<p>I don't know about the telescope, but I know that you will need the telescope that has CCD technology to be able to convert from counts/second (as brightness) that CCD detects to quantitative values easily.</p>

<p>For the observational procedure, here is the standard regardless of what kind telescope you use:</p>

<ol>
<li>Take a picture of your object (let's name it <code>ImObj</code>).</li>
<li>Take a picture of a standard star (let's name it <code>ImStd</code>) or stars (i.e., stars that have real brightness in a database, let's call it <code>MagStdReal</code>). </li>
<li>Take pictures for calibration (let's name it <code>ImCal</code>). If CCD telescope, these images include dark and flat images.</li>
<li>Use <code>ImCal</code> to calibrate both <code>ImObj</code> and <code>ImStd</code> (i.e., removing noise and etc.).</li>
<li>Convert image brightness of calibrated ImStd and ImObj to quantitative values (let's call it <code>MagStdFake</code> and <code>MagObjFake</code>). Note that you can use any arbitrary zero reference point for <code>MagStdFake</code> and <code>MagObjFake</code>, but they use the same reference.</li>
<li>Find conversion equation to <code>MagStdReal = f(MagStdFake)</code>. The simplest form of f() is just linear shift: <code>MagStdReal = a + MagStdFake</code>.</li>
<li>Apply <code>MagObjReal = f(MagObjFake)</code>. And now you get to do some science.</li>
</ol>

<p>Also note that, a telescope filters certain wavelengths with certain response function. So, you have to observe everything in one setting of telescope. You cannot mix images or products of different setting of a telescope. Only <code>MagObjReal</code> or <code>MagStdReal</code> those are telescope insensitive (ideally).</p>

<p>I provide very short and conceptual procedure to give you the idea. There are a bunch of details that are important. If you use keywords in the list procedure here and search in Google, you should get more relevant hits to each topic.</p>

CC BY-SA 3.0
2018-04-14T14:11:58.920Z
2018-04-15T08:24:46.563Z
2018-04-15T08:24:46.563Z
Kornpob Bhirombhakdi
<p>If the target star varies by half a magnitude or more,
it's possible to estimate its magnitude visually
by comparing it to nearby reference stars of similar magnitude.
<a href="http://www.skyatnightmagazine.com/feature/how-guide/how-observe-variable-stars" rel="nofollow noreferrer">Sky at Night</a>,
<a href="http://www.skyandtelescope.com/observing/celestial-objects-to-watch/the-lure-of-variable-stars/" rel="nofollow noreferrer">Sky and Telescope</a>,
and the <a href="http://www.rasc.ca/how-observe-variable-stars" rel="nofollow noreferrer">Royal Astronomical Society of Canada</a>
have articles explaining the procedure.</p>

<p>The American Association of Variable Star Observers (AAVSO) provides a
<a href="https://www.aavso.org/apps/vsp/" rel="nofollow noreferrer">chart plotting tool</a>
and comprehensive
<a href="https://www.aavso.org/observing-manuals" rel="nofollow noreferrer">observing manuals</a>
for visual, CCD, DSLR, and other methods.</p>

CC BY-SA 3.0
2018-04-14T17:24:38.843Z
2018-04-14T17:24:38.843Z
Mike G
<p>You probably want to find how bright the star is when calibrated against stars of known brightness. You take a picture of the region around the star, then compare the brightness of the star with the brightness of stars of known brightness in the same field.</p>

<p>A standard telescope with camera set-up. Then either a good catalogue or a system such as <a href="https://github.com/mommermi/photometrypipeline" rel="nofollow noreferrer">photometry pipeline</a> to compare the brightness of the star to others of known brightness.</p>

CC BY-SA 3.0
2018-04-14T10:12:27.697Z
2018-04-14T10:12:27.697Z
James K
<p>I am planning to conduct a research which involves observing the brightness of a star. So far, I haven't been able to obtain much information as to how I may go forward with the observation process. I'm willing to buy a telescope and other equipment. What telescopes are ideal for this and what other equipment must I require to obtain the apparent brightness value of the star?</p>

CC BY-SA 3.0
2018-04-14T10:14:44.240Z
Just one star? What do you hope to learn from this?
James K
CC BY-SA 3.0
2018-04-14T12:52:41.187Z
@JamesK I plan to model its brightness over a period of time.
Baalateja Kataru
CC BY-SA 3.0
2018-04-14T13:03:02.653Z
Which star? What do you hope to learn from this?
James K
<star><telescope><photometry>
How do I obtain the brightness of a star in the night sky?
Baalateja Kataru
# How do I obtain the brightness of a star in the night sky?

