Dark sites - what have you seen, that you couldn't at home?

[Flame Nebula]

20 minutes ago, Bugdozer said:

This is one thing that I am always curious about when people talk about really dark skies and the descriptions of them given in the Bortle classifications, because some of it doesn't quite make sense to me. 

Firstly, a higher Bortle sky is always going to have more light from the sky overall than a lower Bortle sky. No objects actually lose brightness under a high Bortle sky, they just lose contrast against the increasingly bright background glow that is everywhere, until at some point they are effectively rendered invisible. But their light IS still coming down. 

However, in my experience, once you get down to about Bortle 2.5, there isn't actually enough light to see any shadows at all. The Milky Way could be right overhead, and clear to look at, but I can't distinguish between looking at the ground and having my eyes shut. Basically, the amount of light given off by things like the Milky Way is below the threshold at which my eyes can detect reflected light from objects. I can believe something like Venus could give off enough light to cast a shadow at its brightest, but if I already can't see the ground at all, then having an even darker sky is not going to make shadows on it more visible. Seeing it reflected off water makes sense, but I am dubious of darker skies seeming to make our eyes more sensitive to light which is already below detection threshold.

We need to test this out. 😊

[John]

You can find yourself in an interesting quandary if and when you do get under very dark skies with a scope and that is balancing going for targets that you simply cannot see from your normal observing locations with observing more familiar targets to see how much more you can see of them or in them. Often you do a bit of both, of course. In such circumstances it is good to have an observing buddy (or a number of them at a star party !) who can contribute suggestions as you go along. 

While being under really dark skies is nice on ones own, it does get a whole lot more fun with a few more folks and scopes around 😃

Edited March 21 by John

[jjohnson3803]

As mentioned, there are so many stars in the FOV that I don't always know what I'm looking at.  Forget starhopping. 

Cancer at home has at best one or two stars visible to the naked eye.  Once, in a B2/3 zone, I could see a crab - body, claws, the whole thing - and it was screamingly obvious.

The most memorable view though was of the Leo Triplet of galaxies.  None of them are visible with any of my scopes at home.  In a B2/3 they were so bright that I jumped back from the EP.  It was like getting slapped in the face.  😄

I should also mention globular cluster M4 in Sco.  Extremely difficult to see at home.  Under a dark sky, it's like, "Oh yeah, of course - you can't miss it."

Edited March 21 by jjohnson3803

[PeterStudz]

1 hour ago, Bugdozer said:

This is one thing that I am always curious about when people talk about really dark skies and the descriptions of them given in the Bortle classifications, because some of it doesn't quite make sense to me. 

Firstly, a higher Bortle sky is always going to have more light from the sky overall than a lower Bortle sky. No objects actually lose brightness under a high Bortle sky, they just lose contrast against the increasingly bright background glow that is everywhere, until at some point they are effectively rendered invisible. But their light IS still coming down. 

However, in my experience, once you get down to about Bortle 2.5, there isn't actually enough light to see any shadows at all. The Milky Way could be right overhead, and clear to look at, but I can't distinguish between looking at the ground and having my eyes shut. Basically, the amount of light given off by things like the Milky Way is below the threshold at which my eyes can detect reflected light from objects. I can believe something like Venus could give off enough light to cast a shadow at its brightest, but if I already can't see the ground at all, then having an even darker sky is not going to make shadows on it more visible. Seeing it reflected off water makes sense, but I am dubious of darker skies seeming to make our eyes more sensitive to light which is already below detection threshold.

This is a smartphone single snap. There’s a lot of noise (to be expected from a tiny camera) and no stacking. Even in this picture you can just make out the reflection under the Milky Way on the water. Visually it was more obvious. My 12 yr old daughter who was with me at the time pointed it out straight away.

[pipnina]

1 hour ago, Bugdozer said:

This is one thing that I am always curious about when people talk about really dark skies and the descriptions of them given in the Bortle classifications, because some of it doesn't quite make sense to me. 

Firstly, a higher Bortle sky is always going to have more light from the sky overall than a lower Bortle sky. No objects actually lose brightness under a high Bortle sky, they just lose contrast against the increasingly bright background glow that is everywhere, until at some point they are effectively rendered invisible. But their light IS still coming down. 

