OPTIONAL EXTRA CREDIT: Module 6 Activity Supplement

OPTIONAL EXTRA CREDIT SUPPLEMENT to the Module 6 Activity

Our First Extra-Credit Assignment

First, a word about how extra-credit points work in Canvas: I'm not sure!

I originally wrote this as a normal "Part" of the Module 6 Activity, but I decided it was too long, especially during a week when we have our Midterm exam. So, I wanted to make it an extra-credit assignment. Since Fall 2018 is my first quarter teaching online, I wasn't sure how to designate an assignment as extra-credit.

I checked with a person at De Anza who helps faculty learn to use Canvas, and they suggested the following:

1. Make the assignment worth 0 points.
2. Once the assignment closes, grade the assignment and give students points for the work they did.
3. The points you (i.e. the instructor) give them will work out to be extra credit in the course.

So, that's what we'll try. You don't have to do this supplemental activity, but if you want to try it, you can get up to 15 extra points.

I don't know when I'll get this graded! I will be busy calculating your partial-credit points for the Midterm, so it may be a while before I "unmute" this assignment to reveal how much extra credit you got, if you tried it.

On to the Activity...

In this extra-credit supplement to the Module 6 Activity, you're going to pretend that you own some amateur astronomy equipment. You'll compare 3 "rigs" that I use for visual observing (not for taking pictures - that's a whole other story), and decide which one is your favorite!

You'll also speculate on what might be the drawbacks or difficulties in using your favorite of the three "rigs".

Important: The way you change the magnification (and the field of view) of a telescope is by changing which eyepiece you're using. Each of these telescopes has a set of eyepieces listed after its picture. The combination of telescope, eyepieces, and the mount that the telescope sits on is what makes up a "rig".

The simplest way to do this exercise is to open this link in a new browser tab 3 times, and then follow the instructions in this video.

(Make sure you select "Detailed Simulation: Choose your eyepieces".)

If you want written instructions, here they are:

Rig 1: ED80

This is a small refractor telescope I bought in 2005, called an "ED80":

• Aperture = 80mm
• Focal length = 600mm

That's me looking through my ED80 on late-summer or autumn night at an observing site in the hills above Silicon Valley.

Here is a set of eyepieces I commonly use with it:

Like a telescope, an eyepiece has a measurement called a focal length. Switching from one eyepiece to another in a telescope changes the magnification of the telescope.

Magnification = (telescope focal length) / (eyepiece focal length).

In case you can't read them in the photo, the eyepieces I normally use with the ED80 have these focal lengths:

• 24mm
• 13mm
• 9mm
• 7mm
• 5mm

Rig 2: M603

The M603 is a Russian-made telescope I bought from my friend George in 2003. It's basically a reflector, but with a thin, slightly-curved glass "corrector plate" on the front end.

In this picture, I've set it up for daytime testing prior to going to Idaho to see the total solar eclipse in August 2017. (You can read more about my preparations here if you want.) The thing on the front end made of yellow and white construction paper and foamcore board is a holder for a special solar filter that allowed me to look at the Sun safely during the times when it wasn't totally covered by the Sun. (During the brief 2 minutes when the Moon covered the Sun, I took the filter off, then put it back on just before the bright part of the Sun got exposed again.)

Here's a set of eyepieces I'd be likely to use when I take the M603 out for nighttime observing:

In case you can't read it in the photo, their focal lengths are:

• 31mm
• 24mm
• 13mm
• 7mm
• 5mm

Rig 3: O18

This is a reflector telescope made by a small company in Wisconsin called "Obsession". I'm the third owner of this `scope. It has an aperture of 18" (= 457mm) and a focal length of 2056mm. This picture was taken at the same place as the picture of the ED80 rig.

And here is a selection of eyepieces I'd be likely to use with the O18:

In case you can't read them in the photo, their focal lengths are:

• 31mm
• 22mm
• 17mm
• 9mm
• 7mm

Simulating The Views Through These Telescopes

Now you're going to use an online simulator called Stelvision to create simulated views through these telescopes and eyepieces, of the following three astronomical objects:

• The Earth's Moon
• Saturn
• The Orion nebula (M42)

Here's a link that you'll use three times - I recommend opening it in a new browser tab. (In fact, it wouldn't be a bad idea to open in a new tab three times, so that you can have one simulation for each telescope: ED80, M603, and O18)

Stelvision telescope simulator

There are three images below that show you how to set it up; each time you set it up, you hit Simulate, and you'll get a group of images that looks like this... note that each image is clickable, so you can see what the view looks like through the telescope!

Okay, here are the three different ways to set up Stelvision, one for each telescope "rig":

How to Set Up for ED80

How to Set Up for M603

How To Set Up for O18