Quote Originally Posted by polyglot View Post
The sun is so much stupidly brighter than the background that all you need is lots and lots of ND, perhaps in the form of a Baader solar filter foil. With such a foil on, you could expose all afternoon and have only the sun register on the image, hence the streaks.

Edit: the filter-factor on solar foil is about 100,000, which is over 16 stops.
Baader film was invented in 1999 or so. In 1978, mylar was your best bet though for photographic use only, smoked glass could be used (dangerous by eye due to UV). Glass filters came later, then Baader film. Many used welder's glass visually and the dangerous SUN filters sold with cheap telescopes.

You can get photographic Baader film (3) which isn't nearly as many stops so you can use shorter exposures than the visual stuff. You could use multiple layers of Baader film to really bring it down.