Telescope Magnification | Influencing Variables, Properties, and Limits | Types of Magnification | "Detour" via the Dawes Criterion to the "Common Denominator"... | Bottom Line | Links

On this page I try to make the topic "magnification of telescopes" more understandable for me and to clarify what, besides the "actual" magnification, other magnification terms used in this context do actually mean.

The beginning is simple and can be read in many textbooks and other sources. The following definition is based on Gehrtsen (physics textbook):

- By
we mean the ratio of the angles of view at which we see a distant object in a telescope to that at which we see it without a telescope.*magnification*

It seems to be the ratio of the tangens values of these angles, if you want to be exact, but for small angles the angle in radians is a good approximation for the tangens.

This relation has to be expressed in "telescope parameters" in
order to be usable in practice. For objects that are infinitely far away, the
* magnification* of a telescope is calculated from the

- Magnification = (focal length of the telescope) / (focal length of the eyepiece)
(
*Formula 1*)

A telescope therefore does not have a "magnification per se", but this results from the interaction of telescope and eyepiece and is therefore not "fixed".

Furthermore applies (without derivation):

- Magnification = (diameter of the entrance pupil) / (diameter of the exit
pupil) = (aperture in mm) / (diameter of the exit pupil) (
*Formula 2*)

According to *formula 1* for the magnification, one might make the magnification
as high (and as low) as one likes. However, there are a number of properties
or limits that put an end to this:

- Properties and limits of the telescope optics: e.g. aperture, resolution, amount of light, optical deficiencies,
- Limits of our eye: e.g. resolution, light sensitivity
- Limits to the sky quality: e.g. light pollution, seeing (air turbulence)
- Constructive limits for telescopes and eyepieces: e.g. minimum and maximum focal length, maximum lens and mirror size

Below I will discuss some of these influencing variables/limits in more detail.

There are also a number of other magnification terms for telescopes that are "fixed" because
they depend essentially on the **aperture** of the telescope (or, depending on
your point of view, on its **resolution**, which in turn depends on the aperture).
I would like to introduce the following terms:

- Normal magnification
- Minimum magnification, minimum usable (or: sensibly usable) magnification
- Beneficial magnification
- Maximum usable (or: sensibly usable) magnification
- Maximum magnification

Certainly there are other terms in this context. On the Internet and in the literature I have found that the presented terms are used by different authors in different ways, or with overlapping meanings, or that they lead to different values although the definitions of the terms are the same. In the following, I try to bring some "light into the darkness" for myself...

Why were these additional magnification terms introduced? I suppose they were introduced to give users some orientation on the scale from no magnification at all to infinitely high magnification (although the different uses of the terms seem to be rather confusing...). They refer to certain properties and limits of telescopes and the eye; in addition there are limits, such as air turbulence, which are independent of all this. Therefore, before describing the magnification terms, first a few remarks about influencing variables, properties and limits!

The **amount of light** falling on the eye is determined by the "openings" of
the telescope on the objective and eyepiece ends:

**Entry pupil/aperture of the telescope**: This is determined by the diameter of the front lens or the main mirror; it determines how much light a telescope can capture and will further down turn out to be a central influencing property of a telescope.**Exit pupil of the eyepiece**: Specifies the diameter of the light beam that leaves the telescope and hits the eye. To be more precise, the light beam hits the eye pupil, our "entrance pupil"; its size (5-7 cm), which depends among other things on our age, determines how much light can fall into the eye.

The **aperture** is a characteristic of a telescope that is determined
by its construction, and perhaps it is its most important property of all,
because it determines some other telescope parameters, such as light gathering
power and resolution, exclusively, as well as other parameters (aperture ratio,
magnification, ...) in conjunction with other parameters (focal length, eyepiece
focal length, ...).

The **exit pupil** of a telescope or eyepiece thus determines the maximum amount
of light that can reach the eye:

- If the light beam coming out of the eyepiece has a larger diameter than the pupil of the eye, light is lost (a smaller telescope would suffice...).
- If it has a smaller diameter than the eye pupil, the image appears darkened.

