i have a canon rebel xt, what camera lens do i need to buy for taking pics of the moon?

4 Comments

1. fhotoace says:

   May 11, 2010 at 2:43 am

   You can use your 75-300 mm at 300 mm. The exposure is 1/ISO at f/16 so you can hand hold the shot. Be sure to have your focus set at infinity. You may want to bracket a little. Depending upon where you are in the world, f/16 may give you too much exposure

   At 300 mm the moon will still only fill about a fifth of the cameras frame, but if you shoot using RAW, you can crop a lot of the sky out later.

   I bought an adapter so I can mount my camera on my telescope … That worked the best.
2. mike1942f says:

   May 11, 2010 at 2:43 am

   Take a picture of the moon with your 75-300 on 300 – tripod mount, timed if you need it. Look at the image. If the moon is half the size of the frame then you need to have a 600 or 2x to fill the frame. If 1/3 of frame, the 900. If you want surface features, you may have to get a reflecting telescope.
3. Steve P says:

   May 11, 2010 at 2:43 am

   Ace is giving you the correct answer, but I will try to break it down so it will be somewhat easier for you to understand. You are going to have to spend a HUGE amount of money for a BIG telephoto lens if you want the moon to fill your entire frame. So instead of doing that, use your 75-300 at the max zoom and crop out the empty sky area from the photo. If you shoot in RAW, or at least at the highest JPEG setting, you should be able to do this with no problem.

   Exposure trips up most people when shooting the moon. Most people get nothing but a blown out blob of light. This is because they let the camera do auto exposure settings, and it trys to expose for the dark sky, thus totally blowing out the moon. You have to remember the moon is just reflecting sun light. So you set your exposure the same as shooting on a sunny day on Earth. A starting point is the "sunny 16" rule. Set your shutter speed to match your ISO and set aperture to f16. So, if you are using ISO of 200, you would start with a shutter speed of 1/200 at f16. Check your monitor and histogram to see your results, then adjust if needed with a faster or slower shutter speed and / or smaller or wider aperture.

   You do not necessarily need a tripod if you keep your shutter speed up above about 1/60.

   steve
4. cubfan745 says:

   May 11, 2010 at 2:43 am

   Lots of good answers already. A couple more notes.

   The Rebel uses a smaller senser than some of the other Canon camera (still a great camera, I use one), so your 75-300 will really look like a 120-480. That should be plenty, but a low cost way of bumping it even further is with a small teleconvertor. Don’t know that I would invest in one just for a few pictures, but if you need something longer (at a loss of speed and a bit of quality, depending on the convertor) that might be a relatively inexpensive way to go.

   You definitely need a tripod. The rule of thumb is you can hand hold a lens at 1/focal length. So normally with your 300 mm lens that would be a minimum shutter speed of 1/300. However, this cropped sensor thing comes into play again and you really need a hand held shutter speed of 1/300 * 1.6 (where 1.6 is the crop factor). So 1/480 again. With a tripod you can take pictures with a shutter speed of many seconds.

   As long as you are making the effort to set all this up, take dozens of photos. You may not be able to tell which worked until you get back to your computer. The points about the camera autoexposing and getting too bright a moon are absolutely right on. You need to shift to manual and vary the shutter speed over a wide range. Make sure you get that one photo you really want!