Omen reading, astrology, palmistry and other such things are considered "animal arts" and wrong livelihood for monks in DN 2 quoted below. In general, even for laypersons, this would be considered "animal arts", and therefore unskillful or unwholesome.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as: reading marks on the limbs [e.g., palmistry]; reading omens and
signs; interpreting celestial events [falling stars, comets];
interpreting dreams; reading features of the body [e.g., phrenology];
reading marks on cloth gnawed by mice; offering fire oblations,
oblations from a ladle, oblations of husks, rice powder, rice grains,
ghee, and oil; offering oblations from the mouth; offering
blood-sacrifices; making predictions based on the fingertips;
geomancy; making predictions for state officials; laying demons in a
cemetery; placing spells on spirits; earth-skills [divining water and
gems?]; snake-skills, poison-skills, scorpion-skills, rat-skills,
bird-skills, crow-skills; predicting life spans; giving protective
charms; casting horoscopes — he abstains from wrong livelihood, from
"animal" arts such as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as: determining lucky and unlucky gems, staffs, garments, swords,
arrows, bows, and other weapons; women, men, boys, girls, male slaves,
female slaves; elephants, horses, buffaloes, bulls, cows, goats, rams,
fowl, quails, lizards, rabbits, tortoises, and other animals — he
abstains from wrong livelihood, from "animal" arts such as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as [forecasting]: the rulers will march forth; the rulers will not
march forth; our rulers will attack, and their rulers will retreat;
their rulers will attack, and our rulers will retreat; there will be
triumph for our rulers and defeat for their rulers; there will be
triumph for their rulers and defeat for our rulers; thus there will be
triumph this one, defeat for that one — he abstains from wrong
livelihood, from "animal" arts such as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as [forecasting]: there will be a lunar eclipse; there will be a solar
eclipse; there will be an occultation of [a conjunction of the moon or
a planet with] an asterism; the sun and moon will be favorable; the
sun and moon will be unfavorable; the asterisms will be favorable; the
asterisms will be unfavorable; there will be a meteor shower; there
will be a flickering light on the horizon [an aurora?]; there will be
an earthquake; there will be thunder coming from dry clouds; there
will be a rising, a setting, a darkening, a brightening of the sun,
moon, and asterisms; such will be the result of the lunar eclipse ...
the rising, setting, darkening, brightening of the sun, moon, and
asterisms — he abstains from wrong livelihood, from "animal" arts such
as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as [forecasting]: there will be abundant rain; there will be a
drought; there will be plenty; there will be famine; there will be
rest and security; there will be danger; there will be disease; there
will be freedom from disease; or they earn their living by accounting,
counting, calculation, composing poetry, or teaching hedonistic arts
and doctrines [lokāyata] — he abstains from wrong livelihood, from
"animal" arts such as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as: calculating auspicious dates for marriages — both those in which
the bride is brought home and those in which she is sent out;
calculating auspicious dates for betrothals and divorces; for
collecting debts or making investments and loans; reciting charms to
make people attractive or unattractive; curing women who have
undergone miscarriages or abortions; reciting spells to bind a man's
tongue, to paralyze his jaws, to make him lose control over his hands,
or to bring on deafness; getting oracular answers to questions
addressed to a spirit in a mirror, in a young girl, or to a spirit
medium; worshipping the sun, worshipping the Great Brahmā, bringing
forth flames from the mouth, invoking the goddess of luck — he
abstains from wrong livelihood, from "animal" arts such as these.
"Whereas some contemplatives & brahmans, living off food given in
faith, maintain themselves by wrong livelihood, by such "animal" arts
as: promising gifts to deities in return for favors; fulfilling such
promises; demonology; reciting spells in earth houses [see earth
skills, above]; inducing virility and impotence; preparing sites for
construction; consecrating sites for construction; giving ceremonial
mouthwashes and ceremonial baths; offering sacrificial fires;
administering emetics, purges, purges from above, purges from below,
head-purges; ear-oil, eye-drops, treatments through the nose,
ointments, and counter-ointments; practicing eye-surgery [or:
extractive surgery], general surgery, pediatrics; administering
root-medicines and binding medicinal herbs — he abstains from wrong
livelihood, from "animal" arts such as these. This, too, is part of
his virtue."