In the "eyepiece language" this is means:

- If an eyepiece has an exit pupil that is too large, light that hits the eye outside of the eye pupil is wasted.
- If an eyepiece has an exit pupil that is too small, observational objects become too dark (from 1 mm and smaller for galaxies and nebulae, from 0.7 mm for planets, from 0.5 mm for the moon).

The **exit pupil** can be determined by the **magnification** and
the **aperture of the telescope**, but also by the **focal length of the
eyepiece** and the **aperture ratio of the telescope**, so it is not an "eyepiece property":

- Exit pupil = (opening in mm) / magnification (
*Formula 3*) - Exit pupil = (focal length of eyepiece) / aperture ratio (from
*formula 2*; after entering the formula for the magnification and transformation)

This formula (*formula 3*) can be transformed, for example, in order
to calculate the *(beneficial) magnification* using the exit pupil (see
below).

For a given telescope the entrance pupil/aperture of which is fixed and predetermined (by the primary mirror or the objective lens), the exit pupil of the eyepiece controls the amount of light reaching the eye, at least as long as it is equal to or smaller than the eye pupil. This is done in practice by using different eyepieces and thus different magnifications. The magnification types still to be discussed tell you, among other things, within which range you should use magnifications. However, they do not tell you which magnification or exit pupil is most suitable for which celestial object; this has to be be taken from other sources. They also do not tell you which maximum magnification the current state of the sky (the seeing) allows.

By the way: According to *formula 3*, telescopes with larger apertures
have the advantage over those with smaller apertures that their exit pupil
is larger at the same magnification, namely by the factor by which the apertures
differ. This allows them to present planar objects brighter as long as these
are not larger than the field of view (according to Stoyan, *Deep Sky Reiseführer*).
Here an example calculation with two telescopes having aperture_1 and
aperture_2:

- Exit pupil_1 / exit pupil_2 = (aperture_1 / magnification) / (aperture_2 / magnification) = aperture_1 / aperture_2

In other (or my...) words: The exit pupils behave like the apertures.

The resolution of the human eye is another important parameter or limit in
the following considerations. So here are a few data that I have collected
(according to Stoyan, *Deep Sky Reiseführer*, and *Spektrum der
Wissenschaft*):

- Smallest viewing angle that the human eye (theoretically) can see: 20".
- Practical resolution of the human eye: 1' (60") -> concentrated observation, strained vision
- Resolution for double stars: 2' (120") - is often used as a basis
for the
*beneficial magnification*-> comfortable vision - Resolution for bright surfaces: 3' (180") - by Stoyan (
*Deep Sky Reiseführer*) used as a basis for the*beneficial magnification* - Resolution for small bright areas: 4' (240") - 6' (360"): Maximum magnifications

The **resolution capability** (or only **resolution**) of a telescope
is defined as the ability to display two closely spaced objects (e.g. double
stars) separately. Two criteria have been developed for this purpose:

**Rayleigh criterion**: the diffraction disks of the objects do not touch each other**Dawes criterion**: the diffraction disks of the objects create a ∞ image

In practice, "rules of thumb" are used for both criteria (that is why I leave out the complex mathematics behind):

- Rayleigh criterion: resolution of the telescope (") α = 138 / (aperture in mm)
- Dawes criterion: resolution of the telescope (") α = 116 / (aperture in mm)

The resolution depends solely on the telescope **aperture** (objective
lens or mirror diameter). Obviously, the Dawes criterion is more "practical" than
Rayleigh's (see the article by Stefan
Gotthold, in German), and even the manufacturers
usually only provide this value (probably because it looks "better").

Why do I list the resolution here? On the one hand, as we will see further below, at the in the beneficial magnification, the resolution of the telescope matches that of the eye. On the other hand, other types of magnification are also associated with the resolution because they depend on the aperture.

