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7331Peg
Sirius Observer
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Reged: 09/01/08

Loc: North coast of Oregon
Re: Separation Gamma Equ - SkySafari data new [Re: R Botero]
      #5782000 - 04/06/13 02:40 PM

I've seen that response before on the Sky Safari double star problem, but that really doesn't address the problem. Granted, there are discrepancies between various catalogues, depending on dates of observations, minor differences in measurements, and just plain human error.

But I've run into more than a few cases where the separation and distance info in Sky Safari is just plain way off.

For example, here's one I just came across:

Tau Ursae Majoris -- Sky Safari shows a separation of 0.0" with a PA of 311 degrees. It's actually a triple star, with the WDS showing AB at 52.80" and 37 degrees (2003) and AC at 102.60" at six degrees (1991).

I wish now I had made a list of others, but I've just quit using it as a double star reference. Otherwise, it's really a great little tool.

At any rate, the best advice until this kind of thing is corrected is to stay with the WDS or StelleDoppie sites.


John


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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: Separation Gamma Equ - SkySafari data new [Re: 7331Peg]
      #5782381 - 04/06/13 06:41 PM

John, I find Sky Safari superb for finding doubles, making observing lists and for pointing my scopes to them. I use the WDS for any empirical data I need.

Dave


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Separation Gamma Equ - SkySafari data new [Re: Cotts]
      #5782955 - 04/07/13 12:36 AM

I agree, it has all those strengths. Don't misunderstand me, it's a great little program. I use it quite a bit, and it's a steal for what it costs. When I think of what I've paid for similar programs in the past that had nowhere near the features, I'm amazed. It's just not a reliable source for double star data at the present.

I rely on the WDS almost exclusively -- it's the ultimate source for any other program, anyway.


John


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Separation Gamma Equ - SkySafari data new [Re: 7331Peg]
      #5783049 - 04/07/13 02:39 AM

Yes, looking forward to the full incorporation of WDS in it.

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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Separation Gamma Equ - SkySafari data new [Re: R Botero]
      #5783145 - 04/07/13 05:49 AM

Another point to keep in mind when using SkySafari (certainly no bashing intended here) for double star observing is the fact that SkySafari shows only doubles included in its own database - so when you import session plans from other sources like AstroPlanner you will often end up with fewer objects than planned. But one very nice feature of SkySafari when using object lists is the marking of the objects of a selected list with a circle in the shown star map.
Wilfried


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Bill Boublitz
super member


Reged: 05/04/13

Re: Separation Gamma Equ new [Re: WRAK]
      #5841470 - 05/05/13 11:21 AM

I observed Gamma Equulei in November of 2012. The 178 mm log entry in the Haas project database is mine. It was a positive split and I stand by it. Instrument; Questar 7" Astro Barrel. Ocular; 12 mm Brandon. Magnification; x200. NELM was 4.0 or slightly better. Seeing was excellent with stable star disks showing for 30 seconds or more without a quiver. Primary; white - cream white, secondary topaz - or a rich orange yellow. I rough estimated the P.A. to be 260 degrees and the separation 1.1". The pair was well within the capabilities of the instrument. The most important factor was the steadiness of the air.

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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5841887 - 05/05/13 03:35 PM

Bill, would certainly not question your observation report - perfect seeing enables resolutions that are otherwise impossible. Perfect seeing in terms of Pickering 9 or 10 is very rare - even in favored locations the probability is certainly in the lower single digit probability range. So the question remains how repeatable your observation is with reasonable fair to good seeing conditions most of us have also not very often but at least sometimes.
Gam Equ will come into my field of view end of September and I will try again with my 140mm refractor without much hope but also with a Mewlon 210 and if this fails also with a C925 with 235mm aperture. I have so far no double star observing experience with Cassegrain reflectors but expect at least of the Mewlon a performance equivalent to a good 180mm refractor and this should give me a fair chance for a resolution of Gam Equ with assumed 1" separation.
Wilfried


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5842428 - 05/05/13 08:54 PM

Bill, have you read the discussion of Gamma Equulei that we had last year, August to October, under the heading "Is Gamma Equuleus closing?"?

