The signal-noise performance calculator is a good place to start, not least because it provides a summary of most of the free parameters which go into a proposal.

Detectors.  The CCD detectors available at the AAT  are detailed here.  The field of view and plate scales are shown below:
 

	AAT f/8  (9' max field of view)	AAT  f/15 (5' max field of view)
Tek 1Kx1K (24um pix)	0.594 "/pix	0.315 "/pix
MITLL2, MITLL3 2Kx4K (15um pix)	0.37 "/pix	0.20 "/pix
EEV2 2Kx4K (13.5um pix)	0.33 "/pix	0.18 "/pix

Resolution.  The key TTF  parameter is simply the resolving power you wish to use at a given wavelength. This figure illustrates the range of "safe" resolving powers across the optical window.

Choosing a bandpass. If you are unsure what bandpass to use, here are some useful tips.

• Are there other emission lines that you need to avoid, i.e. night sky lines, astrophysical lines ? If so, select your bandpass to be less than the separation of your chosen line from the neighbouring line. If the other line is a strong atmospheric feature, you should make the bandpass as narrow as possible. Play with the TTF calculator to see the effect of this.
• Are there atmospheric absorption troughs that you need to avoid (see below)? If so, select your band accordingly. Again, the TTF calculator will help here.
• Does your program have internal kinematic structure? If so, choose your band to encompass the internal dispersion. For extragalactic programmes, don't forget the (1+z) factor!
• Alternatively, you may want to see kinematic structure, in which case,  make the band as narrow as possible and step the TTF through the velocity range with maybe a few extra steps to see the continuum level. But of course, this is now a bigger TTF proposal.
• There is an instrumental effect to be aware of: the TTF field of view is far from monochromatic at the highest resolving powers. From centre to edge, there is a parabolic phase shift of 18A. Thus, at f/8, if the central wavelength is 6563A; at a radius of 2.5', thewavelength is 6557A; at a radius of 5', the wavelength is 6545A.  Bland & Tully (1989, AJ) show that the phase effect is (a) wavelength independent, and (b) a fundamental consequence of any form of constructive interference, including monolithic filters. To underline this further, a splendid comparison of the phase effect of the TTF vs. the phase effect of a monolithic 26A filter is given here.  The crucial point is that you can compensate completely with the former, and not at all with the latter.  If your objects extend over large fractions of the field, and your bandpass is 6A say, you will need three steps to compensate for the phase effect. Obviously, the effect is much less important for programmes which exploit broad bandpasses.

This is what the distribution in FSR looks like:

   FSR  =   40 * lambda /  R
 

If you do not block the neighbouring orders, you are susceptible to (a) spurious emission lines appearing within your bands, (b) an increased sky background by a factor of the blocking filter width divided by the FSR. In this event, you will need to degrade the SNR result derived from the calculator by the square root of this factor (assuming, as in most cases, that you are background limited).

The TTF produces 40 independent spectral bandpasses between neighbouring orders, i.e., FSR  =   40  * lambda / R   =   40  * bandpass. Therefore, try to ensure that your blocking filter is at least comparable to this value, if not narrower.

The available broadband blockers are illustrated here. The available intermediate band blockers are shown here.  The RTTF blockers are shown superimposed on the atmospheric airglow lines here.  Note that the intermediate blockers give you 20% more coverage to the blue with filter tilts, as shown here.  Text files for all of the transmission profiles can be retrieved from here.
 

Atmospheric features. Surveyors of arbitrary emission lines at arbitrary redshift routinely forget to check what the atmosphere is doing in the chosen bands.  This is particularly true of  those important off band exposures. The TTF calculator incorporates a detailed model of the atmosphere based on echelle observations at the AAT and at CTIO.  Spend some time trolling through these plots. Note that if you are working in narrow bands, you could end up observing in an atmospheric trough with near zero transmission!
 

Shuffle modes.  The web tool for making arbitrary shuffle files is not quite ready. There are different modes of shuffling one might consider. For now, since the shuffle overhead is essentially negligible in all modes, proceed with your SNR calculations for each of the individual bandpasses required.
 

• 2-shuffles.    The MITLL chips are sufficiently large to allow the full TAURUS field to be shuffled between two discrete frequencies.
• N-shuffles.    You can shuffle any number of frequencies (maximum 250) although the available CCD field begins to decrease like N/(2N-1). For example, a 3-shuffle partitions the 4K rows into 5 parts, and therefore the available field of view for each frequency is 5' x 10' (f/8).
• Straddle shuffles.    Emission line imaging is almost always performed in comparison to an off band image. Rather than observing a single off band in shuffle mode, it is possible to use any number of off bands around the on band, although the off bands are all imaged onto the same detector region. This method is well suited to removing slopes in the underlying continuum imposed by the sky, object or instrumental response.
• Broad-narrow shuffles.  Yet to be commissioned.
• Time series shuffles.     Yet to be commissioned.
• Unidirectional series read out. This method bypasses the N/(2N-1) limit and has been used to good effect by Margon & Deutsch  (1998; PASP, Aug.) and Tinney & Tolley (1998; MNRAS, in press).
• Arc line shuffles.      The instrument sequencer allows up to 250 shuffle steps; this is the current limit on the detail of an arc shuffle image. Since the TTF finesse is 40, Nyquist sampling means that we can map the spectral response fully through three consecutive orders of interference.
• Shutter open/close.    It is possible to open & close the shutter between each shuffle step, or to keep the shutter open for the entire exposure.