The **sky quality** depends on the degree of **light pollution** and
is measured on a scale of 9 steps. It essentially determines the limiting stellar
magnitude. Therefore it is less relevant in the context of magnification
types.

The so-called **seeing** (**air turbulence**, **air movement**) can
disturb the image in the telescope to such an extent that an observation above
a certain magnification makes little or no sense. In the literature and on
the Internet you will find simple rules for maximum magnification under different
conditions based on practical experiences. I have read the different recommendations
for upper magnification limits and list some here without any comments:

- 150 x to 180- 200 x: standard sky
- 200 x
- 400x: Standard sky (Consolmagno & Davies Turn Left at Orion (p. 21))

In other words: No matter which maximum magnification the formulas below provide, if the quality of the sky is low, the seeing of the sets an upper limit to the maximum useful magnification. This upper limit also depends on the object being observed (i.e. whether it is a double star, a two-dimensional object, a planet or the moon).

By the way, the seeing depends on the square of the aperture, because it
is a function of the area (Stoyan, *Deep Sky Reiseführer*). This is why small
telescopes reach their maximum magnification more often than large ones.

Telescopes cannot be built to any size for technical reasons, also because the size of the lenses and/or mirrors reaches technological and weight limits. But the hobby astronomer himself sets limits here as well, especially with regard to the weight. For me, because of the weight, an aperture of 6" (150 mm) is already the upper limit (before that I had tried 8" and 10"...). In the hobby area, the apertures cover a range from 60 mm to a more than 500 mm (20"), which roughly corresponds to a ratio of 1:10.

For technical reasons, eyepieces can also only cover a certain focal length range. In the hobby area, this is between 2 mm and 40 mm (please understand this only as an orientation!). Thus, a range of approximately 1:20 is covered! If you add focal length reducers and extenders, you can increase this range even further, for example by a factor of 15...

In fact, not every telescope aperture can be combined with every eyepiece focal length. I have no idea, how large the actual magnification range is in the hobby area...

In the following, I present a number of magnification terms or types that I have found in literature, on the Internet, and in advertisements.

I found the term ** normal magnification** in three meanings:

- Minimal usable/useful magnification: This seems to be the most common form in which this term is used, for more about it see there!
- "Beneficial magnification," for
more about it see there!

Quote (Source: Astroshop.de): The*normal magnification*of a telescope corresponds approximately to aperture of the telescope in mm. If you choose the normal magnification, you get an exit pupil of about 1 mm. From this magnification on an observer uses the achievable resolution of the telescope. This means that considerably more details are visible, e.g. on planets. - "Normal" magnification at which the exit pupil ranges between
2 and 4 mm.

Quote (Source: Intercon Spacetec):*Normal magnification*- 2 - 4 mm exit pupil: Experience has shown that these eyepieces are used most frequently.
- 4 - 3.5 mm exit pupil: In my opinion, is optimal for most large-area, faint nebulae.
- With an exit pupil of 2 mm, the eye already perceives 80% of the maximum theoretical resolution, for many objects the perceptibility is optimal, e.g. most galaxies.

The * minimum magnification* is defined by the fact that the diameter
of the telescope's exit pupil is the

Values **between 5 and 8 mm** are given for the size of the **eye pupil**. The smaller
values are for older people, but I have also found a source that gives 7 mm
for 70-year-olds... Typically, the minimum magnification is calculated for
an exit pupil/eye pupil of 6.5 or 7 mm.