(Asked by: username_0 on 2018-04-14)

I am planning to conduct a research which involves observing the brightness of a star. So far, I haven't been able to obtain much information as to how I may go forward with the observation process. I'm willing to buy a telescope and other equipment. What telescopes are ideal for this and what other equipment must I require to obtain the apparent brightness value of the star?

**Tags:** star, telescope, photometry
> **Comments:**
> **username_1**: Just one star? What do you hope to learn from this?  
> **username_0**: @JamesK I plan to model its brightness over a period of time.  
> **username_1**: Which star? What do you hope to learn from this?  

---

## 3 answers

### Answer by username_2 on 2018-04-14. Score: 5

I don't know about the telescope, but I know that you will need the telescope that has CCD technology to be able to convert from counts/second (as brightness) that CCD detects to quantitative values easily.

For the observational procedure, here is the standard regardless of what kind telescope you use:

1. Take a picture of your object (let's name it `ImObj`).
2. Take a picture of a standard star (let's name it `ImStd`) or stars (i.e., stars that have real brightness in a database, let's call it `MagStdReal`).
3. Take pictures for calibration (let's name it `ImCal`). If CCD telescope, these images include dark and flat images.
4. Use `ImCal` to calibrate both `ImObj` and `ImStd` (i.e., removing noise and etc.).
5. Convert image brightness of calibrated ImStd and ImObj to quantitative values (let's call it `MagStdFake` and `MagObjFake`). Note that you can use any arbitrary zero reference point for `MagStdFake` and `MagObjFake`, but they use the same reference.
6. Find conversion equation to `MagStdReal = f(MagStdFake)`. The simplest form of f() is just linear shift: `MagStdReal = a + MagStdFake`.
7. Apply `MagObjReal = f(MagObjFake)`. And now you get to do some science.

Also note that, a telescope filters certain wavelengths with certain response function. So, you have to observe everything in one setting of telescope. You cannot mix images or products of different setting of a telescope. Only `MagObjReal` or `MagStdReal` those are telescope insensitive (ideally).

I provide very short and conceptual procedure to give you the idea. There are a bunch of details that are important. If you use keywords in the list procedure here and search in Google, you should get more relevant hits to each topic.


---

### Answer by username_3 on 2018-04-14. Score: 2

If the target star varies by half a magnitude or more,
it's possible to estimate its magnitude visually
by comparing it to nearby reference stars of similar magnitude.
[Sky at Night](http://www.skyatnightmagazine.com/feature/how-guide/how-observe-variable-stars),
[Sky and Telescope](http://www.skyandtelescope.com/observing/celestial-objects-to-watch/the-lure-of-variable-stars/),
and the [Royal Astronomical Society of Canada](http://www.rasc.ca/how-observe-variable-stars)
have articles explaining the procedure.

The American Association of Variable Star Observers (AAVSO) provides a
[chart plotting tool](https://www.aavso.org/apps/vsp/)
and comprehensive
[observing manuals](https://www.aavso.org/observing-manuals)
for visual, CCD, DSLR, and other methods.


---

### Answer by username_1 on 2018-04-14. Score: 1

You probably want to find how bright the star is when calibrated against stars of known brightness. You take a picture of the region around the star, then compare the brightness of the star with the brightness of stars of known brightness in the same field.

A standard telescope with camera set-up. Then either a good catalogue or a system such as [photometry pipeline](https://github.com/mommermi/photometrypipeline) to compare the brightness of the star to others of known brightness.


---

