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How dark is your sky on a moonless night?


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The best moonless zenith reading I've had in my semi-rural village is 20.6 at the back of the house and 20.4 at the front (following a recent change to LED streetlights). This is about 10 km from a city of 250000, around 500m altitude (as is the city). The lights of greater Bilbao are clearly visible 60 km away when there is cloud cover in spite of an intervening 1500m mountain range, so the light is there, just not so visible on clear nights.  I feel luckier than many to be able to observe in reasonable darkness from the garden, but having experienced really dark sites very occasionally all I can say there is a huge difference between 20.5 and 21.5!

Martin

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Dark enough to see andromeda naked eye, but not so light that neighbours can see me naked with their eye John 

There are times that the conditions here just come together and last night was one of them unexpectedly. There are many that know the SQM can be affected by transparency- and it can go either way a bi

21.6    (6.4 NELM) http://www.unihedron.com/projects/darksky/NELM2BCalc.html

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9 minutes ago, pipnina said:

I just googled it, came up with this on their website:

y9fJsG3.png

I guess that's a resounding "No"

Shame, maybe there are alternatives out there?

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Had a look on Google Play but didn't turn up anything either.

Even on the best nights my sky is pretty rubbish which is why I confine myself pretty well to NB imaging, it's the only thing that can cut through the clag

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13 hours ago, ollypenrice said:

Wooo, tonight I saw 22.10 on the SQM, the first time ever over 22. Alas it was a one-off reading, the consistent value being in the 21.76 region. Still it was nice while it lasted!!

Olly

Did you take a few readings to warm the sensor like the instructions say Olly? :grin:

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On 1 May 2016 at 08:40, Stu said:

Doesn't sound too terrible Fozzie! ?

That's what I thought! My garden sounds like yours and I consider myself lucky to have it!

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If I can cut the glare of one particular streetlight with a sheet it's manageable, but I've stone and white render, the latter acts like a mirror and reflects more light than a 16" dob.. The gardens not for faint fuzziness... that been said and to prove the above wrong I picked out 2 of the 3 Leo trio in the 4" with 10mm delos,  faint but defo there.. but then they do say nothing goes as deep as a delos! 

Ta

Fozzie

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Does the phone and its app have a "beam" width? I'm curious as the SQM is wider and the SQM-L is narrower. Skyglow/light domes can really affect the wider beam readings- its reads much more sky than the narrow version.

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1 hour ago, jetstream said:

Does the phone and its app have a "beam" width? I'm curious as the SQM is wider and the SQM-L is narrower. Skyglow/light domes can really affect the wider beam readings- its reads much more sky than the narrow version.

iPhones have a camera FOV of around 58 degrees according to this site: https://developer.apple.com/library/ios/technotes/tn2409/_index.html

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7 hours ago, jetstream said:

Did you take a few readings to warm the sensor like the instructions say Olly? :grin:

Yes but I liked the first warm-up reading so much that I thought I'd post it! :hello2:

Olly

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We're on a roll at the moment. 21.8 zenith, 21.4 at 30 degrees elevation, no wind and literally no visible scintillation at all. Guide traces look like ________________________________________ that!

Olly

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  • 2 months later...

You guys are making me jealous. Alpha and Beta Sagittae are about the best I can do from my garden, and only on the best nights. Absolutely rubbish!

On the plus side, I'm moving soon, probably Monmouthshire, got my eye on St. Arvans and surrounds. From what I can see it should a lot better than Bedford.

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:-(

If I look straight up at Lyra on a good night I can see the double double fairly easily and elsewhere I can just make out some mag ~5.4 stars. I have a very faint trace of the Milky Way, just in Cygnus.

Lower down in north all that's visible is capella until you get up to Cassiopeia and I can only see three stars in Ursa minor, in the south Antares and a couple of stars in the head of scorpius. Best to the East is Delphinus or sagiitta so about 4. I would see more to the west but it's all tree up to about 60 degrees :-(

So I have a usable 'window' from south east to south west, and things low down like Mars and Saturn this year just graze the roof next door and go behind their chimbley.

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Neat topic Piero. Interesting to read through everyone's posts.

Very dependent on direction for me. Maybe NELM 5.5 with a bit of effort from home at the zenith on a good night. It doesn't degrade too badly as the sky drops away to the north or west. It's a bit brighter in the east, but the south unfortunately is just bright grey (or bright orange clouds) and with lights shining directly at me. Can't see much at all in that direction (and it's blocked by houses regardless). I can catch the Milky Way at zenith but not really elsewhere. M31 just about in averted vision naked eye.

