For example, some x-ray binaries produce strong emission lines that vary on 0.1 Hz timescales. With a slit only 4 pixels wide, we can obtain 500 images in the emission line, interleaved with a further 500 images at a reference frequency. The reference frequency is a measure of the atmospheric stability during the time series. This can be used to average out either rapid variations in blocking filters or the underlying spectral continuum. While this is vastly less efficient than using a long-slit spectrograph, this is a fundamental requirement for establishing the parallelism of reflecting mirrors at few micron spacings.
Conventional methods are an order of magnitude slower.
More details can be found on other links at this web site. K. Taylor, have strongly supported the development of TTF . We are indebted to J.R. Barton for implementing the shuffle mode, to L.G. Waller for instrument sequencer hardware, to T.J. Farrell for control software, and to E.J. Penny and C. McCowage for TTF control hardware.