Hubble Heritage Archive: Information Center

The text and images in this section were originally published with the Hubble Heritage Project website (1998–2016), and reflect information available at that time.

Welcome to the Hubble Heritage Project Archived Information Center. This information has been designed to stimulate as well as educate the minds of Heritage visitors.

Here we investigate details about the image creation process, take a look at the people behind our project and explore resources for use by our audience.

Thanks for helping to make the Hubble Heritage Project such a success!

Table of Contents:

Our Projects

The Hubble Space Telescope (HST) is a research tool dedicated to scientific studies of nature. En route to illuminating the forces shaping our cosmos, HST has accumulated a cosmic zoo. The Hubble Heritage Project sees this instrument also as a tool for extending human vision, one that is capable of building a bridge between the endeavors of scientists and the public. By emphasizing compelling HST images distilled from scientific data, we hope to pique curiosity about our astrophysical understanding of the universe we all inhabit. 

The fact that not all members of the Hubble Heritage Project team have backgrounds in astronomy or are professional astrophysicists explains our atypical approach to constructing the pictures you’ll find at our website. Rather than being one individual’s expression, the images and website are visions produced by collaboration. Our process is similar to that of writing a scientific paper, or doing an experiment, with several contributors. In other words, as well as doing specified tasks, each member participates in directing the image composition, color selection, and other aspects. Participation from former team members and support from student interns has aided in the overall success of our project.

Additionally, our astronomical background influences which image processing techniques we employ and our aesthetic decisions. For example, astronomical detectors are much more sensitive than the human eye. So we’ve decided that our final images should not be restricted to the scope of the human visual perception, either in brightness or in spectral range. In most cases, color assignments and brightness contrasts which emphasize subtle structures, as well as physical processes which generate delicate light effects, will take precedence over attaining, say, natural color.

The original source material for the Hubble Heritage Project images is HST data obtained in 2 ways. Primarily we mine the rich HST public archive of exposures that has been accumulating for a decade. Since HST is a research instrument, many of the most visually interesting objects, however, were never selected for study and therefore are missing from this archive. Additionally the favorites that have been scientific targets often lack HST exposures across a color range or the telescope’s field of view only covers a small, unrecognizable portion of the form. Fortunately the Hubble Heritage Project has been granted a small amount of observing time. It is enough to satisfy the dual purpose of obtaining scientifically useful data and generating visually intriguing images of a few objects. A few astronomers have been guest collaborators, helping us acquire some data. As well visitors to this website have been invited to help select a target.

The home of the Hubble Heritage Project is Space Telescope Science Institute in Baltimore MD, which is run by the Association of Universities for Research in Astronomy for NASA. The Hubble Heritage Team wishes to thank the many members of the STScI Office of Public Outreach News and Online Outreach Teams, and the STScI AVL lab. A special thanks goes to our many interns, program coordinators and other contributors.

Our Images

Color Composition

Illustration Credit: Stuart Robbins (CWRU)
Illustration Concept Jayanne English (U. Manitoba)

How Heritage Images were made from HST Data

The Hubble Heritage Project team sees the Hubble Space Telescope, in addition to being a research instrument, as a tool for extending human vision. The detectors on this space observatory are much more sensitive than the human eye. For example, they capture radiation with energies in the electromagnetic (EM) spectrum beyond the human visual range, as well as light that is fainter than we can see. The challenge is to convert these remarkably extended data into visual images that convey the knowledge they’ve captured. 

The detectors measure how the radiation from the sky varies in lightness and darkness and so render only black and white images. However particular energies of radiation can be selected, before it reaches the detector, by inserting filters which pass only specific wavelengths of light; these filters work like colored glass. Sometimes a set of 3 filters are used which approximate the same wavelength range of the EM spectrum as covered by the human eye. Combining black and white images from these filters generate natural color images. The structures in this kind of image are similar to those we would see with our eyes if we could travel to the object of study.

Since there is a lot more than meets the eye in our astronomical subjects, data are usually collected using filters which isolate radiation emitted during astrophysical processes. Exposures made through these filters cannot be made into natural color images and they need to be assigned to the human visual range. If we retain the wavelength direction, as in this figure, then the ordering of filters is referred to as chromatic. If we select other orderings, also in the figure, the order is referred to as composite. Since this color assignment emphasizes subtle structures, as well as delicate light effects, it often takes precedence in Heritage images. 

