Photographing the Moon through a telescope

People often neglect the Moon since they take it for granted.

However the Moon is full of amazing features to photograph.

Although the Moon is fairly big and bright in the night sky, you will either need a very big and expensive telephoto lens for your camera, or a telescope to capture a lot of surface detail.

The method I use is eyepiece projection, i.e. I point a telescope at the Moon and take a photo with my camera through the eyepiece of the telescope.

Since the telescope I use does not have tracking (it does not automatically follow a celestial body), I am limited to only short exposures, therefore this method is best suited for the Moon and bright planets.

The lens I use on my camera is usually the Canon EF 50mm f/1.8II.

I prefer this lens for three reasons:

  1. The fairly large aperture of f/1.8 means that a lot of light can enter the camera, which is absolutely essential for astrophotography.
  2. The second reason is that it gives a good magnification of the object through the eyepiece.
  3. Lastly, the diameter of the eyepieces used in astronomy is usually 30mm and 50mm. The Canon lens has a diameter of 52mm. This means that most of the lens covers the eyepieces.

The technique for taking the photos is very straight forward, however it can be very difficult since you need to align an image that has passed through two optical systems (the telescope eyepiece and the camera lens).

The easiest way to do this is if you keep the camera handheld and look through the viewfinder to see the object.

One thing that must be kept in mind is that it will be very difficult for a camera to automatically focus on the object if the camera does not have many focus points. I therefore always use manual focus for focusing the image.

Another important point to keep in mind is to use the camera's 2 second timer. The reason for this is that you will most likely loose the alignment of the image if you press the shutter button. Therefore press the shutter button and use the two seconds to realign the image.

Since my particular telescope does not have tracking, I need to use very wide aperture and high ISO settings to capture the image since I have to use fairly fast shutter speeds. Here however I sometimes need to brake the handheld rule in photography and use shutter speeds such as 1/20 of a second to get enough light.

The amount of light entering the camera will depend on the eyepiece being used. The image from an eyepiece that does not magnify a lot will be much brighter than the image from an eyepiece that magnifies a lot. The reason for this is that in the magnified image only a small portion of the Moon will be visible, therefore only a small amount of light gets into the camera. A magnification where the whole Moon is visible will be much brighter since the light of the whole Moon enters the camera.

As for eyepieces, the diameter of the eyepiece will make a massive difference to the final image. An eyepiece with a 50mm diameter will give you a much wider field of view than an eyepiece of 30mm, even though the magnification factor might be the same.

A very important point: Never use flash when taking these kinds of images!

The flash will reflect from objects all round you and enter the lens, this will ruin the image.  

Here's a few photos I have taken to illustrate all the points I have mentioned above:

f/1.8 1/40sec ISO 800 with a 30mm eyepiece which gave my telescope a magnification factor of 48 

 

f/1.8 1/80sec ISO 100 with a 50mm eyepiece that gave me a 40 times magnification.

f/1.8 1/30sec ISO 1600 with a 30mm eyepiece that gave me 200 times magnification

f/1.8 1/30sec ISO 1600 with a 30mm eyepiece that gave me 200 times magnification

As can be seen in the above images, my camera setting had to be changed with the different eyepieces I used.

For the last two images I used the same eyepiece, therefore my camera settings were exactly the same.

A last note. The magnification I got from the different lenses is computed by dividing the focal length of my telescope by that of the eyepiece. The focal length of the telescope I used is 1200mm. For the last 2 images I used an eyepiece of focal length 6mm. Dividing 1200mm by 6mm gives 200.

The actual magnification of the telescope depends on the diameter of its mirror or lens, the bigger the mirror/lens, the more light it will gather. This will allow you to observe fainter and smaller objects.

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Comment by Danie Bester on August 7, 2014 at 13:03

Thanks for sharing Jaco. Very useful information :)

Comment by Shawn Marran on August 6, 2014 at 12:09

Awesome article and Awesome pictures :D Love it.

Comment by LEON PELSER on August 6, 2014 at 10:00

Dankie Jaco!

Comment by Debbie Grobler on August 6, 2014 at 9:08

This article is awesome and couldn't have come at a better time.

I love photography and my hubby loves Astronomy so he recently purchased a Celestron NexStar 130SLT.

Photographing the night sky would be an awesome way to marry our two hobbies.

Will definitely give your advice a try this weekend as it is going to be the largest full moon of the year :)

Comment by Kevin Richards on August 6, 2014 at 8:48
Awesome stuff Jaco. Thanks for sharing!

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