Re: (IAAC) Eye vs CCD

At 10:39 AM 4/3/98 -0500, you wrote:
>Hello, Nick - hope your holiday was a good one!
>Please forgive my reposting your message to -announce without permission, by 
>the way... I expect public response will be quite positive though!
Thanks, that was great thanks.
>I think this would be an extremely interesting project to pursue... It really 
>would require some dedication however, as using any sort of light source 
>(including LEDs) in between observations might invalidate results.
I suspect that faint light suitable for drawing may not be such a problem as
the objective is to test the ability of the brain to detect faint contrast
by accumulating information about the object over a prolonged period of
observation rather than to test ultimate dark adaption or sensitivity. There
will anyway be a limit for faintest objects set in most skies by sky
brightness. In my skies you can just about read a newspaper headline.
My theory based on my recent observing experiences with the comet
observations is that the increase in detail I see is due to my visual cortex
accumulating information about the object over the observing period until a
concious perception of items of detail is achieved. This is the process
aided by procedures to enhance contrast perception such as tube wobbling
(scanning the image over the retina) and averted vision. It would very
loosely be analogous to stacking CCD images to see more details.
>In compensation though, spending a whole hour on the same deeply detailed 
>object may prove a breakthrough observing experience for many of us!
>As for objects, I might actually suggest a galaxy field, if the experiment is 
>to be performed in Spring or Fall: the advantage would be several objects in 
>the same FOV, revealing a wide range of details; also a fainter group might 
>still represent a challenge after an hour. In early Summer sky, Abell 2151 in 
>Hercules might be suitable for a test with a larger instrument.

I have some problems with Hercules because of our bright summer skies when
it is nearest the zenith but it could be feasible. If you have it handy,
what is  RA/Dec of Abell 2151?or is there an accesible list of Abell objects?

>At the opposite extreme (and perhaps more humane for an hour-long observing 
>run!), would be an extremely bright object, such as M8, M31, or M17. Logging 
>the details of each observation might prove the hardest part of the experiment 
>however: not everyone is as skilled at sketching as you! (would that I were)
They could be good depending on scope apeture. If too much detail visible
quickly  it would be difficult to record the information in time for the
shorter observation periods. I found the omega nebula a good object to draw,
M51 would be another good test object.
>Also, it must be near 
>impossible to sketch at the eyepiece without any light source. Perhaps a 
>standard verbal logging scheme could be adopted for tape recording?
A tape recorder is very valuable. I do rough sketches in dim light and
supplement them with recordings.
Another useful accessory is a hole in the clouds, sadly mine hole in cloud
kit has not been working for at least three weeks. I hope the next dark moon
period is better as it marks the end of my observing season till mid August.
Nick Martin, Bonnyton House, By Ayr, Ayrshire, Scotland, U.K.
Latitude 55 24'55" Longitude 4 26'00".