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#51 Live_Steam_Mad

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Posted 25 October 2013 - 02:31 PM

The one lucky stroke I have is that our appartment complex has a huge wall built of some kind of thick plastic or something that is designed to block out the road noises (which it accomplishes quite well) I don't think it does anything for the sky mag, but it blocks out many of the immediate area street lights.

I'm almost certain I can't see mag 4 stars when the moon is out here. I'm now second guessing myself, but when there was no moon I believe I made out a mag 4 constellation, well anyway I haven't been able to see it at all since the moon is over the horizon now, not even a single star from it.


I am very interested and curious to hear from you as to whether you can see magnitude 3.8,3.9,4.0, 4.1, 4.2 or 4.3 stars from your location at all, at about 45 degrees or more altitude on a clear nearly moonless night with good transparency? :question:

I use Skymap Pro 9 or 11 free demo, it's a simple but VERY handy and usable and intuitive planetarium program, to see what brightness certain stars are (make sure not to use variable stars if you can!) so I can do the test.

I pick fainter stars in Ursa Minor, Lyra, Draco, Pegasus, etc. since then I am familiar with the constellation shape and can see where a faint star is supposed to be. Use AVERTED VISION to detect the faintest ones, aim your eyes to the right of the faint star by about 1,2 or 3 degrees and then you will see much fainter things than by direct vision. Make sure you have been "dark" adapted by at least 15 to 20 minutes with NO direct lights shining into your eyes from anywhere.

Then finally when you have seen which is the faintest one you can see, do the same test but now pick stars overhead or close to it. That last part is one I need to do soon.

I'd be interested to hear what your results are. So far I got mag. 4.36 with a 75 per cent phase, shielded moon which was 45 degrees up, for stars 40 deg. up from my Northern horizon. I can't hardly begin to imagine what it's like from parts of Nevada or Galloway Forrest Park, Scotland (our darkest place here, even Llampeter Wales is brighter! and that's DARK) or Hawaii where you can see down to mag. 7 with the naked eye :shocked:

Cheers,

Alistair G.

#52 mak17

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Posted 25 October 2013 - 02:46 PM

I live in bortle 7/8 but observe in bortle 4/3/2 only.

#53 AcesDJD

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Posted 26 October 2013 - 01:38 PM

Is this worksheet accurate? http://www.globeatni...llation_at_Y...

According to it, with a half moon I have mag 5 skies. Don't quite buy that. Here's the strange part is that I can just barely make out the head of Orion and yet the sword is clearly visible. I would say 4 makes more sense, the sky is more dark gray than black tonight.

Thanks for the link I downloaded it. Two questions if you don't mind...How do you set your local time and what do you do when your trial period runs out?

Edit After an additional observation with orion moving away from the moon a bit I wouldn't say the head is so hard to see, but the sword still looks somewhat brighter to me. I caught his bow this time, something I've never caught before what mag is that?

#54 Live_Steam_Mad

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Posted 17 November 2013 - 03:46 PM

According to it, with a half moon I have mag 5 skies. Don't quite buy that. Here's the strange part is that I can just barely make out the head of Orion and yet the sword is clearly visible. I would say 4 makes more sense, the sky is more dark gray than black tonight.

Thanks for the link I downloaded it. Two questions if you don't mind...How do you set your local time and what do you do when your trial period runs out?

Edit After an additional observation with orion moving away from the moon a bit I wouldn't say the head is so hard to see, but the sword still looks somewhat brighter to me. I caught his bow this time, something I've never caught before what mag is that?


If you are asking about SkyMap Pro, you don't need to set your time in the program for just the date and time setting, but you do have to make sure your PC has the correct time zone in Control Panel / Date & Time settings / Date & Time tab / Change Date & Time and/or Change Time Zone (GMT / UT for me here in England) if you are using e.g. Windows Vista like I am on this laptop, and I use the Internet Time tab and the Change Settings button and then Update Time to synchronise the PC with an Atomic clock.

In SkyMap Pro you click on the icon of the Earth (for your location and time zone setting) on the left, then use Google Earth and zoom in and find your Longitude and Latitude in degrees, minutes, and seconds (in Google Earth, choose Tools / Options then on the 3D View tab in the Show Lat/Long section choose Degrees, Minutes, Seconds) then put it carefully into SkyMap Pro, then make sure your time zone is correct in SMPro(which would be 540 minutes ahead of UT for South Korea / Seoul, and make sure Daylight Savings is ticked or not ticked as appropriate (for us in England, Daylight Savings is now OFF) then I put in 7 Celcius and 1013 mBar for pessure (cold, fairly high pressure i.e. clear) and I put in my height of 54 meters above Sea Level as I am 1/2 way up a fair sized hill and I took my height reading from Google Earth where it says elev. just between the lat/long and eye alt at the bottom of the screen.

Then choose OK (do NOT click on home) and then select File and Save Defaults. Now your time and location will automatically be correct every time you launch the program.

From here I can see Sigma Orionis, a star of mag. 3.77 is just below to the left side of Orion's belt, and you can see Iota Orionis mag 2.75 which is the star of Orion's Sword. But that part of the sky (South) always has an unpleasant mid orange glow to Orion, from where I am, which is unfortunate as I love Orion.

See if you can make out 29 Orionis mag 4.13, 2.5 degrees left of Rigel and 2/3 degree above Rigel approx. Then try 32 Orionis mag. 4.45, 2 degrees to the left of Gamma, and 1/2 degree below approx. I'll try and do the same next time it's clear with no moon and good transparency. I very much doubt you have a mag. 5 sky, if you do then I am very jealous LOL..the best I seem to do from here is about mag. 4.3 so far in the Northern sky.

I'd be interested to know if you can see those two.

Best Regards,

Alistair G.

#55 Live_Steam_Mad

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Posted 28 December 2013 - 02:26 PM

OK after a few nights, checking now and then with the Moon below the horizon, I see Tau Orionis fairly easily (mag. 3.59) about 3 degrees above and 1.5 degrees to the left of Rigel (1/6 of the way between Rigel and Delta Orionis, the right most star of the Orion's belt), and I can also see 29 Orionis (mag 4.13), 2.5 degrees left of Rigel and 2/3 degree above Rigel approx.

But that's about as faint as I can see in terms of stars in the lower part of Orion. Below mag 4.13 is impossible to see from here. 29 Orionis at mag. 4.13 needs averted vision and some experience to see it, and sometimes I can just hold it with direct vision but it's very difficult.

In the Northern sky with less LP I do better from here with mag 4.3 being fairly easy with averted vision and sometimes direct.

For these people who can see down to mag. 5.5 or 6, I cannot imagine what it's like to see that. Must be wonderful.

When I was about 13 years old, Orion rose over the East in what seemed like a fairly dark sky to me, it looked magnificent. Now in the East from here the LP is horribly worse. Something has definitely gone a LOT worse in St.Helens in the last 25 years in terms of Light Pollution.

Best Regards,

Alistair G.

#56 scottk

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Posted 28 December 2013 - 04:37 PM

Light pollution really is a horrible disgusting thing. I use my unmodified dslr to see things I can't see visually through my scopes. Even that gets quite annoying though, because after seeing the results some people get from setups just like mine from dark skies, it makes me wish I could get images like that.

I read a post from someone not long ago who complained about only being being able to take 7 or 8 minute exposures at iso 1600 because of light pollution.... BWWAAHAHAHAAHHAAA. :roflmao:

My histogram is well beyond one third from left at about 30 seconds.

On an exceptionally clear night, I can count maybe 40 or 50 stars from my back yard, but I try to look on the bright side - I can count at least 64 highway street lights. :p






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