"The Beast" nails Pluto!

On Thursday, July 23, 2015 at 1:27:37 PM UTC-4, palsing wrote:

Actually, the color of the light is not as important as the dimness of the
light, although everyone I know uses red lights as their default.

edit

Ponder this graph for a while:

http://webvision.med.utah.edu/imageswv/KallDark7.jpg

On Thursday, July 23, 2015 at 4:52:41 AM UTC-6, Chris.B wrote:

Thanks for the interesting response.
The longer focus achromat should not need the minus violet filter.
So would help to minimise light loss.

Couldn't you most easily obtain a reversed image star map simply by using Ctrl+PrtSc?
Then reversing the image laterally in some free image handling software before any necessary cropping and printing black on white.
Though that does raise the spectre of having to use illumination to examine the star map in the presence of "The Beast."
Not ideal for pulling off observations on the absolute limit of visual perception.
I suppose I ought to ask: How do you sketch in the dark? Using red light?

I have software that can generate any kind of chart desired, including mirror reversed eyepiece views through the visual magnitude limits of any telescope I own. Yet, I don't make use of that software very often. It's even rarer for me to generate a printout. It's just my way ;-) I use the software primarily on the day after an observation/sketch to check to see which of Saturn's moons I recorded, etc. Doing things this way helps to keep me (more) honest!

For Pluto it seemed more convenient for me to just take out a magazine chart (I currently subscribe to two different astro magazines). That proved to be an error on The Beast's first Pluto attempt. I'm accustomed to U.T. dates and times on charts, but ended up (unknown to me at the time) using a chart that was calibrated for E.T. - in the 'local' evening. In effect, I was looking for Pluto at a location it wouldn't get to for another 48 hours! As a consequence, I failed to see the "dwarf" planet. I used a 90 degree correct-image diagonal (of previously tested and proven quality) to better match the chart while at the telescope.

Prior to the next observation (the one that started this thread) I checked my software and sketched a high-powered eyepiece field, as generated by the software, (omitting Pluto from the sketch, but noting Pluto's path through the field). That was a mirror-reversed sketch to match the view with the 99 percent reflective, 2-inch, 90 degree, mirror-reversed diagnonal I intended to use this time. But, once outside I forgot about the need to first acquire the desired field. I rushed back inside (using an adjustable red flashlight) and grabbed the magazine used earlier! The rest of the story has been related at the top of this thread.

As for sketching in the dark: I have my own forms that I use with a homemade illuminated clipboard (backlit via red LEDs whose brightness is controlled by a variable resistor). I use just enough light to see by. Sometimes I make use of the back-lighting feature. Other times I shine a variable intensity red light (from an astronomer's flashlight) onto the top surface of the paper. If I'm sketching a 'bright' solar system object I'll sometimes switch to a variable intensity white light (better for detecting subtle colors when going back to the eyepiece).

For the most challenging objects (B33 comes to mind) I memorize the eyepiece field and the object's location within it prior to setting up the telescope. Prior to going outside I wear red goggles inside. All inside lights are extinguished before going outside (I have no ouside lights!). I use only ambient starlight to see by while setting up the telescope! Upon seeing B33 (I was using an unfiltered 13cm apo) I committed to memory the object's size, position, orientation and appearance. Then I had little choice. I turned on a red light just barely bright enough to see marks on paper and added the object to the paper. Upon returning to the eyepiece B33 was gone! The dimmest red light was too bright! I had to wait several minutes before I could once more see B33 and make any additions or modifications to the sketch. The Excalibur "Horsehead" observation was made several years ago. I intend to (eventually) use B33 as a final test for The Beast!

Sketcher,
To sketch is to see.

On Thursday, July 23, 2015 at 10:39:04 AM UTC-7, wrote:
On Thursday, July 23, 2015 at 1:27:37 PM UTC-4, palsing wrote:

Actually, the color of the light is not as important as the dimness of the
light, although everyone I know uses red lights as their default.

edit

Ponder this graph for a while:

http://webvision.med.utah.edu/imageswv/KallDark7.jpg

What about it? That test was performed with subjects dark adapted with light at 2000 Ml (2 lumens) whereas in the links I provided it was suggested that a brightness of half that amount was preferred.

