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BU 232 AB in Cass

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#1 rugby

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Posted 20 October 2019 - 10:32 PM

I observed recently BU 232 in Cass. At 8.4 and 8.7 it is the faintest sub arc-second pair I have tried. In the 120mm at 300x I detected elongation east to west with averted vision. This guess is close to the 256 degrees that Stella  Doppie lists.  I had very steady seeing.

Nucleophile may want to include this pair in his research. 


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#2 fred1871

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Posted 20 October 2019 - 11:37 PM

Slightly puzzled, as to why averted vision was used to detect elongation, rather than used for a faint and separated companion. The magnitudes don't sound dim enough for a 120mm aperture to need averted vision. And it can reduce sharpness of vision. Beyond mag 9 would be faint enough, with 120mm, to encourage trying a.v.. Were you observing it when the Full Moon (or nearly Full) was in the sky? - hence "observed recently"?

 

If the separation is 0.9" (as per WDS), this is roughly 0.8-Rayleigh for 120mm aperture, and might therefore in good seeing in a dark sky appear as a notched-elongation pair.


Edited by fred1871, 20 October 2019 - 11:40 PM.

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#3 rugby

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Posted 21 October 2019 - 07:43 AM

Fred1871: Thank-you for responding to this post. I always look forward to your input. I live within the boundaries of a city of nearly a half million people. Probably I am losing two mags to light pollution if not more. Add to that a rising moon. Although I could see the star directly it did not show as an elongation until I used averted vision. I will try again when the moon is absent. 

Despite the shortcomings due to lighting I am blessed with very steady seeing many times per year. Let me blame advancing age instead.

May I ask what are your seeing conditions


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#4 gfeulner

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Posted 21 October 2019 - 08:44 PM

First of all Rugby, I enjoy reading your observations of the fainter double stars. Tonight I observed BU 232 in Cassiopeia with my TEC 140. I was able to elongate it at 288x. The seeing wouldn't allow any higher magnification. The 10th mag star at 24.5 seconds made it easier to identify. While I was in the vicinity I also checked BU 394 (Sao 36427) 8.49 and 8.77 sep 0.90. I was able to split it with black sky between it at 288x  There's an 11th mag companion at 105 arc seconds. Next was BU 235 (Sao 22060) 7.54 and 7.82 sep 0.80. This was also elongated but not split. Nearby was STF 96 (Sao 11631) 7.92 and 8.92 sep 0.90. The one mag difference made it impossible to split in my 3rd mag skies. I'll try it at my dark site next chance I get. The seeing wasn't too bad with 36 Andromeda giving me a beautiful clean split.I got the information from Stelle-Doppie. If you try these, I'd like to read your observations.

Gerry


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#5 fred1871

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Posted 22 October 2019 - 12:05 AM

@rugby  Yes, I also have quite a deal of light pollution, because of living in a suburban area. On moonless nights I can however still see to around magnitude 5 naked eye. At present we have major drought conditions in much of Eastern Australia, so there's more dust in the air than usual; as a result moonlight has more of a brightening effect on the sky background than in periods of normal rain which result in less dust in the air. So around Full Moon I only observe brighter doubles, or planets. The Moonlight kills the dimmer stars too effectively.

 

In moonless conditions I've seen stars to around magnitude 13.2 with my 140mm refractor. Near Full Moon, these days, magnitude 11 tends to disappear, whereas a few years ago mag 11 was still easy enough with moonlight just by using a higher power, say 200x instead of 100x.


Edited by fred1871, 22 October 2019 - 02:30 AM.

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#6 rugby

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Posted 22 October 2019 - 12:33 PM

Gerry: I appreciate the challenges you offered and will hunt for them as soon as possible ( which means tonite weather permitting). Can you tell me what mount you use with the 140 and how much light pollution you have to deal with.

 

Fred 1871: my limit for the 120 is around 11  or so under a moonless sky. I will not be able to match the 13.2 unless I use a bigger aperture. Based on the quality of your observations and depth of knowledge about doubles I can only think you have a professional background.



#7 gfeulner

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Posted 22 October 2019 - 01:25 PM

Gerry: I appreciate the challenges you offered and will hunt for them as soon as possible ( which means tonite weather permitting). Can you tell me what mount you use with the 140 and how much light pollution you have to deal with.

 

Fred 1871: my limit for the 120 is around 11  or so under a moonless sky. I will not be able to match the 13.2 unless I use a bigger aperture. Based on the quality of your observations and depth of knowledge about doubles I can only think you have a professional background.

I use a Skywatcher Atlas PRO in Alt azimuth mode and Go To. I live in New Jersey with a large shopping center half a mile away so the transparency is 4th mag at best. I do have a dark site that I go to where the milky way is faintly visible. At this site the 13th mag star next to M57 is easily visible in my 140.

Gerry


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