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I am amazed by the skill of discoverers

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#1 John Fitzgerald

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Posted 27 July 2019 - 06:29 PM

I may have said this before, but I continue to be amazed by the original discoverers of some of the closer and more unequal pairs.  Wilhelm Struve in particular.  With a relatively small and primitive instrument (9.6 inches), he discovered some tough to see doubles.  S.W. Burnham later did the same, some pairs discovered with only a 6 inch achromat.   The only advantage these men had was the absence of heat islands and light pollution.  They either called out their observations to an assistant or ruined their dark adaptation by writing them down by lamp or candle light.  I suspect at least Struve may have employed a scribe.

 

Does anyone on here verbally record their observations and write them down later?


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#2 Nucleophile

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Posted 27 July 2019 - 06:51 PM

Does anyone on here verbally record their observations and write them down later?

I sometimes do this.  More often of late I just head back inside a few feet and jot down what I saw at the various magnifications employed and then head back out for the next target.

 

When I was in to observing galaxies, I did this routinely.  I still have some tape that is over 5 years old that has yet to be transcribed.



#3 John Fitzgerald

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Posted 27 July 2019 - 07:07 PM

I sometimes do this.  More often of late I just head back inside a few feet and jot down what I saw at the various magnifications employed and then head back out for the next target.

 

When I was in to observing galaxies, I did this routinely.  I still have some tape that is over 5 years old that has yet to be transcribed.

I might not get to transcribing either.  Also recording it on a cell phone lights up the screen.  Might as well write it right after I see it.  I need a brain to computer interface.cool.gif



#4 clearwaterdave

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Posted 27 July 2019 - 07:52 PM

There are digital recorders.,I have an Olympus an it doesn't light up.,Easy on/off recording buttons.,cheers.,



#5 Astrojensen

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Posted 28 July 2019 - 01:55 AM

 

Wilhelm Struve in particular.  With a relatively small and primitive instrument (9.6 inches), he discovered some tough to see doubles.

I would hesitate to call the 9.6" Dorpat refractor a "relatively small and primitive instrument". A diffraction limited 9.6" refractor on a tracking mount is a telescope many amateurs today can only dream of. 

 

 

Clear skies!
Thomas, Denmark


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#6 The Ardent

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Posted 28 July 2019 - 02:26 AM

Every time I find a faint double , Espin and Jonckheere found it first.

#7 Uwe Pilz

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Posted 28 July 2019 - 05:03 AM

I make comments and mostly even sketches form my double observation. Most of them you may find at our double star page, which was mentioned in this forum ago:

 http://deepsky.vdsas...tars_index.html

unfolded here

http://deepsky.vdsas...stars.html#idx0

Please use the find function of the explorer to go to a particular star.

 

Double stars don't are nebulae. The role of dark adaption is not this important. Even with my beloved comets I make sketches. If I need to use dim light I have to sketch larger, that's all.



#8 fred1871

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Posted 28 July 2019 - 05:43 AM

I would hesitate to call the 9.6" Dorpat refractor a "relatively small and primitive instrument". A diffraction limited 9.6" refractor on a tracking mount is a telescope many amateurs today can only dream of. 

 

 

Clear skies!
Thomas, Denmark

Thomas is correct. It was a major step forward at the time in refractor optical quality, and had the first proper tracking mount, weight-driven, the version we now call German equatorial. Both from the work of Joseph von Fraunhofer.

 

Back in the 1980s I sometimes used a 9-inch refractor, built perhaps 60 years after Fraunhofer's, by Grubb of Dublin - a scope  that was possible because of F's work. It gave very fine image quality for doubles and planets, and showed fine detail on Mars and the Moon at 600x. Some false colour, but it was not a problem, especially with doubles. That scope also used a weight-drive, immune to power failures. One can become time-parochial about some older technologies and too easily dismiss them. 


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#9 John Fitzgerald

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Posted 28 July 2019 - 08:18 AM

I did not mean the Dorpat refractor is inferior. Many people today have 16 to 25 inch reflectors on tracking mounts and would be challenged by some of those doubles. They have the advantage of already knowing to look for a double . Struve, as the discoverer, had no idea whether that star was double or not. Struve was using an uncoated achromat with uncoated eyepieces. A modern 200 mm Apo should have close to the same light grasp.


Edited by John Fitzgerald, 28 July 2019 - 10:32 AM.


#10 fred1871

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Posted 28 July 2019 - 09:50 AM

Struve sensibly limited himself to stars not too faint, for examining to discover which ones were doubles. That didn't stretch his scope's light grasp too far, and had the benefit of allowing the eye to see nearer the resolution limit with the less bright pairs, so giving a better yield of discoveries.