Two dark sites I visit: One that's a couple of miles up the road gets about NELM 6.2, but is still rubbish in the south. Further away (and in a different direction to ensure I'm no longer north of the city) and I still get about NELM 6 and a bit, but the south clears up beautifully, so I tend to go there for southern targets, but stay nearby for everything else.

Those faint targets really come to life at the dark sites! Although, from home there's still plenty to enjoy with bright galaxies and particularly open clusters and doubles... just not in the south... :icon_biggrin:

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Thanks Paul :).  I forgot to say that I found a place where I recorded 21 mag. It's about 1h cycle from my home deep into the countryside. Cycling in such a darkness is quite an experience.. Thankfully the "road" built by Romans 2000 years ago is all straight! 

 

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10 minutes ago, Piero said:

Thanks Paul :).  I forgot to say that I found a place where I recorded 21 mag. It's about 1h cycle from my home deep into the countryside. Cycling in such a darkness is quite an experience.. Thankfully the "road" built by Romans 2000 years ago is all straight! 

 

Interesting. Do you cycle in darkness? No headlamps? Surely dark adaptation is crucial ! :wink:

Wow what skies you have! When I cycle back home from my darkish place 12 km from my Stockholm suburb, I do not need lamps, as I can see the path ahead in the forest with the LP alone :undecided:

 

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11 minutes ago, Cinco Sauces said:

Interesting. Do you cycle in darkness? No headlamps? Surely dark adaptation is crucial ! :wink:

Wow what skies you have! When I cycle back home from my darkish place 12 km from my Stockholm suburb, I do not need lamps, as I can see the path ahead in the forest with the LP alone :undecided:

:) I definitely use a lamp, but not on my head. I cannot even see my feet in the last part of the road! At about half the way it is ~20.4, but it's better to use a lamp for safety and because you don't want to fall over with your equipment inside your backpack! :) At home it is 19.6 mag on a moonless night instead, but a lamp is still necessary because of cars instead.

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Now that we're getting proper darkness again, I'm wondering whether I can fit my Startravel and AZ3 on the bicycle somehow. :icon_biggrin:

There's a definite appeal in going by bike rather than car as it gives you a lot more options on observing spots (within the distance you're preparing to pedal of course). Wouldn't fancy a mechanical issue late at night in the middle of winter though...

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16 minutes ago, Size9Hex said:

Now that we're getting proper darkness again, I'm wondering whether I can fit my Startravel and AZ3 on the bicycle somehow. :icon_biggrin:

There's a definite appeal in going by bike rather than car as it gives you a lot more options on observing spots (within the distance you're preparing to pedal of course). Wouldn't fancy a mechanical issue late at night in the middle of winter though...

I find quite exciting cycling in the countryside in the dark (in roads without cars). :rolleyes: 

To me, the only issue is the right selection of clothes. You need to wear enough clothes, but not too much otherwise there is a chance to sweat and then catch a cold. On the other side, you need to be light with your equipment. Just a thought of course!

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10 hours ago, Size9Hex said:

Now that we're getting proper darkness again, I'm wondering whether I can fit my Startravel and AZ3 on the bicycle somehow. :icon_biggrin:

There's a definite appeal in going by bike rather than car as it gives you a lot more options on observing spots (within the distance you're preparing to pedal of course). Wouldn't fancy a mechanical issue late at night in the middle of winter though...

I often cycle to dark(ish) and quiet places about 10-15 km from home. It takes between 30 or 50 min relaxed cycling.It mostly means bringing my 15x70 binocular in a backpack, but a couple of times I have taken my SW 200 PDS in a large hiking backpack, together with tripod and EQ5 in a wagon of the kind made for children (croozer kids). That was a bit near the edge, but it worked.

As @Piero writes clothing is a crucial matter. In my case it often means two sets of clothes: one for cycling (that gets invariably wet no matter how slow I cycle) and a change for staying warm and dry while observing.

Regarding the risk for mechanical failures, I always bring a small set of tools for fixing punctures and small chain problems. If the problems are too complicated I am mentally prepared to just leave the bike in the forest and walk home or to the closest bus stop (if any). Luckily that never happened to me while observing, though.

I cycle a lot and know the forest trails around my home very well from my daytime tours. I consider this an important aspect as it is easy to loose the orientation at night. I recommend you do the same with your area.

Cheers and good luck!

