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BU 619 in Serpens Caput

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#1 rugby

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Posted 26 June 2019 - 11:48 AM

I have run across an interesting double star challenge in Serpens Caput . It is BU 619 lying just south of the familiar triangular asterism on the north edge of the constellation. Its current separation is 0".6 with a delta M of 1. I studied it with a Meade 8 using moderately high magnification of 250x. My optics are not great but I can see the Airy disc despite the seeing problems.    What I saw were two discs touching with the northern component obviously fainter.  There was no black between. I suppose this is as close to separation as I can get with this aperture



#2 Nucleophile

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Posted 26 June 2019 - 03:02 PM

Fine observation, Rugby.  Thanks for pointing this one out--I've added it to my 8" reflector study list and will likely get a shot at it tomorrow night.  It looks like it needs a fresh measure as well--maybe can get one this week also (fingers crossed).

 

This is a well studied object according to the 4th Interferometric Catalog.  The WDS listed value of 0.647" seems solid but it is a bit old now (2012).  There is no  Gaia DR2 data for the secondary.

 

If you get another chance, try upping the magnitude to the 300-400x range to see if it splits--that will give additional data on how close this one is.  One version of the calculator I am developing for 8" instruments puts the minimum separation for resolution for this object right at 0.64"--sounds like it is close.



#3 rugby

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Posted 26 June 2019 - 05:14 PM

Nucleophile:   what are you using to measure separation and PA?  I will be returning to BU 619 this evening. 



#4 Nucleophile

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Posted 26 June 2019 - 05:25 PM

Nucleophile:   what are you using to measure separation and PA?  I will be returning to BU 619 this evening. 

My imaging system is calibrated and it gives a rather fixed value of E (plate scale; which generates rho).

I use a drift method just prior to imaging the double--this gives Delta (which generates theta).

 

I use the reference star modality of speckle tool box to do an autocorrelation; the E and Delta values mentioned above are plugged into the program to generate rho and theta.  I try to do at least 6 runs and then I average the data.

 

I image with my 15" reflector--it is tricky, lots of things have to go just right.  If I had the cash, I know of a few things I could change that would greatly improve my throughput.  If I had the cash.....



#5 R Botero

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Posted 27 June 2019 - 02:14 AM

I have observed BU619 a couple of times over the last two summers with my 10” f/20 Mak at around 300x. My notes were:

June 2017
“Secondary due north. Comes in and out of view in poor seeing. Touching.”

June 2018
“Clearly split in better seeing. Secondary almost touching. Due N. White yellow.”

Roberto
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#6 Nucleophile

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Posted 27 June 2019 - 07:49 AM

I was able to catch this one with the 8" f/5.9 reflector last night between clouds.  The seeing was a 3+ out of 5.  The transparency was poor due to high clouds and African dust--but this was of little import for this target.

 

345x:  object vacillates between elongated and resolved with secondary clearly of lesser magnitude

460x:  during moments of better seeing, object is just split

627x:  easier to see as split when seeing permits clarification of the image

 

So I am going to call this one above the resolution limit for my instrument and go on to suggest the separation may be more like 0.66" or greater.

 

It has been a real cat and mouse game with the haze, high clouds, dust and fog these past few weeks.  If I am lucky, I can get a measure of this one in the next day or so...



#7 Nucleophile

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Posted 27 June 2019 - 07:54 AM

I have observed BU619 a couple of times over the last two summers with my 10” f/20 Mak at around 300x. My notes were:

June 2017
“Secondary due north. Comes in and out of view in poor seeing. Touching.”

June 2018
“Clearly split in better seeing. Secondary almost touching. Due N. White yellow.”

Roberto

Hi Roberto,

 

did you manage to record the magnification used for your June 2018 successful split of Bu 619?

 

ED:  oops, I see it now (300x); thanks for the report Roberto.


Edited by Nucleophile, 27 June 2019 - 08:12 AM.

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#8 fred1871

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Posted 27 June 2019 - 09:27 PM

Looking at the (overlong) interferometer measures list, it's clear enough that there's been very little change in recent decades. Not every pair needs frequent measures, because orbital periods can be very long and change in some parts of an orbit can be very slow. I'm not sure why this one has received so much professional attention....

