LESSON PLAN

Name: Elise Briseno

Title of lesson: Installation of Spider and Eyepiece

Date of lesson:

Length of lesson: 90 minutes

Description of the class:

Name of course:

Grade level:

Honors or regular:

Source of the lesson:

Information and resources found at the website: http://members.aol.com/sfsidewalk/sectiona.htm.

TEKS addressed:

Give identification number and letter and write out the TEKS.

I. Overview

Students should be able to use (and redirect) the focal point to understand the purpose of the secondary mirror. Students should also be able to install a spider and an eyepiece for the telescope.

II. Performance or learner outcomes

Students will be able to:

-Install the spider at the appropriate distance and to center the secondary mirror to reflect into the eyepiece.

-Install the eyepiece into the telescope.

-Tell the difference between a primary mirror and a secondary mirror.

-Describe the reflections of both the primary and secondary mirrors.

III. Resources, materials and supplies needed

-Eyepiece embedded in cardboard

-Drilling tool to make the hole for the eyepiece

-Pre-made Spider with secondary mirror

-Handsaw

-Sandpaper

-Wood glue

-Questions for the post assessment “quiz”

IV. Supplementary materials, handouts.

Not needed.

Five-E Organization

Teacher Does Probing Questions Student Does

Engage: -Introduction of who I am, “My name is Elise Briseno and I am here to help you complete your telescopes.” -Determine what the focal length, “Okay so I know that you have determined the focal length in the previous lesson and who can tell me that value.” -Write on the blackboard that value.

-“Now, what parts to we have in your telescopes?” -“What is the focal point, what happens at the focal point?” -Ask one of the students to come up to the blackboard and draw the picture of the parallel lines coming into the mirror and then bouncing off to the focal point.

- We have a large mirror at the end of the tube. -It’s the point where all the parallel rays entering the tube converge after bouncing off the large mirror. -The student draws what the previous student has explained.

Explore:  -We need to determine how to see the images from inside the tube. -I need to draw out that we need an eyepiece and more important a second mirror to catch the path of the reflection rays that converge at the focal point. -As the students are trying to find out how to see the image with the telescope, I need to be drawing a large side view of the telescope as in the website (resource).

-“Well, how do we see this image in the tube? Can we place our head inside the tube to see the image?” -“Well, since you explained why we can’t place out head at the end of the tube, what else could we do to see the image?” -“The hole in the tube is a good idea, but how do we get the light rays (the light cone) to come out the hole?”

-If we put our head in the tube, then we are blocking all the light rays coming into the mirror. -We could look into the tube through a hole (in particular an eyepiece). -We can use another mirror to reflect the rays out of the tube through the hole.

Explain: -Explain to the students that the spider is a part of the telescope that will allow light to pass through the tube without blocking most of the rays and that it will reflect into the eyepiece because the secondary mirror is positioned on a forty-five degree angle. -Explain to the students that the distance at which the hole is positioned on the tube is critical for the construction of the telescope. -Discuss and explain to the students that the spider must be centered to redirect the light cone into the eyepiece.

-Ask the students to picture (they may want to draw this down) the light cone coming from the primary mirror bending as it reflects off the secondary mirror, making sure that they keep the sizes of the mirror in mind. -“Does the position of the spider in the tube matter? What happens if the spider is too close to the primary? Too far?” -“Should the spider be at the focal point, why or why not?” -“How do we find the exact point to install the spider?” -“Well, we need to obtain certain information about our telescope to find this distance. What is the radius of our tube? How can we figure that out?” Write the radius down on the blackboard under the focal point distance. “I need one of you the measure the eyepiece.” Write it down on the blackboard. “We are going to add one inch to this measurement because we need some ‘play’ with the eyepiece. In other words, the image will hover Fht + 1” above the tube before being magnified by the eyepiece. What is the distance at which the primary mirror is sitting in the tube?” Write it down on the blackboard. “So we can add the radius and the fht +1” to get the distance at with the reflection will bend at the secondary mirror outside the tube. So subtract this value from the focal length, this is the distance from the face of the mirror to the focuser hole and the diagonal. However, we need to add the distance of the face of the primary mirror to the back of the tube to get measurement that we can use to draw the hole on the outside of the tube. Reminder this values should be checked again as you construct the hole in the telescope for accuracy.” -“What is a good idea in getting the spider inside the telescope tube?”

-Students draw out on paper the concept of the reflections from the primary to the secondary. -The position matters in the tube because if we don’t center to spider the rays won’t be reflected correctly. If we have the spider really close to the primary we won’t get any of the light rays in the secondary because the outside rays will reflect over the secondary mirror. If the secondary mirror is too far then we will miss the focal point and won’t be able to see anything. -If the spider is at the focal point then the image we want to see will not be reflected correctly into the eyepiece. The spider must be a little more into the tube to get the focal point of the light cone to bend out of the telescope tube so our eye is exactly where the focal point is. -If the students cannot figure this out exactly then go back to the explanation part. Students should write down the steps so that they can execute them on the telescope. -We need to find the diameter of the tube and cut the spider a little large to fit in the tube so that the secondary mirror is centers in the tube. Using the sand paper we can fit the spider perfectly and glue it down. Remind the student that before they glue the spider in they need to make sure the secondary mirror is positioned correctly. The angled part should be facing the hole.

Extend / Elaborate:  -The students are allowed time to use the information above to place an X on the tube where the hole needs to be drilled. -As the students get close to installing the eyepiece give them the proper tools and directions.

-“Explain to me how you determined where to put the X.”

-The students should explain the X by a similar procedure as in the section above.

Evaluate: -Pass out a sheet of paper to all students for assessment of the main topics of the lesson plan.

Sheet of paper should read:  -Draw a large primary mirror and show the incoming rays of light and their reflections that create a focal point. Use two to three sentences to explain your drawing. -Draw a side view diagram of the telescope tube with all the parts we have assembled today. Make sure to label all parts. (There should be a light cone in your drawing.)

The students will complete and turn in the post assessment quiz.

Percent effort each team member contributed to this lesson plan:

___%___ ____Name of group member_____________________

___%___ ____Name of group member_____________________