<p>This really comes down to the usual sky conditions at your observing location.</p>
<p>If you generally have good seeing and transparency then I would go for the 5mm eyepiece because you'll be able to use it.</p>
<p>If you don't, then go for the Barlow.</p>
<p>The reason is that under bad seeing conditions a 5mm eyepiece in that telescope will give a blurry image because it won't be able to handle the high magnification. A Barlow would be more useful because you can use it with multiple eyepieces. And for the handful of nights a year with good seeing then you can Barlow your 10mm.</p>
<p><sub><sup>
I'm quite lucky where I am in that I get many nights of good seeing in a year, and can use even 3.3mm and 4mm eyepieces fairly frequently.<br />
I have a telescope that's the same aperture and focal length as yours.
</sup></sub></p>

CC BY-SA 4.0
2024-07-18T00:01:07.190Z
2024-07-18T00:01:07.190Z
Aaron F
<p>An eyepiece designed for high magnification will always give a better image than a Barlow. That's just a crude (but clever) kludge -- a negative lens shoved into the optical path.</p>

CC BY-SA 4.0
2024-06-18T13:20:17.960Z
This is generally but not always true.  A barlow can let you use longer-focal-length eyepieces which allow greater eye-relief, which is sometimes a necessity (if you need to wear glasses for example)
antlersoft
CC BY-SA 4.0
2024-06-18T16:19:09.383Z
Ooo, good point.
Miss Understands
CC BY-SA 4.0
2024-06-17T18:01:33.027Z
2024-06-17T18:01:33.027Z
Miss Understands
<p>While <a href="https://astronomy.stackexchange.com/a/57923/14094">the answer by Miss_Understands</a> is right that a single eyepiece will give better images as opposed to an eyepiece-plus-Barlow combination, and while <a href="https://astronomy.stackexchange.com/q/57922#comment132792_57923">antlersoft's comment</a> is right that a Barlow can help those who need longer eye relief, there are other factors at play.</p>
<p>I don’t know all the details about your telescope, as I’m not familiar with the “250P” by Sky-Watcher, but I own a very similar telescope: a 10-inch Sky-Watcher SynScan “goto” telescope on Dobsonian mount. Optically, it’s probably the same, but mine is motorized; not sure about yours. <strong>If yours is motorized</strong>, I would advise <em>against</em> using higher magnification powers, as the guiding system gives “bumps” that are annoying at high magnifications — the drive is not smooth but done by stepper motors.</p>
<p>Another thing is you’re asking about a 5 mm eyepiece, while you already have a 10 mm eyepiece. Using a 2× Barlow would give the same result, so why not get it <strong>and</strong> another eyepiece (if your budget allows it, but you mention the possibility, so I suppose it does), but <strong>not</strong> the 5 mm one? For example, a 6 mm or a 3 mm. This way, you’d have different powers and not just a repeat of the same ones.</p>

CC BY-SA 4.0
2024-07-17T19:47:55.940Z
2024-07-19T00:54:28.727Z
2024-07-19T00:54:28.727Z
Pierre Paquette
<p>I have recently gotten a Dobsonian 250P Sky-Watcher telescope and just wanted to ask whether it would be better to get a Celestron X-Cel Barlow 2× magnification or Celestron X-Cel LX 5 mm eyepiece. The default eyepieces that come with the telescope are the 10 mm and 25 mm, but I was looking for a nice upgrade to the collection of eyepieces. Both the 5 mm and Celestron Barlow are quality pieces, but I wanted to know whether it would be better to get one or the other or even both. My main goal is visual planetary astronomy but also nebulae and galaxies.</p>

<telescope><eyepiece><barlow>
Celestron X-Cel Barlow 2x magnification or Celestron X-Cel LX eyepiece 5 mm for 250P Dobsonian Sky-Watcher Telescope
CarlGaussian
# Celestron X-Cel Barlow 2x magnification or Celestron X-Cel LX eyepiece 5 mm for 250P Dobsonian Sky-Watcher Telescope

(Asked by: username_0 on 2024-06-17)

I have recently gotten a Dobsonian 250P Sky-Watcher telescope and just wanted to ask whether it would be better to get a Celestron X-Cel Barlow 2× magnification or Celestron X-Cel LX 5 mm eyepiece. The default eyepieces that come with the telescope are the 10 mm and 25 mm, but I was looking for a nice upgrade to the collection of eyepieces. Both the 5 mm and Celestron Barlow are quality pieces, but I wanted to know whether it would be better to get one or the other or even both. My main goal is visual planetary astronomy but also nebulae and galaxies.

**Tags:** telescope, eyepiece, barlow

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## 3 answers

### Answer by username_1 on 2024-07-18. Score: 2 | Accepted answer

This really comes down to the usual sky conditions at your observing location.

If you generally have good seeing and transparency then I would go for the 5mm eyepiece because you'll be able to use it.

If you don't, then go for the Barlow.

The reason is that under bad seeing conditions a 5mm eyepiece in that telescope will give a blurry image because it won't be able to handle the high magnification. A Barlow would be more useful because you can use it with multiple eyepieces. And for the handful of nights a year with good seeing then you can Barlow your 10mm.

I'm quite lucky where I am in that I get many nights of good seeing in a year, and can use even 3.3mm and 4mm eyepieces fairly frequently.  
I have a telescope that's the same aperture and focal length as yours.


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### Answer by username_2 on 2024-06-17. Score: 2

An eyepiece designed for high magnification will always give a better image than a Barlow. That's just a crude (but clever) kludge -- a negative lens shoved into the optical path.

> **Comments:**
> **username_3**: This is generally but not always true.  A barlow can let you use longer-focal-length eyepieces which allow greater eye-relief, which is sometimes a necessity (if you need to wear glasses for example)  
> **username_2**: Ooo, good point.  

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### Answer by username_4 on 2024-07-17. Score: 2

While [the answer by Miss\_Understands](https://astronomy.stackexchange.com/a/57923/14094) is right that a single eyepiece will give better images as opposed to an eyepiece-plus-Barlow combination, and while [antlersoft's comment](https://astronomy.stackexchange.com/q/57922#comment132792_57923) is right that a Barlow can help those who need longer eye relief, there are other factors at play.

I don’t know all the details about your telescope, as I’m not familiar with the “250P” by Sky-Watcher, but I own a very similar telescope: a 10-inch Sky-Watcher SynScan “goto” telescope on Dobsonian mount. Optically, it’s probably the same, but mine is motorized; not sure about yours. **If yours is motorized**, I would advise *against* using higher magnification powers, as the guiding system gives “bumps” that are annoying at high magnifications — the drive is not smooth but done by stepper motors.

Another thing is you’re asking about a 5 mm eyepiece, while you already have a 10 mm eyepiece. Using a 2× Barlow would give the same result, so why not get it **and** another eyepiece (if your budget allows it, but you mention the possibility, so I suppose it does), but **not** the 5 mm one? For example, a 6 mm or a 3 mm. This way, you’d have different powers and not just a repeat of the same ones.


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