In the final production of these images we also attempt to reveal detail usually hidden to the human eye. To do so we use methods that are either similar to astronomical techniques for studying observations or those that are standard in photography (for example, the digital equivalent of dodging and burning). When using these techniques we do our best to avoid generating features in the image that were not originally in the data. 

Each image is a vision produced by the collaboration of the Hubble Heritage team rather than the expression of a single individual.

Challenges We Face

The challenges of using the Hubble Space Telescope (HST) are numerous. The links below sometimes demonstrate the complexity of the instrument and sometimes simplify the story about creating images from HST exposures.

Scheduling the Hubble Space Telescope

Imagine using a telescope that is orbiting around the earth. How does one keep it pointed and steady without the earth for support? What happens if it points towards the moon or the sun? Who worries about these things and makes sure the telescope doesn’t get damaged? One of the people is the Program Coordinator (PC). The following notes were written by Mike Asbury who was PC for the observations of NGC 4650A.

Under normal circumstances, when an astronomer wants to use the Hubble Space Telescope (HST) to observe an object in the sky, he/she submits a proposal specifying what he/she would like to observe and why HST is needed for such an observation. This is submitted when the Space Telescope Science Institute (STScI) issues a ”Call for Proposals.” The astronomer is in “competition” with other astronomers for time on the telescope. Thus, it is important for the astronomer to stress the need for HST as opposed to ground-based observations. 

Once the proposal is submitted to STScI, a panel of scientists review the proposal to see if it truly warrants HST time and is technically feasible. If the proposal is accepted, the astronomer is notified and assigned two contact personnel at STScI. They are assigned a “Program Coordinator” and a “Contact Scientist.” The Program Coordinator (PC) is the person responsible for the overall scheduling of the observations. The Contact Scientist (CS) is responsible for the scientific aspects of the observation. 

After the astronomer is notified that his or her proposal has been accepted, the astronomer must submit a more concise version of the proposal, giving exact observing strategies. They do this through software that is provided to them from STScI. Once received by the PC, the proposal is processed to see when the observations can be performed. Many aspects can affect when an observation is performed. For instance, the astronomer might want to observe the object at only certain times of the year. Another aspect that affects scheduling is the fact that the object cannot be too close to the Sun or Moon, because those objects are so bright that they may damage the instruments on the telescope. Yet another aspect that affects scheduling is acquiring “guide stars.” These are stars that HST “lock” onto to avoid drifting when observing a target. If the target is in an area of the sky where there are few stars or an overabundance of stars, then acquiring guide stars may be a problem.

After all the scheduling issues are worked out, the CS does a review of the proposal to make sure all the scientific aspects of the observations will be achieved without harming the telescope. Once this is done, as it gets closer to the time that the observations are to be performed, the observations are put on a “flight calendar.” This is a week-long calendar filled with observations. Flight calendars are built three weeks in advance. After an observation is put on a flight calendar, there is nothing left for the PC, CS or astronomer to do other than sit back and wait for the data.

Pointing the Hubble Space Telescope

Imagine a square window on the universe. Wouldn’t it be easy to center your favorite astronomical object in that window? But what if you are using the Wide Field Planetary Camera 2 (WFPC2) detector? Because 1 of the 4 cameras has a different spatial resolution than the others, when all 4 images are scaled to match each other the field of view is “chevron” shaped. so the astronomers have to consider where to place their target in the field of view and how to rotate the telescope, orient the detector, so that all of the target falls in the field of view.

For example, using the image of NGC 253 on the Hubble Heritage website, compare HST’s field of view with that of a large ground-based telescope.

Want to see whether the HST field of view will cover your favorite astronomical object? Visit the archive . There you can search for data taken with WFPC2 and ask for the field of view to be plotted on the Digitized Sky Survey (DSS).

Final Image

The Raw Data of NGC 4650A, The Polar Ring Galaxy

This WFPC2 image of NGC 4650A was taken on April 9th, 1999. This image is an example of the raw data that comes directly from the telescope. No processing has been done to the image other than a format change so that it may be viewed via the web and a mosaicking so that all four chips appear as one image. 

