<p>My first telescope was made from the lens and eyepiece of an old discarded pair of binoculars. I used a paper towel roll cardboard tube with the objective taped on the front and a flat, circular piece of card stock (with radial cuts near the edge for folding) taped over the other end. It had a hole big enough for the eyepiece to fit, and pieces of tape slightly covering one edge of the hole for friction.</p>
<p>Sliding the eyepiece in and out slightly against the friction provided focus.</p>
<p>It's exciting to see the world big and upside down.</p>
<p>I'd go ahead and try the fresnel lenses for both objective and eyepiece if you can find a pair with different focal lengths, but I think you can also find short focal length lenses in novelty, &quot;dollar&quot;, toy, or other random-object store as pocket tools or toys, or in hobby or tool stores as cheap imitation <a href="https://en.wikipedia.org/wiki/Loupe" rel="nofollow noreferrer">jewler, gemologist or stamp-collector's loupes</a>.</p>
<p>For a short focal length lens you can even try <a href="https://en.wikipedia.org/wiki/Drop_(liquid)#Capillary_length" rel="nofollow noreferrer">a drop of water stuck on a glass slide</a>, or a transparent material that hardens transparent.</p>
<p>Or a spherical transparent marble or bead: <a href="https://www.edmundoptics.com.tw/knowledge-center/tech-tools/ball-lens/" rel="nofollow noreferrer">Ball lens calculator</a>, <a href="https://www.rp-photonics.com/ball_lenses.html" rel="nofollow noreferrer">Ball lens</a>.</p>
<p>If you'd like to &quot;go small&quot; afterwards and explore the microcosm, see <a href="https://www.foldscope.com/" rel="nofollow noreferrer">foldscope.com</a>, <a href="https://teamfoldscope.myshopify.com/" rel="nofollow noreferrer">teamfoldscope</a>, <a href="https://en.wikipedia.org/wiki/Foldscope" rel="nofollow noreferrer">Foldscope</a> for more ideas how low-cost projects can be fun and educational.</p>

CC BY-SA 4.0
2021-01-16T00:35:26.820Z
2021-01-16T00:44:04.713Z
2021-01-16T00:44:04.713Z
uhoh
<p>For a kindergarden (pirate) party, friends of me want to build together with the 4 year old kids a functional pirate's telescope for each of the kids. On the web I found full constuction sets, e.g. <a href="http://www.astromediashop.co.uk/Telescopes.html" rel="nofollow noreferrer">http://www.astromediashop.co.uk/Telescopes.html</a> (I am not affiliated), but that is only half the fun than improvising and building with household things.</p>
<p><strong>Does anybody has experience building a makeshift telescope using the cardboard tube from a paper kitchen roll, in particular which lenses to use and how to fix them?</strong></p>
<p>The rolls are e.g. 25.5cm long and have an approximate diameter of 4cm. Ideally, we would need two fresnel lenses, I guess, but I am not sure which ones to choose, how to fix them nicely to the tube etc.</p>
<p>Looking forward to your ideas.</p>
<p><strong>Edit:</strong> In the meantime, I also found <a href="https://www.nymetroparents.com/article/diy-telescope-from-national-geographic-kids-get-outside-guide" rel="nofollow noreferrer">View the Stars Through a DIY Telescope</a> which just states:</p>
<blockquote>
<p>[You neeed]: 2 convex lenses (you can get these from a pair of magnifying glasses or by ordering lenses online)</p>
</blockquote>
<p>Finding suitable lenses (with right focal length, diameter, weight) is actually the hard part.</p>
<p>Thinking further how I recycle things from home, I got the rough idea to <a href="https://www.instructables.com/DIY-Adjustable-Focal-Length-Fluid-Lens/" rel="nofollow noreferrer">build water lenses</a> but this is clearly out of scope of a kindergarden project, or is it?</p>

CC BY-SA 4.0
2021-01-15T14:11:51.503Z
A Fresnel lens may be ok for the objective lens (the front lens), but I don't think a Fresnel lens would work well as an eyepiece, the segments would be very obvious.
PM 2Ring
CC BY-SA 4.0
2021-01-21T12:50:23.053Z
your question has inspired me to ask [Is it possible to use something besides emulsion to directly record the image of a nighttime object using a telescope?](https://astronomy.stackexchange.com/q/40973/7982)
uhoh
<telescope><amateur-observing><telescope-lens>
Fresnel lenses for a makeshift Galilei telescope?
B--rian
# Fresnel lenses for a makeshift Galilei telescope?

