NGC 6790 - Planetary Nebula
NGC 6790 is a planetary nebula in the constellation Aquila and is located about 1.7° southwest of the star Delta Aql. The PN was discovered
in July 1882 by the US astronomer Edward Charles Pickering.
The distance to this PN is about 10,000 light years, which is quite a lot compared to many other planetary nebulae. Nevertheless, the apparent
brightness is given as 10.5mag, so that the PN, in combination with a high surface brightness, is easy to see even in smaller telescopes. However,
the large distance leads to a small apparent size of only 10" (arc seconds), which corresponds to a true diameter of 0.5 light years.
----------------------------------------------------------------------------------------------------------------------------------------------
In my 20" Dobsonian, NGC 6790 appears as a small but very bright nebulous disk and looks slightly greenish. The brightness of the nebula
envelope is not uniform, but increases towards the centre, first slowly, then faster and faster. In the centre there is something like a stellar
condensation, but I am not sure whether this is actually the central star.
