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Effects of Light Pollution on Resolving Doubles

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#1 WRAK

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Posted 24 February 2013 - 04:09 PM

When I started observing doubles from my light polluted location I was convinced that light pollution had to have some negative effects - but reality showed different at least for doubles with companions brighter than +10mag where I found no noticeable impact.
Only with increasing faintness of the companion things get different as the telescope magnitude limit is reduced to some degree by light pollution depending on NEML and the size of the telescope - the smaller the less the impact.
Another impact is the reduced possibility to increase magnification beyond 2xD_mm also depending on the size of the scope (also the smaller the less the impact) - light grey blobs on slightly darker light grey background are no pretty sight and especially fainter companions simply disappear against the background.
So there are some limitations under specific conditions but not very serious ones - double stars are certainly the objects of choice for light polluted skies.
Wilfried

#2 Tom and Beth

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Posted 24 February 2013 - 04:34 PM

Another reason why you shouldn't put your scope away during Full Moon. If not for an approaching Storm last night would have been spectacular! It was just a matter of balancing the power between sky background and smearing effects due to the turbulance.

#3 PJ Anway

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Posted 24 February 2013 - 06:34 PM

I would think that light pollution would have only a small effect on "resolving doubles". A much larger effect on "finding doubles" though. :grin:

#4 Ed D

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Posted 24 February 2013 - 07:54 PM

I would think that light pollution would have only a small effect on "resolving doubles". A much larger effect on "finding doubles" though. :grin:


That has also been my experience in heavy LP.

Ed D

#5 Rich (RLTYS)

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Posted 25 February 2013 - 06:39 AM

True, finding doubles in LP skies can be a challange.

Rich (RLTYS)

#6 Bonco

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Posted 25 February 2013 - 04:08 PM

For small scopes,4 inch or less, minimal effect for doubles brighter than 6th magnitude or so. Significant effect on dim doubles or a dim secondary like Propus. Bright doubles like Castor, Alnitak, Eta Orionis, Rigel, Izar, Pi Aquilae, Almach, to name a few are not significantly affected.
Bill

#7 David Knisely

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Posted 25 February 2013 - 09:33 PM

I really like using my NexStar 9.25 inch SCT on my driveway on moon-lit nights to look at double stars, since its Go-To will find just about any double I might be interested in. Indeed, I often use it with my laptop and MEGASTAR to just "click and point" to any double that is shown on-screen by the software. I have scoured old lists for color-contrasting doubles that way and found that many don't show either much color contrast at all or have a different color set than is shown in the literature. It has allowed me to hone my "color contrast" list down to something reasonable while still introducing me to a lot of interesting double stars. The 9.25 is about the perfect size a scope for me since it has enough aperture to go to my local seeing levels without being too much of a hassle to set up and run.

#8 Sarkikos

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Posted 27 March 2013 - 07:55 AM

David,

I really like using my NexStar 9.25 inch SCT on my driveway on moon-lit nights to look at double stars, since its Go-To will find just about any double I might be interested in. Indeed, I often use it with my laptop and MEGASTAR to just "click and point" to any double that is shown on-screen by the software. I have scoured old lists for color-contrasting doubles that way and found that many don't show either much color contrast at all or have a different color set than is shown in the literature. It has allowed me to hone my "color contrast" list down to something reasonable while still introducing me to a lot of interesting double stars.


Do you have your scrubbed and cleaned color-contrast list available in a form you could post here or online elsewhere? That sounds like something a lot of observers would be interested in. I know I would. CC's are some of my favorite doubles.

:grin:
Mike

#9 WRAK

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Posted 27 March 2013 - 03:42 PM

I really like using my NexStar 9.25 inch SCT on my driveway on moon-lit nights to look at double stars...


