Hemisphere:  Northern  ·  Constellation: Andromeda (And)  ·  Contains:  Andromeda Galaxy  ·  M 110  ·  M 31  ·  M 32  ·  NGC 205  ·  NGC 221  ·  NGC 224  ·  The star 32And  ·  The star νAnd
How big is Andromeda really?, 



    
        

            Giuseppe Donatiello
How big is Andromeda really?
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How big is Andromeda really?

How big is Andromeda really?, 



    
        

            Giuseppe Donatiello
How big is Andromeda really?
Powered byPixInsight

How big is Andromeda really?

Equipment

Imaging Telescopes Or Lenses
Zenit TAIR-3S 300mm f/4.5
Mounts
Synta EQ5 · Avalon Instruments M-Zero Fast Reverse
Software
Auriga Imaging RegiStar 1.0.9 · Corel PaintShop Pro X8
Guiding Telescopes Or Lenses
(DIY) Achro 80/400

Acquisition details

Dates:
Aug. 20, 2020
Frames:
Integration:
0
Avg. Moon age:
1.57 days
Avg. Moon phase:
2.75%

Basic astrometry details

Astrometry.net job: 4000906

RA center: 00h43m05s.8

DEC center: +41°2454

Pixel scale: 2.947 arcsec/pixel

Orientation: 270.544 degrees

Field radius: 2.565 degrees

Resolution: 5187x3519

Locations: Home site, Oria, Brindisi, Italy; Piano Visitone - Pollino, Rotonda, Potenza, Italy

Data source: Traveller

Description

Same telephoto lens for M31 and the Moon, 300mm

Let's try to graphically dispel a cliché: "Andromeda as big as 6 full moons".

Meanwhile, if by "big" we mean the major axis of the galaxy, roughly this ratio is correct, as long as we specify that we are talking about the disk (yellow dashed ellipse).

If, on the other hand, we mean "extension", the estimate is completely wrong.

Just considering the regions normally photographable from a good dark site, the galaxy occupies a region in the sky at least as large as 17 full moons. Limited to the galactic disk, there are 12, as I reported some time ago. However, if we also consider the faintest regions that can be recorded in very deep images, the extension is not less than 25 full moons, without considering the complex of tidal structures.

Enough as proof?

Comments

Sky plot

Sky plot

Histogram

How big is Andromeda really?, 



    
        

            Giuseppe Donatiello