File:Hubble First Light, First Released Image (STScI-1990-04a).png

English: This image is part of the first image taken with NASA's Hubble Space Telescope's (HST) Wide Field/Planetary Camera. All objects seen are stars within open cluster NGC 3532 in the Milky Way galaxy. Stars pictured in the HST frame are sharper than ground telescope images and well resolved, as shown by the double star at the top of the image. By avoiding the Earth's atmosphere, the HST gives sharper images and better resolution. In this early engineering picture, the HST images are roughly 50 percent sharper than the ground-based images.

Technical Details: The first image taken with the HST is intended to assist in focusing the telescope. The region observed is centered on the 8.2 magnitude star HD96755 in the open cluster NGC 3532, in the southern constellation Carina. Identical small subsections of the HST and ground-based image pictures were chosen to highlight the difference in resolution. The field shown is approximately 11 x 14 arcseconds in size and does not contain HD96755.

The HST image is a thirty-second exposure taken by the Wide Field/Planetary Camera. The picture shown was extracted from the area observed by the WF-3 OCD using the F555W broadband filter. The measured width of star profiles (FWFM) gives a good indication of the angular resolution. The FWFM of the stars in the HST picture is about 0.8 arcseconds, compared to 1.1 arcseconds for normal ground telescopes, which points out the remarkable increase in resolution of the HST even at this early stage of the focusing task.