Red light

[nikooo]

Hi guys, I bought a red but I don't know why do people always use red light while watching through their telescopes?

 

[Budgie1]

Because the red light allows you to see things in the dark without destroying you night vision.

All is explained here: https://www.telescopefinder.com/why-red-flashlight-is-used-for-astronomy/ 😉

[glafnazur]

From S@N mag

'A red torch enables you to check charts without ruining dark adapted vision. Red light torches help you see in the dark and won't spoil your night vision. As such, they are among the most important accessories in an astronomer's arsenal. A red torch must provide a dim red light that enables you to read.'

and from Astro Night Astronomy Torches website

'Human vision is produced with the help of Cones and Rods inside our eyes, cones for daylight and white light, while rods are used for low light and our night vision.

To preserve our night vision a red light is essential for your telescope accessory kit, the red light wavelength is hard for rods to absorb, and at this wavelength the cones will not be functioning which leaves the rods to work as normal and our eyes to stay dilated.

Within the rods and cones are photoreceptor proteins which differ in their sensitivity to different light colour and wavelengths, it takes time for these proteins to activate and absorb light in dark environments.

 

We want our eyes fully dilated and our pupils to allow as much light in as possible when stargazing, which takes approximately 20 to 30 minutes in darkness. At this point our eyes are at their optimum for night vision.'

 

[Elp]

1 hour ago, nikooo said:

Hi guys, I bought a red but I don't know why do people always use red light while watching through their telescopes?

 

What I don't get is when I see AP videos with them using red lights, they're going to be looking at a screen in between setting up so it doesn't make sense. Best for when visual observing, if you're at a dark site.

[Marvin Jenkins]

Yeh but it looks good on the YouTube vid. White light at night detracts from the whole visual at night thing. 
It matters not a jot that they are not going to look through the scope. What matters is that to appear to be astronomers out in the darkness.

I am not criticising anyone. It is just a prop that is used to make these vids digestible to the general public.

Off to watch the new Astrobuscuit vid now, hoping to see a red torch in an AP challenge.

Marv

[John]

No light at all is best if your targets are faint ones.

 

[RT65CB-SWL]

Simply put, red preserves your 'dark-adapted' night vision.

It takes the human eye about half an hour to become 'dark-adaped' and less than half a second to lose it!

Some Android OS & iOS apps have a function to change the display from monochrome (B&W) and/or colour to red in increments or in one touch.

Alternatively, you can purchase a sheet of red/ruby transparent film and apply it to your smartphone, tablet or laptop screen.

Edited June 18, 2023 by RT65CB-SWL

[saac]

3 hours ago, Marvin Jenkins said:

Yeh but it looks good on the YouTube vid. White light at night detracts from the whole visual at night thing. 
It matters not a jot that they are not going to look through the scope. What matters is that to appear to be astronomers out in the darkness.

I am not criticising anyone. It is just a prop that is used to make these vids digestible to the general public.

Off to watch the new Astrobuscuit vid now, hoping to see a red torch in an AP challenge.

Marv

Mmm maybe, maybe not.  I think there are an awful lot of folk like me where once the AP run is set and up rolling we turn our attention to visual, so red light is just as important. I honestly can't think of the last time I just set up for an AP session only, would seem to much like a wasted opportunity to me.

Jim 

[Marvin Jenkins]

2 hours ago, John said:

No light at all is best if your targets are faint ones.

 

Couldn’t agree more. I hate even using a tiny red pencil light on my star charts but I do have to look at them to find my way around.

I find any device screen at minimum, turned to red light sooooo bright I wouldn’t dream of using a phone app at the EP.

I use a five inch newt for visual however I do have a six inch newt on a goto and cannot understand why the lowest setting for the handset is still way to much.

Marvin

[Marvin Jenkins]

8 minutes ago, saac said:

Mmm maybe, maybe not.  I think there are an awful lot of folk like me where once the AP run is set and up rolling we turn our attention to visual, so red light is just as important. I honestly can't think of the last time I just set up for an AP session only, would seem to much like a wasted opportunity to me.

Jim 

I get what you are saying. I however am on the opposite run of things.

I seem to get so few opportunities due to weather, life, work and all the rest that wasting a precious minute of observing trying to setup an imaging session seems madness right now.

Now if I had a permanent setup that would be different.

Marv

Edited June 17, 2023 by Marvin Jenkins
Typo on wasting

[saac]

16 minutes ago, Marvin Jenkins said:

I get what you are saying. I however am on the opposite run of things.

I seem to get so few opportunities due to weather, life, work and all the rest that wasting a precious minute of observing trying to setup an imaging session seems madness right now.

Now if I had a permanent setup that would be different.

Marv

Yeah a permeant setup is a game changer; almost getting to the stage weatherwise where a permeant setup is almost an essential. 

Jim

[DirkSteele]

As @John stated above, no light is better than red light. Many incorrectly believe red light is not damaging to night vision. That is simply not true. It is less damaging than other wavelengths but it’s still does some harm. As such, if you must use a red light (and realistically for astronomy it is needed) use as dim a setting as possible on the red light torch that allows you to see what you need.

[SwiMatt]

So, related to this: I've seen many UV lights targeted to amateur astronomers, are these worth it at all? Are they better than red light?  (although, of course, no light is always best)

[saac]

19 minutes ago, SwiMatt said:

So, related to this: I've seen many UV lights targeted to amateur astronomers, are these worth it at all? Are they better than red light?  (although, of course, no light is always best)

Have you got any links?