- Minimum useable magnification = (opening in mm) / (exit pupil in mm) = (opening
in mm) / 7*

*) 7 mm for the exit pupil = eye pupil assumed

As far as the telescope is concerned, the minimum magnification depends only
on its **aperture** (and indirectly on its resolution). The minimum magnification
corresponds to the **maximum (reasonable) usable focal length of the eyepiece**,
which can be determined using the magnification formula (*Formula 1*) after inserting
the minimum magnification in order to select your eyepieces accordingly (if
such long focal length eyepieces exist at all...):

- Minimum usable magnification = (Focal length of the telescope) / (Maximum
usable eyepiece focal length)

=> (Maximum usable eyepiece focal length) = (Focal length of the telescope) / (Minimum usable magnification)

The * beneficial magnification* of a telescope is defined by the
fact that the resolution of the telescope and that of the eye match exactly*.
It is the highest magnification at which there is still a gain in detail**.
Only at this magnification, the resolution and light gathering capacity
of the telescope are fully exploited and its limiting visual stellar magnitude
reached. Beyond that no further details become visible and one speaks of "empty
magnification".

) This can be interpreted as follows: the telescope resolution is magnified
exactly to the extent that it has the same value as the resolution of the eye.

**) The details result from the **assumed resolution of the eye**, more about this
later.

As far as the *pure definition *is concerned, most sources still agree,
but then the differences begin. Different sources assume, for example,
different values for the resolution of the eye, mostly without specifying this
explicitly: the majority of sources assume a resolution of 2" (Astroshop.de,
for example, under the label "normal
magnification", without specifying the resolution), but some assume a
resolution of 3" (Stoyan, *Deep Sky Reiseführer*, ...). This
leads to a difference in the magnification of at least 50%, as the following
formulas exemplify:

- Resolution of 2": beneficial magnification = (aperture in mm),
- Resolution of 3": beneficial magnification = 1,5 * (aperture in mm).

With an assumed resolution of the eye of 2", the exit pupil is exactly
1 mm (which is sometimes indicated), with one of 3" it is only 0.67 mm.
Stoyan (*Deep Sky Reiseführer*) assumes a resolution of about 3" and
provides a value of 0.7 mm for the exit pupil. This results in a magnification
according to formula 2:

- Beneficial magnification = (aperture in mm) / 0.7

This value is close to the value determined with the factor 1.5, but unfortunately not exactly (1/0.7 = 1.43; 1/0.67 = 1.5; however, Stoyan does not specify 0.67 as the exact value for the exit pupil, he uses 0.645 mm: 1/0.645 = 1.55)... Well, one should not take such "rough calculations" too seriously anyway!

If one chooses a value of 3" or even 4" for the resolution of the
eye, one however gets already into a magnification range, which is
also called *maximum usable/sensible (or: maximum usable) magnification*.
I deal with this in the following!

The * maximum usable magnification* of a telescope
is often

The* maximum usable magnification* depends essentially on the
aperture (diameter of the primary mirror or lens opening) of the telescope:

- (maximum usable magnification) = (aperture in mm) * X

The factor X amounts to:

- 1.5 for Newton reflector (including Dobsonians), Rich-Field refractors, Schmidt-Cassegrain telescopes
- 2 for refractors from f/8 on, Maksutov-Cassegrain telescopes

For X = 2, the exit pupil amounts to exactly 0.5 mm at this magnification, for X = 1.5 it amounts to 0.67 mm (see above).

According to the explanations for the *beneficial magnification*,
these are, in my opinion, actually only variants of the beneficial magnification,
namely those with a lower assumed **resolution of the eye**, that is, **3"** and
**4"** (see also below). In other words, for
other authors, Stoyan's
*beneficial magnification* is, at least for some telescope types, already
the
*maximum usable magnification*. For other telescope types, they apply
a factor of 2. Sometimes, a factor of 2 is also given for all telescope types,
which look better when advertising telescopes... Stoyan, on the other hand,
assumes the lower value of almost 1.5 for all telescope types. In the end,
one might say that, for Stoyan, the exit pupil is the "measure of all
things."
This can also be concluded from his eyepiece recommendations in the *Deep
Sky Reiseführer*.