I still maintain that, if dim enough, any color of flashlight can be used to read a star chart and have minimal affect on your night vision. I can find lots and lots of acceptable links that claim the same thing. If you can tell what color the light is, it is too bright. At about 1 lumen, all colors are untinted.

Almost all amateur astronomers, myself included, use red lights for several good reasons, mostly because that's what everyone else uses and also because that is practically the only color you can buy that has the ability to be sufficiently dimmed. Just try and buy a white or green or purple light that can be dimmed to a single lumen, and good luck with that!

I've done all those things at one time or another. Once I designed and built a pair of goggles to use while comet hunting (several years ago). The goggles were designed in such a way that an insert could be used to cover either eye while the other side had an opening large enough to accomodate the large, wide-field eyepiece I was using. From time to time I would switch eyes for eyepiece use.

Memorizing star fields is one of my preferred methods for observing with 20x80 binoculars (handheld). Inside (with a dim red light) I check on the locations for the next few targets, commit to short-term memory their locations and go out for a quick look with the binoculars. Then I come back in and repeat the process for the next set of objects - repeated over and over again until I feel like quiting.

Sketcher,
To sketch is to see.

On Thursday, July 23, 2015 at 9:59:36 AM UTC-6, wrote:

A correctly designed red light should work, however a patch for the observing eye can be added to the configuration. It might be possible to simply memorize the field, given adequate preparation.

On Thursday, July 23, 2015 at 11:08:16 AM UTC-6, Chris L Peterson wrote:

Another option is a dim white light, and a white pencil on black
paper.

That's an interesting option that I've never seriously considered. The materials would not be available for me locally, but the next time I go to 'the city' I can *try* to find time to shop around.

A strong plus for white on black is that less light gets reflected back to the eye. Only the pencil marks would be illuminated! On the minus side: I would probably still have to use a red light. White lights tend to shine too brightly.

Sketcher,
To sketch is to see.

Clearly color doesn't matter. Just consider the light one sees from the night sky itself!

OTOH, red goggles make a dramatic impact as an aid in dark adaptation while in a (bright) white-light environment. You even see them used by submariners (actors) in old WWII movies prior to surfacing at night. Therein may lie a prime reason that red has become the dominate color for astronomical eyes.

Sketcher,
To sketch is to see.

On Thursday, July 23, 2015 at 11:27:37 AM UTC-6, palsing wrote:

Actually, the color of the light is not as important as the dimness of the light, although everyone I know uses red lights as their default. This link claims that using a red light to preserve your night vision is a myth...

http://stlplaces.com/night_vision_red_myth/

... and this link does a great job of further explanations...

http://www.flashlightreviews.com/qa/nightvision.htm

\Paul A

On Thu, 23 Jul 2015 11:54:44 -0700 (PDT), Sketcher
wrote:

On Thursday, July 23, 2015 at 11:08:16 AM UTC-6, Chris L Peterson wrote:

Another option is a dim white light, and a white pencil on black
paper.

That's an interesting option that I've never seriously considered. The materials would not be available for me locally, but the next time I go to 'the city' I can *try* to find time to shop around.

A strong plus for white on black is that less light gets reflected back to the eye. Only the pencil marks would be illuminated! On the minus side: I would probably still have to use a red light. White lights tend to shine too brightly.

Many people have poor acuity in the deep red range where scotopic
vision is protected. For them, I normally recommend dim white light
and printed charts that are white on black. With dim enough light (I
usually have to add a series resistor with white LED lamps), the
impact on night vision is extremely minor, often unnoticeable.

If you're familiar with lighting in situations where both visual
acuity and good night vision are required (e.g. military observation
posts and ship conns), deep red light is used for area lighting, and
instruments are typically black with white, green, or yellow
information. The red keeps you from falling, the instruments utilize
colors that preserve acuity.

