# Integrated Visual Magnitude

• tony873004
In summary, the conversation discusses determining the integrated visual magnitude of a certain globular cluster with 10^4 stars, 100 of which have MV=0.0 and the rest have MV=+5.0. Although the term "integrated visual magnitude" is not defined in the class notes or textbook, it is found through a weighted average calculation of the stars' magnitudes. The resulting integrated visual magnitude for the cluster is approximately 5.0. However, the link provided as an example is not accessible.
tony873004
Gold Member
A certain globular cluster has a total of 10^4 stars; 100 of them have MV=0.0, and the rest have MV=+5.0. What is the integrated visual magnitude of the cluster?

Nowhere in our class notes or textbook is the term "integrated visual magnitude" defined. Googling it, I find the term used, but not defined.

If I had to guess how to do this problem, I'd just do a weighted average:

$$M_{cluster}=\frac{(100*0.0)+(9900*5.0)}{10000}$$

$$M_{cluster}=4.95$$

Which when rounded for significant figures = 5.0

See if these notes and examples help -

http://ottawa.rasc.ca/observers/an9811p9.html

I am a bit surprised that this is not covered in your textbook.

Last edited by a moderator:
I was also given this question and I tried clicking the link and it doesn't work. How would I go about starting this? We too didn't learn anything about integrated visual magnitude so I have no idea what to do with this. Is there some type of formula or something?

## 1. What is Integrated Visual Magnitude?

Integrated Visual Magnitude is a measure of the total brightness of an object as seen by an observer, taking into account all wavelengths of light that are visible to the human eye. It is commonly used in astronomy to describe the apparent brightness of stars and galaxies.

## 2. How is Integrated Visual Magnitude calculated?

Integrated Visual Magnitude is calculated using a logarithmic scale, with lower numbers representing brighter objects and higher numbers representing dimmer objects. The formula used is based on the ratio of the object's brightness compared to a reference star of known magnitude.

## 3. What is the difference between Integrated Visual Magnitude and Absolute Magnitude?

Integrated Visual Magnitude is a measure of how bright an object appears to us on Earth, while Absolute Magnitude is a measure of an object's true brightness at a standard distance of 10 parsecs (about 32.6 light years) away from Earth. Absolute Magnitude takes into account both the intrinsic brightness of an object and its distance from Earth.

## 4. Can Integrated Visual Magnitude be used for all types of astronomical objects?

Integrated Visual Magnitude is commonly used for stars and galaxies, but it can also be used for other types of objects such as planets, comets, and nebulae. However, for objects that emit light at non-visible wavelengths, other magnitude systems may be used.

## 5. Is there a limit to the values of Integrated Visual Magnitude?

Yes, the values for Integrated Visual Magnitude can range from around -27 (for the brightest objects such as the Sun and full Moon) to +30 (for the dimmest objects visible with the largest telescopes). However, the human eye can typically only detect objects with magnitudes between +6 and -6 under dark skies.

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