you are only moving one at a time and have a good level of control when doing so.
These knobs adjust the distance between the primary lens and the eyepiece, and they will either improve or worsen the view that you are getting.
If you are still not getting an image with great resolution, then there might be something you want to change with your telescope. Sometimes you just need a more powerful scope to get a better view.
Incidentally, the type of focuser shown in the photograph is a Crayford Focuser.
Summary
Hopefully, this guide has given you all the information you need to ensure that you are focusing your telescope correctly.
Something to keep in mind when you are working with telescopes, especially if you do not have much experience, is to keep your goals measured.
You will want to know how powerful your telescope is so you are only trying to look for something that it can achieve.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
