<P> The effect of the mirror flaw on scientific observations depended on the particular observation--the core of the aberrated PSF was sharp enough to permit high - resolution observations of bright objects, and spectroscopy of point sources was only affected through a sensitivity loss . However, the loss of light to the large, out - of - focus halo severely reduced the usefulness of the telescope for faint objects or high - contrast imaging . This meant that nearly all of the cosmological programs were essentially impossible, since they required observation of exceptionally faint objects . NASA and the telescope became the butt of many jokes, and the project was popularly regarded as a white elephant . For instance, in the 1991 comedy The Naked Gun 21⁄2: The Smell of Fear, Hubble was pictured with Lusitania, the Hindenburg, and the Edsel . Nonetheless, during the first three years of the Hubble mission, before the optical corrections, the telescope still carried out a large number of productive observations of less demanding targets . The error was well characterized and stable, enabling astronomers to partially compensate for the defective mirror by using sophisticated image processing techniques such as deconvolution . </P> <P> A commission headed by Lew Allen, director of the Jet Propulsion Laboratory, was established to determine how the error could have arisen . The Allen Commission found that a reflective null corrector, a testing device used to achieve a properly shaped non-spherical mirror, had been incorrectly assembled--one lens was out of position by 1.3 mm (0.051 in). During the initial grinding and polishing of the mirror, Perkin - Elmer analyzed its surface with two conventional refractive null correctors . However, for the final manufacturing step (figuring), they switched to the custom - built reflective null corrector, designed explicitly to meet very strict tolerances . The incorrect assembly of the device resulted in the mirror being ground very precisely but to the wrong shape . A few final tests, using the conventional null correctors, correctly reported spherical aberration . But these results were dismissed, thus missing the opportunity to catch the error, because the reflective null corrector was considered more accurate . </P> <P> The commission blamed the failings primarily on Perkin - Elmer . Relations between NASA and the optics company had been severely strained during the telescope construction, due to frequent schedule slippage and cost overruns . NASA found that Perkin - Elmer did not review or supervise the mirror construction adequately, did not assign its best optical scientists to the project (as it had for the prototype), and in particular did not involve the optical designers in the construction and verification of the mirror . While the commission heavily criticized Perkin - Elmer for these managerial failings, NASA was also criticized for not picking up on the quality control shortcomings, such as relying totally on test results from a single instrument . </P> <P> The design of the telescope had always incorporated servicing missions, and astronomers immediately began to seek potential solutions to the problem that could be applied at the first servicing mission, scheduled for 1993 . While Kodak had ground a back - up mirror for Hubble, it would have been impossible to replace the mirror in orbit, and too expensive and time - consuming to bring the telescope back to Earth for a refit . Instead, the fact that the mirror had been ground so precisely to the wrong shape led to the design of new optical components with exactly the same error but in the opposite sense, to be added to the telescope at the servicing mission, effectively acting as "spectacles" to correct the spherical aberration . </P>

How much zoom does the hubble telescope have