F814W

Other background galaxies are visible in the field. The speckle pattern that appears as faint dots and dashes is actually produced by cosmic rays (high energy particles, usually protons or electrons) that hit our detector during the time that the telescope was collecting light from our source object. The galaxy was purposely placed lengthwise along chips 3 and 4 and just above the chip seam.

The Cleaned Data

Further processing of the data has include removal of cosmic rays and combining several pointings of the same filter into one single image of that filter.

The background galaxies and foreground stars now stand out clearly. Other features in the spiral arms are also clearly visible.

Differences Among Filters

Placing each filter next to each other and at approximately the same display level shows differences among the filters. Notice intensity changes in the stars, the center of the galaxy and fine structures in the spiral arms. The faint line appearing in each image is the chip seam between the two adjacent chips.

A Simple Color Image

A sample color image is created using all three filters. The filters are arranged chromatically such that the reddest filter F814 is assigned the color red, and likewise for the filters F606 (green) and F450 (blue). This draft color composite begins to tell the story of the object—this galaxy has two prominent features— a smooth reddish disk with older stars and a thin narrow polar ring that lies perpendicular to the disk. Where the two cross each other, the thick dust lane from the polar ring becomes reddened, and as well, it obscures star light from that portion of the disk behind it.

These are a few of the color renditions explored before selecting the color image of NGC 4650A for the release on May 6th.

Image Product

The Natural Resolution of the Heritage Images

In the case of Hubble Heritage images, larger files do not necessarily mean more detail. Hubble’s digital cameras produce images of fixed size (a maximum dimension of 1600 pixels as in the above image) that are not large by usual graphics standards. Therefore, we recommend copying and printing the “big” JPEG images available from the Heritage site. These are nearly the quality of the originals but will download much faster than a full-size, uncompressed image (see formats below). Although any image can be reproduced at larger reproduction sizes (for example poster size), individual pixels may be visible even in our uncompressed tiff images. An attempt to increase the resolution by increasing the number of pixels beyond the data’s original dimensions will degrade the image. So we match the dimensions of the image to the dimensions of the data rather than convert it to sizes standard for monitor wallpaper or posters.

Display Tips

Note that if you are running color-intensive applications, your computer will not use a full color table to display the image. Monitor wallpaper, and even the borders of windows steal colors from the available palette. Additionally, if your monitor is 8-bit your image might appear dotted or hatched. Often you can set your applications to compensate for these effects. 

Here’s an example for ensuring the UNIX XV application displays a reasonable texture and color rendition even on an 8-bit monitor. After loading the tiff or jpeg file into XV, open the XV control panel by clicking on the image with the right mouse button. In the “24/8 Bit” menu select the algorithm “Slow 24->8” and then select “8-bit mode.” Then in the “Display” menu select “Perfect Colors” or “Use Own Colormap.” A line near the bottom of the XV control panel will state whether or not you are now using all 256 available colors. 

Note that you may wish to dim the overhead lights and/or adjust the intensity and contrast settings of your monitor. As an aside, your browser permits you to select your own colors for hyperlinks and select your font size for the text. In the browser’s “Edit” menu, explore the “Preferences” control panel to customize your display.

Format and File Size

The information in the smaller format release images, which are roughly 400×500 pixels square, has been compressed so that they download more quickly. Their file size is usually under 120 kilobytes. The larger-sized images, 800×1000 pixels, range from 50–400 kilobytes. To check the file size of a specific image, move your cursor on top of the small version. A window will appear with the number of kilobytes of both that image and the big image it links to. 

The release images are presented in JPEG format which includes image file compression. This may slightly degrade the image from the original. Note that editing a JPEG and saving it as another JPEG will degrade the image further.

Downloading Images

You can use your browser functions to download these files to your disk. For example, in Netscape, go to the image you want, click the RIGHT mouse key and select “Save Image As…” Your browser should open a window asking for a directory on your computer and what you would like to name the file. Similarly, in Internet Explorer, click the RIGHT mouse button on the image and select “Save Image As…” Also note that the image may already be stored on your disk in the browser cache area, in which case you simply have to move it to another directory in order to save it.