 

With only 4 air-glass surfaces in the objective there won't be huge losses due to reflection; and the eyepieces were likely the 2-element versions of the period. His decision on how faint to go (and not go) meant he did not have a problem with light grasp, though obviously some dim companions could be overlooked. Resolution will be that of 9.6-inches, not 8-inches.

 

The stars examined by the elder Struve (FGW, usually called Wilhelm) were those down to the 8th magnitude, and the brighter ones between magnitude 8 and 9. He examined 120,000 stars in his survey, working at a very fast pace in his discovery survey, then returned later to measure the pairs found. 3,110 systems were discovered. Not all these were new, quite a few having been seen by earlier observers.

 

One of the better summary descriptions of Struve's work is in RG Aitken's book The Binary Stars, a very useful book still, despite being dated 1935 for the 2nd (enlarged) edition. It can still be found in the Dover reprints series from 1964, via dealers in used books.


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#11 RadioAstronomer

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Posted 28 July 2019 - 03:51 PM

Every time I find a faint double , Espin and Jonckheere found it first.

There are still thousands of doubles faint and not so faint that are not yet cataloged. Check the latest IAU double star information circular published two weeks ago http://www.usc.es/as...ares/cir198.pdf and the objects reported by Andre Debackere (for example DBR 320 with mags 10.3/12.4 2") or WRS 8 found by yours truly with mags 10.2/10.8 3.2".

As many have pointed out, thanks to Gaia we now can ascertain the nature of these pairs and whether they are physical systems or optical.

Naturally, Brian Mason form the WDS recommends only reporting new pairs that have some indication of physicality. We don't need more optical pairs in the WDS...



#12 The Ardent

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Posted 28 July 2019 - 07:35 PM

I see Gaia pairs all the time. I use Sky Safari at the eyepiece to identify various stars and doubles. There are many faint, close pairs that are just two Gaia stars.

#13 3c_273

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Posted 30 July 2019 - 07:33 PM

FWIW, I record my observations with a small computer at the telescope.

 

  https://mainsequence...uble_Stars.html

 

I too am amazed at the skill of the early observers. What Burnham did with a 6" (15cm) Clark is extraordinary.

 

Virtually all of today's double star discoveries are of wide pairs with dissimilar magnitudes, and are made by mining the Gaia DR2 data. To a visual observer, these stars just didn't seem to be a binary.



#14 Michael Covington

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Posted 30 July 2019 - 07:36 PM

Does anyone on here verbally record their observations and write them down later?

I do routinely during astrophoto sessions, often using voice recorder software on the same computer that is capturing the pictures.

 

Naturally this shades into visual observing too -- if I have the recorder set up, I'll use it during the visual part of the session.

 

Accurate timestamps are a plus.



#15 Cotts

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Posted 04 August 2019 - 10:22 AM

I'll add to the FGW Struve 'mystique' by pointing out how he did measures, which, by the way, were very accurate and are still accepted today as high quality..

 

He used a bi-filar micrometer.  It has tiny crosshairs which move, allowing the measurement of separation and PA.

 

Here's the amazing part.  His cross hairs were spider silk!  He kept spiders in a terrarium and had to re-apply new cross hairs almost nightly.

 

Amazing #2.  In 1790-1835, Struve's 'era', the crosshairs had to be illuminated by a candle in a small enclosure on the side of the micrometer...no electrical illumination would exist for 100 years or so...

 

Dave


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#16 dmdouglass

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Posted 04 August 2019 - 11:07 AM

I'll add to the FGW Struve 'mystique' by pointing out how he did measures, which, by the way, were very accurate and are still accepted today as high quality..

 

He used a bi-filar micrometer.  It has tiny crosshairs which move, allowing the measurement of separation and PA.

 

Here's the amazing part.  His cross hairs were spider silk!  He kept spiders in a terrarium and had to re-apply new cross hairs almost nightly.

 

Amazing #2.  In 1790-1835, Struve's 'era', the crosshairs had to be illuminated by a candle in a small enclosure on the side of the micrometer...no electrical illumination would exist for 100 years or so...

 

Dave

Amazing Indeed !


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#17 John Fitzgerald

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Posted 04 August 2019 - 01:08 PM

Amazing Indeed !

Yes.  Amazing that the candle didn't mess something up, or eventually cause a fire.  Struve would be amazed by how far we've come today in instrumentation, but dismayed by the light pollution.




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