SIGNAL calculates the number of object and sky photons which will be detected during an imaging or spectroscopic exposure of a point or extended source with one of the common-user instruments of the Isaac Newton Group of Telescopes.

If bandwidth, extinction and sky brightness are left set at zero, SIGNAL assumes sensible defaults (click on parameter name for details). A UBVRI sky-brightness calculator is available.

For details of the assumptions made by SIGNAL, or to access the code, please see the SIGNAL help page, or click on a parameter name above (NB the help page may open in a separate tab).

This is version 14.5 of SIGNAL. Last Updated: 6 May 2014.

Instrument	Instrument: WHT ISIS WHT ACAM imaging WHT ACAM spectroscopy WHT prime-focus imaging WHT AF2 (small fibres) WHT NAOMI/INGRID INT wide-field camera INT IDS 235 camera Detector: EEV12 2048*4100 (for ISIS) RED+ 2048*4096 (for ISIS, IDS) QUCAM2/3 1024*1024 (for ISIS) AUXCAM 2048*2048 (for ACAM) RED+4 4096*4112 (for AF2, PF) WHTWFC 4096*4096 (for AF2, PF) INGRID 1024*1024 (for INGRID) INTWFC 2048*4100 (for INTWFC) EEV10a 2048*4096 (for IDS) Marconi 2148*4700 (backup for ISIS) TEK 1024*1024 (backup for various) Grating: NONE V400 (ACAM) R158R (ISIS) R316R (ISIS) R600R (ISIS) R1200R (ISIS) R158B (ISIS) R300B (ISIS) R600B (ISIS) R1200B (ISIS) H2400B (ISIS) R150V (IDS) R300V (IDS) R400B (IDS) R400V (IDS) R400R (IDS) R600R (IDS) R600IR (IDS) R632V (IDS) R813R (IDS) R900V (IDS) R1200U (IDS) R1200B (IDS) R1200V (IDS) R1200R (IDS) H1800V (IDS) H2400B (IDS) Band: U (3600A) B (4300A) V (5500A) R (6500A) I (8200A) Z (9500A) J (12500A) H (16700A) Ks (21600A) Bandwidth: Slit width, or fibre or lenslet diameter (arcsec): Exposure time (sec):
Object	Object: Point Extended Apparent magnitude: (/arcsec2 if extended) (to enter Jy, add a minus sign)
Sky	Seeing (FWHM in arcsec): Airmass: Extinction(mag/airmass): Sky brightness: (mag/arcsec2) (D, G or B for typical dark, grey or bright; or 0 for darkest sky on La Palma)