equipment damage - How do I photograph the sunset without damaging my camera?

This applies to the Sony NEX-5R, and the iPhone 5S. I want to shoot a timelapse of the sunset. The Sony manual says not to point it at the sun. Other questions on photo.SE agree with that advice, but say it's okay to shoot the setting sun.

So the question is, what counts as a setting sun? The last 1 hour before sunset? The last 30 minutes? Only when it's comfortable to look at the sun with the naked eye?

Google search says that the sun will set in my city at 6:03PM today, so when can I start my timelapse and be sure not to damage my equipment, either my NEX or my iPhone?

This is assuming I don't use an ND filter.

Answer

First off, let's talk about your eyes. Just because you feel no discomfort is no guarantee you are safe to look at the sun with your naked eye. From a NASA news release about safe solar viewing during an eclipse:

Damage to the eyes comes predominantly from invisible infrared wavelengths. The fact that the Sun appears dark in a filter or that you feel no discomfort does not guarantee that your eyes are safe.

If you really want to read about what happens when you stare at the sun too long, read this article from Sky and Telescope. An excerpt:

When longer wavelengths of visible and near-infrared radiation pass into the eye, they are absorbed by the dark pigment epithelium below the retina. The energy is converted into heat that can literally cook the exposed tissue. Photocoagulation destroys the rods and cones, leaving a permanently blind area in the retina. This thermal damage also occurs during extended exposure to blue and green light.

Both photochemical and thermal retinal injuries occur without the victim's knowledge, as there are no pain receptors in the retina, and the visual effects do not occur for at least several hours after the damage is done.

Now, for your cameras.

You would be much better off shooting a series of time lapse photos of the sun with a camera that protects the sensor from the energy in the light of the sun during the time between shots. Although I don't use either camera mentioned in your question, I'm assuming both use a form of Live View as a viewfinder and to compose shots.

What this means is that the sensor will be exposed to the same energy of the sun in the long intervals between shots as it will be exposed to during the short time the picture is actually taken. Here's what Stan Horaczek at PopPhoto.com has to say about it:

With a DSLR, the mirror gets between the sun and your sensor most of the time. It's only when the shutter is open that you get direct exposure and it's usually only for fractions of a second, so taking a few pictures of the sun shouldn't pose much of a problem. If you're looking through the viewfinder, though, it can certainly damage your eye, so don't linger too long.

Smaller cameras, like interchangeable-lens compacts and traditional compacts don't have the mirror for protection, though. Same thing goes for your DSLR if you have it set to liveview mode. Those cameras use the sensor to give you a preview image, so if the sun is in the frame, it's being channeled through the lens and right at your chip. It's easier on your eyes, but a lot tougher on your gear. Leave it on long enough and you could easily cause things to overheat, especially if you're shooting on a day when it's already hot out.