There you'll find that various of us failed to split this double - myself with C9.25, Cotts with 6-inch apo and 16-inch Newt, Ron Price with a 24-inch Newt. Ron's notes on other pairs he did split are informative - suggesting that Gamma Equ should have been a split IF the separation was similar to older measures.

That's why your report is a puzzle, even allowing for perfect seeing conditions. The history of measures of this pair strongly suggests it's currently closing. That would be consistent with the "no-split" observations by various observers. I've provided some notes on past measures of Gamma Equ in that thread last year. I'll add further notes and analysis here if it appears likely to be useful.

Obviously, what we need to help this discussion is a new measure of the pair, after 2010 preferably and done with a large telescope for accuracy. Speckle interferometry is not practical with large-delta-m pairs - it was tried, unsuccessfully, on Gamma Equ in 1975 and 1984. Which is no doubt why the 2002 measure on a large telescope (142-inch) was done with adaptive optics. That, unfortunately, is the most recent measure currently listed - 0.96" in PA 258.


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Bill Boublitz
super member


Reged: 05/04/13

Re: Separation Gamma Equ new [Re: fred1871]
      #5842745 - 05/06/13 12:24 AM

Yes Fred, I read the discussion. That's why I posted my observation. I do not feel privileged to comment on others experiences or equipment; only to read and note them with interest. I urge you to continue looking. Good wishes ~ Bill

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inZet
member


Reged: 02/12/09

Loc: Milan, Italy
Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5844346 - 05/06/13 08:03 PM

I reported wrong data to SkySafari developers with detailed examples.
I'm sorry but they "official" response in Yahoo Groups doesn't convince me. I'm involved in database data as much as they are, you know...
It is my thought they imported their double star data from the CDS of Strasbourg; but the CDS updated their *7-years-old* WDS catalog just in january, after my report emails and insistence. Today, they could easly re-import their data. Or ask me a polished database, along with other catalogs' related info... for free!

Gianluca

Edited by inZet (05/06/13 08:08 PM)


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5844378 - 05/06/13 08:24 PM

That's fine, Bill, but evaluating observations - from all and sundry - is a significant, indeed essential, part of the Haas Project. And it's done every time someone calculates an orbit for a binary star - if you look at the orbit diagrams in the 6th Orbit Catalog (online via the US Naval Observatory) you'll see that the quality of observations varies quite a lot, especially with older techniques such as filar micrometers. The observations have to be evaluated in order to establish an orbit. Some of them are well off the orbital path.

The point of my reference to observations by myself and others is that these were consistent - in their failure to resolve Gamma Equ - with the data available for that pair. Gamma Equ has been closing gradually since the early 20th century, then likely more quickly in recent times.

My comments on the 1994 measure were to the effect that it was inconsistent with the previous data points and the single later one. Which is what an orbit calculator would also conclude, simply evaluating the evidence. Of course, we now need a new, more recent data point, to establish where things have got to with this pair.

And with regard to any particular observation - one of the requirements of science is "repeatability". So, it's all eyes to Gamma Equ when it comes back into view in a few months time.
I'm planning to ask some of the experienced observers in my local astronomy club to try it, with a variety of medium and larger telescopes. And I'll re-observe it myself, hoping for a night or two of excellent seeing, which can occur here.


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Separation Gamma Equ new [Re: fred1871]
      #5844462 - 05/06/13 09:15 PM

A further thought on Gamma Equ. I looked at Sissy Haas's book, and she had no personal observation recorded for Gamma Equ. However she did quote TW Webb (from long ago) : "Yellow, white. A striking pair". So I looked up the object in my copy of Webb, because this struck me as being an odd description.