However, in my experience, once you get down to about Bortle 2.5, there isn't actually enough light to see any shadows at all. The Milky Way could be right overhead, and clear to look at, but I can't distinguish between looking at the ground and having my eyes shut. Basically, the amount of light given off by things like the Milky Way is below the threshold at which my eyes can detect reflected light from objects. I can believe something like Venus could give off enough light to cast a shadow at its brightest, but if I already can't see the ground at all, then having an even darker sky is not going to make shadows on it more visible. Seeing it reflected off water makes sense, but I am dubious of darker skies seeming to make our eyes more sensitive to light which is already below detection threshold.

The sky at my home has an Exposure Value (EV) of about -5.5 or so, and it's already dark enough that the ground is very hard to see even once I'm adjusted.

However a place near me is much darker, dark enough to see the MW core and even sometimes the outer spirals, which means it's probably closer to EV-7 or even EV-8, I can see the ground at this level but not clearly. I would guess if it were just the MW core in the sky and no sky glow at all, I'd struggle to see any ground at all as you say. The milky way just isn't that bright!

[Flame Nebula]

2 hours ago, PeterStudz said:

This is a smartphone single snap. There’s a lot of noise (to be expected from a tiny camera) and no stacking. Even in this picture you can just make out the reflection under the Milky Way on the water. Visually it was more obvious. My 12 yr old daughter who was with me at the time pointed it out straight away.

Smartphone single snap! Impressive! 👏

These sort of photos really bring it home where we lie in the arms of the milky way! 

Imagine how bright it would be without the dust lanes! 

[Whistlin Bob]

Reading this topic just reminds me again that what most of us do is the equivalent of playing football with our shoelaces tied together. It speaks to the wonder of what's over our heads that we bother at all. 

My experience of really dark skies is limited but a few years back we were holidaying in Cumbria and I had a superb time with my dob- thinking back to it still gives me a tingle. 

To answer the op question: Stephan's Quintet and NGC891. At the time I would also have said the Horsehead, but the experience of doing it in Cumbria helped me find it at home, and on average I manage to catch it about once a season now. 

I wrote it up at the time- definitely my best experience with a telescope, and probably my best report as well! I really need to do this again...

 

[DirkSteele]

15 hours ago, Beulah said:

My rough calculation is an increase of 2 inches of aperture for 1 Bortle reduction

For example, a 12 inch telescope in a Bortle 4 sky is more like a 14 inch telescope in a Bortle 3 sky...

That is a good rule of thumb based on my experience.  My 105mm refractor vastly outperformed my 11" when I was in Oman in Bortle 1 compared the Bortle 5 location it was located at in the UK.  Using a 12" scope in Namibia in a Bortle 1 location was quite something else!  Same for my 76mm Takahashi in Mozambique under a Bortle1/2 sky.  Seeing details I would not see in an 8" scope at home.

 

I would also say not all Bortle classifications are created quite equal.  In Namibia you can just about see shadows from the combined light of the Milky Way and stars and you only know where the horizon is because the stars stop.  I have found these African and Middle East type of sites to outperform other similarly classified locations because it is that dark all the way to the horizon, rather than just at higher elevations.

[Flame Nebula]

2 hours ago, Whistlin Bob said:

Reading this topic just reminds me again that what most of us do is the equivalent of playing football with our shoelaces tied together. It speaks to the wonder of what's over our heads that we bother at all. 

My experience of really dark skies is limited but a few years back we were holidaying in Cumbria and I had a superb time with my dob- thinking back to it still gives me a tingle. 

To answer the op question: Stephan's Quintet and NGC891. At the time I would also have said the Horsehead, but the experience of doing it in Cumbria helped me find it at home, and on average I manage to catch it about once a season now. 

I wrote it up at the time- definitely my best experience with a telescope, and probably my best report as well! I really need to do this again...

 

Thanks Bob, 

What sized dob did you use to see it at home? 

[Flame Nebula]

2 hours ago, DirkSteele said:

That is a good rule of thumb based on my experience.  My 105mm refractor vastly outperformed my 11" when I was in Oman in Bortle 1 compared the Bortle 5 location it was located at in the UK.  Using a 12" scope in Namibia in a Bortle 1 location was quite something else!  Same for my 76mm Takahashi in Mozambique under a Bortle1/2 sky.  Seeing details I would not see in an 8" scope at home.

