Edgar Degas would love Washington, D.C., right now, for the place is dancing. The Joffrey Ballet has just been and gone. The American Ballet Theatre is in town until Jan. 6, and the Dance Theatre of Harlem is due in February. These are the kinds of performances that Degas went to religiously. They are the kind of art of which his art was made. Although dance is linked with the name of Degas in the popular imagination, few people realize that half of this Impressionist's mature work dealt with dance subjects - some 1,500 known pieces.
Degas is a graceful partner in Washington's current dance fest, for the National Gallery of Art is host, through March 6, of an exhibition entitled ''Degas: The Dancers.'' The exhibition commemorates the 150th anniversary of the artist's birth, and according to J. Carter Brown, gallery director, ''This is the first time (Degas's) objects all interrelated with dance are shown together.''
The exhibit was painstakingly pulled together over a three-year period by George Shackleford, curator of The Museum of Fine Arts in Houston. It is small - just 58 pieces. But it is a jewel. Each piece is there on purpose and helps accomplish Shackleford's goals: to present ''the broad range of Degas's treatments of ballet subjects . . . in every medium,'' and to reveal ''the interrelationships between so-called preparatory works and final realizations.''
Some critics complain that important works are missing in this show. But clearly Mr. Shackleford was not aiming for a vast retrospective. ''My point,'' he says, ''was to bring together selected objects in a context that teaches and gives pleasure.'' What the show teaches is that Degas was passionate about dance , and that the crux of his work method was to expand his insight and artistry through repetition - through returning to the same subject again and again. Degas called this ''a collaboration between imagination and memory,'' and the exhibit skillfully re-creates for the viewer this experience of seeing something familiar with a fresh perspective: a dancer adjusts her shoulder strap in one work after another; in charcoal, in pastel, and in oil a ballerina stretches to scratch her back; and many times we see that determined young dance student, sketched or sculptured with her feet in fourth position and her hands clasped behind her spine. To walk through this particular collection of related works is to discover that Degas was a poetic draftsman who drew from life, then in the course of years studied and redrew his own drawings, searching for essence. ''Art does not expand,'' he wrote, ''It distills itself.'' The show makes this point vividly.
The exhibit presents Degas's work in five adjoining galleries - small intimate spaces that do not overpower the art. Each room centers on a theme that offers particular insight into Degas the man and artist. Room 1, the ''Opera Ballet,'' introduces us to the splendid entertainment that was the height of 19 th-century Parisian pastime. As a subscriber to one of the three weekly opera performances, Degas had free run of the theater. Looking at the works on display here, it is quickly evident that Degas often drew from these privileged backstage positions.
In this first gallery hangs Degas's 1868 oil ''Orchestra of the Opera,'' the first of his paintings in which ballet dancers appear. The work is actually a portrait of the artist's friend Desire Dihau, a bassoonist in the orchestra of the Paris Opera House. Compared with Dihau and his cohorts, the dancers are somewhat incidental in this work, a headless sweep of pastel tulle along the upper margins of the painting.
Four years later, Degas created ''Musicians of the Orchestra.'' But something about them must have caught Degas's imagination. He ultimately affixed a seven-inch strip to the top of the work and painted in the full figures of the dancers. The addition, says Shackleford, marks ''an important step in the development of Degas dance pictures.''
The second gallery is called ''The Master of the Dance,'' and takes us behind the scenes of the Opera Ballet. Here hangs Degas's ''The Dance Class,'' announcing the most enduring and explored of Degas's subjects: ballerinas in practice. Ultimately he was more drawn to the stoic beauty of a dancer struggling to obtain grace, than to smooth grace itself.
This is nowhere more evident than in the third room, entitled ''A Way of Seeing Form.'' Here stands ''The Fourteen-Year-Old Dancer,'' the archetype of a charmingly awkward young ballet student. As far as the public was concerned, this statuette, now the most renowned and perhaps most treasured of Degas's works, was just too true to be good.
The figure now on exhibit at the National Gallery is a bronze replica of the original wax sculpture. On the walls surrounding it hang a series of charcoal, pastel, and pencil drawings of a young dancer in fourth position. The sculpture and most of the drawings are modeled after Belgian born Marie van Goethem, a dance student (or ''rat'' as they were called) at the Paris Ballet School. In Shackleford's words, ''The drawings served not only as models in the creation of the sculpture but were also the genesis of the sculptural idea.''
While the public was embittered by the statuette's lack of elegance, Degas was deeply touched by the intensity with which girls like Marie pursued their craft. In his sonnet about a young dancer, Degas wishes her fame, then adds, ''But for my well-known taste - keep her firm on her feet/To hold fast in the palace to the race of her street.''
In the last two rooms of the exhibit, the fact that Degas hones his art through treating old subjects in ever new ways is driven home. His habit of repainting pictures is vividly displayed in the fourth room, where we see ''suites'' of related works - oil paintings that he traced, then reworked in pastel, charcoal, or oil. ''It is necessary to do a subject ten times, a hundred times. Nothing in art must seem an accident,'' he wrote in 1886.
Twenty years later, he felt the same way, only more so. In the final room, ''The Last Dancers,'' we see pastel renderings full of light. Toward the end of his art career, Degas's eyes were dimming. He worked almost exclusively in pastel and relied all the more on his own earlier work for inspiration, for reference. He reached back to his older pieces as if to say, ''I saw, but did I understand?'' Then, like changing lights, his pastels transformed the familiar dancers.
Whether drawing the dancers from backstage or from a back collection of his own works, Degas carried images of them to the end of his life. To a cherished friend of his old age he wrote, ''The dancers have sewn (my heart) up in a sack of pink satin, pink satin a little bit worn, like their dancing slippers.''