(Asked by: username_0 on 2021-01-15)

For a kindergarden (pirate) party, friends of me want to build together with the 4 year old kids a functional pirate's telescope for each of the kids. On the web I found full constuction sets, e.g. <http://www.astromediashop.co.uk/Telescopes.html> (I am not affiliated), but that is only half the fun than improvising and building with household things.

**Does anybody has experience building a makeshift telescope using the cardboard tube from a paper kitchen roll, in particular which lenses to use and how to fix them?**

The rolls are e.g. 25.5cm long and have an approximate diameter of 4cm. Ideally, we would need two fresnel lenses, I guess, but I am not sure which ones to choose, how to fix them nicely to the tube etc.

Looking forward to your ideas.

**Edit:** In the meantime, I also found [View the Stars Through a DIY Telescope](https://www.nymetroparents.com/article/diy-telescope-from-national-geographic-kids-get-outside-guide) which just states:

> [You neeed]: 2 convex lenses (you can get these from a pair of magnifying glasses or by ordering lenses online)

Finding suitable lenses (with right focal length, diameter, weight) is actually the hard part.

Thinking further how I recycle things from home, I got the rough idea to [build water lenses](https://www.instructables.com/DIY-Adjustable-Focal-Length-Fluid-Lens/) but this is clearly out of scope of a kindergarden project, or is it?

**Tags:** telescope, amateur-observing, telescope-lens
> **Comments:**
> **username_1**: A Fresnel lens may be ok for the objective lens (the front lens), but I don't think a Fresnel lens would work well as an eyepiece, the segments would be very obvious.  
> **username_2**: your question has inspired me to ask [Is it possible to use something besides emulsion to directly record the image of a nighttime object using a telescope?](https://astronomy.stackexchange.com/q/40973/7982)  

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## 1 answers

### Answer by username_2 on 2021-01-16. Score: 3

My first telescope was made from the lens and eyepiece of an old discarded pair of binoculars. I used a paper towel roll cardboard tube with the objective taped on the front and a flat, circular piece of card stock (with radial cuts near the edge for folding) taped over the other end. It had a hole big enough for the eyepiece to fit, and pieces of tape slightly covering one edge of the hole for friction.

Sliding the eyepiece in and out slightly against the friction provided focus.

It's exciting to see the world big and upside down.

I'd go ahead and try the fresnel lenses for both objective and eyepiece if you can find a pair with different focal lengths, but I think you can also find short focal length lenses in novelty, "dollar", toy, or other random-object store as pocket tools or toys, or in hobby or tool stores as cheap imitation [jewler, gemologist or stamp-collector's loupes](https://en.wikipedia.org/wiki/Loupe).

For a short focal length lens you can even try [a drop of water stuck on a glass slide](https://en.wikipedia.org/wiki/Drop_(liquid)#Capillary_length), or a transparent material that hardens transparent.

Or a spherical transparent marble or bead: [Ball lens calculator](https://www.edmundoptics.com.tw/knowledge-center/tech-tools/ball-lens/), [Ball lens](https://www.rp-photonics.com/ball_lenses.html).

If you'd like to "go small" afterwards and explore the microcosm, see [foldscope.com](https://www.foldscope.com/), [teamfoldscope](https://teamfoldscope.myshopify.com/), [Foldscope](https://en.wikipedia.org/wiki/Foldscope) for more ideas how low-cost projects can be fun and educational.


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