 

I would also say not all Bortle classifications are created quite equal.  In Namibia you can just about see shadows from the combined light of the Milky Way and stars and you only know where the horizon is because the stars stop.  I have found these African and Middle East type of sites to outperform other similarly classified locations because it is that dark all the way to the horizon, rather than just at higher elevations.

So what this means is, we should all get a 4" Tak(😁) to cover going to dark skies, travelling light. 

[John]

Bob's comments are very interesting.

Seeing something for the 1st time is always the big challenge. Once you have done it and know what to look for, you often find you can achieve something similar under slightly less favourable conditions and / or with a smaller aperture.

Perhaps it's a good argument for having larger apertures earlier in your "career" in the hobby rather than later ?

 

 

[James]

55 minutes ago, John said:

Seeing something for the 1st time is always the big challenge. Once you have done it and know what to look for, you often find you can achieve something similar under slightly less favourable conditions and / or with a smaller aperture.

That's a good point..

I've been lucky enough to visit La Palma twice in the last ten years or so, generally with a DSLR for time lapsing rather than a scope though I did get a twirl with an Evolution 8 for a couple of nights. The primary difference telescope-wise was objects generally appearing much brighter and therefore often more detailed - and up near the observatories the seeing was usually excellent so planetary viewing was much improved. I figured the view was really only limited by the aperture and optics at that point. Oh, and my then 46 year old eyes..

The main difference that I found was zodiacal light being much brighter than the Milky Way from home, much less twinkling of stars and the Milky Way itself was ridiculously bright and detailed - I could see it from inside the kitchen where we were staying with a dim 40watt light bulb on above me. One particular night there was no twinkling pretty much down to the last few degrees near the horizon and I was able to walk around and follow paths without needing a torch (I was careful!). I guess proper dark skies allow for proper dark adaption, sort of a virtuous cycle... I'm pretty sure the Milky Way and Jupiter were casting a shadow that particular night. I took my son, then 11, up to the top with me and the things he described like the number of stars visible in the Pleiades was pretty mind boggling.

Of course, that meant even though I could see all that extra stuff he could see more... 🙄

So, in answer to the OP... actually there was nothing I could see that I couldn't see at home (well, except the Zodiacal light - have to go to Kielder for that) but everything was way brighter, clearer and more detailed. 

James

 

[mikeDnight]

M33 with the naked eye is my memorable moment, and that was only a few miles from where I live. But as regards deep sky, everything gets better; black nebulosity often becomes even more obvious than the light nebula giving a real depth of perspective to the view - 3D views in 2D.

[Elp]

Such a simple thing but the shadow created from moonlight, you don't see it at all in areas with perpetual lighting, many people have probably never experienced it.

[Bugdozer]

20 hours ago, PeterStudz said:

This is a smartphone single snap. There’s a lot of noise (to be expected from a tiny camera) and no stacking. Even in this picture you can just make out the reflection under the Milky Way on the water. Visually it was more obvious. My 12 yr old daughter who was with me at the time pointed it out straight away.

I don't dispute seeing its reflection in water. I DO dispute that it is bright enough that it illuminates the ground sufficiently on its own that you can distinguish between an area that's shaded and one that isn't. 

[Whistlin Bob]

6 hours ago, Flame Nebula said:

What sized dob did you use to see it at home? 

It's the same kit- a 14" dob 😃. 

[ollypenrice]

On 21/03/2024 at 21:28, pipnina said:

The sky at my home has an Exposure Value (EV) of about -5.5 or so, and it's already dark enough that the ground is very hard to see even once I'm adjusted.

However a place near me is much darker, dark enough to see the MW core and even sometimes the outer spirals, which means it's probably closer to EV-7 or even EV-8, I can see the ground at this level but not clearly. I would guess if it were just the MW core in the sky and no sky glow at all, I'd struggle to see any ground at all as you say. The milky way just isn't that bright!

Dark sites are not dark, a fact which has been discussed on SGL before. At a dark site it is easy to see the ground and easy to walk around without bumping into things. When it hits SQM22 here, and you are dark adapted, you walk around easily and have no need of a head torch. We've even discussed whether or not Jupiter was casting a shadow.

When there's haze or cloud, though, a dark site is dark and a place where you may struggle to see your hand in front of your face. 

Olly