Monitor Wallpaper

Convert downloaded images to monitor wallpaper using a standard graphics package such as GIMP or Adobe Photoshop. Alternatively, your computer software may provide specific applications for making desktop backgrounds. Note that replicating pixels in order to increase the resolution of the Heritage images to fill your monitor area may make them blurry. (See notes about the images natural resolution above.) This is why the Hubble Heritage Project does not provide wallpaper or screensavers. Check our copyright if you wish to use any image for a purpose other than for your own personal use.

Reprinting Images and Copyright 

Hubble Heritage images can be reproduced without requests for permission if the credit line is “NASA, ESA, and The Hubble Heritage Team (STScI/AURA).” (Hubble Heritage image credits are listed in each image’s description and links to descriptions are on the gallery page.) Please remember to properly credit or acknowledge the credit line in the reproduction of the image. However, if a credit line or a credit note beside the image includes other institutions and individuals, then these individuals must also be contacted for permission. More information on Copyright issues at STScI is available. 

Posters and Photographs

Posters and prints are produced by many outside vendors. Doing a net search on “Hubble Poster” will point you to a number of these sources. Among them, the Astronomical Society of the Pacific and Sky Publishing, have been known to sell posters and prints of Hubble images. 

For educators: There are some resources specifically designed for education available here at the Education Group at Space Telescope Science Institute and NASA provides educational resources through NASA CORE.

Awards

IMAGES from SCIENCE 2008

Hubble Heritage image of V838 Mon was selected to be in the 2008 Rochester Institute of Technology Images from Science 2 Gallery.

Electronics “Skins”

Hubble Heritage Carina Nebula image offered as Xbox, laptop and DS skins in 2008.

The Washington Times Newspaper

Arp 87 is prominently displayed on the front page of the October 31, 2007 edition of The Washington Times Newspaper.

American Astronomical Society Education Prize

On behalf of the Hubble Heritage Team, principle investigator Keith Noll wins the 2007 AAS Education Prize for his role in creating and leading the Hubble Heritage Project.

Time Magazine

Time image of the week for June 4–10, 2005.
LMC N 63A

Heritage Image Used on World Book Binding

The World Book at http://store.worldbook.com is using V838 Monocerotis as a choice for the binding on their 2005 Encyclopedia.

The 2003 Klumpke-Roberts Award of the Astronomical Society of the Pacific

The Astronomical Society of the Pacific has announced that the Hubble Heritage Team has been awarded the Klumpke-Roberts award for “outstanding contributions to the public understanding and appreciation of astronomy.”

UK Postage stamp showing NGC 6751 and MZ3

Three of four Hubble images selected to be part of the British “Across the Universe.”

Stamp Collection First date of issue: 24 September 2002

IMAGES from SCIENCE

“Organized to showcase photographs made in pursuit of science, IMAGES from SCIENCE welcomes pictures made with any imaging tools as the source, not only traditional photographic ones.”

The Heritage Team was invited to submit up to four images to to the Rochester Institute of Technology IMAGES from SCIENCE call for images. M51 and The Keyhole Nebula were selected and hung in a gallery exhibition along with 53 other images from various disciplines.

A reception for the final images and their creators was held in October 2002 at RIT. The show is now an international traveling exhibit.

MSNBC.com The Year in Pictures 2001

Two images from Hubble Heritage Project were selected as Readers’ Choice Images of the Year for 2001.

The US Postage stamp showing the Ring Nebula 

One of five Hubble images selected to be part of a commemorative series of postage stamps honoring astronomer Edwin P. Hubble.

First date of issue: 10 April 2000

2000 Infinity Award for Applied Photography

This award was given to Hubble Heritage team, by the International Center of Photography in New York, in recognition for our excellence in the field of photography and writing.

Critical Mass Award 

This general www award recognizes “critical” web sites that have useful content, good design and presentation, and that are easy to navigate.

Griffith Observatory STAR Award

This award was given to Hubble Heritage Web site in January 1999, only three months after our October 1998 debut, for promoting excellent public awareness of astronomy.

USATODAY.com Hot Site 

Hubble Heritage Web site was picked as a “hot site of the day” by the USA Today.com site in November 1998.


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