Good news for me - I use primarily a 140mm recfractor for my double star observing sessions (means more or less all) as I am so far not this satisfied with my C925 for this purpose. But I intend to test it again as I would like to get some own limit observations with larger apertures than 140mm but before I invest in an expensive iris diaphragm this large I need to see if the C925 is up to my requirements. But the so far not this good performance seems to be due to the micro climate on my second observation location with not so heavy light pollution but with a sharp drop of temperature in the evening and therefore turbulent air and therefore problems with quality of seeing and also dew.
Concerning locating doubles with heavy LP: As I do old fashioned star hopping this is another reason to use a short APO as this means large field of view of in my case up to 3° and I make my session plan routes with a brigth entry point of +3mag or brighter with hops less than 3° and I need very seldom hops not beeing doubles themselves.
Wilfried

#10 David Knisely

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Posted 27 March 2013 - 09:53 PM

David,

I really like using my NexStar 9.25 inch SCT on my driveway on moon-lit nights to look at double stars, since its Go-To will find just about any double I might be interested in. Indeed, I often use it with my laptop and MEGASTAR to just "click and point" to any double that is shown on-screen by the software. I have scoured old lists for color-contrasting doubles that way and found that many don't show either much color contrast at all or have a different color set than is shown in the literature. It has allowed me to hone my "color contrast" list down to something reasonable while still introducing me to a lot of interesting double stars.


Do you have your scrubbed and cleaned color-contrast list available in a form you could post here or online elsewhere? That sounds like something a lot of observers would be interested in. I know I would. CC's are some of my favorite doubles.

:grin:
Mike


Yup, here it is:

* * * * * * COMMON DOUBLE STARS WITH SIGNIFICANT COLOR CONTRAST * * * * * *
. . . . . . . . . . . (positions, separations, and position angles for eq. 2000) . . . . . . . . .

LEGEND: R.A. = Right Ascension (2000.0) Dec. = Declination
mag. = apparent visual magnitude sp. = spectral type
Sep. = separation (in arc seconds) P.A. = position angle
********************************************************************

Otto Struve (STT) 254, R.A. 0h 1.3m Dec. +60d 21.3'
Primary: mag. 7.2~ (variable) Sp. C5p, Secondary mag. 8.3, sp. A
Sep. 58" arc, P.A. 90 deg. (multiple optical double)
Colors seen in 10 inch: deep reddish-orange and bluish-white.
(primary is Carbon star WZ Cas, other stars also nearby)

Sturve 3053, R.A. 0h 2.6m Dec. +66d 6.0'
Primary: mag. 5.9, sp. G9III, Secondary mag. 7.3, sp. A1V
Sep. 15.0" arc, P.A. 70 deg.
Colors seen in 10 inch: Yellow and pale bluish.

Eta Cassiopeiae, R.A. 0h 49.10m Dec. +57d 49.0'
Primary: mag. 3.4, sp. G0V, Secondary: mag. 7.5, sp. dM0
Sep. 12.8" arc, P.A. 317 deg. (period: 480 years)
Colors seen in 10 inch: Off-white and faint reddish-orange.

ALMACH (Gamma And.), R.A. 2h 3.90m Dec. +42d 19.8'
Primary: mag. 2.2 sp. K3III, Secondary: mag. 4.8 sp. B8V
Sep. 9.8" arc, P.A. 64 deg. (mag. 6.3 companion of Gamma-B at 0.4" arc,
p.a. 103 deg., closing separation).
Colors seen in 10 inch: Yellow (Gold) and light blue.

6 Triangulae (Struve 227), R.A. 2h 12.37m Dec. +30d. 18.3'
Primary: mag. 4.9, Sp. G5III, Secondary: mag. 6.5, Sp. F6V
Sep. 3.9" arc, P.A. 69 deg.
Colors seen in 9.25" SCT: Yellowish-white and bluish-white.

32 Eridani, R.A. 3h 54.29m Dec. -2d 57.3'
Primary: mag. 4.5, sp. G8III, Secondary: mag. 6.1, sp. A2V
Sep. 6.9" arc, P.A. 348 deg.
Colors seen in 10 inch: Yellow and pale blue.