 

Anyway, the most recent measure I have for it isn't yet entered in the Interferometer Catalog because, as noted on the USNO/WDS web site, that catalogue has not been updated with new entries since January 2018 (staffing shortage). However measuring goes on, and there's a 2018 measure at 0.645". Remarkably similar to the 2012 measure which was 0.647".  And to Bill Hartkopf's measures in 1996 at 0.647"/0.648". There is a suggestion that the PA may have reduced a tiny bit - 1996 was around 2 degrees, 2012 was 358, 2018 was 357.

 

So, this one isn't moving very quickly. The early measures, in the late 19th century (listed by Burnham in his Catalogue of his own discoveries), has PA measures showing modest scatter around 360/000. Separation measures back then were more erratic, but 0.6" occurs as a rough number and 0.5" might be the alternative: modest scopes in some cases and with the usual vagaries of using bifilar micrometers. Conclusion again: not much has changed. Burnham regarded the pair as not having changed in the 16 years of measures he had, reading the separation differences as measuring wobbles. He notes the pair as a discovery with the 18.5-inch Chicago refractor.


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#9 fred1871

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Posted 27 June 2019 - 09:57 PM

I've now found a couple of past observations I made of BU 619 (15432+1340). My earliest one was in 1998 using a 7-inch (18cm) apo refractor : at 330x a very tight pair, somewhat unequal brightness, in contact (discs touching). Given the separation and aperture, this is a Dawes Limit observation.

 

More recently, in 2015, using a Mewlon 210, so the benefit of slightly more aperture, at 300x, a barely separated somewhat unequal pair. This matches pretty closely to the Rayleigh Criterion.

 

Overall, BU 619 makes a neat test object for the two apertures I happened to use, for viewing Dawes and Rayleigh, even though 17 years apart. If opportunity occurs, I may try it again with my 14cm refractor - to see the extent of elongation that shows, as that aperture certainly won't split a pair at that separation. But it's wider than the closest I've so far attempted and succeeded with at 14cm, 0.48"-0.50" showing slight elongation.



#10 rugby

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Posted 28 June 2019 - 12:25 AM

I would like to thank everyone for their input regarding BU 619. I feel I am in illustrious company here. My equipment and experience pale in comparison. 

Returned to this pair using a 120  at 225x with no positive results. I have  recently purchased a 3.7 Ethos. If I barlow using x2 I can reach almost 490x 


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#11 Nucleophile

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Posted 28 June 2019 - 08:04 AM

Looking at the (overlong) interferometer measures list, it's clear enough that there's been very little change in recent decades. Not every pair needs frequent measures, because orbital periods can be very long and change in some parts of an orbit can be very slow. I'm not sure why this one has received so much professional attention....

 

Anyway, the most recent measure I have for it isn't yet entered in the Interferometer Catalog because, as noted on the USNO/WDS web site, that catalogue has not been updated with new entries since January 2018 (staffing shortage). However measuring goes on, and there's a 2018 measure at 0.645". Remarkably similar to the 2012 measure which was 0.647".  And to Bill Hartkopf's measures in 1996 at 0.647"/0.648". There is a suggestion that the PA may have reduced a tiny bit - 1996 was around 2 degrees, 2012 was 358, 2018 was 357.

 

So, this one isn't moving very quickly. The early measures, in the late 19th century (listed by Burnham in his Catalogue of his own discoveries), has PA measures showing modest scatter around 360/000. Separation measures back then were more erratic, but 0.6" occurs as a rough number and 0.5" might be the alternative: modest scopes in some cases and with the usual vagaries of using bifilar micrometers. Conclusion again: not much has changed. Burnham regarded the pair as not having changed in the 16 years of measures he had, reading the separation differences as measuring wobbles. He notes the pair as a discovery with the 18.5-inch Chicago refractor.

Fred:  can you provide a reference for the 2018 data you reference?  Thanks.



#12 John Fitzgerald

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Posted 28 June 2019 - 10:11 AM

My imaging system is calibrated and it gives a rather fixed value of E (plate scale; which generates rho).

I use a drift method just prior to imaging the double--this gives Delta (which generates theta).

