Light pollution

[devdusty]

One of the reasons I wanted to buy a telescope was to observe the colourful double stars. Just read in July edition of Astronomy Now magazine that Albireo ,s wonderful colours will be washed out to some degree in a light polluted area.

it would seem pointless to buy a telescope for a light polluted back garden., If this is the case.

Chris P

[Gfamily]

I would expect to see the colours of Albireo in my own light polluted garden, as both components are bright enough to show up, and the eye can make out the difference in colour quite easily. 

I've not read that page in AN yet. What scope do you have? 

[cletrac1922]

Chris

What you see posted in magazines, is not what you see through a scope

Even looking at the Orion Nebula, through a bigger scope, the Orion Nebula, will still appear mono, due to human eye not been able to pick up detail

Was a bit of a forum on this, last week, and a good explanation limitation human eye to colour was posted

John

 

[GlenM]

No, not pointless. I see colour in lots of doubles. Albireo is especially beautiful.

 

Glen.

 

 

[Alan64]

Quite a few double-stars require higher powers to split them, and to see the differing colors.  A short-focus achromat(refractor) and a short-focus Newtonian/"Dobsonian" are going to be problematic in that regard.

Still, refractors and Maksutovs are best for double-star observations.

In so far as light-pollution, there are several ways to lessen its effects whilst observing, and with some requiring a bit of DIY, arts-and-crafts type work.

[Alexandros]

Hello Dusty!

I live in a part of Greece near Athens, which means I have severely light polluted skies. I would classify it as a Bortle 6-7 ( https://en.wikipedia.org/wiki/Bortle_scale ).

I own a 130mm reflector and with it I managed to separate the colours of Albireo. The thing is that since they are stars they are easier to see and discern their colours because they produce their light and are pinpoint sources. From my experience, I have found out I can discern colour of up to mag 5 stars. If you want, I can go on a binary star search and report my results as to how far down I can push the apparent magnitude and still notice the difference in colour. 

I will however re-iterate the aforementioned point, viewing throught the eyepiece of  your telescope will be a lot different than the astrophotographs you may have seen. A good post that was recently suggested to me was this ( https://stargazerslounge.com/topic/196278-what-can-i-expect-to-see/ ). Do not lose your enthusiasm, though. The universe is a sight to behold and there are many things to see in it! Sure, light pollution is very annoying, but when you finally get that glimpse of the item you were hunting down, it is even more exciting. I remember my excitement when I managed to get a glimpse of the Sombrero galaxy. Plus when you finally get to a dark site you will be able to discern many more things from that hunting experience. 

[farunj]

Hi Dusty,

I come from a big city in India (called Pune) and there is a lot of light pollution where I used to live. I used to own a 5" f/7.2 reflector back then and I could quite easily resolve Albiero. In fact I remember being really excited on looking at the red and blue of the stars! I could resolve them with a 20mm eyepiece and they looked fantastic with a 10mm eyepiece. I recently moved to New Haven, CT, in the US, and this is much less light polluted than my old city. I enjoy much better views from here, and can easily split Albiero! So, unless you are severely light polluted and cannot see any stars when you look up, you should definitely be able to resolve and enjoy Albiero and many other double stars. 

I would also like to mention that if you are contemplating buying a telescope for observation purposes, then you should definitely consider buying a dobsonian. These are the best bang for the buck for visual astronomy as almost all of your money goes into the optics of the scope. An 8" dob from any of the big companies will guarantee not only that you will be able to split Albiero, but also be able to observe most of the Messiers! So do consider purchasing a dob!

As always though, there is nothing that can beat a dark sky. You will always get your best views from a really dark new moon night from far outside the city. 

Hope this helps!

Varun.

[Phillips6549]

Based in the suburbs of Birmingham (Bortle 8 ) I have no problems with seeing the different colours of the Albireo pair.  

LP does limit viewing the faint and the fuzzy but stars and planets in the darkest parts of the sky are fine.  

On 04/07/2019 at 23:42, devdusty said:

it would seem pointless to buy a telescope for a light polluted back garden.

Never, it's fascinating whatever you can see!

Clear skies.

Mark

[Mr niall]

Oh no you’ll be fine. Albireo is high until mid autumn right now - the closer to the zenith it is the less it’s affected by LP anyway. Double stars are affected much less by light pollution than galaxies for example. Most of us are plagued by significant light pollution these days. 

