The triangle is known since ancient times, but it has changed its shape over the millenia. In 270 BC, 12 Trianguli marked the western corner of the then equilateral triangle – today γ Trianguli is one of the corner stars. The brightest star is β Trianguli (3.0m), while α Trianguli is only 3.4m bright. The inconspicuous constellation contains many galaxies, of which only M 33 is bright enough for binoculars.
The Pinwheel- or Triangulum-Galaxy M 33 is only 3.1 million light-years away and 5.7 to 6.3m bright. Nevertheless, it is not a simple object – with an area of 73 × 45 arcmin it has a very low surface brightness and requires a really dark sky. Since its center is brighter than the spiral arms, it appears in binoculars as a pale, about full Moon large patch of light. M 33 has a third of the luminosity of the Milky Way and a diameter of 40,000 light-years. Even if that makes it one of the smaller galaxies, it is the third largest member of the Local Group.
NGC 604 is an emission nebula in the northeastern spiral arm of the 3.1 million light-years distant galaxy M 33. It is ten times larger than the Orion Nebula and with a diameter of 1,000 light-years, the largest known HII region. In binoculars, it appears as a diffuse small star about 10 arc minutes northeast of the center of M 33. If you can use an UHC filter, it may be easier to recognize than the vast galaxy itself. Its apparent diameter is about two minutes of arc.