The classroom becomes a universe! Making a DIY Cardboard Planetarium Dome

I’m Ken Kuwako, a science trainer. Every day is an experiment.

A Classroom Full of Stars! How to Make a DIY Cardboard Planetarium

Have you ever made a planetarium for a school festival? This time, I’d like to introduce a project our science club took on: creating a “cardboard planetarium dome.” Last year, our school festival theme was “earthquakes,” and we put together an interactive exhibit. For this year’s theme, one of the club members suggested, “I want to do a planetarium!”

So, we first went to see a real planetarium in Shibuya to learn how to present a starry sky and get a feel for the atmosphere. Afterward, the students researched “how to make one by hand” and discovered that JAXA’s official website had instructions for a cardboard planetarium dome. We immediately downloaded the blueprint and adjusted the scale to fit our classroom’s ceiling height. You can find it here.

https://www.kaguya.jaxa.jp/ja/document/DomeProject.htm

The website even has a small-scale model and paper patterns. How helpful!

Students Take the Lead on Design and Construction

This is where the students really shined. With calculators in hand, they did the scale calculations and ordered cardboard with a white interior online. This was a clever trick to ensure the projected stars would show up beautifully on the inside. The cardboard cost about 15,000 yen, but ordering it pre-cut to the right sizes significantly improved our work efficiency. The students handled everything from design to procurement to assembly, and I only offered a little advice. This is how we completed a full-scale planetarium dome that covered half the classroom.

Materials & Tools:

• Cardboard (white interior, pre-cut to specified sizes)
• Box cutter, tape, adhesive
• Planetarium projector (like HOMESTAR)
• Laser pointer
• Calculator or PC for scale calculations
• Star chart reference materials (Winter constellations are perfect for an introduction)

Estimated time required:
• Design & Ordering: Approx. 2 days
• Assembly: Approx. 1 week (after-school basis)
• Commentary Prep: Approx. 1 week or more (script + practice)

From DIY to Commercial Projector

Initially, we planned to build our own pinhole-style projector, but due to the tight schedule before the school festival, we decided to use a commercially available home planetarium called “HOMESTAR.” With this device, we could fill the entire classroom with a starry sky with just the flip of a switch. You can buy it on Amazon or Rakuten for around 15,000 yen. The sight of the stars appearing in the dark classroom made both adults and children gasp in awe.

The projector is available on Amazon here, and on Rakuten here.

【売り尽くしセール★最大1200円オフクーポン配布】 HOMESTAR Classic (ホームスター クラシック) パールホワイト 価格：14724円（税込、送料別) (2022/6/21時点) Buy on Rakuten

Once we built it and turned on the projector, the entire room went dark and a starry sky appeared right before our eyes!

Commentary by the Students! Using a Laser Pointer to Trace Constellations

The star commentary was a 5-minute mini-lecture on winter constellations. It was so impressive to see the students create their own scripts and use a laser pointer to clearly show the shapes of the constellations as they spoke. This technique was an application of something we learned on a star-gazing tour in Okinawa, and it works just like it would in the real night sky.

A Project Well Worth It! The Exhibit’s Appeal and Adaptability

The exhibit was a huge hit with visiting parents and elementary school students, and we got many comments like, “I can’t believe you can see so many stars in a classroom!” A great thing about this project is that once you’ve built it, you can use it every year. And if you get the hang of storing and assembling it, it’s easy to reuse. In another corner of the exhibit, we also had an interactive quiz called “Which planet floats on water?” where visitors could actually float model planets to check, making it another hands-on science exhibit.

How about making your own planetarium projector next?

「星空」を創ろう！ピンホールカメラで実現する、光の不思議手作りプラネタリウム

Contact & Requests

Get closer to the wonders and fun of science! I’ve put together easy-to-understand summaries of fun science experiments you can do at home and tips for them. Feel free to search around!
・About the operator, Ken Kuwako: here
・For various requests (writing, lectures, science workshops, TV supervision, appearances, etc.): here
・Updates on new articles are available on X!

The Science Channel is streaming experiment videos!

６月のイチオシ実験！

レモンやオレンジで風船を割ろう！インパクトが抜群のリモネン風船の実験

テレビ番組監修・イベント等のお知らせ

• ６月３日（水）20:30〜　「バカリズムのちょっとバカりハカってみた！」（テレビ東京）を科学監修・出演します。テーマは「そばの出前は何人前まで運べるのか、限界を測ってみた」です。　
• ６月４日(木)　7:00〜　「THE突破ファイル」（日本テレビ）について科学監修しました。
• 6月14日（日）　千葉大学インスタレーション「探究」にて講師を務めます
• 6月26日（金）　公開研究会「脱作業化！デジタル化と段階的指導で実現する オームの法則の探究」
• ６月28日（日）　ダビンチマスターズ＠昭和女子
• 7月18日（土）　教員向け実験講習会「ナリカカサイエンスアカデミー」の講師をします。お会いしましょう。

書籍のお知らせ

• 『大人のための高校物理復習帳』（講談社）…一般向けに日常の物理について公式を元に紐解きました。特設サイトでは実験を多数紹介しています。※増刷がかかり６刷となりました（2026/02/01）
  
  
• 『きめる!共通テスト 物理基礎 改訂版』（学研）…　高校物理の参考書です。イラストを多くしてイメージが持てるように描きました。授業についていけない、物理が苦手、そんな生徒におすすめです。特設サイトはこちら。
  

各種SNS（更新情報をお届け！）

X(Twitter)／instagram／Facebook（日本語）

BlueSky／Threads（英語）

Explore

• 楽しい実験…お子さんと一緒に夢中になれるイチオシの科学実験を多数紹介しています。また、高校物理の理解を深めるための動画教材も用意しました。
• 理科の教材… 理科教師をバックアップ！授業の質を高め、準備を効率化するための選りすぐりの教材を紹介しています。
• Youtube…科学実験等の動画を配信しています。
• 科学ラジオ …科学トピックをほぼ毎日配信中！AI技術を駆使して作成した「耳で楽しむ科学」をお届けします。
• 講演 …全国各地で実験講習会・サイエンスショー等を行っています。
• About …「科学のネタ帳」のコンセプトや、運営者である桑子研のプロフィール・想いをまとめています。
• お問い合わせ …実験教室のご依頼、執筆・講演の相談、科学監修等はこちらのフォームからお寄せください。