**Table 10:** Estimates of the diffuse dust content in the Tau(V) scale defined by models in Witt et al. (1992, Wal92), using the correlations $\Delta _{VK}-\Delta _{UB}$ , $\Delta _{VJ}-\Delta _{UB}$ , $\Delta _{VK}-\Delta _{BV}$ , and $\Delta _{VJ}-\Delta _{BV}$ (see Sect. 4.2). Doubtfull cases are noted with a colon.
NGC	n	$\tau_V$	$\sigma$	Notes
1052	3	0.7	0.5	-
1404	3	0.6:	0.5	-
1537	1	2.0:	0.7	noUB
1549	3	1.3	0.3	-
2768	3	1.0	0.6	-
2974	3	2.1	0.4	-
2986	3	1.8:	0.6	smBV
3377	3	2.9	0.5	-
3608	3	1.8:	0.8	-
4125	3	2.9	0.7	-
4261	3	1.2	0.3	-
4278	3	1.8	0.4	-
4365	3	1.2	0.7	-
4589	1	2.3:	-	noUB
4660	1	>4.:	-	noUB, smBV

(1): NGC; (2) n number of usable correlations. This is generally 3 but may be reduced to 1 in a few cases; (3) $\tau_V$ : Tau(V) parameter; (4) $\sigma$ : standard deviation; (5) notes. Notes: noUB no U-B data; smBV $\Delta _{BV}$ too small for assumed $\tau_V$ .

Source LaTeX | All tables | In the text

	1 Introduction
	2 Collecting the gradients
	3 Properties of colour gradients
	4 Simulated datasets of colour gradients
	5 Concluding summary
	References