On Thu, 23 Jul 2015 10:27:35 -0700 (PDT), palsing
wrote:

Actually, the color of the light is not as important as the dimness of the light, although everyone I know uses red lights as their default. This link claims that using a red light to preserve your night vision is a myth...

It's not a myth, but it's true that very dim white light has only a
small impact on night vision, but can greatly enhance your
productivity because of the better acuity it offers most people.

In practice, very few people actually use red light sources that are
long enough wavelength and dim enough to preserve night vision.
They're just fooling themselves.

On Thursday, July 23, 2015 at 12:47:08 PM UTC-7, Chris L Peterson wrote:

It's not a myth, but it's true that very dim white light has only a
small impact on night vision, but can greatly enhance your
productivity because of the better acuity it offers most people.

In practice, very few people actually use red light sources that are
long enough wavelength and dim enough to preserve night vision.
They're just fooling themselves.

I totally agree, way too many folks think that any red light is just fine, and think that a couple of layers of red cellophane on their Mag-light is good-to-go... and then they get all defensive when I tell them that they are causing a big problem. The worst offenders are those who show up with those dual head-lamp 'landing lights' and proceed to look you straight in the eye while talking to you. I send them right over to the vendors and tell them to get a Starlite... and keep it pointed to the ground...

You're bringing back some old memories! I do happen to know 'a little' about military ships and their lighting - having once worked in a Guided Missile Cruiser's CIC with occasional duties on the ship's bridge. . .

One of my first solutions to maintaining dark adaptation (in the late '60s!) was to use *very* dim (white!) lighting (I didn't have access to red!) while sketching with thick-line dark markers. Note: the thick, dark markers were necessary due to the dimness of the lighting - even though it was white. For *most* of my current astro-sketching purposes I use a 'bright enough' red light to permit the use of pencils (with their thinner lines) - allowing for finer details in the sketches. This choice compromises my dark adaptation a bit more. I'll generally spend quite a while at the eyepiece (no lights on) before turning on a dim red light for sketching. The light goes off again when I return to the eyepiece. If the object is unusually faint I spend more time without lighting at the eyepiece - looking for more faint details - and less time with the lighting necessary to add details to the sketch. My methods work adequately for my purposes - as my results show: In particular, Pluto (a few years ago) was observed and sketched with the aid of a 4-inch aperture. The Horsehead Nebula was observed and sketched using an unfiltered 5-inch aperture.

The debate over light color for astronomical use is an old one. Prior to finallizing the construction of my illuminated clipboard (I don't recall how long ago.) I experimented with the use of LEDs of different colors. My choice of red (for the clipboard) was based on the results of those experiments - not on the popularity of red. Unfortunately I don't recall the test procedure that led me to that result, but it (as memory slowly returns) probably involved dimming the LEDs until I had the lowest level at which I could still read by followed by judging how much I could see of my dark surroundings. Regardless of the procedure, red came out the winner.

One more detail on my illuminated clipboard construction: I have an opaque overlay that blocks all light except that beneath the 6.5-inch circle within which the sketch is made. Around that circle are spaces for various pieces of information such as telescope, magnification, etc. There's no need to keep those areas illuminated while working on the sketch - so they're covered! I try to mimimize my exposure to light as much as is practical.

Regardless, it appears that compromises have to be made. Which ones are made and/or which ones are 'better' are (IMO) more a matter of personal preference and less a matter of one being better than the others. My current methods work for me, but that doesn't mean they can't be improved upon.

Sketcher,
To sketch is to see.

On Thursday, July 23, 2015 at 1:44:12 PM UTC-6, Chris L Peterson wrote:

Many people have poor acuity in the deep red range where scotopic
vision is protected. For them, I normally recommend dim white light
and printed charts that are white on black. With dim enough light (I
usually have to add a series resistor with white LED lamps), the
impact on night vision is extremely minor, often unnoticeable.

If you're familiar with lighting in situations where both visual
acuity and good night vision are required (e.g. military observation
posts and ship conns), deep red light is used for area lighting, and
instruments are typically black with white, green, or yellow
information. The red keeps you from falling, the instruments utilize
colors that preserve acuity.