<p>Treating as a school question</p>

<p>Each change of 1 magnitude changes brightness by how much? So <a href="https://en.wikipedia.org/wiki/Magnitude_(astronomy)" rel="nofollow noreferrer">by what factor will a change of 5 magnitudes give</a>? (5 magnitudes is a very convenient number for this question)</p>

<p>You will need to reduce the area of the telescope by the same factor.</p>

CC BY-SA 3.0
2017-08-29T06:21:48.180Z
2017-08-29T06:21:48.180Z
James K
<p>Suppose we have a variable star with a change in magnitude between maximum and minimum of 5 mag.</p>

<p>How much would you need to stop down a telescope (block some of the area) so that the star at maximum brightness appears to be the same brightness as when it is at minimum magnitude with no stop.</p>

CC BY-SA 3.0
2017-08-28T22:04:15.293Z
I think the question is this: how much would you need to stop down a telescope (block some of the area) so that the star at maximum brightness appears to be the same brightness as when it is at minimum magnitude with no stop. Since the OP has not replied, I assume that his homework is past due :-)
JohnHoltz
CC BY-SA 3.0
2017-08-28T22:05:57.593Z
Yes that's exactly the question. I apologise for not conveying the meaning of it. I did a rough translation of the question. And actually no,it's not a due homework. I found it on a past paper.
Dimension Obscura
<variable-star>
Stopping down a telescope to reduce brightness by 5 magnitudes
Dimension Obscura
# Stopping down a telescope to reduce brightness by 5 magnitudes

(Asked by: username_0 on 2017-08-26)

Suppose we have a variable star with a change in magnitude between maximum and minimum of 5 mag.

How much would you need to stop down a telescope (block some of the area) so that the star at maximum brightness appears to be the same brightness as when it is at minimum magnitude with no stop.

**Tags:** variable-star

> **Comments:**
> **username_1**: I think the question is this: how much would you need to stop down a telescope (block some of the area) so that the star at maximum brightness appears to be the same brightness as when it is at minimum magnitude with no stop. Since the OP has not replied, I assume that his homework is past due :-)  
> **username_0**: Yes that's exactly the question. I apologise for not conveying the meaning of it. I did a rough translation of the question. And actually no,it's not a due homework. I found it on a past paper.  

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## 1 answers

### Answer by username_2 on 2017-08-29. Score: 1

Treating as a school question

Each change of 1 magnitude changes brightness by how much? So [by what factor will a change of 5 magnitudes give](https://en.wikipedia.org/wiki/Magnitude_(astronomy))? (5 magnitudes is a very convenient number for this question)

You will need to reduce the area of the telescope by the same factor.


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