What magnificatoin are professional telescopes?

I’m talking about the big telescopes at observatories that profession astronomers use. What magnification are those?

Hi. The upper limit of magnification, or resolution, is a function of objective size for ALL telescopes. And the higher the magnification the smaller the field of view. If you need a number then say 250x – 1,000x.


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What magnificatoin are professional telescopes? — 8 Comments

  1. Hi. The upper limit of magnification, or resolution, is a function of objective size for ALL telescopes. And the higher the magnification the smaller the field of view. If you need a number then say 250x – 1,000x.
    References :

  2. I would say, without polling every scope on the face of the earth, that a magnification of about 1,200 to 1,800 is the limit of earth-bound professional optical scopes, the ones that you can observe with your eye through the atmosphere. For more info, look up Kitt Peak Observatory or, better yet, Haleakala and Mona Kea, Hawaii.

    Then there are spectrographic scopes with "charge coupled devices" that collect light emissions over time and render digital pictures. These scopes go up to a magnification of 65,000 or more (with ever-changing technology). Newer systems now use liquified Nitrogen to keep the devices very cold and enhance their sensitivity.

    That’s the extent of my exposure.
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  3. In practice, most optical telescopes have maximum magnifications in the 100x to 1000x magnification, regardless of their size or cost.

    The limiting factor is not actually magnification. A higher magnification also reduces your field of view and makes finding objects much harder. A higher power is also more sensitive to ground vibrations and atmospheric distortion, of which there is always some, so you won’t see earthbound optical telescopes go much higher.

    The REAL limiting factor is light amplification. You can get 1000x with a cheap 3" reflective telescope, but the image would be so dim you couldn’t make anything out. Put a 1000x on a 24" mirror, and you could start making out some details on dim celestial objects.

    So those telescopes the professional astronomers may not be much more powerful than the one you have, but they collect a LOT more light, letting them see much dimmer objects.

    Of course, if you use NON-optical, digital CCD telescopes, you have many more options in terms of image enhancement, stabilization and photography. With these telescopes, you can go much higher than 1000x, and this is how telescopes can look at the super-distant and tiny galaxies.
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  4. The big qualities of professional telescopes are the ability to gather lots of light (in order to see very faint object) and the ability to separate objects that appear very close (called resolution).

    The diameter of the mirror is the key factor in both cases, even though most modern telescopes (because they need to stay in business for decades in order to provide a return for the investment), use devices to help them:

    CCD cameras (with photo-multipliers) in order to make use of every least bit of light, and corrective optics in order to correct for the changing refraction of the atmosphere.

    Without these devices, the best resolution is about 0.5" (1 arc-second = 1/3600 of a degree) which is equivalent to a bit less than a km on the Moon’s surface.

    This is not very good resolution as it corresponds to the theoretical limit of a 250 mm telescope (10 inches). Adaptive optics give much better results.

    The big thing is gathering light and seeing very faint objects.

    Without the CCD, the limiting magnitude of a large telescope (for example, the 5 m Mount Palomar) is around magnitude 21 or 22 (the naked eye sees down to magnitude 6 — the bigger the number, the fainter the star. The 5 m telescope makes stars appear one million times brighter than does the eye. With normal photography, we could reach 23 or 24 (no, I will not say how old I am).

    With any telescope, the maximum useful magnification is 2 times the diameter in mm. So, the 5 metre telescope has a 5000 mm diameter (1000 mm per metre) and could, in theory, handle a magnification up to 10,000 times. But no one does that. In practice, the mirror gathers as much light as possible which is then analysed by devices (such as spectrographs) or recorded by CCD cameras.

    My personnal record is approximately 1500 times, on a 1.6 m telescope (64-inch diameter), on a night when the seeing was too poor to do anything useful. I remember seeing Saturn as never before (but with lots of jiggling around because of atmospheric disturbance) and visiting the Moon with the impression that I was hovering just a few kilometres above the surface.

    But in general, people do not use a big professional telescope in a manner where the word ‘magnification’ has much meaning.
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  5. Well, most professional telescopes are somewhat lower in power as they are more interested in light gathering.

    Generally they put cameras and sensors at what is called prime focus

    Since 4mm is the most powerful maginifer it can allow some telescopes to go up to 1,000x or more, by they rarely do this.

    At Griffith Observatory in Los Angeles they generally let the public look at 100 to 150x which any scope can do

    Griffith can probalby easly get up to 1,000x if they wanted to
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  6. Almost without exception, no one actually _looks_ through professional telescopes. They are used exclusively for photography, photometry, and spectrography: cameras or other instruments are attached to them, but never an eyepiece. So the term magnification is meaningless for professional telescopes.
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  7. A very typical question which I get all the time.
    But it is the wrong question!
    Just to summarize: The purpose of a Telescope is to gather light !!
    The magnification of a Telescope is determined by the eyepiece. If you had the right eyepiece, any telescope can magnify as many times as you want.
    But in practical terms, useful magnification is limited by two things. The diameter of the Telescope’s lens or mirror and the earth’s atmosphere.
    A common conservative figure for practical magnification is 50 times per inch of diameter of the Telescope’s lens or mirror. ( on exceptionally steady nights this can be exceeded).
    That’s why we always advise foks new to Astronomy NEVER to buy a Telescope advertised by it’s magnifying power. 625X on the box of a 2.4" Telescope is utterly ridiculous.!!
    Due to the unsteadyness of the earth’s atmosphere 600X magnification is about the
    maximum, regardless of the size of Telescope. Professional Observatories are built on mountaintops to get above the worst of the atmospheric disturbances and so can reach higher values of magnification.
    But again, this is really meaningless since, as far as I know, most professional telescopes don’t even have an eyepiece available. Think of them as Cameras, because that’s what they are. Nobody magnifies anything !
    The reason they keep building bigger and bigger Telescopes is to collect more light, and thus detect fainter and fainter objects which are farther away. The size of the object on a film plate or a CCD chip is solely determined by the focal length of the Telescope which of course increases right along with the diameter.
    Any magnifying done, if at all, is done on the images by computer programs.
    Even Amateur Astronomers today routinely use the same procedures as the big boys, just at a reduced scale. Many images produced by Amateurs today outdo anything Mount Palomar could do as little as 20 years ago. All thanks to the CCD chip and software.

    Adolph
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  8. Theoretically, you can use just about any magnification in any telescope BUT if the magnification exceeds the resolution limit of the telescope, you won’t see anything but a blurry image.

    The maximum practical magnification that can be used in a telescope can be approximated by multiplying the diameter of the mirror in inches, by 50.

    A 100 inch telescope can theoretically resolve things that have been magnified 5000 times.

    Of course Earth based telescopes have to look through the atmosphere and this limits the resolving ability so it’s often difficult for Earth based telescopes to achieve their maximum practical magnification unless they have adaptive optics.
    References :

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