No (although, depending on the questions being asked, image analysis may be preferred. In the case of genetic toxicology testing, it has been recommended to use image analysis – see Hartmann et al. (2003), Mutagenesis 18, 45-51).
As an alternative, you can use the visual scoring approach, assigning each comet to a class according to how developed the tail is. Conventionally, 5 classes are distinguished, from 0 (no visible tail) to 4 (almost all DNA in tail). [It turns out that the human eye and brain are good at categorising visual appearance – of various kinds – in up to 5 grades, but can’t cope well with more distinctions than that.]
A visual score is computed (for 100 comets) by giving each comet the value corresponding to its class, so that the total ranges between 0 and 400 arbitrary units. The correspondence between visual score and image analysis results (% tail DNA) has been determined. There is an excellent correlation between visual score and % tail DNA for different samples analysed by both methods. Visual scoring is fast.
Or you can download free image analysis programmes. If you decide to try such a programme, make sure that the counting rate is relatively high. It should not take more than 10 min to score 50 comets, preferably less. The cost of counting time should not be forgotten.
"FAQ by Andrew Collins, Gunnar Brunborg and Jonas Nygren, 2006, NewGeneris FP7-project"