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Can anyone see this secondary.....

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#1 HowardK

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Posted 19 August 2013 - 11:32 AM


I can't in a C8 under average seeing...

Burnham 363
20h 31.0m
+20,36'

PA 70
Sep: 6.0"
A...mag 6.2
B...mag ??????

#2 blb

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Posted 19 August 2013 - 12:48 PM

My guess is that there is to much light pollution where you are located, because I have seen mag. 13.5 stars in my 4-inch TV102 refractor from a dark site and Sissy Haas's book "Double Stars for Small Telescopes" has a chart that shows I should be able to seperate a double star with a difference in magnitude of 4.0 and a seperation of 2.8". So my question would be, what is your telescopes limiting magnitude for the site your observing from?

The information for this double star from the Washington Double Star data base web site is:
Burnham 363 20h31.0m +20d36m
Pair _ PA _ Sep. _ Mag.A _ Mag.B _ Epoch
AB __ 81* __6.6" __6.18 _ 10.0 _ 2008
AC _ 206* _54.1" _ 6.18 _ 13.0 _ 2006

#3 WRAK

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Posted 19 August 2013 - 02:01 PM

Even severe light pollution has a rather moderate influence on TML - so a +10mag companion cannot with this large separation be a topic of TML and this double should even with NEML +3.5mag be doable with apertures below 100mm. Did not try it myself so far but Del is from mid Septemver in my field of view so I will include it in my planned sessions.
WDS indicates 13 observations but interestingly this double is also listed in the neglected sub catalog but with a +11.8" separation.

Wilfried

#4 HowardK

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Posted 19 August 2013 - 02:24 PM

Would be very interested in your observing notes on this AB pair.

I suspect that the B component is much fainter than mag10

#5 WRAK

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Posted 19 August 2013 - 03:08 PM

Checked AAVSO - no measurements for this position

#6 HowardK

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Posted 19 August 2013 - 05:23 PM

Give it a go next time out.
Let us know what you see...or don't !

#7 3c_273

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Posted 19 August 2013 - 05:31 PM

Here's the entry for this star in the most recent edition of the WDS:

17543-2558B 363 1926 1991 4 42 43 0.3 0.3 9.62 10.23 G1/2V +029-012 -2512413 175418.35-255743.7

For a detailed explanation of the columns, go to:

http://ad.usno.navy....snewframe3.html

Note that in columns 8-9, the star is listed as being 0.3" apart. That's tough for a C-8. The best I've been able to do with mine so far is to elongate, not split 0.5" stars. This is, of course, what you'd expect, given the Dawes' limit for our 'scopes is ~0.6".

Note also that it's easy to find inaccurate information about double stars in a wide variety of sources, especially the older ones. The WDS is hardly immune, I've made a listing of some of the anomalies I've found in it:

http://mainsequence....sAnomalies.html

#8 fred1871

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Posted 19 August 2013 - 06:00 PM

Tom, you've got the wrong star - if you look at the data line you've copied from WDS, you'll see the star you've found data for is B 363 - but the question was about BU 363.

B is the abbreviation for WH van den Bos.
BU is the abbreviation for Sherburne Wesley Burnham.

#9 fred1871

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Posted 19 August 2013 - 06:15 PM

Howard, I looked at BU 363 a few years ago, and found exactly the problem you're describing. With both 140mm refractor and C9.25 I could not definitely see the closer companion of what the WDS lists as a triple. With both telescopes I could see the wider mag 13.0 companion.

As Wilfried has pointed out, if the numbers on the closer companion are correct, it should be visible with 100mm aperture. I've seen various other doubles with similar separation and brightness as listed for this one, without difficulty in my 140mm refractor.

Likely answer is again photometry - that the 'B' star is a lot fainter than listed. I looked at BU 363 in 2008 and 2010 without seeing what should be a not too difficult pair.

I notice that Sissy Haas in her book remarks that she (also) did not see the companion with a 125mm refractor.

#10 3c_273

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Posted 19 August 2013 - 07:00 PM

Akkk! Apologies!

