It might sound like a stereotype, but a lot of people that decide to indulge in astronomy wear glasses. Since their eyes are not the only thing coming into contact with the telescope lens, they could have their reservations when it comes to levels of comfort, but there’s more to it. With that being said, is it possible to look through these devices while wearing glasses? The answer will be shown in a bit.
Depending on their needs and prescription, it is likely that they will have to experiment with different sizes of eyepieces until they find the one that helps their sight the most. This might seem evident, but it becomes crucial when buying a telescope for the first time. On a side note, it cannot be stressed enough how important it is to refocus it while removing the eyeglasses.
A common question…
According to Howard L. Cohen, author of To Wear or Not to Wear Glasses, from FirstLight’s October/November edition (2006), this is one of the most common questions that people who desire to delve into this beautiful hobby, at least for those who have prescripted glasses.
Whereas the more experienced astronomers know what to do to avoid problems like tunnel vision, most beginners have been shocked to find out that they are an obstacle for them catching a glimpse of their favorite celestial phenomenon. To say it is frustrating would be an understatement.
Contrary to popular belief, wearing glasses shouldn’t put a damper on exploring the starry skies with a telescope.
The only issue so far is that the corrective lenses that are part of them are likely to distort the light that passes through the eye.
Of course, what happens to the image relies on the problem that the glasses aim to fix. One of the factors that can become an obstacle to the experience is astigmatism. This is mainly because its level of severity is key to how much it affects what the astronomer can see and the problems they will find.
However, near and farsighted people can easily look through a telescope without needing glasses. They would have to tweak its focus to have a clear view, yes, but it will be worth not having the tunnel effect that comes with keeping the eye too far from the eyepiece.
Best Eyepiece for glasses….
The telescope that they would need heavily relies on the quality of their sight as well. People with mild astigmatism can make do with an eyepiece of 25 millimeters and a view diameter of around 14 to 24 millimeters.
For less powerful equipment, Barlow lenses can magnify the image on the telescope without breaking a sweat. I recommend using a wide field-of-view optical device, as well as keeping the magnification at a small exit pupil diameter, another factor that has an impact on the viewing quality, which is something that will be detailed below.
This will prevent astigmatism from affecting the edges, which will translate into the planet turning from a blurry spot to a celestial being. On the other hand, they also suggest focusing the telescope on the brightest star and slowly rotate the eyepiece to check for any distortions on the image.
This will determine whether these unwanted bits stay in the same place or move with it.
What is needed for near and farsighted people?
Near and farsighted people, however, will require equipment within the 1.5x and 3x power range. These fellows allow them to increase their viewing capability, providing the same quality that it would have for someone that has a 20:20 vision.
Another thing to take into consideration is the aforementioned exit pupil diameter, mainly because it’s one of the most common limitations for people that wear glasses, especially for those who have been prescribed glasses for astigmatism.
It is defined as the diameter of light that goes from the eyepiece to the eye. Under circumstances where there are no imperfections in the eyepiece nor any sort of sight condition, the image shown in the telescope should have an exit pupil diameter of 7 millimeters, which is the ideal measurement.
This changes with age, the elderly often needing around 5 to 6 but, when it comes to telescopes, this should be neither above nor below this range.
Not only that but also the image can get distorted for near and farsighted people, as well as those with astigmatism, who seem to have it the hardest for when it comes to looking through a telescope.
But fret not, since this can be easily resolved by making the aperture of the tube smaller, using a donut ring. The only drawback? It will block the light that comes through the equipment, although it’s slightly better than a blurry and bright image.
About telescope eye relief…
The eye relief is next on this list. This is how far from the telescope the user can be to have a clear view of the planet or star that they fancy.
The reason behind this? Simple: The glasses restrict the pupil from getting closer to the telescope, which minimizes the magnification power of the telescope.
Barrow lenses are our go-to to prevent this mild inconvenience, as well as an eyepiece with a wider and longer focal length of at least 15 millimeters. The useful tips don’t stop there since they also suggest to upgrade the glasses to APO lenses to have a better view of the cosmos.
Why? Because their quality will also be the end of the image that they’re aiming to capture with the telescope, similar to what happens with the eyepieces, mainly due to how it affects their refractive properties.
One interesting thing about all of this is that a rule was created to determine which magnification level would suit best for each prescription.
Invented by Richard Buchroeder, it states that if the amount of cylinders on the eyeglasses is a certain quantity, it is possible to look through a telescope without glasses when it is one fraction of its square root or smaller.
By that equation, an uncorrected eye will be more useful than a quarter-wave of aberration if the telescope has a larger exit pupil. This rule applies for people with astigmatism, which means that near and farsighted individuals won’t have to worry about making these calculations.
We hope this shows that with a little planning and getting the right equipment. You can enjoy stargazing even if you have to wear glasses.