As just described, a factor of X = 2 is often given for the *maximum
usable magnification*. In his article "*Vergrößerung und
Grenzgröße im Teleskop – Fallbeispiel M 13* (Magnification
and limiting magnification in telescopes - case study M 13)" on the
astronmie.de Website Stoyan writes: "There
is no optically defined maximum magnification for flat objects - rules like "double
the objective diameter" (see above) are without
fundament." This makes
me wonder whether the *maximum usable magnification* can be "discarded,"
particularly since Stoyan's "accompanying" factor
X = 1.5 was already assigned to the *beneficial magnification*. If I
understand him correctly, it looks much like this...

Accordingly, Stoyan takes a more "generous" approach to the topic of "maximum
magnification." According to his *Deep Sky Reiseführer*, it
is often better for secure perception to exceed the *beneficial magnification*,
for example, in order to increase the distance between stars. Even with smaller
flat objects, it makes sense for Stoyan to go far beyond this. According to
him, the so-called ** maximum magnifications** are therefore

- Maximum Magnification = 3 * (Aperture in mm) ≈ 2 * (Aperture in mm) / 0.7 = (Aperture in mm) / 0.35

At maximum magnification, the exit pupil amounts, according to Stoyan, to 0.35 mm, being already fairly small, and the resolution of the eye to 6'.

The **seeing** sets the limit for the maximum magnification, particularly for
telescopes with large apertures. For examples, see above.

A definition, various types of magnification that use it and partly overlap in their meaning, partly lead to different results, while different types of magnification lead to the same result, in addition to different resolution of the human eye - how can all this be put together? This is exactly what I would like to attempt in the next section!

In the above remarks, the **resolution of the human eye** is mentioned
again and again, so that I have come to the conclusion that this is the central
variable in describing the different types of magnification (the exit pupil
plays a similar role, but I regard it as a "derived" variable).
Therefore, I have searched for a "common denominator" for all types
of magnification and found it (as I believe...) by making a detour via the **Dawes
formula** for
the **resolution of a telescope**. This approach **makes the resolution
of the human eye explicit** and thus, the central variable.

I start from the **beneficial magnification**, which is characterized by
the fact that **the resolution of the telescope is matched to that of the
eye**.
This means that the **resolution of the telescope** has to be multiplied
by a **magnification factor** (in the following simply called "magnification"),
so that the **resolution of the human eye** results:

- (Resolution of the telescope) * (Beneficial magnification) =

(Resolution of the human eye)

If one resolves the equation for the beneficial magnification, this results in:

- (Beneficial magnification) = (Resolution of the human eye) / (Resolution of the telescope)

The **Dawes formula** for the resolution of the telescope (the most commonly used
form of resolution) is:

- (Resolution of the telescope) =
**116**/ (Aperture in mm)

The Dawes formula used in the formula for the beneficial magnification yields:

- (Beneficial magnification) = (Resolution of the human eye in seconds) /
(
**116**/ (Aperture in mm))

= (Aperture in mm) * (Resolution of the human eye in seconds) /**116**

Often the Dawes formula is simplified too:

- (Resolution of the telescope in seconds) =
**120**/ (Aperture in mm)

(I have also seen values of 115 or 117...) With this, for easier calculating with minutes and seconds, we get approximately:

- (Beneficial magnification) = (Aperture in mm) * (Resolution of the human
eye in seconds) /
**120**

This leads me "formally" back to the known relationship for the
*beneficial magnification*, because when I use 120" (2') for the
resolution of the eye, exactly the relationship given above for 2' results:
*the beneficial magnification corresponds numerically to the aperture of
the telescope in mm*. I can also use it to describe the different *maximum
magnifications* if I insert the *corresponding assumed resolution of
the eye* into the formula.
In this way, I make the assumed resolution of the human eye explicit in the
formula, which rarely happens in practice. In other words, the various magnifications
listed above can all be described by a specific value for the resolution of
the human eye:

- 20":
**Minimum Magnification**= (Aperture in mm) / 7

(Exit/eye pupil = 7 mm; creates the brightest view in the eyepiece) - 60" (1'):
**"Normal Magnification"**= Aperture in mm / 2

