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Active & Experiential Learning with Low-cost Telescopes

Project Lead: I. Song

Students are attracted to astronomy initially because of the awes and beauties of celestial objects. However, students rarely have an opportunity to see celestial objects with a telescope even if they take astronomy courses. Even for astronomy majors, course activities using a telescope are greatly limited because of (1) the necessity of using the department-owned, centralized large & expensive telescopes, (2) the need for night-time gathering at the campus for astronomical observations, and (3) weather limitations including the light pollution at the campus site. Pedagogical night-time observations are done traditionally with expensive telescopes (8 inches to 14 inches in size with a price tag of up to a few thousand dollars) owned by the department, and such observations require students to be gathered at a campus at night which can raises a security concern in addition to the diminished active learning opportunity because of the shared telescope. An ability to deploy a telescope to an individual student or a small (N<3) group of students can alleviate these problems and greatly enhance active learning and experiential learning opportunities. With the advance of relevant technology & manufacturing, good quality optics become cheap and a very low-cost telescope (LCT; under \$100, e.g., Celestron's FirstScope Telescope) is readily available nowadays. In conjunction with this LCT, a smartphone owned by a student can be used as a digital detector or a cheap (<\$5) digital camera such as ESP32-CAM can be used with the LCT. This combination allows many observational projects that were impractical before.

We can develop several active-learning and experiential learning opportunities by using low-cost telescopes or DIY telescopes.

To use a smartphone as a digital detector for astronomical observations, we need a special camera app that allows a much longer exposure time than possible. Use one of the following apps depending on your phone type.

Things to consider It would be beneficial to adopt a similar approach to the one showcased in the poster below when it comes to sharing lab instructions with students. Not only does this method help us utilize lab time more efficiently, but it also ensures that instructions are delivered clearly to students. Additionally, it presents an excellent opportunity for TAs to practice science communication skills. NJW had implemented this approach in his PHYS 1251/52 courses, and it was proven to be very effective.

Quick demonstration of the Telescope + Smartphone setup

Here is the quick display on the setup of the telescope + smartphone and some sample images.

Preliminary works from ASTR 3010 students (2024 Fall)

Lab Topics suitable with Low-Cost Telescopes

  1. Introduction to the telescope + smartphone
  2. Collimation of telescope mirrors
  3. Camera operation (ISO, exposure, repeat, etc.)
  4. Data analysis (preprocessing + stacking)
  5. Image enhancement (photoshop etc.)
  1. Astrophotography → imaging of the brightest galaxy. any significant scientific gains?
  2. Phase of the Moon, Libration Movie → Specifics of scientific activities? Can be done on non-photometric nights
  3. Phase of Venus; phase-size dependency → Specifics of scientific activities? Can be done on non-photometric nights
  4. Movement of Uranus → estimate its “circular” speed and estimate its distance (Uranus is 6th mag). Uranus moves about 0.7 arcmin per day.
  5. Mapping the light pollution in your area
  6. Color-scale of your camera: measure the relationship b/w RGB color and Teff
  7. Asteroid observation: (1) known asteroid and recover its orbit or (2) blind hunting for asteroids
  8. Any oppotunistic objects such as comets
  9. Observe Galilean Moons (or Titan) → create a movie → and measure periods → calculate distances from the central planet (max angular sep of Io/…/Callisto is b/w 2 and 10 arcmin and Io's period is 1.77 days. Titan's max angular sep from Saturn is 0.3 arcmin with an orbital period of 16 days).
  10. Obtain the limit of the deep observation → how deep one can go with this setup? Related to the light pollution mapping
  11. Color-Magnitude diagram of bright, nearby clusters (Pleiades, Hyades, Beehive, etc.) → Need photometric nights
  12. Observations of short-period variables (Cepheids, Eclipsing binaries, etc.) → recover known periods. Can be done on non-photometric nights
  13. Standard transformation of your smartphone camera
  1. Engineering projects: creating ESP32 camera holder, creating a finderscope, spectrograph, etc.
  2. Post Image processing (by Marni Shindelman)

Low-Cost Digital Detector or Camera

ESP32-CAM

As a start, we can use the smartphone as a digital detector. However, fine controlling of the phone is limited with the general purpose SmartPhone camera app. For example, subsampling, well-depth issue, raw image format saving are limited at best. We can use a low-cost digital detector (CMOS image sensor = e.g., OV2640 [\$9.99 in Amazon]) controlled by an Arduino ESP32 (three for \$15.99 in Amazon). A combination board (ESP32-CAM + ESP32-CAM-MB) can be purchase at low cost in Amazon (3 for about \$15). Using this, we need to develop a holder of the camera to the eyepiece. 3D printing of such a model can be done. In addition, we can also consider manufacturing a DIY spectrograph.

More detailed descriptions on the ESP32-CAM can be found at ESP32 Setup/

WiFi Telescope Eyepiece

Alternatively, we can use an eyepiece camera that can be attached over the eyepiece and images can be captured through wifi-connected smartphones. It is listed at \$73 in amazon (search for “WiFi Telescope Eyepiece Camera” on Amazon). I tested out this eyepiece, and it should be used on top of an eyepiece and the aligning the camera over an eyepiece still needs to be done carefully. Other then providing a convenient WiFi connection, there seems to be not much of additional benefits. Furthermore, image/video can only be seen and obtained via a dedicated smartphone app.

Other low-cost "planetary cameras"

There are some cheap (<\$100) CMOS cameras on the market labeled as “planetary cameras”. These cameras have a max exposure of 1 sec. Some examples are:

Software

Camera Software

A Potentially Useful Combination

SharpCap allows a user to use a webcam as the imaging device. With the free app called iriun, a smartphone can be used as a webcam which can be controlled from a computer (Windows, Linux, or MacOS). Then, without replying on the use of an external camera app (e.g., NightCap or DeepSkyCam), a student can take night sky images via SharpCap.

Image Analysis software

DeepSkyStacker, a free software available for Windows/Linux/MacOS, can do:

A quick image display + saturation check

An example of displaying an image with Python including a quick saturation check can be found from Quick Image Check.

DIY telescopes & Digital Detectors

Alternative to the use of off-the-shelf LCTs like FirstScope, we can build a DIY low-cost telescopes from parts. This DIY approach has a different set of pedagogical benefits. A student can build a small (~11 cm primary mirror) reflecting telescope from parts (mirrors, focuser, eyepieces, other material) and the total building cost can be kept under \$100 per telescope. The DIY telescope can have many “teachable” moments.

Parts

Presentation of the project (at early stage) during the CURO Symposium

— Inseok Song 2024/05/03 15:36