<p>Your calculated estimate may be about correct for the limiting magnitude of stars, but lots of what you might want to see through a telescope consists of extended objects-- galaxies, nebulae, and unresolved clusters.  The magnitude estimates of these objects tend to consider them as point sources, but as extended objects they have much less of a contrast difference with the sky.  In my experience in an equally light-polluted location with a similar-size telescope, the sky brightness makes the limiting magnitude of extended objects between 7 and 8, even with a light-pollution reduction filter in use.</p>
<p>That isn't to say a telescope is worthless in the city; you can still observe the Moon and planets, resolved clusters are pretty, and you can observer the brighter extended objects.  But bringing the telescope to a dark-sky location makes an incredible difference with many more objects visible.</p>

CC BY-SA 4.0
2021-03-27T20:27:12.877Z
Light pollution filters may help a bit, but my experience from a bortle 8 location, is not very much.
Dr Chuck
CC BY-SA 4.0
2021-03-27T16:48:23.550Z
2021-03-27T16:48:23.550Z
antlersoft
<p>I live in an extremely light polluted place. On a new moon night,  magnitude 3.5 stars are at the limit of  naked eye visiblity on clear nights, and the Orion nebula is visible as a smudge through my binoculars and I can see 6-7 stars of the Pleaidies (apparent magnitude about 5.5 I guess)</p>
<p>If I buy a 130 mm reflector telescope, roughly what will be the limiting magnitude of the objects I can see?</p>
<p>I used <span class="math-container">$5log(130/6.5)=6.5$</span>, which means I would be able to see upto about magnitude 10 even from a light polluted city.</p>
<p>This sounds too good to be true...</p>
<p>Is my estimate roughly accurate and do you think spending a few hundred dollars on the telescope is worth it if I never intend to leave the city for a while?</p>

<telescope><apparent-magnitude><light-pollution>
Limiting magnitudes for different telescopes
aman
# Limiting magnitudes for different telescopes

(Asked by: username_0 on 2021-03-27)

I live in an extremely light polluted place. On a new moon night, magnitude 3.5 stars are at the limit of naked eye visiblity on clear nights, and the Orion nebula is visible as a smudge through my binoculars and I can see 6-7 stars of the Pleaidies (apparent magnitude about 5.5 I guess)

If I buy a 130 mm reflector telescope, roughly what will be the limiting magnitude of the objects I can see?

I used $5log(130/6.5)=6.5$, which means I would be able to see upto about magnitude 10 even from a light polluted city.

This sounds too good to be true...

Is my estimate roughly accurate and do you think spending a few hundred dollars on the telescope is worth it if I never intend to leave the city for a while?

**Tags:** telescope, apparent-magnitude, light-pollution

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## 1 answers

### Answer by username_1 on 2021-03-27. Score: 4 | Accepted answer

Your calculated estimate may be about correct for the limiting magnitude of stars, but lots of what you might want to see through a telescope consists of extended objects-- galaxies, nebulae, and unresolved clusters. The magnitude estimates of these objects tend to consider them as point sources, but as extended objects they have much less of a contrast difference with the sky. In my experience in an equally light-polluted location with a similar-size telescope, the sky brightness makes the limiting magnitude of extended objects between 7 and 8, even with a light-pollution reduction filter in use.

That isn't to say a telescope is worthless in the city; you can still observe the Moon and planets, resolved clusters are pretty, and you can observer the brighter extended objects. But bringing the telescope to a dark-sky location makes an incredible difference with many more objects visible.

> **Comments:**
> **username_2**: Light pollution filters may help a bit, but my experience from a bortle 8 location, is not very much.  

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