Clusters aren’t that badly affected and some planetary nebula are fine too. Planets and moon of course. Still lots to see!

Gamma delphini is another cracker - two little yellow dots on a sea of blue stars.

Edited July 12, 2019 by Mr niall

[Martthebass]

I think you'll be fine.  I was in a heavily LP area and got a great colour contrast on Albireo, when it rose out of the murk, with my 8" SCT.  Alpha Hercules was another great colour contrast. 

[StarryEyed]

Dont worry about light polution. Doubles and clusters etc are great. The trick is to pick your targets. There are some great lists for observing. Tske a look at the Astronomy League observing sections. The trick with colour is to find two stars with contrasting colours this helps tremendously. The leage have a really nice binocular double list. You can just get the list and work through them without submitting anything. During the summer these are great fun when daylight is a bigger problem than skyglow. Its also fun to watch the sky darken whilst observing and the brightness come up along with the colours. This always make me happy. Skyglow I dont think so I am out the back as soon as I can see couple of stars long before its dark.

And I have lived in London all my life.

Edited July 16, 2019 by StarryEyed

[Beulah]

From my experience the colours of Albireo are a little more intense under light polluted skies. 😊

[barkis]

A 6"F8 Newtonian would serve you well for Double Star   observations.
With a secondary not too large, but big enough to collect all the reflected  light,
and a suitable focuser with a low profile too, the scope would also  make a nice planetary instrument.
Observing planets and the moon in a light mist is worth doing too, it ensures the earth's atmosphere is relatively still
and so no boiling or shimmering to annoy you.
A well corrected 8"F8 Newt. would be a better choice mind you, depends on your budget of course.
There's always the used market for a bargain.
Ron.

[rwilkey]

Hi Chris, I live just one mile from the town centre in Swindon and the colours of Alberio and many other well known double stars is amazing, you will not be dissappointed!  I find my refractor the best scope for looking at double stars.

[Mr Spock]

From my heavily polluted skies double stars are one of few targets available. Doesn't matter whether I use my 80mm apo or C9.25, they all look colourful. The apo is especially pleasing; I don't know why, it just gets star images right.

[cletrac1922]

Hi Guys

Where I am have Bortle 4

Further inland, now getting issue with light pollution due to mining and coal seam gas power generation

Have never looked for double stars

John

[Alan64]

On 25/07/2019 at 17:07, cletrac1922 said:

Hi Guys

Where I am have Bortle 4

Further inland, now getting issue with light pollution due to mining and coal seam gas power generation

Have never looked for double stars

John

My skies are at about that, and I haven't really pursued double-stars myself, but that's about to change, and with this...

...a 5" Maksutov, and with a 1900mm focal-length; considerably longer than that of a 10" "Dobsonian".   Zowie!  I've only had it out at night once.  Reaching the higher powers for the splitting of double-stars is most readily accomplished with that one, and I'm referring to the physical act of popping this short focal-length eyepiece and that into the focusser; the scaling upwards fluid and butter-smooth, the images sharp and crisp, and all in a compact, ergonomic package. 

Per the design, a 5" Maksutov is not too small, nor too large, just right rather.  

[PlanetGazer]

On 05/07/2019 at 20:25, Alan64 said:

Quite a few double-stars require higher powers to split them, and to see the differing colors.  A short-focus achromat(refractor) and a short-focus Newtonian/"Dobsonian" are going to be problematic in that regard.

Still, refractors and Maksutovs are best for double-star observations.

In so far as light-pollution, there are several ways to lessen its effects whilst observing, and with some requiring a bit of DIY, arts-and-crafts type work.

Would love to hear about the arts and crafts that would reduce the effects of Light Pollution

[vlaiv]

7 minutes ago, PlanetGazer said:

Would love to hear about the arts and crafts that would reduce the effects of Light Pollution

I can name a few that I'm aware of:

- observe target when it is highest in the sky and in region the least effected by light pollution.

- use filters that are appropriate for target you are observing that lessen effects of light pollution (there are several choices of filters but not all filters are suited to all targets, UHC tends to work the best but it's suited to emission nebulae for example)

- transparency of the sky is related to LP levels - aim for transparent skies for best results. It has dual effect - target light is attenuated the least and LP is scattered much less when sky is very transparent. Avoid haze and too much moisture in the air. There are online services that give you transparency forecast - that is useful when planning a session.

