Telescopes are much better at peering into the distant Universe than the human eye. But how are they able to see such faint and distant objects, and why is it that our eyes can’t? In this activity students will carry out experiments to investigate just how much more powerful the robotic telescopes are than their own eyes.
Human Eye Vs Robotic Telescope Teacher Guide
Human Eye Vs Robotic Telescope Student Worksheet
Full Instructions
Learning Objectives
- Investigate the capabilities of the human eye; including resolving power, refresh rate, light gathering area and field of view.
- Compare the observational power of the human eye to that of a 1-metre LCOGT robotic telescope.
- Carry out hands-on, enquiry-led investigations, compare and contrast, create and share conclusions and practise team-work skills.
Materials
- 1-metre ruler
- Chalk or sticker labels
- Calculator per pair
Per Student
- Printed Human Eye Vs Robotic Telescope Student Worksheet per student
- Protractor or Printed protractor per pair
- Calculator per pair
- Rulers
- Pens or Pencils
- x1 piece of card
Background Information
Telescope Class: Your eye is a simple telescope. It has a lens which focuses light to a point where it is detected and carried to your brain to be interpreted as an image. But it is a telescope with a very small pupil, or light-gathering opening, and therefore it can only gather a very small amount of light. Unlike most telescopes, our eye can change it's pupil size to let in more light. However, the change is very slight and is not enough to allow us to see very faint, dim objects.
The fainter an object, the larger the opening that is needed to let in enough light to see (resolve) that image. Even with our pupils fully dilated, the human pupil can only get to about 7mm diameter (slightly bigger than 1/4 inch). Cats, which are renowned for their night vision, have the ability to expand their pupils to fill almost their entire eyes, thus giving them a wider area to gather more light onto their retinas, and see better in the dark. They have a bigger eye-telescope than we humans do. With telescopes (and pupils), bigger is definitely better in the dark!
Field of View: The Field of View is the circle of sky visible through the eyepiece. Generally speaking, as you get a higher magnification, the field of view is smaller.
Exposure Time: exposure time determines how light or dark an image will appear: fainter targets need a longer exposure time as more light needs to be collected.
Resolution: Resolution describes the ability of a telescope to distinguish small details of an object.
Step-by-Step
Preparation
1) Before beginning this activity you will need to prepare a demonstration for Part C of the activity. To do this, start at the classroom window and measure 1-metre away on the floor.
2) Mark the 1-metre point with chalk, paper or similar, then continue marking out metre increments to the other side of the classroom. Ideally you would like around 8 metre-markers.
3) The next step is to take a small piece of semi-thick card, a sharp pen or pencil, and a ruler.
4) Make two small holes in the card exactly 3-mm apart using the nib of a sharp pen or pencil. Then stick the card again the window using tape or similar so that light shines through the holes.
A. Test you ability to gather light
4) Divide the class into pairs. Describe what a pupil (eye) is, or ask the children to read the description on their worksheet.
5) Ask each pair to look at their partner’s eyes. They will choose the pupil size from the table provided on their worksheets that looks most similar in size to their partner’s pupil.
{{
6) Based on the size chosen, they can use the table to work out how much larger the “pupil” of the LCOGT robotic telescope is. The area of an LCOGT 1-metre telescope opening is 7853cm2.
B. Test your reaction time
7) The next thing we want to test is how long the human eye can collect light. The more light than can be collected, the fainter the objects that can be seen.
8) To test their reaction time, one member of each pair will hold a ruler between two fingers, a few centimetres above the desk (hold the top of the ruler). When they let go of the ruler, their partner will try to catch it before it touches the table. Can they do it?
{{
9) Ask the students to try recording the number they manage to grasp on the ruler as it falls. Can they beat their previous number? (Alternately, you can use a stopwatch and have a third person time how quickly the students can catch the pen).
10) Ask the students to now consider how quickly they were able to react and circle their answer on their worksheet. (Options: 1 Second, Half a second, Quarter of a second, Tenth of a second).
11) The average reaction time is actually about a tenth of a second (that’s 0.1 seconds). This means the average person can collect light for 0.1 seconds at a time. The students will divide 300s (telescope exposure time) by 0.1s (human reaction time) to find out how much longer the telescopes can gather light than the human eye
C. Test the sharpness of your eyes
12) Direct the class to the card you placed on the window before the activity.
13) Ask the students to begin by standing at the 1-metre marker and look towards the piece of card (no more than 4 students at a time). Can they distinguish the two holes? If so, ask them to move back to the next marker and check again.
{{
14) They will repeat this until they find the distance at which they can no longer see two separate holes (the holes should merge into one). Ask them to mark this distance on their worksheet.
15) The telescope can see these two small holes from 4.5 km away or 4500 metres. How many times more detail can the telescope see than their eye? To find out they will divide 4500 metres by the maximum distance from which you can distinguish the two holes (in metres).
D. Measure your Field of View
16) The students will now measure their Field of View. Working in pairs, the first student will sit with their right arm extended in front of them and their eyes focused on their thumb. Their left arm will be held outstretched to the side. They will move their outstretched arm back, out of view (see image below)
17) Still staring straight ahead they will move their arm slowly into view, with their thumb wiggling. As soon as their arm enters their vision tell them to pause.
{{
18) Their partner will then hold a protractor to their chest to measure the angle of their arm as accurately as possible. When they have repeated this with the right arm they will add the two angles together and note the final angle down on their worksheet.
19) The telescope can see around half a degree (0.5°), how much more can they see? To find out they will divide their field of view by the telescope’s.
20) The telescope can see around half a degree (0.5°). This is much less than the human eye. Ask the class to discuss why they think this is: i) humans need a wide field of view to see dangers such as predators and cars, ii) telescopes are designed to focus on small patches of sky to see tiny, distant objects.
E. Compare your vision to a telescope's
Ask your class to finish the activity by filling in the final statements on their worksheet to find out exactly how powerful their eyes are compared to the telescope.
Now that the class understand how much more powerful the robotic telescopes are than their eyes, use the telescopes to peer deep into space and take some fantastic pictures of objects you could never see with your eyes alone: from galaxies to stellar nurseries (nebulae) and exploding stars (supernovae)!
Conclusion
Now that the class understand how much more powerful the robotic telescopes are than their eyes, use the telescopes to peer deep into space and take some fantastic pictures of objects you could never see with your eyes alone: from galaxies to stellar nurseries (nebulae) and exploding stars (supernovae)!
Curriculum Links
KS2 Science in the Welsh National Curriculum, The Sustainable Earth:
“a comparison of the features and properties of some natural and made materials.”
KS2 Science in the Welsh National Curriculum, Skills:
“Make careful observations and accurate measurements…make comparisons and identify and describe trends or patterns in data and information…use some prior knowledge to explain links between cause and effect when concluding.