Astrophotography & telescopes

Question 1

What is WASP?

Answer 1

Wide Angle Search for Planets (there are two of these on Earth looking for exoplanets)

Question 2

What is Kepler?

Answer 2

Since 2009 (until May 2013) it has been staring a small portion at the sky in the constellation of CYGNUS watching c150k sun-like stars (c3k lightyears away).

Question 3

What are the main type of telescopes?

Answer 3

1. Refractor (uses lenses)

2. Newton Reflector (uses mirrors) - also includes two further types = Maksutov-Cassegrain and Schmidt-Cassegrain

Question 4

What are the main types of mount?

Answer 4

1. Altitude-Azimuth “Altazimuth” Mount (Up-down/Left-right)

2. Equatorial Mount (Up-down/circles around celestial pole) - better for astro-photography

Question 5

What does the magnification of a telescope depend on?

Answer 5

The Magnification of the telescope depends on the eye-piece you’re using. BUT the bigger the telescope the sharper the image in relation to the eye piece e.g. £20k telescope you can use a 4mm eye piece whereas tytpical home telsescopes c£700 would probably only be 25mm.

Question 6

How big is the largest reflector telescope?

Answer 6

The largest is Gran Telscopio in La Palma (10.4m).

Question 7

Why are there no research telescopes in the UK?

Answer 7

No research telescopes in the UK due to weather and light pollution.

Therefore telescopes are sited where there is little rainfall and at high altitude (e.g. 4200m) to reduce the impact of the atmosphere blurring the image e.g. Canary Islands, Hawaii and the Atacama Desert in Chile.

Question 8

What are adaptive optics?

Answer 8

The onboard mirror will bend the mirror several times a minute. This is due the star’s light being bent by our atmosphere - the mirror is deformed to cancel this out to result in a sharper image.

Question 9

What is interferometry?

Answer 9

Combining light from multiple telescopes (e.g. The Very Large Telescope). It is incredbly difficult as the light needs to be combined at incredible precision.

Question 10

What is the next generation telescope?

Answer 10

Next generation telescope 39m - European Extremely Large Telescope (E-ELT). Due to be completed in 2022 in Chile.

Question 11

What is OWL?

Answer 11

There are plans for the OWL (Overwhelmingly Large Telescope) - 100m wide but wll cost 1.bn euros and therefore plans were cancelled due to costs.

Question 12

What will replace the Hubble Space Telescope?

Answer 12

New space telescope due to be launched in 2018 (8m at the cost of $9bn) = James Webb Space Telescope will be the replacement for the Hubble Space Telescope.

One of the advantages of Hubble is that it is close enough that you can repair it but it costs so much. The James Webb will be further out in space so repairs will not be ecnomically viable.

Question 13

What is XMM-Newton?

Answer 13

An infrared telescope. XMM-Newton is also in space because it would not be possible to get the clear infrared pictures of space.

Question 14

What is Rosetta & Philae?

Answer 14

First comet landing.

The landing was quite rough - first bounce was 1km and 2 hours and two bounces later it landed in a shadow. So they managed to get around 60hrs of data before the battery ran out. Couldn’t drill into the comet!

Question 15

What affects resolution?

Answer 15

Resolution of your telescope depends on the size of your lens.

Question 16

What 3 things do you need to consider when taking a photograph?

Answer 16

1. Exposure
2. ISO Setting
3. Aperture

Question 17

What is Exposure?

Answer 17

Exposure time e.g. to photograph Saturn’s moons you would need a couple of seconds exposure whereas Saturn would need much less as it is brighter in the sky.

Using the rotation of the Earth to your advantage: The spiral image is made up of 1200 photos stacked on top of each other. Each photo is 30 seconds exposure. Overnight of 10hrs using a pre-programmable remote.

Question 18

What is ISO Setting?

Answer 18

How sensitive your camera’s sensor (“film”) is to light.

Sensitivity can be increased 100 = low and 1600 = high.

Whilst this amplifies what you see it also increases the “noise” you see - imperfections in the camera. Bad pixels can be mistaken for stars!

To try and over come noise first take a photo and then with the same settings take another with the lens cap on. And the layer the photos to subtract the noise from the photograph.

Temperature affects the noise as well.

It is a balance between sensitivity versus noise.

Question 19

What is Aperture?

Answer 19

Focal length of a lens, in terms of aperture size.

Affects focal depth. The small the aperture the more focus your image will have - just like squinting to see more clarity!

f/1.4 - the aperture is wider than f/22 that is very small.

f/22 (a high f number) would require more light than f/1.4 (a low number).

When you use a high f number you get a ‘starburst’ affect.