As an amateur astronomer living in a place with harsh winters, you may have wondered – can I just use my telescope through the window when it’s freezing outside?
The thought of staying warm and cozy indoors while still getting to stargaze is amazing.
But before you get too excited, let me break it to you – using your telescope through a window is generally not recommended.
In this post, I’ll explain why and give you some tips if you just HAVE to use it through a window.
Now I know what you’re thinking – “But the internet said it’s possible! Surely a little window glass can’t mess things up that bad?”
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Well, my stargazing friends, let me explain why aiming that telescope through a window, no matter how clean and pristine it looks, is a surefire way to get disappointing, blurry views.
The main issue with observing through window glass is that it simply wasn’t designed with astronomical observation in mind.
Most residential windows are made of sheet glass that looks smooth to the naked eye but is actually full of tiny distortions and imperfections under a microscope.
These little bumps and waves in the glass are enough to scatter light coming through your telescope, degrading image quality significantly.
And what if you have double or triple pane windows?
Well, you’re just compounding the problem by adding more layers of optically imperfect glass.
Let’s not forget about window tints, coatings, and even smudges from those inevitable fingerprints – they can all contribute to scattering light and reducing clarity.
So unless you have optically-perfect glass especially made for telescopes (which no normal house window is), you’re going to be fighting an uphill battle.
But say you decide to open the window to avoid the glass barrier altogether.
Unfortunately, you’ll be inviting a whole new problem – air currents and turbulence.
Telescopes work best in stable air conditions. The temperature difference between your warm room and the cooler night air outside can create air currents around the window, causing the image to wobble and flicker.
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It’s like tossing a wool blanket in front of your telescope’s line of sight.
Not ideal for getting crisp, clear views.
Putting optics aside for a moment, there’s also the very real issue of a limited field of view when observing through a window or door.
You’re basically looking through a small porthole into the vast universe, missing out on huge swaths of the night sky.
Sure, you could try hopping from window to window like an over-caffeinated bunny to track objects, but that’s hardly practical or immersive.
One of the greatest joys of stargazing is drinking in the entire celestial scene.
Why settle for a tiny snapshot?
Look, I get it – sometimes going outdoors just isn’t an option, whether due to injury, mobility issues, or those inevitable blizzard conditions.
In those cases, a warm indoor viewing session trumps no stargazing at all. If you absolutely must observe through a window, here are some tips to make the best of it:
This is one way to get a better image using your scope through a window glass.
The smaller the telescope aperture, the smaller the portion of distorted window glass you’re looking through.
So you’ll suffer less from the window’s imperfections compared to a large aperture scope.
This involves adjusting your thermostat.
Make sure the room you’re observing from is about the same temperature as outdoors. This minimizes nasty air currents that can further degrade image quality.
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My next tip for you is about the power of your telescope’s eyepiece.
Higher magnifications will only amplify every distortion caused by the imperfections of the window glass. Stick to lower eyepiece powers of around 20-40x for the best possible views.
How close your telescope is to the window can be significant in this situation too.
Having your telescope as close to the window as possible opens up more of the sky to view and reduces the angle of incidence through the glass, marginally improving sharpness.
You won’t be able to get clear views due to the imperfections in window glass that scatter light and reduce clarity. And even opening the window will introduce heat currents and turbulence that will blur the observations.
But if you have no other option, consider using a small refractor, maintaining a consistent room temperature, and using lower eyepieces.
Also position the telescope close to the window for a better experience.
Despite the challenges, with adjustments, you can still enjoy stargazing from indoors, albeit with some compromises in quality.
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