Cleopatra’s Eye

NGC 1535

Object type: Planetary Nebula
Apparent magnitude: +9.4
Apparent dimensions: 0.8 x 0.7 arc-mins
Constellation: Eridanus

“Cleopatra’s Eye” is a very apt name for this bewitching planetary nebula. It shows up blue in my telescope but some observers report it as being blue-green or even green.

The hot white dwarf at the centre is surrounded by two distinct shells of gas, both with distinct boundaries. The inner shell is a bright aqua colour with some dark gaps where the intense solar radiation from the star has begun clearing the gas in its vicinity. The outer shell is less bright with a darker blue hue and seems more circular than the inner shell.

I wasn’t really prepared for the beauty of this object. When it began to reveal itself on my laptop, all I could think was a word that I try not to over use: “Wow!”

Being a bit lost for word’s, here are some descriptions from four different books on my shelf:

• Hartung’s Astronomical Objects for Southern Telescopes (1995): “In an effective field of scattered stars this bright pale blue planetary nebula stands out conspicuously, being about 30″ across and well defined with fairly even light. No central star is visible….” 🤨 I’ll stop right there because the central star really is quite obvious!
• Planetary Nebulae by Martin Griffiths (2012): “a fabulous planetary in Eridanus, a real showpiece (winter) object…….. In a low power eyepiece it is a smooth blue-green shell…… The nebula is a little elliptical, with the axis lying NE/SW but no central condensation and no hint of a central star….” 🙄 What? You didn’t see it either?
• Burnham’s Celestial Handbook (1966): “Pale bluish disc with 11.5 mag central star”. That’s more like it! Robert Burnham saw it in 1966! 😃
• Night Sky Observer’s Guide by Kepple and Sanner (1998): “A nice diversion from all the galaxies in Eridanus – a real showpiece! NGC 1535 has a bright blue disc with a well concentrated central area surrounded by a misty outer ring. The central star is clearly visible.” 😁 Of course it is!

The central star certainly is visible. It’s hard to understand how two of these four distinguished authors could miss an obvious 11th magnitude star.

However, when I look at the (unattributed) image posted in Griffiths’ book, the surrounding star patterns are identical but the nebula itself is a well over-exposed blob, so if he used that to draw his conclusion, it is understandable.

I’ve made the same mistake myself in the past. When imaging planetary nebulae you need a lower exposure to bring out the detail, so take care not to over-expose the camera.

Image exposure: 60 minutes

Image field of view: estimated 7.5′ x 7.5′

Image date: 2021-12-02

Cosmic Focus Observatory

34° South

Above us only sky….

34

Telescope:	Meade LX-90 200mm Schmidt-Cassegrain ; 2000 mm f/l @ f/10 (deforked).
Optics:	Astronomik light pollution filter.
Mount & Guiding:	SkyWatcher EQ6-R Pro mount.
Imaging camera:	ZWO ASI 071 MC cooled.

^{Images © Roger Powell}
G’day!

🙃 I’m one of the founder members of Macarthur Astronomical Society