Dark adapted vs not dark adapted

[sorrimen]

Hi all

I mainly observe with some slightly visible streetlights a couple hundred metres away and most of the night use my phone for stellarium to find objects. As a result, I’ve never got truly dark adapted and am really intrigued to see the difference. Does anyone have any sketches or edited images that highlight what difference you guys see? Even a written comparison e.g. could see no spiral arms, then adapted could see them would be really helpful to me!

TIA

 

[ollypenrice]

Surely your best bet would be to try it yourself? To my mind, screens of any kind have no place at all near a dark sky observer. The very idea is absurd. I'd also try a dark cloth over the head, or snorkel mask without glass, or all the other tricks folks use to make the most of a compromised site. You can't be sure that other people's findings with match your own.

Olly

[Jiggy 67]

It's an impossible question to answer, it depends on a number of factors....level of your dark adaption, level of light pollution and your own eyes, it will be different for everyone. I too, use a smartphone (with SkySafari) at the scope (sorry @ollypenrice 😉) but I have it set to the red screen and the brightness turned down (iPhone). It's not the ideal situation but everything is a trade off....I love Skysafari, it makes everything so much easier so it's worth risking a minimal amount of dark adaption, surely anyone using a paper star atlas, which I sometimes do aswell would have to use a light source to see it...probably white light if it's really dark

[sorrimen]

20 hours ago, ollypenrice said:

Surely your best bet would be to try it yourself? To my mind, screens of any kind have no place at all near a dark sky observer. The very idea is absurd. I'd also try a dark cloth over the head, or snorkel mask without glass, or all the other tricks folks use to make the most of a compromised site. You can't be sure that other people's findings with match your own.

Olly

Quite right that that would be the best bet, but with cloudy skies for a while and my observation site not being quite out of the dark, I would still love to hear others’ experiences! With my limited experience, I’ve only got 4 or 5 targets I can comfortably find without a star chart so I’m essentially weighing up if it’s worth spending a precious clear night restricted to those targets but getting fully dark adapted, if that makes sense. The dark cloth and snorkel mask ideas are really helpful, thank you!

[sorrimen]

16 hours ago, Jiggy 67 said:

It's an impossible question to answer, it depends on a number of factors....level of your dark adaption, level of light pollution and your own eyes, it will be different for everyone. I too, use a smartphone (with SkySafari) at the scope (sorry @ollypenrice 😉) but I have it set to the red screen and the brightness turned down (iPhone). It's not the ideal situation but everything is a trade off....I love Skysafari, it makes everything so much easier so it's worth risking a minimal amount of dark adaption, surely anyone using a paper star atlas, which I sometimes do aswell would have to use a light source to see it...probably white light if it's really dark

I imagined everyone would have different experiences, but didn’t gauge how light pollution and different levels of dark adaptation would make the question so hard to answer; my mistake! You’ve kind of matched my thought train at the end there though, as I’ve seen some people say they take dark adaptation extremely seriously and to me that means no lights at all. Do people then just find all their targets by memory, or does everyone just use dim red lights? 

[ollypenrice]

47 minutes ago, sorrimen said:

I imagined everyone would have different experiences, but didn’t gauge how light pollution and different levels of dark adaptation would make the question so hard to answer; my mistake! You’ve kind of matched my thought train at the end there though, as I’ve seen some people say they take dark adaptation extremely seriously and to me that means no lights at all. Do people then just find all their targets by memory, or does everyone just use dim red lights? 

It's twenty years since I observed anywhere other than at a dark site but the first thing to say is that a dark site isn't dark. You can walk around without difficulty from starlight and the Milky Way (which is, of course, starlight.) I can't read a star chart that way but I can do so using a dim red light kept on for only moments and sometimes a magnifying glass. This is dimmer than any dimmed screen I've ever used and I've also tried red acetate over screens but I consider that useless, to be quite honest.

It is only dark at a dark site when it's cloudy, and then it really is totally dark and you can see absolutely nothing.

Olly

[AstroKeith]

1 hour ago, sorrimen said:

I imagined everyone would have different experiences, but didn’t gauge how light pollution and different levels of dark adaptation would make the question so hard to answer; my mistake! You’ve kind of matched my thought train at the end there though, as I’ve seen some people say they take dark adaptation extremely seriously and to me that means no lights at all. Do people then just find all their targets by memory, or does everyone just use dim red lights? 

You asked for a description of the difference when dark adapted - its ENORMOUS! I cant be precise as just how bright your phone/tablet or lights are is unknown. I'll suggest you'll see at least a magnitude or two deeper.

A dim red LED lamp for reading star charts and finding your way about (although once dark adapted you won't need a torch!)

I recommend a phone or table that has an OLED type display. These arent back lit and are truly red on black. 

[globular]

I tend to keep my observing eye closed when not at the eyepiece.  And use only very dim red light head torch to keep the other eye fairly dark adapted when making eyepiece changes or finding new targets - including looking at SkySafari in night mode (on OLED display).

Also, when I'm studying targets that benefit the most from full dark adaptation, I naturally tend to spend long periods at the eyepiece really studying it - so dark adaptation comes quite easily and stays for the duration because there are no distractions.

Observing in a sitting position helps greatly too.  And sketching what you are observing (closing observing eye when off the eyepiece) also helps to slow down the observing process and really take in what's on offer in the eyepiece.

Observing sessions where I flit from one target to the next and only fleetingly (few minutes each) enjoy each one are really good fun too - but here I select targets where dark adaptation is less important and take less care to preserve it.  (Although still only use dim red light and keep observing eye closed).

I don't have any stray light from neighbours or streetlights to contend with - but if I did then I'd look into screens to block them and/or an observing hood.

Edited July 30, 2022 by globular
typo

[Jiggy 67]

1 hour ago, globular said:

I tend to keep my observing eye closed when not at the eyepiece.

Really good idea….consider an eyepatch, serves two purposes. You don’t have to squint when you have it over your non observing eye whilst at the eyepiece and when you walk away switch it to the observing eye to protect dark adaption. There are plenty of ways to minimize the effects of screens without giving up a really useful tool all together IMHO

[Paz]

Dark adaptstion makes a lot of difference, If im observing dim targets I observe with one eye and check sky safari with the other.  I find though it is easy to lose my night vision by looking at something bright by mistake with my observing eye.

If I'm doing something super tough I'll learn the location and the star hop and I won't use maps or apps at all.

[Kon]

Being dark adapted is paramount especially for dim objects; moon and planets not so much. I am on a fairly dark side and when my wife puts a light on in our kitchen, it is enough to lose the object or make it completely washed out.

Another example is the Horse Head; even the brightness of Alnitak is enough to kill any chance of viewing it. Last time I saw it, I needed a good one hour in darkness.

If you can dark adapt or at least avoid some bright sources, give it a try. I also avoid any kind of screens.