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1 hour ago, Cinco Sauces said:

I often cycle to dark(ish) and quiet places about 10-15 km from home. It takes between 30 or 50 min relaxed cycling.It mostly means bringing my 15x70 binocular in a backpack, but a couple of times I have taken my SW 200 PDS in a large hiking backpack, together with tripod and EQ5 in a wagon of the kind made for children (croozer kids). That was a bit near the edge, but it worked.

As @Piero writes clothing is a crucial matter. In my case it often means two sets of clothes: one for cycling (that gets invariably wet no matter how slow I cycle) and a change for staying warm and dry while observing.

Regarding the risk for mechanical failures, I always bring a small set of tools for fixing punctures and small chain problems. If the problems are too complicated I am mentally prepared to just leave the bike in the forest and walk home or to the closest bus stop (if any). Luckily that never happened to me while observing, though.

I cycle a lot and know the forest trails around my home very well from my daytime tours. I consider this an important aspect as it is easy to loose the orientation at night. I recommend you do the same with your area.

Cheers and good luck!

wow! :eek: Never thought about carrying a large telescope inside a children wagon! Nice idea! :thumbsup: 

To me yours is the way to do things properly! I should learn!

My way is way more spartan! :huh2: For these sort of trips, I put my three light eyepieces + TV60 inside the TV60 bag and put this inside my backpack (~2kg). Light tripod (1kg) attached to my backpack externally. Just one t-shirt for changing when I am at destination. No bike tools except for a small wheel pump. If something happens, I will walk home. I generally alternate cycling and walking to limit the chance to get wet.

Once back home, I have a :coffee22:of tea and a hot shower.

As you say, knowing the way is very important, particularly when off-road in the dark. 

Here is where I go when I want to see more. I have to say that the light from little abington seems a bit exaggerated to me. From the "X" at least, there is no sign of light around. Trees are barely recogniseable too!  

dark_spot.png

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1 hour ago, Piero said:

wow! :eek: Never thought about carrying a large telescope inside a children wagon! Nice idea! :thumbsup: 

To me yours is the way to do things properly! I should learn!

My way is way more spartan! :huh2: For these sort of trips, I put my three light eyepieces + TV60 inside the TV60 bag and put this inside my backpack (~2kg). Light tripod (1kg) attached to my backpack externally. Just one t-shirt for changing when I am at destination. No bike tools except for a small wheel pump. If something happens, I will walk home. I generally alternate cycling and walking to limit the chance to get wet.

Once back home, I have a :coffee22:of tea and a hot shower.

As you say, knowing the way is very important, particularly when off-road in the dark. 

Here is where I go when I want to see more. I have to say that the light from little abington seems a bit exaggerated to me. From the "X" at least, there is no sign of light around. Trees are barely recogniseable too!  

 

Hi Piero,

Where do you get the light pollution layer from? I use QGIS and with that data I could make my own custom LP maps.

Neil

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12 minutes ago, Stub Mandrel said:

Where do you get the light pollution layer from? I use QGIS and with that data I could make my own custom LP maps.

http://www.lightpollutionmap.info

I also use QGIS a lot, the problem here seems that there is no WMS service available to include in a project and combine with other layers. Tell me if I am wrong, as I also would like to add some LP layers to QGIS.

Cheers

Edited by Cinco Sauces
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1 hour ago, Piero said:

wow! :eek: Never thought about carrying a large telescope inside a children wagon! Nice idea! :thumbsup: 

To me yours is the way to do things properly! I should learn!

My way is way more spartan! :huh2: For these sort of trips, I put my three light eyepieces + TV60 inside the TV60 bag and put this inside my backpack (~2kg). Light tripod (1kg) attached to my backpack externally. Just one t-shirt for changing when I am at destination. No bike tools except for a small wheel pump. If something happens, I will walk home. I generally alternate cycling and walking to limit the chance to get wet.

Once back home, I have a :coffee22:of tea and a hot shower.

As you say, knowing the way is very important, particularly when off-road in the dark. 

Here is where I go when I want to see more. I have to say that the light from little abington seems a bit exaggerated to me. From the "X" at least, there is no sign of light around. Trees are barely recogniseable too!  

dark_spot.png

Piero, it seems that you get nicer skies than I get at cycling distance! Lucky you :happy11:!

I use a children's wagon for carrying almost everything and it works fine. I only tried with the full kit twice and worked just ok, but in all honesty is not very comfortable. The problem is not whatever you put in the wagon, but the 1 m OTA in the large backpack, as I don't put it in the wagon to avoid it being knocked off by the vibrations and path holes.

Cheers

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