#11 HowardK

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Posted 19 August 2013 - 09:53 PM

Thanks Fred

Good to know im not alone

#12 WRAK

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Posted 21 August 2013 - 04:59 PM

Tried tonight with an 120mm refractor from my second observing location with an earlier view on Del but nearly full moon and especially fast moving clouds made it impossible for me to even locate BU363. Maybe next time ...

#13 HowardK

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Posted 24 August 2013 - 12:30 PM

Keep in touch

#14 WRAK

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Posted 25 August 2013 - 05:12 AM

Last night unexpected clear skies with only a few thin clouds, 3/4 moon below horizon, NEML about +3.5mag. High humidity, brighter stars up to +4mag showed some halo, fair seeing Pickering ~5.
Using a 120mm refractor I started with Alpha Del (BU298, HJ1554) giving with +3.86mag some halo. Could detect BU298F at 5 o'clock. WDS gives +10.9mag for this companion, AAVSO lists +11.76mag. Could not detect HJ1554/BU298C with +11.9mag according to WDS but no AAVSO entry. I could resolve two faint stars at 9 o'clock at about 150/190" distance with +11.966mag and +12.498mag according to AAVSO. So despite the not this excellent conditions a +10mag star should be easy. After some for a 120mm refractor far too difficult doubles like BU288 5.2" +5.97/12.4mag and therefore negative results and some easier ones like STF2720 3.9" +9.22/9.56mag which I could resolve with aperture mask sizes slightly above the RoT values (therefore reasonable performance with the given conditions) I visited BU363. Halo was with +6.18mag for the primary no longer an issue and a +10mag companion at 6.6" separation should be visible with a magnification of x45 but nothing to see, same with x100 and x180.
In my list of limit observations I do not have entries with the exact same paramters but some similar or more difficult ones like for example STT111 2.8" +5.65/9.68mag with 120mm aperture or STF1772 4.5"DS +5.76/9.6mag with 70mm aperture or Fred reported a resolution of A524 2.7" +6.14/10.17mag with 140mm.
So this does not look good for a +10mag companion given the non existence of an AAVSO entry and the listing also in the WDS "neglected" catalog even if with the seemingly wrong 11.8" separation Burnham noted.
Last observation according to WDS from 2008 - have no records for this observation.
Wilfried

#15 HowardK

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Posted 27 August 2013 - 05:28 PM

So the secondary must be really faint...??

#16 WRAK

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Posted 28 August 2013 - 03:34 AM

Had a look at the DSS image. HIP 101213 is too bright to show a +10mag companion at 6.6" separation although one would expect some distortion of the spikes on the right side of the star. A companion with 11.8" separation does certainly not exist as such a secondary would be perceivable in the image. Both possibilities are indicated by the two black disks according to the expected size and position of the assumed companion.
Wilfried

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#17 fred1871

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Posted 28 August 2013 - 05:44 AM

Wilfried, with DSS images I think East is left and West is right; the mag 13.0 companion is visible lower right, looking quite bright.

I'm inclined to think a mag 10 companion could be lost in image spread. This image isn't helped by the asymmetric flare etc from the bright star being well off-centre in the original plates, a common artefact with Schmidt photos.

So, I'm thinking that the DSS pics don't tell us enough to be sure what is or is not there in the measured position for the close companion. But my observations and those of others do suggest there's no companion star in that position as bright as magnitude 10.

Further observations needed. :grin:

#18 WRAK

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Posted 28 August 2013 - 06:00 AM

Wilfried, with DSS images I think East is left and West is right...

Fred, you are right and I knew it - but I did it wrong as I am used to the horizontal flip. Therefore the black disks should positioned counter clock wise. But this does not change much in interpreting the image that it shows nothing conclusive for a 6.6" companion but makes a 11.8" companion rather implausible.
Wilfried

#19 HowardK

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Posted 28 August 2013 - 06:16 AM

Thanku

#20 R Botero

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Posted 04 September 2013 - 03:47 AM

I tried BU363 last night when finishing my session and could not see the companion either. Very strange given the seeing was very good (more on that in another post) and I had observed some much more difficult pairs earlier in the evening.

This with a 6" f/7.5 refractor at both 290x and 450x.

Roberto






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