15 Geminorum, R.A. 6h 27.8m Dec. +20d 47.3'
Primary: mag. 4.6, sp. K0, Secondary: mag. 8.5, sp. G0
Sep. 6.9" arc, P.A. 64 deg.
Colors seen in 10 inch: Yellowish-orange and white.

Psi-5 Aurigae, R.A. 6h 46.75m Dec. +43d 34.6'
Primary: Mag. 5.3 sp. G0V, Secondary: mag. 8.5 sp. M0V
Sep. 31.1" arc, P.A. 38 deg.
Colors seen in 10 inch: Off-white and faint orange.

38 Geminorum (STF 982), R.A. 6h 54.64m Dec. +13d 10.7'
Primary: mag. 4.7, sp. A8/F0V, Secondary: mag. 7.7, sp. G6V
Sep. 7.1" arc, P.A. 144 deg.
Colors seen in 10 inch: White and faint orangish.

h3945 (ADS 5951, CMa), R.A. 7h 16.61m Dec. -23d 18.9'
Primary: mag. 4.8 sp. K4III, Secondary: mag. 6.8, sp. A5
Sep. 26.6" arc, P.A. 55 deg.
Colors seen in 10 inch: Orange and bluish-white.
"The Winter Albireo"

S 548 (ADS 6087, Gem), R.A. 7h 27.7m Dec. +22d 8.0'
Primary: mag. 6.9 sp. K5, Secondary mag. 8.9 sp. ?
Sep. 35.5" arc, P.A. 277 deg.
Colors: Orangish and bluish

Iota Cancri, R.A. 8h 46.70m Dec. +28d 45.6'
Primary: mag. 4.0 sp. G8II, Secondary: mag. 6.6 sp. A3V
Sep. 30.5" arc, P.A. 307 deg.
Colors seen in 10 inch: Light yellow and pale blue.

Tau Leonis, R.A. 11h 27.94m Dec. +2d 51.3'
Primary: mag. 4.9 sp. G8Iab, Secondary: mag. 7.4 sp. G5
Sep. 89.7' arc, P.A. 180 deg.
Colors seen in 10 inch: Yellow and white.
*nice low power pair with double 83 Leonis 20' at P.A. 298 deg.

2 Canum Venaticorum, R.A. 12h 16.13m Dec. +40d 39.6'
Primary: mag. 5.7, sp. M1III, Secondary: mag. 8.7, sp. F7V
Sep. 11.3" arc, P.A. 260 deg (2003).
Colors seen in 10 inch: Yellowish-orange and pale bluish-white.

24 Comae Berenices, R.A. 12h 35.13m Dec. +18d 22.6'
Primary: mag. 5.0 sp. K2III, Secondary: mag. 6.6 sp. A7V
Sep. 20.3" arc, P.A. 271 deg.
Colors seen in 10 inch: Yellow and pale blue.

Cor Caroli (Alpha CVn), R.A. 12h 56.00m Dec. +38d 19.1'
Primary: mag. 2.9 sp. A0spe, Secondary: mag. 5.6, sp. F0V
Sep. 18.8" arc, P.A. 230 deg.
Colors seen in 10 inch: Bluish-white and off-white (cream).

Izar (Epsilon Bootis), R.A. 14h 44.99m Dec. +27d 4.5'
Primary: mag. 2.4 sp. K0II, Secondary: mag. 5.1, sp. A2V
Sep. 2.8" arc P.A. 339 deg.
Colors seen in 10 inch: Yellow and light blue.

Xi Bootis, R.A. 14h 51.39m Dec. +19d 6.0'
Primary: mag. 4.5, sp. G8V, Secondary: mag. 6.8, sp. K5V
Sep. 6.8" arc P.A. 320 deg.
Colors seen in 10 inch: Pale yellowish white and orange.