Jim 

[SwiMatt]

14 minutes ago, saac said:

Have you got any links?

Jim 

I've seen 2-3 on Astroshop.eu, e.g. https://www.astroshop.eu/astronomy-torches/astromedia-astronomy-torch-schwarzlicht-zoomlampe/p,77540 or https://www.astroshop.eu/astronomy-torches/omegon-astronomy-torch-black-light-combination-lamp/p,1314

[saac]

20 minutes ago, SwiMatt said:

I've seen 2-3 on Astroshop.eu, e.g. https://www.astroshop.eu/astronomy-torches/astromedia-astronomy-torch-schwarzlicht-zoomlampe/p,77540 or https://www.astroshop.eu/astronomy-torches/omegon-astronomy-torch-black-light-combination-lamp/p,1314

Thanks, I'd never seen UV lights marketed specifically for astro use. I guess the idea being these would be used with stars charts which react to uv light ( fluoresce ), that part makes sense I guess. How it affects dark adaptation though I'm not sure. I think I'd stick to red light, if anything just for eye safety. 

Jim 

Edited June 23, 2023 by saac

[Elp]

That's what I thought, UV light isn't particularly good for the eyes even if they might be a low power variety. Trying to innovate unnecessarily, if your lights too bright just diffuse it as much as possible by covering it. Another solution I thought of is wearing red safety glasses and a normal light, if you try it during the day and take off the glasses your vision is usually very bright temporarily.

Edited June 23, 2023 by Elp

[PEMS]

Amusingly I looked around at the "Red Light" aspect.

Interesting:

Use Red because it uses the night vision aspect of the eye. Problem the night vision aspect of the eye is monochromatic so you don't see red. So if you see red it is not using the night vision but the day vision.

Next was Amber: Study by a Canadian university into this. Never read the paper, couldn't find it or didn't bother. But some university study at least.

Next was Green: The eye is most sensative to green so need less brightness. Sort of half sensible.

Next was (oddly) Cyan:  No idea why but it was the next option.

Finally: Dim white. Equally some sense as the eye is polychromatic so white but dim seems half reasonable. Basically use the eye in the manner to which it has evolved over the last half million years or so.

So a reasonable Google search sort of helped not at all. Will say in military applications have not seen Red used, Amber and Green yes, Red no.

Does make you question how many astronomers have been effectively burnt at the stake for not having a red light.

Throw in the now common use of a computer/tablet/phone screen which is certainly not red and perhaps a small rethink is required.

[skybadger]

I  always thought the definitive source on this was in 'visual astronomy of the deep sky' by Clarke,; basically it doesn;t matter which colour you use as long as its dim and you give your eyes hours to recover from a bright day or make sure you wear sunglasses religiously. 

 

[Louis D]

On 23/06/2023 at 16:32, Elp said:

Another solution I thought of is wearing red safety glasses and a normal light,

That's the idea behind Orion's AstroGoggles.  You start wearing them early, during twilight setup, to cut dark adaptation time.  They've been selling them for decades.  I have no idea if they actually help or not.  They would just make my face sweat during our hot and humid summers.

[Elp]

1 hour ago, Louis D said:

if they actually help or not

Other than looking like a raving idiot, I think they do something. Using them in daylight, after one or two minutes and taking them off my eyesight is very temporarily overly bright. Haven't tried it during an observation as there's little point where I am as straight away my retinas will burn from led lights and reflections nearby. They're cheap as chips from usually online sites, no special equipment needed.

[Ratlet]

45 minutes ago, Elp said:

Other than looking like a raving idiot, I think they do something. Using them in daylight, after one or two minutes and taking them off my eyesight is very temporarily overly bright. Haven't tried it during an observation as there's little point where I am as straight away my retinas will burn from led lights and reflections nearby. They're cheap as chips from usually online sites, no special equipment needed.

I've been using a hat to cover one eye whilst observing as I find it quite tiring looking through they eyepiece shutting the other eye.  Seriously considering getting an eye patch and swapping it over for observing and reading charts...

 

Yaaarrr

[Franklin]

5 minutes ago, Ratlet said:

Seriously considering getting an eye patch

Another idea that works well, is to get a pair of Roy Orbison style sunglasses and knock one of the lenses out, Jack Duckworth style😁.

[Elp]

10 minutes ago, Ratlet said:

I've been using a hat to cover one eye whilst observing as I find it quite tiring looking through they eyepiece shutting the other eye.  Seriously considering getting an eye patch and swapping it over for observing and reading charts...

 

Yaaarrr

I's be in accord.

I literally can't keep one open for more than 10s or so, the other one just ends up looking at surrounding led light as a result.

[Franklin]

31 minutes ago, Ratlet said:

I find it quite tiring looking through they eyepiece shutting the other eye

 

19 minutes ago, Elp said:

I literally can't keep one open for more than 10s or so

The general advice is to observe with both eyes open, keeping one shut, as you've found can be quite straining. If at a dark moonless site then this is all well and good but for most of us finding some way to blank off the non-observing eye whilst keeping it open will make for a much more comfortable session. It is possible to ignore what the non-observing eye is seeing by concentrating on what you are observing with the other, but if there is too much ambient light around your site this can be difficult. Solar observing comes to mind where you need an eyepatch or at the very least, cup your hand over your non-observing eye.

The absolute best advice is to get some binoviewers!

Edited June 26, 2023 by Franklin