In Webb, the reference is clearly to the very wide pairing of 5 and 6 Equ, which are ~335" apart at present. This is the pairing of stars with quoted magnitudes in Webb of 4.2 and 5.7, and given a number by FGW Struve (STFA 54) which Webb gives. Webb then goes on to mention "K. doubled 4.2, 11..." referring to George Knott's discovery measure of Gamma (=5 Equ).

Reading the note in Haas, which refers to a pairing visible in a finder or binoculars, though this is not mentioned, one might easily expect something different from the real Gamma Equ AB pairing - which has a delta-m of 4.0 magnitudes on current photometry, and greater than 4 mags on old estimates, and is certainly very close.


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Bill Boublitz
super member


Reged: 05/04/13

Re: Separation Gamma Equ new [Re: fred1871]
      #5844770 - 05/07/13 12:13 AM

Hi Fred. I understand and quite agree with everything you're saying. I am familiar with many of the zealous pitfalls of observational astronomy. (In fact, I remind myself of them every night in the field I have read and understand your comments regarding other's attempts. And that is the essence of why I posted my log. It's there for a challenge to others. By all means go out and refute it! I have about six hours total on the star. Did not split on three previous nights. What I claim to be a successful split was not a quick or casual observation. I studied the object for two hours that evening, with a few pauses for eye relief, etc. I'm not sure what you were eluding to in your second post, but can confirm I was not confusing 5/6 Equ with 5 A-B. 6 Equ remained visible in the 0.21 degree field throughout. As I recall, 6 was lighter, more lemon yellow in color. All I have at this point are my notes and recollections of the evening. I would add for the record; Gamma Equ A is a dazzler. Even in moderately good seeing it tends to jump and dance and mask the companion. I found the split difficult visually due to magnitude difference and glare, not separation. I have split far closer objects with the instrument. Pulling the companion out of the glare and holding it steadily in vision was the challenge on this one. Suffice to say, there is little more any of us can do until Gamma Equ rolls back into the F.O.V. Yes, in the interest of repeatability, I will observe again and hope many others do the same. Let's hope it hasn't moved too much and we find ourselves with another COU 1900 mystery. (Smiles.)

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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5844907 - 05/07/13 04:51 AM

My current data base of limit observations indicate that a resolution of Gam Equ with an assumed separation of 1" requires a 222mm reflector with 26% CO to have a fair 50% chance and with 190mm you are already outside the standard deviation meaning a much lower chance of about 15% and with 178mm you are then in the very low single digit probability of less than 5% - this means not impossible but in terms of Chris Lord "eXceedingly Difficult".
But my data of limit observations with reflectors is a bit shaky as I myself have so far only used refractors for double star observing - but this will soon change. At least I hope as currently in terms of visual astronomy the foul winter weather is followed by foul spring weather.
Wilfried


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Astrodj
professor emeritus
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Reged: 08/24/11

Loc: Missouri
Re: Separation Gamma Equ new [Re: WRAK]
      #5845972 - 05/07/13 03:45 PM

Well I must say this thread has inspired me to give Gamma Equ a try. From what I have been reading here it is going to take a rare night of great seeing for me to even have a slim to none chance, but I'm always up for a challenge. As we roll into summer I will keep this on my to do list.

Thanks to all for your input here!


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Separation Gamma Equ new [Re: WRAK]
      #5846533 - 05/07/13 08:24 PM

Fairly optimistic, Wilfried, but you might be right. I'm still using my older version of the Rule of Thumb, which suggests 320mm for delta-m of 4.0 and 1" separation, and an extreme limit (based on a few observations of mine, of "beyond the limit" pairs being seen, with great difficulty, under exceptional conditions) about 2/3 of that again - so about 210mm. However, that's based on zero CO - refractors. Enhanced energy in the rings from central obstruction will make any significantly uneven pair more difficult. Typical SCT and Mak scopes have OC figures around 0.3 to 0.36. An OC ratio that large provides plenty of transferred energy into the diffraction rings, even with (near-)perfect optics.

And my current analysis of Gamma Equ is that the separation is now most probably less than 1". If that's the case, that makes it harder again.


