Since my childhood. I had aspirations of discovering comets and sometimes enjoy the views of the moon & planets from time to time. It was not that easy then like it is today. Exploring our amazing universe is moments away with a quality telescope these days. Just focus on a telescope into the sky and explore it.
If you can’t focus properly with your telescope and are not enjoying a crystal clear view of the object you are looking at, you are not utilizing your telescope properly.
Focusing is usually a very easy task to do, but sometimes it might seem a very hard job too, especially for beginners. You might struggle to use a telescope properly in the beginning. But once you are adapted to this, you will enjoy the view quite often. Whatever your astronomy goals might be, there is one thing that you must do is to use a telescope and focus rightly with it.
We will be discussing focusing on a telescope in this article. Along with that, we will explain different types of the focuser, and many more. You will have an ultimate guide about focusing on a telescope. So stay with us.
How Do You Focus on a Telescope?
The framing, zooming, and measuring (the process called ‘magnification’) of your image will vary a lot depending on the optical instrument you are using in astrophotography. Instruments like high-quality smartphone cameras and DSLR cameras with the help of exceptionally qualified lenses can do astrophotography these days. But telescopes are incomparable to these.
Whatever your focus to capture might be, whether it is a massive area of the night sky i.e. the core of the Milky Way or a narrow area i.e. small nebulae and galaxies for a closer look, your focus must be spot-on for a sharp image.
There are many ways to better your focus. The following tips from our experts will help you focus better:
- Using a camera for focusing and that too by an unaided eye will not be a good choice. It may give you inaccurate results too.
- Test the infinity focus before using autofocus, because many of them focus past infinity. Which may ultimately result in inaccurate outcomes.
- Try for a flat focal plane.You may not find a flat focal plane that easy in many telescopes.
- It is suggested to bear in mind that temperature change plays a crucial role in focus drift.
There are numerous methods you can use for focusing. Some of them may work better than others and it may vary from one individual to another. We have included both traditional approaches and modern approaches here.
You will require to spend quite a good amount of time and effort in focusing to enjoy your hobby like astrophotography. There are several methods with whom you might get accustomed to, but we suggest to repeat only that method that brings better results for you. Let’s have a look at some popular methods of focusing.
Focusing on a Newtonian telescope
If you have a reflector or refractor telescope, you might want to get the focus accurately to enjoy the best view. And it can be done by following the given steps
- You just need to rotate the focus knob slowly.
- Rotate the knob until the object you targeted becomes focused.
- Move just a little bit beyond the sharp focus and switch the direction.
- When you will get a sharp focus, tighten the focus knob until it is locked.
- If you don’t lock it, your focus may slip. So don’t skip the step.
- When you are ready to refocus on a new object, loosen the focus lock knob again.
- The focus lock knob should also be turned while changing your eyepieces.
- Try frequently and the focusing will be easier for you.
In this way, you can easily adjust your focusing and enjoy sharp images.
Getting a Cassegrain in focus
Focusing on a Cassegrain is not the same as a reflector or refractor telescope. But it’s not something difficult. Just follow the given instructions:
- First, find out the focusing knob on a Cassegrain. If you get a small knob on the back of it, you are at the focusing knob.
- Here you don’t have to move your eyepiece back and forth against the telescope.
- You just need to move the primary mirror backward and forward.
- By doing this, you can have a long throw of focus.
- And one more thing, now it’s ready to accept any kind of various camera or eyepieces.
Using a camera lens
The camera technology has improved by a large margin in the past few years. And you can do astrophotography using your camera lenses too. Experts suggest using manual focus settings rather than autofocus as the stars are too small and too dim for autofocus. But you can use the autofocus feature too, in that case, you might need some additional hardware and software.
You can rectify and hide camera noise and slight star trailing to an extent but out-of-focus shots are unrecoverable, so take time to focus your camera for a perfect shot. Don’t hurry to capture a moment because while doing so, you might damage the image.
Select the brightest star in the night sky using the “live-view” mode of your camera. Other planets and the moon can be focused too for better understanding at the beginning. The benefit of the “live-view” mode is it will turn your display screen into a live video of what your sensor sees.
Make sure you change your settings in the following pattern.
- Mode: Manual or Bulb
- Lens Mode: Manual Focus
- Aperture: f/4 or below (as low as it goes)
- White Balance: Daylight or Auto
- Exposure: 30-seconds or Bulb
- ISO: 1600 or above (Higher will show more stars)
If you still fail to focus and see a black screen only, then you might have one or more of the following issues:
- The lens cap is still on your lens, take it off if it’s still on.
- Recheck the settings and adjust ISO, exposure, and f-stop.
The benefit of focusing with a camera attached
Turn the knob of your focuser till you have a clear view of your subject to lock the focuser with the camera attached telescope. Locking the focuser is crucial. When you are pointing the telescope to a certain angle, due to the weight of the focuser it may fall out of the position. So choose the focus wisely and handle it with care.
Telescopes with refractor focusers are easier than camera lenses for focusing especially in astrophotography. The major reason behind this is telescopes have better precision and robust focuser than any camera lenses. The benefit of having a robust focuser is that it doesn’t move here and there like camera lenses and locks the focus into a place.
These are the most popular and easy to execute focusing methods. But, there are few other methods that can be used for focusing. Such as:
- Right-Angle Finder
- Digital Zoom Trial and Error
- Hartmann Mask
- Diffraction Spikes
- Star Trail Test
- Hybrid Method
Tips for Focusing
We have discussed the easiest methods for focusing. Hopefully, that will be helpful for you to start exploring our universe. Here are some tips to ease your focusing efforts.
- The easiest method of focusing is the live video feeds out of a DSLR.
- Auto-focus camera lenses might focus past infinity sometimes.
- Lock the focuser once you have achieved the focus.
- Be very careful that the focus should not change while locking it.
Knife-edge focusers are easy to use and much accurate. For example the Stiletto and Mitsuboshi.
Astrophotography and Focusing
Do you know what is the first photograph of an astronomical object? It was a photograph of the Moon, taken back in 1840. But the technology of astrophotography started to evolve from the 19th century. And today, astrophotography has come a long way to be considered as a subdiscipline in amateur astronomy.
If you wish to be a master in astrophotography or even want to enjoy the art of astrophotography, the very first skill you need to adapt is focusing. It is considered one of the most critical skills of astrophotography. Focusing on a telescope is found much harder than focusing on a DSLR camera. Especially for the beginners.
Well, it may seem a little bit difficult while reading, but you will find these methods very easy in practice. We have discussed several simple ways of making your focus perfect. Get your telescope out now and try your favorite method of focusing.
Write back to us about how you enjoyed this. If you have any queries let us know. And mention any suggestions too for the beginners.