William Herschel discovered NGC 7635 = H IV-52 = h2235 on 3 Nov 1787 (sweep 773) and recorded "a bright star with F nebulosity; but I saw it too late to verify it, as in the north I cannot follow the stars. I rather suspect a deception." On 26 Nov 1788 (sweep 887) he added "a star about 9m with vF nebulosity of very little extent."

Hubble considered NGC 7635 a giant planetary nebula in his 1922 paper "A general study of diffuse galactic nebulae." Even in the early 1970's it was considered a possible or probable planetary (see ApJ, 167, 491-498 (1971)), though it was not included in Kohoutek's CGPN.

John Mallas coined the nickname "Bubble Nebula" in his Aug/Sep 1963 article "Visual Atlas of Planetary Nebulae-VI", published in the "Review of Popular Astronomy".

300/350mm - 13.1" (9/29/84): unusual appearance - surrounds a mag 8 star with a mag 7 star nearby to the SW. The nebulosity mostly appears north of the mag 8 star with a suspected dark lane to the north of this nebulosity. Very faint nebulosity appears close north of this lane. The main section hooks around the involved star to the east.

400/500mm - 17.5" the "Bubble Nebula" extends mainly north of the ionizing emission-line star, mag 8.7 BD+60°2522 (O6.5-type supergiant). Dark lanes are suspected to the north with very faint nebulosity just north of this gap. The main piece of nebulosity curves away from the involved star towards the east but appears brightest at the western edge near the bright star. Only the portion of the rim extending from north to east of the 3' diameter "Bubble" was seen (not the south edge). The view improved with both OIII and UHC filters but not dramatically. Located 6.5' NE of mag 7 HD 220057. M52 lies 35' NE.

Notes by Steve Gottlieb