- when observing point sources like stars, atmospheric seeing also has effect. Steady atmosphere lets star light be concentrated in single point and not smeared so it is at peak intensity and easier to see - both to detect and to detect color as threshold for both depends on amount of light

- if looking for faint stuff be sure that you are dark adapted. This means shielding from local light sources and creating dark environment. It can be as simple as putting dark cloth over your head when you are at the eyepiece. Mind you, point is not to cover your head but rather to shield from surrounding light - so make cloth long enough and possibly keep it wrapped from below with one hand or something.

- dark adaptation hurts your color vision, so if you plan to look at doubles trying to see their color, or when observing planets - don't get fully dark adapted, keep some soft light on nearby (if you are in the back yard for example - soft light coming from your windows is enough - no need to turn on porch light or anything like that). On nights of full moon - moonshine will be enough of light to keep you from dark adaptation.

[Alan64]

2 minutes ago, PlanetGazer said:

Would love to hear about the arts and crafts that would reduce the effects of Light Pollution

You want the entire interior of the telescope to be dead to all stray-light, to all reflections, for example...

The inside of that tube was flocked.  This is flocking...

The flocking is self-adhesive.  It's like very low pile carpeting, but for the telescope, and jet-black.  The surface should be glossed before applying the flocking.  It eats light instead of reflecting it, improving the contrast; blacker sky backgrounds, blacker shadows within the craters and other features of the Moon.  Stray light sources include street, porch, security, and automobile lights.  If observing deep-sky objects, the Moon can be a source of stray light as well.

For those areas inside a telescope that cannot be flocked, those are painted with the flattest and blackest paint available per locale.  For example, these nuts for adjusting the spider-vanes, on the outside of the tube, protrude into the telescope, and were blackened...

In the case of that Newtonian, the only areas that reflect are the mirrors themselves.  External light shields, made from PVC tubing and tarps, and a black drape over the head, like that of yesteryear's photographers, also help to combat light pollution.  Sky-glow however is improved with special filters, or once were.  

 

[vlaiv]

2 minutes ago, Alan64 said:

You want the entire interior of the telescope to be dead to all stray-light, to all reflections, for example...

I forgot flocking, very important thing with some telescope designs (some that use internal baffling are less affected).

With newtonian design, you want to extend tube (can be blackened cardboard / plastic extension like dew shield) so that focuser is at least 1.5 times diameter of tube from the scope aperture. This again prevents stray light reaching tube walls opposite focuser and improves contrast (although you have flocking and light absorbing paint it is better if light does not reach those places at all).

[Alan64]

1 minute ago, vlaiv said:

I forgot flocking, very important thing with some telescope designs (some that use internal baffling are less affected).

With newtonian design, you want to extend tube (can be blackened cardboard / plastic extension like dew shield) so that focuser is at least 1.5 times diameter of tube from the scope aperture. This again prevents stray light reaching tube walls opposite focuser and improves contrast (although you have flocking and light absorbing paint it is better if light does not reach those places at all).

In turn, I had forgotten about the dew-shield, in this case a light-shade...

https://stargazerslounge.com/uploads/monthly_04_2011/post-21419-133877556647.jpg

[PlanetGazer]

Thanks! Very good info. I already use a LP filter and observe objects that are only high and at a manageable angle, to tackle the atmosphere and LP issues.

 

I will consider flocking and using a cloth, wonder what will my neighbors think of the blanket xD

[PlanetGazer]

6 minutes ago, Alan64 said:

In turn, I had forgotten about the dew-shield, in this case a light-shade...

https://stargazerslounge.com/uploads/monthly_04_2011/post-21419-133877556647.jpg 71.11 kB · 0 downloads

sorry for this question, but won't the shield extend the focal length of the telescope? which could be an advantage for fast telscopes

[vlaiv]

2 minutes ago, PlanetGazer said:

sorry for this question, but won't the shield extend the focal length of the telescope? which could be an advantage for fast telscopes

No it won't. It is just a physical extension of the tube, it neither changes distance between the mirrors nor shape of them, and those are things that define focal length of scope (actually just shapes, but they need to be properly spaced so you can reach focus and get proper illumination at eyepiece). It is concern only if you extend physical tube between primary and secondary mirror but this is extension outside of this zone.