[Content moved from http://photographingtransitofvenus.wordpress.com/]
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:
- Protect your eyes — Well, I really didn’t want to start off with this; however, it is THE most important recommendation. Use an appropriate solar filter. Also, if you are ever going to look into the Sun, please don’t EVER, look towards it directly, use a solar viewing goggle. They are really not expensive! I am going to be using one for focusing through my camera’s view finder. Look at this post where I have described how to make an solar filter from the Baader AstroSolar film. Also, avoid using a photographic neutral density filter in lieu of a solar filter for reasons explained in this post. If you don’t have a proper solar filter, at least use a “double-layered” Mylar emergency thermal blanket, which you can get from any outdoor activity stores and at Amazon.com
- Focus – Commonly recommended advice in the astronomy community is that one should try to focus on the Sun spot which are an excellent proxy for Venus. While you could do so if you have a long-range telescope or an extreme telephoto lens, it is not possible to “see” the solar spots using a medium telephoto lens. So the next best thing is to focus on the outer edge of the solar disk, which by the way is known as the solar limb.
- Exposure – Set the exposure yourself, manually. If you are going to be using short-telephoto lenses (between 300mm and 1000mm) the Sun will cover a small portion of the sensor (depending on the focal length), a large portion of the image will be “dark.” If you leave the auto-exposure on, then it will overexpose the photograph. So, please set the exposure mode to manual, and set your exposure using the histogram and/or by looking at few of trial photographs (chimping). Also, note that the exact exposure will depend on the time of the day and weather conditions. If you use the histogram, make sure that the second peak (corresponding to the sun’s bright image) of the bi-modal (two-peaked) histogram is about 80% to 90% towards the right, but still “inside” the histogram plot.
- Take multiple shots at different exposures — In photography community this is known as “bracketing.” Try to bracket by about one stop above or below the medium grey. [Note: Multi-exposure may not be very important from the standpoint of the transit of Venus photography as I assume you will mostly be zooming in as much as possible and the exposure difference between the sky and the sun is too huge to be captured even using exposure bracketing.]
- Take multiple shots anyway — this is very important! I think that this is more important than the previous point if you are really good at setting the “correct” exposure anyways. There are a lot of things that you cannot control such as the wind blowing into your camera and the ever-changing atmospheric turbulence. So even if your focus and exposure are perfect, you might sill end up getting lots of “less-than-tack-sharp” images. One way to circumvent this problem is play the game of probability — If you take enough pictures, you may end up with lots of blurry images; but there will surely be some that will be “perfect”. This is not silly, really! Serious astronomers do something very very similar, and it is called “Lucky imaging.” Also, if you take a sequence of images that are very “close” to each other in time, you can combine the image stack in some software such as RegiStax to get a “better” image.
- Use fast shutter speeds — If you are taking photographs of the Sun, it is most likely that you have the shutter speeds set faster than 1/1000 of a second. However, for any reason such as partial cloud cover, or near the Sun set, etc., your may have to reduce the shutter speed. Make sure that you are at least above 1/250 of a second. Otherwise, you might end up with a some amount of blur in your images. This is because the longer the exposure time, the more will be the apparent effect of the atmospheric turbulence.
- Use mirror-lockup– If your camera allows mirror-lockup, then use it anyway. This will prevent blurring from vibration which are more apparent in telephoto shots.
- Remote trigger — Use a remote trigger or a cable release in order to avoid vibrating the camera when you push the trigger.
- Tripod – I also assume that you have a study tripod. When I was starting out in photography, this is one of the first things I learnt!
On planning and preparation:
- Think about the type of photographs you are going to make. Here are just a few possibilities:
- Wide angle shot of the transit with surrounding object in the foreground.
- Zoomed-in photo of the Venus in front of the Sun at the 5 critical positions — 4 contacts and the mid-transit.
- Time-lapse video/animation of the transit.
- A single composite image of the transit showing Venus at different positions.
- See this post to get an idea about the image-size of the Sun and Venus in your particular camera-body-and-lens combination.
- Think about what you are going to photograph — the black drop effect, the bright ring around Venus (called an aureole) at the time of the ingress, etc. This mental preparation will get you up and ready for the task.
- Note that although the entire event is for about 6 hours and 40 minutes, you might see only “part” of the event based on your location. Also, the first and the last 18 minutes are the most interesting because you may see the black drop effect and the aureole during those times. So, use some of the tools mentioned in the Map & Timing section to pre-plan your shoot.
- GPS — If you have a GPS and you are planning to submit your photographs of the transit of Venus to some organization who can use the data for scientific study, please synchronize your GPS’s clock, the camera’s clock and make sure that the time readings are accurate.
- Batteries and memory card — This may sound silly, but oh boy! I have kicked my self several times in the field when I took out my camera to shoot something really interesting only to realize that I left my memory card inside card reader attached to my computer, or I forgot to replace the batteries that are about to die.
- Chimping — Chimping is a good thing, and I am sure we are going to be doing a lot of them especially to make sure that we aren’t over exposing the Sun. But also be aware of what is going on, else you might regret when you come to realize that you just missed the plane (or something interesting) moving in front of the Sun!
Lastly, I suggest that you practice at least a couple of times before 5/6th June if you are really serious.
I have used my Canon EF 70-300mm IS USM lens attached with a Canon Rebel XT body to take these photographs (they have been cropped). I also attached a solar filter that I made in front of the lens.
[This content was originally posted by me at http://photographingtransitofvenus.wordpress.com/, a blog dedicated to the 2012 transit of Venus]