Two views of a small (4.6 by 6.2 arcsecond) star field in the galactic cluster NGC 188 containing two stars separated by 2.9 arcseconds in the sky. Located at a distance of about 5,000 light years, both stars are far too remote for their surfaces to be resolved, and are therefore suitable point sources for evaluating optical imaging quality.
The ground-based image on the left was obtained with the 2.5 meter Nordic Optical Telescope at the Observatorio del Roque de los Muchachos on the island of La Palma. At the time this exposure was taken the atmospheric conditions were such that the stellar images were blurred to an apparent diameter of 1.9 arcseconds - somewhat poorer than typically found at this excellent site.
The image on the right is a portion of one of the first images obtained with ESA's Faint Object Camera onboard the NASA Hubble Space Telescope. Even though this test image was taken with the telescope still not yet completely in focus, the dramatic improvement in spatial resolution provided by the Faint Object Camera is immediately apparent. The stellar images display a sharp core of diameter less than 0.1 arcseconds surrounded by an approximately 8 times larger diffuse "halo".
It is expected that as the focus of the Hubble Space Telescope is further improved in the coming weeks, the light currently present in the halo will be concentrated within the 0.1 arcsecond diameter core – thereby yielding still sharper images.
Credits
NASA, ESA, and STScI;Ground Image: Nordic Optical Telescope/Observatorio del Roque de los Muchachos /La Palma.
| About The Object | |
|---|---|
| Object Name | NGC 188 |
| R.A. Position | 00h 48m 25.99s |
| Dec. Position | 85° 15' 18.0" |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
