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Illusions in M104

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#1 IVM

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Posted 22 May 2013 - 10:05 PM

I was reviewing my notes and other materials about M104 and came up with the following list of visual features in this galaxy that I believe to be illusory:

1) The northern edge of the dust lane forms an obtuse angle rather than an arc. I haven't heard of others seeing this, though - maybe it is just me. The edge is not ideally circular in good photos, but the degree of straightness on either side of the nucleus that I perceive must be illusory.

2) Bright enhancements within the northern half, E and W of the central core. Nothing comparable can be seen in photos (including the specially scaled ones in the de Vaucouleurs Atlas). What is perceived visually must rather be similar to "arcs" next to the core that are often seen in elliptical galaxies - where it is certainly an illusion.

3) The glow south of the dust lane curves around the ends of the lane. Photos do show a halo enveloping the galaxy, but it is exceedingly faint. The glow we perceive is most likely illusory and due to the excessive contrast formed by the bright edge-on with the background sky: the eye-brain "pads" it to soften the transition.

4) Details in the dust lane. There are some in photographs that may conceivably be visible with really large scopes; I refer however to those "details" that are relatively easily seen. I see the dark lane as broken E and W of the nucleus at lower magnifications in my 16" but not at higher ones. Since these should be small, high-contrast features, they should be seen better at higher magnifications. I conclude that they are illusory.

In conclusion, M104's real beauty lies in its striking visual simplicity. By rights it should be a relatively plain-looking galaxy, but it is adorned with illusions.

What do you think?

#2 John K

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Posted 22 May 2013 - 10:36 PM

I had a chance to do a long study and sketch of this galaxy last spring.have I caught some of the details you were referring to? I found that the dust lane had a slight cure to it.although I find that I may have over emphasized it in my illustration.

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#3 Astrojensen

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Posted 23 May 2013 - 01:38 AM

John, that is the finest sketch of M104 I've ever seen.


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#4 IVM

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Posted 23 May 2013 - 02:09 PM

I understand, John, what you said about overemphasizing the curve. I have a sketch in my notebook (not a fine drawing like yours!) right next to the notes about how the lane edge was two straight segments instead of an arc. Still the sketch depicted an arc!

#5 hbanich

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Posted 23 May 2013 - 03:28 PM

You're right that we sometimes perceive illusions in the eyepiece but often photos don't tell the whole story either. A photo can be processed so it brings out various details in different proportions than their actual brightness. Although it's not often an option, the view through a substantially larger scope will give a more accurate eyeball view of what's there to see whether its real or an illusion.

Regardless, we see what we see and it's great fun to compare that to photos, especially if you've made a sketch. This often leads to more observing and sketching of the same object which more often than not will lead to seeing more and more with increasing certainty.

#6 IVM

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Posted 23 May 2013 - 10:41 PM

I agree that photos often don't tell the whole story. Coincidentally M104 seems to be a challenging object for photographic reproduction because of the bright bulge almost overlapping the sharp equatorial dust lane.






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