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Double Star Session in Boo with faint companions

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#1 WRAK

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Posted 28 June 2013 - 04:31 PM

Last night I got the present of a 2 hour window with clear sky with the bonus of fair Pickering ~7 seeing. Rising 3/4 moon made the sky rather bright with NEML ~2.8mag. I was at the beginning of the session not aware of the very good transparency thus I did not expect much but simply tried with my 140mm refractor besides some other doubles:

STT270 HIP 67275, WDS13473+1727 13h 47m 15,7s +17:27:24,8 2,7" +4,5/11,1mag: x280 egg pointing at noon = ~ position according to WDS 31°. Must have been a lucky guess as this seems impossible with 140mm

HJ533 WDS13388+1926 13h 38m 44,0s +19:25:47,4 13,4" +10,29/12,29mag: x200 companion dedected at 7:30 with averted vision. If the magnitude for the companion is correct than this the faintest star I have ever seen with the 140mm refractor with this amount of light pollution

COU58 WDS13587+1711 13h 58m 39,3s +17:10:48,4 1,4" +10,27/11,64mag: x200 tiny rod pointing to 11 o'clock meaning the ~ right position of 2°. This should require a much larger aperture - just another lucky hit?

A2064 WDS14034+1740 14h 03m 24,6s +17:40:00,1 1,1" +9,61/11mag: This one did not work - no resolution, not even a hint for a double

BU30 HIP 68237, WDS13581+1928 13h 58m 07,4s +19:27:29,8 8,1" +8,82/11,78mag: x75 very faint at 5 o'clock. Companion disappears with higher magnifications.

I got then a bit cocky and tried Theta CrB - should have been possible even with 140mm with this seeing conditions if the advertised parameters would be valid. No hint of a double but thin clouds have meanwhile appeare so this was it.
Wilfried

#2 Nucleophile

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Posted 28 June 2013 - 06:55 PM

Thank you for the fine report, Wilfried.
I checked my notes and I havent looked at any of these yet.

The following are of the most interest:

COU58 WDS13587+1711 13h 58m 39,3s +17:10:48,4 1,4" +10,27/11,64mag: x200 tiny rod pointing to 11 o'clock meaning the ~ right position of 2°. This should require a much larger aperture - just another lucky hit?"
This is a pretty good result I would think--congrats!

"A2064 WDS14034+1740 14h 03m 24,6s +17:40:00,1 1,1" +9,61/11mag: This one did not work - no resolution, not even a hint for a double"
I want to take a peek at this one tonight with the 8 inch---the pA calculator gives a value of 169mm for this instrument---should be a good test. May even look at it with the stepped down 15 inch to 6 inch..........

Finally, I also have been viewing doubles with faint companions--mostly with negative results--I believe I have had the magnification cranked up too high.

I continue to take cracks at Epsilon CrB--just seems like I should be able to see it with the 15 inch---the latest version of my calculator for this instrument seems to think so as well. Negative results are of great interest, however, particularly if they are replicated over many nights.



I have to admit, I am becoming allergic to COU doubles as I have had severe trouble with many of them in the past week

#3 Nucleophile

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Posted 29 June 2013 - 11:01 PM

A2064 WDS14034+1740 14h 03m 24,6s +17:40:00,1 1,1" +9,61/11mag: This one did not work - no resolution, not even a hint for a double


I tried this one last night with several instruments on a night of good transparency and average seeing (Pickering 6-7):

A) 8 inch reflector: no hint of a companion up to 276x ( I should have tried other magnifications, but needed to move along).

B) 15 inch reflector fitted with off axis mask yielding 6 inch f/10-like refractor: no hint of companion at 398x; primary appears quite dim (probably should have looked at lower magnifications)

C) 15 inch reflector fitted with on axis mask yielding 11 inch f/7 reflector with CO = 0.25: companion suspected quite close to primary in correct position angle at 398x; increasing magnification to 569x shows the secondary as a faint speck that is resolved from the primary

D) 15 inch reflector: 569x: despite issues with seeing, companion clearly seen as resolved in same place as seen with the "11 inch"; going down in magnification to 398x only shows the secondary as a pointy extension.

The object seemed harder to split than a 1.1" variety with not too faint stars of modest delta magnitude (at least for the 15 inch instrument)---I wonder if it is actually a bit closer now?

The WRAK calculator gives it a value of 169 when using the 8 inch reflector---something is amiss. I should like to try this one again with the 8 inch.

#4 WRAK

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Posted 30 June 2013 - 03:07 AM

The change from 1.4" in 1909 to 1.1" in 2010 suggests a slow closing or simply more precision. +11mag for the secondary makes me cautious - these zero digit numbers are usually wrong.
AAVSO lists for the primary +9.418mag but there is no value for the secondary.
Wilfried


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