Slow query: select * order by XXX desc offset 10 limit 10

Hello,

I use PostgreSQL 8.4.7 on CentOS 6.0 / 64 bit machine
with Quad-Core AMD Opteron(tm) Processor 2352 and
16 GB RAM and use it for 1 PHP script - which selects
and displays data in jQuery DataTables (i.e. an
HTML-table which can be viewed page by page).

I select records from 1 view which unites 2 identical tables:

quincy=> \d quincyview
View "public.quincyview"
Column | Type | Modifiers
-------------+-----------------------------+-----------
qdatetime | timestamp without time zone |
id | character varying(20) |
name | character varying(20) |
category | character varying(120) |
appsversion | character varying(30) |
osversion | character varying(30) |
beta_prog | character varying(20) |
catinfo | character varying(120) |
details | character varying(50) |
devinfo | character varying(4000) |
email | character varying(320) |
emailid | character varying(16) |
imei | character varying(25) |
pin | character varying(12) |
formfactor | character varying(10) |
copied | timestamp without time zone |
View definition:
SELECT quincynoreset.qdatetime, quincynoreset.id,
quincynoreset.name, quincynoreset.category, quincynoreset.appsversion,
quincynoreset.osversion, quincynoreset.beta_prog,
quincynoreset.catinfo, quincynoreset.details, quincynoreset.devinfo,
quincynoreset.email, quincynoreset.emailid, quincynoreset.imei,
quincynoreset.pin, quincynoreset.formfactor, quincynoreset.copied
FROM quincynoreset
UNION
SELECT quincytrack.qdatetime, quincytrack.id,
quincytrack.name, quincytrack.category, quincytrack.appsversion,
quincytrack.osversion, quincytrack.beta_prog, quincytrack.catinfo,
quincytrack.details, quincytrack.devinfo, quincytrack.email,
quincytrack.emailid, quincytrack.imei, quincytrack.pin,
quincytrack.formfactor, quincytrack.copied
FROM quincytrack;

And here is 1 of the 2 tables (the other is same, except its name):

quincy=> \d quincytrack;
Table "public.quincytrack"
Column | Type | Modifiers
-------------+-----------------------------+---------------
appsversion | character varying(30) |
beta_prog | character varying(20) |
category | character varying(120) |
catinfo | character varying(120) |
details | character varying(50) |
devinfo | character varying(4000) |
emailid | character varying(16) |
email | character varying(320) |
formfactor | character varying(10) |
id | character varying(20) | not null
imei | character varying(25) |
name | character varying(20) |
osversion | character varying(30) |
pin | character varying(12) |
qdatetime | timestamp without time zone |
copied | timestamp without time zone | default now()
Indexes:
"quincytrack_pkey" PRIMARY KEY, btree (id)

There are around 1 mio records in the view:

quincy=> select count(*) from quincyview ;
count
--------
950476
(1 row)

My problem is, that select's are very slow and
using my script is no fun despite all the AJAX stuff -
which only tries to retrieve "offset X limit Y" records:

quincy=> explain select to_char(qdatetime, 'YYYY-MM-DD') as
QDATETIME,ID,NAME,CATEGORY,APPSVERSION,OSVERSION,DETAILS,DEVINFO from
quincyview where qdatetime <= now() order by QDATETIME desc offset 10
limit 10;

QUERY PLAN

----------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------------
----------------------------------------------
Limit (cost=600344.67..600344.70 rows=10 width=1172)
-> Sort (cost=600344.65..602859.16 rows=1005804 width=1172)
Sort Key: (to_char(quincyview.qdatetime, 'YYYY-MM-DD'::text))
-> Subquery Scan quincyview (cost=518261.35..573580.57
rows=1005804 width=1172)
-> Unique (cost=518261.35..561008.02 rows=1005804 width=252)
-> Sort (cost=518261.35..520775.86 rows=1005804
width=252)
Sort Key: quincynoreset.qdatetime,
quincynoreset.id, quincynoreset.name, quincynoreset.cate
gory, quincynoreset.appsversion, quincynoreset.osversion,
quincynoreset.beta_prog, quincynoreset.catinfo, quincynorese
t.details, quincynoreset.devinfo, quincynoreset.email,
quincynoreset.emailid, quincynoreset.imei, quincynoreset.pin, q
uincynoreset.formfactor, quincynoreset.copied
-> Append (cost=0.00..57003.60
rows=1005804 width=252)
-> Seq Scan on quincynoreset
(cost=0.00..40011.20 rows=863394 width=242)
Filter: (qdatetime <= now())
-> Seq Scan on quincytrack
(cost=0.00..6934.36 rows=142410 width=312)
Filter: (qdatetime <= now())

Does anybody please have an idea,
how to speed up my select statements?

Regards
Alex