 

I use the reference star modality of speckle tool box to do an autocorrelation; the E and Delta values mentioned above are plugged into the program to generate rho and theta.  I try to do at least 6 runs and then I average the data.

 

I image with my 15" reflector--it is tricky, lots of things have to go just right.  If I had the cash, I know of a few things I could change that would greatly improve my throughput.  If I had the cash.....

Your double star images are amazing!  Would you give the particulars on your 15" reflector?



#13 Nucleophile

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Posted 28 June 2019 - 10:24 AM

Your double star images are amazing!  Would you give the particulars on your 15" reflector?

Thanks, John

 

The 15" scope is an Obsession with an OMI mirror and has  a native f/4.5 with a focal length of 1732mm (etched onto the mirror side)

I have used all variety of powermates with it to give higher f numbers; right now I have it calibrated for a 2.5x powermate/paracorr type 1 train to give about f/13 when used with my ASI 290MM CMOS camera.  I also use an orange Baader filter most times to sharpen the images.



#14 John Fitzgerald

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Posted 28 June 2019 - 11:20 AM

I have a much modified and improved 15 inch f5.05  Discovery with Terry O. mirror.  I have an eq platform for this, but the 15 inch hasn't been used in the last few years due to hauling to dark site and set up time involved.

  What are the issues involved with imaging double stars?  I have been a fairly avid visual observer for over 50 years, but have not been into digital astrophotography very much.  The only real digital camera I have is an old Nikon Coolpix, other than a cellphone camera.



#15 markgravitygood

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Posted 28 June 2019 - 01:43 PM

Hi, Newbie here, so be gentle.

 

I'd like to take a crack at this one with my LX90 10" ACF. Problem is, I don't find BU 619 listed on any double star list. 

Is there an alternate designation for this double? Maybe a finder chart?

 

Check that:

 

15432+1340BU  619      1878 2018  160 357   0   0.4   0.6  6.95  7.94 G4IV      -016-030 -016-030 +14 2922 N    154310.53+134003.7


Edited by markgravitygood, 28 June 2019 - 01:48 PM.


#16 Nucleophile

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Posted 28 June 2019 - 02:00 PM

I have a much modified and improved 15 inch f5.05  Discovery with Terry O. mirror.  I have an eq platform for this, but the 15 inch hasn't been used in the last few years due to hauling to dark site and set up time involved.

  What are the issues involved with imaging double stars?  I have been a fairly avid visual observer for over 50 years, but have not been into digital astrophotography very much.  The only real digital camera I have is an old Nikon Coolpix, other than a cellphone camera.

Using what you have, I would try the cell phone--I have seen some good pics of doubles on here using those.  There are even phone holders that can be purchased to keep the camera steady and positioned correctly.  I think this is called afocal photography and it has the advantage of capturing what you see through the eyepiece (including color)

 

Of course, you would probably still need to snap a fair number of pics to get one that is just right due to seeing messing up the others.



#17 John Fitzgerald

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Posted 28 June 2019 - 03:53 PM

Using what you have, I would try the cell phone--I have seen some good pics of doubles on here using those.  There are even phone holders that can be purchased to keep the camera steady and positioned correctly.  I think this is called afocal photography and it has the advantage of capturing what you see through the eyepiece (including color)

 

Of course, you would probably still need to snap a fair number of pics to get one that is just right due to seeing messing up the others.

Thank you.  The seeing is usually bad here.  There are lots of timbered hills, valleys, and cut up terrain.  I am located in a small valley, about a mile wide, and the air seems to drain from higher terrain during the night.

 

  I wonder if a cell phone camera is sensitive enough to even record a 7th mag star even with use of a telescope?   I also have the same paracorr and 2.5x powermate that you have, would probably give me about f/14.5, which would be about a 5,500 mm focal length with the 15".

 

I'm getting off topic here, so going to start a new thread.


Edited by John Fitzgerald, 28 June 2019 - 04:00 PM.


#18 John Fitzgerald

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Posted 28 June 2019 - 03:59 PM

Hi, Newbie here, so be gentle.

 

I'd like to take a crack at this one with my LX90 10" ACF. Problem is, I don't find BU 619 listed on any double star list. 

