Category Archives: Photography Notebook

Photos from the Transit of Venus 2012

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One in a life-time opportunity, Threatening clouds, 96 F heat, 958 photographs.

After all the anticipation and wait, the day finally arrived. It was a once-in-a-lifetime opportunity as the next transit of Venus will happen in the Christmas of 2117. The weather decided to play menace, with threatening clouds and high heat. However, we weren’t just going to cringe and we went to the planned location with a camera and solar filter anyway. With the clouds showing up every now and then, the temperature at 96 F, and after 958 photos it was a tough day, but in the end it was well worth the pain. Here are few of the memorable photographs from the rarest of the celestial event of our time.

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Why can’t I use a ND filter to photograph the transit of Venus?

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Summary: Although you can probably use (a combination of) photographic neutral density (ND) filters to reduce the same amount of light as a typical solar filter (e.g. Baader solar filter), it is not SAFE for your eyes as it will not filter out the harmful Ultraviolet (UV) and infra-red (IR) light.

The table below shows the reduction in light intensity obtained by using different filters — both photographic ND filters of various Optical Density (OD) and the Baader solar filter. Just from the standpoint of intensity reduction, it is evident that one would require a 12-stop ND filter (OD 3.8) to match the Baader Photographic AstroSolar film. However, the following reasons undoubtedly makes the photographic Neutral Density filters unsuitable for solar photography: 

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How big will Venus be in my camera?

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Summary: Estimate the apparent image size of the solar disk and Venus in pixels for certain camera and simulate the ideal observed image.

Disclaimer:In this post, all discussions are based on the apparent image SIZE of the subjects — solar disk and Venus. I have not discussed any issue of resolving fine details, which is very important, and that shall be discussed in another post. Whether you will be able to capture the fine details such as the Granule, Lanes and Bright points on the solar spots, will depend on the ability to resolve fine details called the “spatial resolution”. The spatial resolution that you can achieve depend on the quality of the lens, quality of the sensor, pixel size of the sensor, the focus, presence (or absence) of vibration during the exposure, and lastly but perhaps the most limiting of all in the case of astro-photography is “seeing.” For today’s discussion we are not concerned with any of those, assuming our camera is the perfect camera and there is not air-turbulence.

You may have been wondering whether the focal length of the lens that you have will be “good enough” (see disclaimer) for taking photographs of the transit. The answer to that question really depends on what you want to photograph and the focal-length of the optics that you have at your disposal. While a 300 mm lens attached to a camera with APS-C sensor will suffice (not ideal) for taking pictures of the entire solar disk with Venus (see the simulated images below & some photographs of the Sun that I took during the past few days), you will need focal length beyond 2000 mm if you want to take frame-filling close up Venus in front of a partly visible solar disk.

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It’s only 7 more days and the weather Gods are being merciless

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Summary: What can you do if it is a cloudy day?

My attempt at practicing solar photography yesterday evening was a mega disaster! I had only taken 3 to 4 photographs, when the western sky was filled with thick layer of dark clouds (rain came later in the night). So I came back home feeling very gloomy. The photograph below pretty-much sums up my feelings, as well as the weather conditions of the day.

Sun behind the dark clouds. (Taken with a Canon EF 70-300mm lens on a Canon Rebel XT body)

What happens when you prepare for a long time for a certain photograph only to be disappointed to find the weather conditions are not the way you wish it were? For example, what would you do if you see clouds filling the sky on the afternoon of June 5 (in Northern America) or the morning of June 6 (in Europe)? Of course, I guess that you will not be very happy, especially if you had been waiting for this moment, waiting for a chance to see the last Venus transit of (most of) our lifetime?

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Recommendations on photographing the transit of Venus

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As the big day is approaching, I think it is important that we have a strategy in place in order to make the best of the situation with whatever constraints we have. Some of us may have the best equipment and some of us may not. Our (gadget) limitations must not stop us from trying what we want to do. In fact, sometimes we can get incredible results if we apply our knowledge and creativity to make use of the constraints. But understanding and preparation is a must. In this post I am going to outline a few general comments that I think we must keep in mind if we are seriously interested in photographing the transit of Venus. Since I do not have a telescope, and I will be photographing the transit of Venus using a D-SLR, my comments may not be applicable if you are going to use a telescope. These comments are generally from a standpoint of using a D-SLR to photograph the transit.

I will be more than happy to welcome anyone who is interested in writing a few tips on photographing the transit of Venus using a telescope.

Also, if you are going to use a point & shoot camera and a telescope to make photographs, here is a great resource.

[Don’t forget to see some of the practice shots that I took yesterday evening at the end of this page]

So, without further adieu, the following are my comments:

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