Antares (Alpha Sco). R.A. 16h 29.41m Dec. -26d 25.9'
Primary: mag. 1.0v sp. M1I, Secondary: mag. 5.4 sp. B4
Sep. 2.6" arc P.A. 274 deg.
Colors seen in 10 inch: Orange and light blue.

Ras Algethi (Alpha Her) R.A. 17h 14.65m Dec. +14d 23.4'
Primary: mag. 3.2v sp. M5II Secondary: mag. 5.4, sp. F2/G3
Sep. 4.6" arc P.A. 104 deg.
Colors seen in 10 inch: Reddish-orange and pale bluish-white.

95 Herculis. R.A. 18h 1.5m Dec. +21 deg. 36'
Primary: mag. 4.9, Sp. A5III, Secondary: Mag. 5.2 sp. G5?
Sep. 6.3" arc P.A. 256 deg.
Colors seen in 10 inch: pale bluish-white and gold.

59 Serpentis, R.A. 18h 27.2m Dec. +0d 45.9'
Primary: mag. 5.2, Sp. GOIII, Secondary: mag. 7.4, sp. ?
Sep. 3.9" arc P.A. 320 deg.
Colors seen in 10 inch: Yellowish-white and pale bluish-white

Omicron Draconis, R.A. 18h 51.20m Dec. +59d 23.3'
Primary: mag. 4.6, Sp. G9III, Secondary: mag. 8.1, sp. K3III
Sep. 36.5" arc P.A. 319 deg.
Colors seen in 10 inch: Yellow and faint orangish

SHJ 282 (O. Struve 525), Lyra), R.A. 18h 54.90m Dec. +33d 58.0'
Primary: mag. 6.1, sp. G8III Secondary(s): mag. 9.1, sp. A8
B component Sep. 1.8" arc, P.A.188 deg . (O. Str 525)
C component: mag. 7.7 Sp. A1, Sep. 45.4" arc P.A. 350 deg.
Colors seen in 10 inch: Yellowish-white and bluish-white.

Albireo (Beta Cyg) 19h 30.72m Dec. +27d 57.6'
Primary: mag. 3.1 sp. K3II Secondary: mag. 5.1 sp. B8V
Sep. 34.3" arc P.A. 54 deg.
Colors seen in 10 inch: Yellow and light blue.

ADS 12900 (Cyg). 19h 45.86m Dec. +35d 0.77'
Primary: mag. 6.1 sp. K2? Secondary: mag. 8.6 sp. A2V
Sep. 37.5" arc P.A. 25 deg.
Colors seen in 10 inch: Yellow and blue.

Gamma Delphini, R.A. 20h 46.73m Dec. +16 deg. 7.8'
Primary: mag. 4.4 sp. K1IV, Secondary: mag. 5.0 sp. F7V.
Sep. 9.6" arc P.A. 268 deg.
Colors seen in 10 inch: Yellowish and white (hint of blue)?

12 Aquari, R.A. 21h 4.1m Dec. -5 deg. 49'
Primary: mag. 5.8 sp. G4III, Secondary: mag. 7.5 sp.?
Sep. 2.5" arc P.A. 196 deg. (2003)
Colors seen in 10 inch: Yellowish-white and pale bluish-white.

Delta Cephei R.A. 22h 29.20m Dec. +58d 25'
Prmary: mag. 4.07 (variable) sp. F5-G3 Secondary: mag. 6.27 sp. B7
Sep. 40.8" arc P.A. 191 deg.
Colors seen in 10 inch: Yellowish-white and light blue.

Clear skies to you.

#11 Sarkikos

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Posted 28 March 2013 - 05:50 AM

Thanks, David.

A few of these are already familiar to me. But I'm still a newbie to doubles, so I'm sure there are a number in your list that will be fresh to my eyes.

