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NGC 457

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open cluster
NGC 457 (catalog)
C 13Cr 12Mel 7OCL 321Raab 3Lund 43


Position (epoch J2000)[1]
Constellation Cassiopeia
Position Ra 01:19:32.6
Dec +58:17:27
DSS images

10' · 20' · 30' · 45' ·

Appearance[1]
NGC 457 by André Hartmann.jpg
Photo by André Hartmann, 150/2250 Coudé Refractor, FOV:34'x23', 4 September 2012, Berlin Archenhold Observatory
NGC 457 by Vedran Vrhovac.jpg
Sketch by Vedran Vrhovac, 200/1200 Dobson, 80, 15mm WA, FOV:50 ', 18 August 2006, LM: 5.7
Apparent mag. 6.4


Size 13 '


Class II 3 r
Stars
Dreyer's description  Cl B L pRi st 7 8 10


Other
Notes
List:Open clusters in Cassiopeia
Map: RA 1.5, DEC 56.25Edit this infobox

NGC 457 is an open cluster in Cassiopeia. It forms an asterism with a few neighboring stars.

Contents

[edit] How to find it

This cluster can be found 2° S of Ruchbah, next to 5.5-magmitude star Phi 1 Cas. The star itself doesn't belong to the cluster, but together with 7-magnitude Phi 2 Cas (at PA 250), a bright star from the cluster to the W, make "eyes" of the "ET". Eyes are actualy a double star Phi Cas. Around 15' to the N are 2 stars that make the "shoes". Neither of those 2 stars are part of the cluster. The cluster is actually between "eyes" and "shoes".

Once you recognise the "eyes" and the "shoes", it is easy to see the rest of the ET's "body", providing you have enough aperture.

[edit] Appearance

This cluster is favorite to many observers because of its resemblence to ET, Owl, Kachina doll and propably some other things.

The "eyes" (Phi Cas pair) must be up in the FOV for the illusion to work best. Beside the "eyes", that are the brightest and most striking part of the asterism, there is no other stars in the "head".

A chain of stars stretches between "eyes" and "shoes", with 2 lateral chains extending from the "chest" and forming the arms or wings (if you see this an an owl). Asterism's arms are raised at a 45° angle above its shoulder, and a little bit longer than one would expect. Bright 8th magnitude red star is in east "hand", 3' E from the center.

The stars are of mags 7 and dimmer.

Some observers compared the shape of the cluster with constellations of Gemini [2] (because of 2 pairs of bright stars at the edges) or Cygnus[3] (because of cross-like appearence of the cluster itself).

It is not visible to the naked eye, so you need at least a good finder or small binoculars to find its brightest stars and small telscope to recognise it as an ET.

[edit] Binoculars and finders

In smaller finder, like 5x10, "eyes" and "shoes" are visible. The cluster looks like a moderately bright round glow, 10' in diameter, starting from "eyes" and stretching 2/3 of the way to the "shoes".[4]

In somewhat bigger finder, like 11X80, in very good conditions, together with "eyes" and "shoes", at least 8 stars in the area next to the "eyes" are visible[5].

In bad viewing conditions, in small binoculars (like 12x45), the cluster can be seen as a moderately bright round glow, 10' in diameter, starting from "eyes" and stretching 2/3 of the way to the "shoes". [4]. Sometimes, 2 or 3 stars can be discerned from this glow.[6]

[edit] Telescopes up to 4"

In 60 mm scope, like ETX60, it is hard to see anything reminiscent of the body. All you can see is a small cluster[7]. Since there are some stars of 7th magnitude, you should be able[Citation needed] to recognise the cluster at higher power.

[edit] In 4" telescopes

In 4" telescopes, at lower power (up to 20x), cluster appears well concentrated, with dozens of stars of various brightness, from quite bright to faint[8].

At moderate power (20x to 60x), around 30 stars can be seen, concentrated along a well defined central line, with stars of magnitude from 8.5 to 10+. Phi Cas double shows gold/violet-bluish color.[9].

At 22x, cluster can be recognised as "body", the way kids draw it, with the hands and legs made out of lines only. You can recognise asterism's raised arms.[10]. At 100x, nebulosity gives away to many stars. In moderate conditions, you can see "eyes", 2 hands with 3 stars in each, 2 legs and 2 shoes. On the "chest", where the "hands" connect, there are two groups of 3 to 4 *, each cramped within less than 1'[11].

[edit] In 6" telescopes

In 6" telescopes, at 48x, between 20 and 30 stars are visible[12].

[edit] In 8" telescopes

In 8" telescopes, about 40 stars with mags 6-12 are visible, concentrated towards the center. Few double stars can bee seen among those. In the center, V-shaped dark area can be seen. "Owl"-shape is easy to recognise[13]. Some have seen up to 50 stars with this aperture[14].

[edit] In telescopes above 8"

With 10" telescope, a few 'dark' red stars, can be seen.[2]

The 13" telescope provides the view of around 80 stars (at 100x) in the 15' cluster that is bright, large, rich and compressed. At higher power (150x), ne new stars are visible, and cluster appears to be fully resolved, without fuzzy background to the grouping[5].

[edit] Notes

Phi Cas is a double star.

Closest DSO is open cluster NGC 436. Other than that, closest DSO is open cluster M 103, around 3° to the NE.

[edit] References

[edit] Links

W.pngikipedia has an article on NGC 457

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