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Separation Gamma Equ new [Re: fred1871]
      #5891449 - 05/29/13 10:11 PM

Interesting thread.

I just sent my completed results to Sissy last Sunday.

I was able to both resolve and split this double with my 8 inch Orion reflector.

Here are my notes: " 240x [5mm Pentax XW]: resolved; 300x [4mm Radian]: just split; 340x [Pentax 3.5mm XW]: confirmed split"
The seeing on this night was a II (using scale in Chris Lord's paper where he relates his empirical formula for spitting uneven binaries).

I spend a LOT of time looking at uneven double stars and only pen what I am certain of. Frankly, I found 42 ORI from this list to be much more difficult. 46 VIR was no walk in the park either--but it also yielded a split.

I will give this gamma EQU a go again this spring with my 15 inch reflector and report back these additional results.


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Bill Boublitz
super member


Reged: 05/04/13

Re: Separation Gamma Equ new [Re: Nucleophile]
      #5891467 - 05/29/13 10:25 PM

Thanks so much for reporting in! I concur; 42 Ori was far more challenging.

I neglected to post (in my earlier notes) my first two attempts at Gamma Equ were with a 4" refractor. Only after I e-mailed Sissy with a double negative, did she respond to inform me of this thread discussion and possible changes in the system. Curiosity aroused, went back with 178 mm aperture and first night suspected, second night split. Difference being better seeing and different ocular. The proof for me was defocusing slightly in and out and noting behavior of image. There were two sets of diffraction rings, so I felt satisfied I had seen the companion.

As Fred stated, repeatability is the thing. I for one, will welcome Gamma Equ back for another look. Many thanks, ~ Bill


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Separation Gamma Equ new [Re: Bill Boublitz]
      #5893134 - 05/30/13 08:02 PM

Bill, I find your comments, and those of Nucleophile immediately above, of some interest when both of you agree that 42 Orionis was more difficult than Gamma Equ to split.

Looking at the table of data for these two doubles, we find:

42 Ori mags 4.6 7.5 1.1" Dm 2.9
Gamma Equ mags 4.7 8.7 1.0" Dm 4.0

On the numbers one would expect Gamma Equ to be more difficult - primary stars virtually the same brightness, secondary star much less bright with Gamma Equ, and separation of Gamma Equ a tiny bit less.

As I pointed out in another thread on Gamma Equ, it appeared as of 2002 to be continuing to close. In order for Gamma Equ to be easier than 42 Ori, because delta-m is larger (4.0 compared to 2.9), it would have to widen considerably since 2002.

Alternatives - the 2002 measure is wrong. Very unlikely - and Brian Mason at the US Naval Observatory (where the WDS lives) is of the view that the 1994 measure is more likely not correct (2002 is consistent with a closing pair, vide earlier measures including Hipparcos).

Other possibility - photometry is wrong. However we have Tycho magnitudes for these so that's unlikely.

Final possibility - the secondary star of Gamma Equ is variable, previously undetected as such, and observers who happen to look when the secondary is brighter see it, and those who happen to look when the secondary is dimmer, don't.

Following correspondence with Brian Mason I'm hopeful that we'll get a new measure of Gamma Equ in the near future, and that should help "resolve" the discussion. Closer? Wider? The same? We'll see. Meanwhile, I'm intrigued by the 42 Ori/ Gamma Equ comparison, given the descriptions of 42 Ori being "much more difficult" and "far more challenging".


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Separation Gamma Equ new [Re: fred1871]
      #5893493 - 05/31/13 01:01 AM

Hi Fred,

Could it be that 42 ORI is tightening? The most recent WDS entry is from 1995.

What I do know is that I couldn't definitively split 42ORI even after 3 good tries on nights of very good seeing until I resorted to putting a Paracorr lens into the optical train to tighten up the stars.

With gamma equ, I didnt need to stick in the Paracorr, nor try multiple times to observe the split.

-Mark


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