Taking a picture of Mercury

Followers of my Twitter will know that on the 9th May, I managed to snap a picture of the Mercury transit across the Sun.

Picture of Mercury Transit

Can you see it? That tiny little dark pixel on the left hand side is not a dead pixel, that is Mercury. There is also a sunspot on the upper center.

Ever since getting a digital camera that I was able to have some degree of manual control over, I have had an interest in astronomical photography. When I got my DSLR, I knew I would be able to take this to the next level.

The picture was taken with a 300mm lens. This is hardly a powerful zoom but it is pretty reasonable. The picture above was zoomed in a bit on the computer, the actual image is below.

Zoomed out Picture of the Mercury Transit

As you can see, you can hardly see Mercury. It is even harder on the small screen of the camera in the bright sunshine. I found it particularly challenging to get the exposure just right and to try and focus it using auto-focus. Obviously, these would have been made easier with a lens of a bigger focal length - still, given the circumstances, I am pretty pleased with final image.

Solar Lens Filter

It goes without saying that the Sun is very bright. You should never look at the Sun through anything other than a proper solar filter. Even looking via the camera screen is not a good idea as you can permanently damage the sensor of the camera.

To be able to both look at the Sun safely and get rid of enough glare to see the features of the Sun you need to get a proper solar filter. The problem I found when searching online for one, is that a majority of them are made for telescopes, not for cameras. The few that were made for cameras were limited in size choice and expensive.

Luckily, trophygeek wrote a great tutorial on instructables on how to make your own one for a fraction of the cost. So I thought that I would give it a go.

Materials

You need 3 items.

A step-up ring adapter

Step-up ring adapter

This is usually used for fitting a filter onto your lens that is bigger than your lens. For this project, it will hold the solar filter for us. You need to make sure that is steps up from your current lens size. For example, my lens requires filters to be 58mm so I bought a 58-62mm one. It was the smallest 'step' for 58mm.

A UV Filter

UV Filter

To protect the outside of the solar paper, you need to get a lens filter of some kind. I chose to get a UV filter since we were pointing this at the Sun and doesn't effect the image too much. You must must make sure that the size of the filter is the size of the step-up ring. In my case, that meant getting a 62mm one.

Solar Paper

Solar paper

The most important part. This is what will actually make it safe to look at the Sun, so you must make sure that it is genuine. I bought this one from Thousand Oaks Optical. The 8"x8" should be enough as you only need a small circle out of it. But you can get more if you like in case you make a mistake. This took about 10 days to arrive as it is shipped from Israel. But it is worth the wait as you know you will be getting right stuff. It is surprisingly dark and just goes to show how bright the Sun really is as it is the only thing that you can see through it.

Putting it together

Once you have all of the materials, time to put it all together. I found this quite tricky - I have never been good at the arts and crafts type thing, so I was not able to make this look as perfect as trophygeek was able to.

First, I used a compass to draw around of the step-up ring onto the filter. This gives a guide to cut around. I did it towards the edge so that I could try again if I had to (and I did).

Scoring the filter
Filter scored

Next, trophygeek suggests using a sharp knife, like a Stanley knife, to carve around it. I struggled with this, so I just used a pair of scissors.

Cutting the filter

The tricky part with this stage is that once you have cut it, you have to continue to trim it until it fits inside the step up ring. This takes careful trial and erro. Trophygeek made it look easy but it was during this stage that it went wrong a few times and I had to start again. Be careful not to leave finger prints on the filter or to crease it.

Eventually, the filter fitted inside. At this stage you can now simply screw on the UV filter on the front and your lens is finished. As you can see below, it is not perfect, there is a tiny gap on one side. But I found that this did not let any light in.

Finished
Gap in the lens

I found that when screwing it onto the front of the solar filter can become creased if you go to maximum tightness, so I personally leave it a bit loose.

Camera Settings

Time to take some pictures! As I said earlier, I used a 300mm lens. This isn't the most powerful zoom in the world, but I have been able to capture some of the big sun-spots and in this case Mercury.

As for the settings. I had to do a lot of tweaking and trial and error. At first, I went for a lower shutter speed to stop more light (like when snapping the Moon, less light more features), however that didn't pick up anything other than a clean orange ball.

You actually want the shutter speed to be longer as I guess the filter cuts out a lot of the features. So it is a delicate balance: go too high and the Sun is too bright, too low and you do not see anything.

Sun and Mercury

This image was taken near the very start of transit, you can just about see Mercury right near the edge of the Sun on the left hand side (it is clearer when you zoom so I have cropped it), but you can clearly see the sunspot. This was taken with a shutter speed of 1/125 seconds and ISO 400.

The thing that I could do better is get a better zoom lens. 300mm is good and has picked up some detail, but I have had to zoom a bit more on the computer to see it clearly.

Hope you found some of this useful. I would be interested in hearing some of your tips when photographing the Sun or other celestial body (and maybe some pictures!) in the comments below. Thanks for reading!


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