Is there an alternate designation for this double? Maybe a finder chart?

 

Check that:

 

15432+1340BU  619      1878 2018  160 357   0   0.4   0.6  6.95  7.94 G4IV      -016-030 -016-030 +14 2922 N    154310.53+134003.7

SAO 101699   Coord (2000) 15h 43m 10.53s +13d 40m 03.7s  (Serpens)



#19 fred1871

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Posted 28 June 2019 - 08:39 PM

SAO numbers are the preferred option for software writers. BU 619 is the long-time designation of the pair in question. Personally, I use the same method I started using in the 1990s, before I knew of (or perhaps before there was) software defaulting to SAO - RA and Dec, from lists computer compiled, using go-to or push-to mrthod. On a busy night with my preferred method I've observed 40-plus doubles, without rushing, trying several powersw on many of them, and hand-writing notes on each.

 

When I started off with doubles, pre-home computer era, I used lists such as those in Webb and Burnham (the later one), along with resources such as the Atlas Coeli Katalog. Other old fogeys will remember it. Sky Catalog 2000 for doubles and deep sky was useful too. One doesn't need the modern aids to observe doubles, though they undoubtedly can help. Back in the day with non-computerised mounts finding doubles was done with Atlas (hard copy) and star-hopping. I was still doing that in the mid-1990s in some circumstances.

 

BU 619 is on some of the old listings I have. Likewise thousands of other doubles. And now we have searchable data-bases online, such as the very useful Stelle Doppie - eg hunt for doubles within a particular constellation, to a certain magnitude limit, and within a range of separations... etc. Voila - a list that can be used for finding the objects, with basic information attached.



#20 fred1871

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Posted 28 June 2019 - 09:12 PM

And the 2018 measure of BU 619. Recently on arxiv.org the USNO folk published the SOAR measures for 2018, mentioned recently on this forum by Wilfried Knapp. There's a long list of measures (not on the arxiv site) that go with the descriptive paper, speckle interferometry measures using the 4-metre SOAR telescope. Only useful for folk seriously into monitoring the Southern and Equatorial doubles (the SOAR telescope is in Chile). I obtained a copy of the measures list from Brian Mason at USNO, as part of my work these last 5 years in analysing data files for the purpose of suggesting doubles currently in need of new measures, as likely to be changing sufficiently since the last measure for a new one to be useful. So it's a proper measure with a proper telescope and technique and professional astronomer who's specialised in doubles. Read the paper (easily found, only out some weeks ago) for detailed descriptions, methodologies, etc.


Edited by fred1871, 28 June 2019 - 09:12 PM.

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#21 Nucleophile

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Posted 29 June 2019 - 10:39 PM

I was able to measure BU 619 last night using my 15" reflector and an ASI 290MM camera.  The reference star enhanced autocorrelation function of Speckle Tool Box allowed the separation to be determined.  I did not obtain measures on the position angle in this instance. 

 

A total of nine movies yielded the following:

 

rho = 0.650 +/- 0.004"

 

This value is pretty well in line with the last listed speckle and the more recent speckle measure mentioned by Fred.

 

A composite of some lucky images is shown below (N is up, E is left).

 

          BU619_SER.jpg


Edited by Nucleophile, 29 June 2019 - 10:44 PM.

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#22 Uwe Pilz

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Posted 30 June 2019 - 12:00 PM

> My optics are not great but I can see the Airy disc despite the seeing problems.

 

If you see the Airy disc your optics *is* great. 



#23 fred1871

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Posted 30 June 2019 - 07:30 PM

I was able to measure BU 619 last night using my 15" reflector and an ASI 290MM camera.  The reference star enhanced autocorrelation function of Speckle Tool Box allowed the separation to be determined.  I did not obtain measures on the position angle in this instance. 

 

A total of nine movies yielded the following:

 

rho = 0.650 +/- 0.004"

 

This value is pretty well in line with the last listed speckle and the more recent speckle measure mentioned by Fred.

 

A composite of some lucky images is shown below (N is up, E is left).

 

          attachicon.gif BU619_SER.jpg

That confirms the accuracy of your measure, given the measures history of BU 619.  smile.gif


Edited by fred1871, 01 July 2019 - 04:50 AM.



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