(Exit pupil = 2 mm) (I denote this as "normal magnification"...) - 120" (2'):
**Beneficial****Magnification**= Aperture in mm

(Exit pupil = 1 mm; corresponds to "Normal Magnification" at Astroshop.de) - 180" (3') :
**Maximum Usable****Magnification**= (Aperture in mm) * 1,5

(Exit pupil = 0.67 mm; corresponds to the "maximum usable magnification" for Newtonian telescopes; corresponds about to Stoyan's"**beneficial Magnification**" with an exit pupil of 0.7 mm) - 240" (4'):
**Maximum Usable****Magnification**= (Aperture in mm) * 2

(Exit pupil = 0.5 mm; corresponds to the "maximum usable magnification" for refractors, Maksutov-Cassegrain, Schmidt-Cassegrains; often generally called**maximum magnification**for telescopes) - 360" (6'):
**Maximum****Magnification**= (Aperture in mm) * 3

(exit pupil = 0.33 mm; corresponds about to Stoyan's"maximum magnification" = 2 * (Aperture in mm) / 0.7; exit pupil = 0.35 mm)

I suppose that I only "rediscovered" what everyone already knows, but many sources do not explicitly write this down. And that is why I had to find out myself...

What else is to be done now? In my opinion, it is now a matter of understanding
more precisely what the different values for the resolution of the human
eye mean in practice. For this, I have looked around again in the literature
and found the following information about "sky structures."
The basic definition, together with the determined magnification
values, then applies, so to speak, only to the corresponding structures. Here
is a list of what I have found so far (*in progress*):

- With 1' resolution one assumes the "practical" resolution of the eye (Astroshop.de); it corresponds to a strained vision in microscopy.
- 2' resolution is about the separation of double stars (most sources); it corresponds to comfortable vision in microscopy.
- With a resolution of 3' it is about the recognition of bright surfaces (Stoyan).
- With 6' resolution it is about the recognition of smaller bright areas (Stoyan).

In other words, when you use strained vision, you need less magnification than when you use comfortable vision, when you want to separate double stars, less than when you want to recognize bright areas or even smaller bright areas, etc. and so on.

Obviously, the standard definition of* maximum usable magnification* refers
to the separation of double stars (2'), whereas Stoyan's *beneficial magnification* refers
to bright areas (and his *maximum
magnification* to small bright areas).
This is exactly what Stoyan writes in his *Deep Sky Reiseführer*.

A further todo would be to clarify which consequences result from the different exit pupils, which correspond to the different values of the resolving power...

For the *normal magnification*, as well as for the *beneficial
magnification* and the *maximum usable magnification* (and its
variants) I have read that this is the magnification which shows maximum
details and that, beyond that magnification, you only get "empty" magnification
(which can also be useful because it magnifies small details and thus, sometimes
makes them visible at all). This has confused me to a certain extent!

A first hint to an approach that unites everything was given by the fact that some sources indicate the underlying resolution of the eye and/or the exit pupil, sometimes explicitly, sometimes hidden or indirectly. The resolution of the eye varies between 1' and 3', the exit pupil between 2 mm and 0.67 mm, accordingly. Obviously, the above statement "maximum details" or the definition "equal resolution of eye and telescope" is to be understood on the basis of the resolution of the human eye which the respective source uses. Here once again as a reminder:

- With an exit pupil of 6-7 mm, the maximum brightness is obtained for sky objects that do not exceed this size; it seems to approximately correspond to the theoretical resolution of the human eye (20").
- At 1' resolution (exit pupil 2 mm) one assumes the "practical" resolution of the eye (Astroshop.de),
- 2' resolution (exit pupil 1 mm) is about the separation of double stars (most sources),
- 3' resolution (exit pupil 0.67 mm) ia about detecting bright surfaces (Stoyan) and
- 6' resolution (exit pupil 0.33 mm) is about detecting smaller bright areas (Stoyan).

