How to fetch values at regular hours?

Hello all!

I am logging my electricity meeter every five minute!

But the problem is that I would like to get values *just before* every hour
- like

select * from counter_log_view where name='CNT-3' and timestamp <
'2010-05-23 22:00:00' order by timestamp desc limit 1;
name | timestamp | count
-------+----------------------------+-------
CNT-3 | 2010-05-23 21:53:20.844422 | 69
(1 rad)

But I don't want to do a lot of selections and gather all the data in a
file.
Is there any better way to create the query so that I get the values just
before
every hour?

I would like to do;

freescada=> select * from counter_log_view where name='CNT-3' and timestamp
< '2010-05-23 18:00:00' order by timestamp desc limit 1;
name | timestamp | count
-------+---------------------------+-------
CNT-3 | 2010-05-23 17:53:18.58674 | 43
(1 rad)

freescada=> select * from counter_log_view where name='CNT-3' and timestamp
< '2010-05-23 19:00:00' order by timestamp desc limit 1;
name | timestamp | count
-------+----------------------------+-------
CNT-3 | 2010-05-23 18:53:19.151988 | 50
(1 rad)

freescada=> select * from counter_log_view where name='CNT-3' and timestamp
< '2010-05-23 20:00:00' order by timestamp desc limit 1;
name | timestamp | count
-------+----------------------------+-------
CNT-3 | 2010-05-23 19:53:19.683514 | 51
(1 rad)

In one query. Is this possible in *any* way?

--
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