I've seen many such paintings that date from around this time period but hadn't seen this particular one. Chris was kind enough to make some enquiries as to the particulars of this painting and I thought I'd share them with you all.
"I confirm that the painting of The Baptism of Christ by Aert de
Gelder (1645-1727). Details of
the painting are as follows: Oil on canvas, 48.3 x 37.1 cm Given by
Lord Alwym Compton, Bishop of Ely, 1905 PROV: Marianne, Countess of
Alford, who bequeathed oit to the donor, 1888 Perhaps c. 1710.
NB : Other paintings showing Jesus Christ and UFO are very presents
in art until french revolution when the subject was began to be a
threat for Vatican (people before this time were uneducated and does
not interrested in art and paintings, except in the Renaissance time
were paintings and UFO are particularly presents) De Gelder as
Rembrandt had access to Vatican's paintings and litterature on Jesus
Christ. Ha had surely see other paintings with UFOs and decided to
do the same. Everyone knows that Vatican owns secret paintings and
litterature : all works that put the religion in dander were
censured. Other pics in arts and UFO in history on this french web
site :
http://marcogee.free.fr/ovni/histovni.html
Many thanks to Chris from UFORCE for allowing me to display the painting plus giving me the details about the painting.

Emmanuel (from france)