Mike

#12 exparrot

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Posted 31 March 2013 - 12:03 AM

I have a Meade 8" SCT that does pretty well in my light polluted skies. I can see some pretty faint companions, of 10 mag and maybe 11 mag on occasion, but the sky has to be really stable and transparent. I was just looking back at a list of doubles near Rigel that I observed in early December. I wrote in my log that I could see the faint 12.5 mag B companion of HD 32394 (8.9+12.5 mag, PA 57° Sep 20.80"). But, I could only see it with averted vision. That's not an uncommon experience for me with very dim companions and light pollution.

Jerry

#13 WRAK

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Posted 01 April 2013 - 04:25 AM

Jerry, +12.5mag with averted vision for an 8" scope with TML ~14.2 seems combined with light pollution plausible. With NEML ~3 I get a limit of ~11.8mag for my 5.5" scope with TML +13.4mag. Do you remember the Naked Eye Magnitude Limit for this observation?
Wilfried

#14 exparrot

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Posted 01 April 2013 - 08:15 AM

No, I didn't note it, but the typical NEML from my backyard location is Mag 3.

On that same night, I was unable to split SAO 131902 (AB: 9.68+12.26 mag, PA 352° Sep 6.57"), which is tighter in separation.

Here's a copy of the list I worked in pdf format. All fairly easy splits.

Attached Files



#15 blb

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Posted 01 April 2013 - 10:04 AM

I do not see any effect from light pollution on the seperation that can be resolved, but light pollution has a big effect on the faintest star that can be seen. From home my typical NELM is about 4 mag. and that means I can only see to about 11th to 11.5 mag. with my C11. However from a dark sky site I have seen to mag. 13.5 with my 4-inch TV102 refractor. Light pollution has a big effect on how faint a star can be seen but no effect on the seperation that can be resolved, that may mean that I can not see a fainter companion that could be easily seen if the sky were darker.

#16 cildastun

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Posted 01 April 2013 - 01:12 PM

Worth noting perhaps that there are cases reported (eg the Pup of Sirius) where the fainter companion star can be seen better with LP. I've certainly found the Pup easier with moonlight or a dawn-lit sky.

Chris

#17 WRAK

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Posted 01 April 2013 - 01:49 PM

Jerry, I think with separations in the single digit range it gets harder to resolve very faint companions near the TML modified accordingly to light pollution. I am happy to add your 8" scope +12.5mag limit with NEML +3mag to my data set for this research as bad weather prohibits so far own observations.

Buddy, your remark regarding the non influence of separation surprises me a little bit, I see it the other way as mentioned above. Also NEML of +4mag and limit observation of +11 to 11.5mag with a C11 seems not very plausible to me as +11.8mag is so far my own observed limit for a 5.5" scope with NEML +3mag - I would at least expect +13.2mag for the combination 11" scope with NEML +4mag.

Chris - Sirius, Rigel et al. with a glaring primary and a much fainter companion are certainly in a special class regarding resolution of unequal bright doubles. LP helps a bit to reduce the glare of the primary.
Wilfried

#18 acafar

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Posted 08 April 2013 - 01:34 PM

I use color filters to split some unequal bright pairs. They really help. Maybe LP can serve as a filter for these special pairs.

Thank you, David for the list of pairs

#19 dUbeni

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Posted 26 April 2013 - 07:57 AM

I use color filters to split some unequal bright pairs. They really help.


Great solution, never thought of it.
Which color filter do you use on your 4"?
I use a 4,5", so the same color filter would problably work for me also.

CS
bernardo

#20 blb

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Posted 26 April 2013 - 01:51 PM

Buddy, your remark regarding the non influence of separation surprises me a little bit, I see it the other way as mentioned above. Also NEML of +4mag and limit observation of +11 to 11.5mag with a C11 seems not very plausible to me as +11.8mag is so far my own observed limit for a 5.5" scope with NEML +3mag - I would at least expect +13.2mag for the combination 11" scope with NEML +4mag.


I would think that you are probabily correct because I was not using a very high magnification when I was looking for this limit. I will have to check it out again since over the years I have learned that the higher the mag. the fainter the stars that can be seen.
:foreheadslap:






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