The magnifications presented here beyond the minimum magnification thus represent a continuum of increasing assumed resolution of the human eye (from 1' to 6'), which makes certain structures in celestial objects only visible at all. On the other hand, the exit pupil decreases from 2 mm (or from 6-7 mm, if the minimum magnification is included) to 1/3 mm, where you can hardly see anything anyway, if I understand this correctly... The minimum magnification is the magnification at which the exit pupil is at maximum (6-7 mm), that is, equal to the eye pupil (and the resolution seems to be close to the theoretical limit...).

"Normal Magnification"

- 2 - 4 mm exit pupil: Experience has shown that these eyepieces are used most frequently.
- 4 - 3.5 mm exit pupil is optimal for most large-area, faint nebulae.
- With an exit pupil of 2 mm, the eye already perceives 80% of the maximum theoretical resolution; for many objects the perceptibility is optimal, e.g. for most galaxies.

"Maximum Magnification"

- 1 mm (up to min. 0.8 - 0.5 mm) exit pupil: With exit pupil of 1 mm, 95% of the theoretically maximum possible resolution is perceived. Any further magnification only makes sense if the telescope and eyes are good.
- An exit pupil of 0.8 mm provides the maximum perceptibility of small, low-contrast details with perfect seeing, and is the sensible maximum magnification for planets.
- An exit pupil of 0.5 mm represents the maximum magnification, further magnification adds nothing. The 0.5 mm exit pupil can only be used to separate narrow double stars and at the extreme limit of the telescope to perceive the weakest details.

Basically, it does not matter what different authors mean by the individual
magnification types, as long as one knows on which assumptions they base their
statements. In any case, one can also consider the whole matter from the point
of view that the numerical value of the aperture (in mm) represents a "good
standard/usage magnification",
1.5 * aperture (in mm) represents the "maximum standard/usage magnification" and
3 * aperture (in mm) represents the "absolute maximum that can be achieved
under certain circumstances". The brightest image in the eyepiece is offered
by the *minimum magnification*.

And a magnification that corresponds to twice the numerical value of the aperture
(in mm) (resolution 4', exit pupil 0.5 mm) should perhaps be perceived as a
little "too
ambitious for "standard use" and remember that, according to Stoyan,
there is no evidence to regard this particular magnification as *maximum
magnification*...

However, as before, I will operate my telescopes by default with maximum magnifications
of 1.5 to 2 times the numerical value of the aperture (in mm) and try *larger
factors* on the moon, and perhaps also on planets (up to 3 to 4 times the
numerical value of the aperture in mm).

- Vergrößerung (Jürgen Weiprecht, Uni Jena): www.astro.uni-jena.de/Teaching/Praktikum/pra2002/node17.html
- Vergrößerung und Grenzgröße im Teleskop – Fallbeispiel M 13 (Ronald Stoyan, astronomie.de): www.astronomie.de/einstieg-in-die-astronomie/teleskopkauf/vergroesserung-und-grenzgroesse-im-teleskop-fallbeispiel-m-13
- Das Sichtbarmachen flächiger Objekte - Die Austrittspupille und die sinnvollen Vergrößerungen (Andreas Schupies): www.andreas-schupies.de/astronomie/2-das-sichtbarmachen-flächiger-objekte-die-austrittspupille-und-die-sinnvollen-vergrößereungen
- Ronald Stoyan (2014).
*Deep Sky Reiseführer*. Erlangen: Oculum Verlag - Lambert Spix (2011).
*Der Moonhopper*. Erlangen: Oculum Verlag - Vergrößerung (Astroshop.de): www.astroshop.de/beratung/teleskop/teleskop-wissen/grundsaetzliche-ueberlegungen-zur-teleskop-wahl/vergroesserung/c,8695
- Okularberatung (Intercon Spacetec): www.televue.de/beratung-okular
- Vergrößerung (Lexikon der Optik, Spektum der Wissenschaft): www.spektrum.de/lexikon/optik/vergroesserung/3518

05.11.2018 |