by David Fenton Health correspondent, BBC South

But they are an important way of telling which hospitals are doing well - and which need to buck up their ideas.

Basically the best hospital trusts get three stars - the worst none. Most of course are somewhere in between.

Portsmouth NHS Trust has rocketed from no star to two stars

In Hampshire, Southampton and North Hampshire were three-star trusts, and the Isle of Wight a no star.

But the big success story was Portsmouth, which had laboured for two years without a single star and has now rocketed up to two-star status, mainly by hitting all its important targets on waiting lists.

This is where things get difficult.

Every trust which runs an acute hospital is given nine key targets to achieve over the year - these are things like reducing the waiting list for operations from 15 months to 12 months.

Making sure patients in Accident and Emergency are seen within 12 hours is another, as is making sure that the financial accounts are balanced at the end of the year.

Usually, those hospitals which fail to get a star fall down on one or more of these areas.

That does not mean they do not do good work in other areas but this is what the government considers important, and this is what they are judged by.

Big Brother

For a no star trust, the consequences can be fairly dramatic.

They do not lose any money, but they do get a very beady eye cast over them for the next year by the Department of Health.

That may sound innocuous but actually it can be quite an experience for managers and staff - who can feel they are working under the eye of Big Brother.

One chief executive I spoke to said that he could not even send out a press release without having it approved in advance - such are the penalties of failure.

But more importantly it can seriously hamper a hospital's attempts to recruit new staff.

Not whole picture

If you were a doctor, nurse or medical professional looking to move to the south coast - which hospitals would you think of applying to first? Probably not the no star trust.

Insiders say these league tables and star charts are useful, as far as they go, but there is a whiff of lies, damned lies and statistics about them.

In other words, they do not tell the whole picture.

Sometimes trusts can lose out on a star simply by amassing a few too many cancelled operations, and, as is always the case with these things, the media look to the worst and to the best and label hospitals successes or failures when the bigger picture is actually much more complicated.