<p>Neptune is a tricky one: its color is not very different from a type A star,
and its angular diameter is only twice that of the <a href="https://en.wikipedia.org/wiki/Airy_disk" rel="nofollow noreferrer">Airy disk</a> of a star in a 20cm reflector.
Even with good optics in good seeing conditions, the planetary disk will be a little blurry.
To me it looks like a small piece of colored chalk, but that's not enough to be sure.</p>
<p>The keys to positive identification are a good finder chart and optics that help you match it.
It's possible to locate it using a 1× sight and a 1° low-power eyepiece field, but something in between makes it easier.
I use an 8×50 straight-through finder, which shows a ~5° field to magnitude ≲9.</p>
<p>The <a href="https://in-the-sky.org/findercharts2.php?id=P8" rel="nofollow noreferrer">year-long charts</a> at in-the-sky.org are at a useful scale.
In <a href="https://stellarium.org/" rel="nofollow noreferrer">Stellarium</a> you might try a 10° field of view (ctrl-alt-6) and use the View &gt; Markings panel to add a circular FOV corresponding to your finder scope.
Remember that some optics will invert the view.
If you can confirm that the stars you see match the ones on the chart, then the other object is Neptune.</p>

CC BY-SA 4.0
2022-10-17T17:47:17.627Z
2022-10-17T21:34:41.140Z
2022-10-17T21:34:41.140Z
Mike G
<p>So, recently I went out for a look at Neptune with my telescope and I found the general area of where Neptune was. However, when I took a see for myself, there were a ton of blue stars everywhere and I had a really hard time deciphering which one was actually Neptune, because along with all the other stars, Neptune is blue too and it blends in easily with the rest. How do I know which is the blue planet?</p>

CC BY-SA 4.0
2022-10-11T23:59:38.873Z
Do stars seen from your telescope have diffraction spikes? If they do, that’s an easy way to distinguish a planet from a star, since a planet won’t have them
Justin T
CC BY-SA 4.0
2022-10-12T00:02:51.677Z
Can you mention what kind of optics you are using to look for Neptune? Binoculars? Telescope? Focal length and aperture diameter? Also, potentially helpful: [How am I supposed to locate the planets Uranus and Neptune with a 70 mm f/5.7 refractor?](https://astronomy.stackexchange.com/q/49081/7982)
uhoh
CC BY-SA 4.0
2022-10-12T00:41:28.250Z
At about 200x power, you should see a recognizable disk.  At low power, use a planetarium program (or star chart) to "star hop" and recognized it based on its position to other stars.
Greg Miller
CC BY-SA 4.0
2022-10-17T23:27:37.870Z
d’Arrest confirmed Le Verrier’s Neptune solution with a… oh, nine inch refractor (off the top of my head), and could tell immediately it was nonstellar. I believe the remark was that it was ‘a big boy’ (except in German). I presume you are _not_ using a world-class nine-incher?
caInstrument
CC BY-SA 4.0
2022-10-18T01:15:47.027Z
Even at 125x (with 50cm aperture) one sees clearly that it is a disk compared to stars. IMHO the blueish colour is also quite distinctive, differing from blueish stars.
planetmaker
<telescope><amateur-observing><night-sky><neptune>
How do I know that I’ve found Neptune?
Prince Pugs
# How do I know that I’ve found Neptune?

(Asked by: username_0 on 2022-10-11)

So, recently I went out for a look at Neptune with my telescope and I found the general area of where Neptune was. However, when I took a see for myself, there were a ton of blue stars everywhere and I had a really hard time deciphering which one was actually Neptune, because along with all the other stars, Neptune is blue too and it blends in easily with the rest. How do I know which is the blue planet?

**Tags:** telescope, amateur-observing, night-sky, neptune

> **Comments:**
> **username_1**: Do stars seen from your telescope have diffraction spikes? If they do, that’s an easy way to distinguish a planet from a star, since a planet won’t have them  
> **username_2**: Can you mention what kind of optics you are using to look for Neptune? Binoculars? Telescope? Focal length and aperture diameter? Also, potentially helpful: [How am I supposed to locate the planets Uranus and Neptune with a 70 mm f/5.7 refractor?](https://astronomy.stackexchange.com/q/49081/7982)  
> **username_3**: At about 200x power, you should see a recognizable disk.  At low power, use a planetarium program (or star chart) to "star hop" and recognized it based on its position to other stars.  
> **username_4**: d’Arrest confirmed Le Verrier’s Neptune solution with a… oh, nine inch refractor (off the top of my head), and could tell immediately it was nonstellar. I believe the remark was that it was ‘a big boy’ (except in German). I presume you are _not_ using a world-class nine-incher?  
> **username_5**: Even at 125x (with 50cm aperture) one sees clearly that it is a disk compared to stars. IMHO the blueish colour is also quite distinctive, differing from blueish stars.  

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## 1 answers

### Answer by username_6 on 2022-10-17. Score: 6 | Accepted answer

Neptune is a tricky one: its color is not very different from a type A star,
and its angular diameter is only twice that of the [Airy disk](https://en.wikipedia.org/wiki/Airy_disk) of a star in a 20cm reflector.
Even with good optics in good seeing conditions, the planetary disk will be a little blurry.
To me it looks like a small piece of colored chalk, but that's not enough to be sure.

The keys to positive identification are a good finder chart and optics that help you match it.
It's possible to locate it using a 1× sight and a 1° low-power eyepiece field, but something in between makes it easier.
I use an 8×50 straight-through finder, which shows a ~5° field to magnitude ≲9.

The [year-long charts](https://in-the-sky.org/findercharts2.php?id=P8) at in-the-sky.org are at a useful scale.
In [Stellarium](https://stellarium.org/) you might try a 10° field of view (ctrl-alt-6) and use the View > Markings panel to add a circular FOV corresponding to your finder scope.
Remember that some optics will invert the view.
If you can confirm that the stars you see match the ones on the chart, then the other object is Neptune.


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