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Old 06-10-2013, 09:12 AM
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madbadgalaxyman (Robert)
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Join Date: Mar 2011
Location: Brisbane
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Quote:
Originally Posted by Suzy View Post
Robert you're amazing, thank you so much for all that fabulous information.
G'day Suzy,

I think that the "square" look of the bulge of NGC 6771 could be difficult to see visually, even in a dark sky, if these near infrared isophotes of this galaxy are anything to go by:

Click image for larger version

Name:	N6771_Ks Band isophotes(filled contours)__(Black Lines are MODEL)_[M.J. Williams & M.Bureau +__(.jpg
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In general, because isophotes are lines of equal surface brightness, the outlines of the inner isophotes of a galaxy are all that the visual observer tends to see, unless conditions are absolutely superb. So this galaxy will probably look boxy only if the observer can see to faint levels...... which is tough unless you have CCDs in the back of the eyes.

A better match for visual observations is the near infrared JHK (or J+H+K) images of galaxies from the 2MASS survey. While these are infrared images, they are very short exposures of modest angular resolution, so they are closer to what an observer might view in perfect dark sky conditions.
Here is the 2MASS image of NGC 6771:

Click image for larger version

Name:	N6771_J+H+K__(from 2MASS ).jpg
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By the way, thanks for the positive review of my posts; most flattering.

I also do find your posts to be interesting; because I have gradually moved progressively ever further away from having the perspective of a dedicated and enthusiastic visual observer ("kicking the 4 inch Apo onto the verandah from time to time, does not a serious visual observer make" - R.L. ). You are good at describing what you see at the eyepiece, and this makes for interesting reading.

I don't do much serious "looking" these days, instead navigating "data space" and the scientific literature and the vast databases of galaxy images. There are billions of unanalyzed observations out there, so I find it a more efficient use of my time to use "other peoples data". In any case, the Visual Galaxy Observation that was my bread and butter till the late 1990s required extremely dark and transparent skies; which meant long commutes with lots of heavy equipment to dark sky sites.....very time consuming.

Best regards,
Robert Lang
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