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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Overdue analysis of the RoT behavior new [Re: Asbytec]
      #6050133 - 08/28/13 07:10 AM Attachment (16 downloads)

Finally the seventh factor: size of Central obstruction CO.
The RoT model does not have a separate module for CO as it is included in the first module for separation (giving some benefit due to the smaller size of the Airy disk) and in the second module for Delta_M (negative influence for larger values of delta_m) but maybe an additinal separate CO module is necessary.
I have selected by random observations from my list sorted by size of CO shown in the graph below - while this seems to work fine for CO up to 0.35 all observations with larger CO show crass errors in the calculated proposed aperture. This may not be such a problem as CO larger 0.4 is no real issue but I would prefer a better behavior of the RoT model even for extreme values of CO especially in the range 0.3-0.4.
My problem here is that I have not enough observations with large apertures with many different sizes of CO. My own approach with an iris for a C925 only demonstrates the drastic negative effect of really large CO but only with smaller apertures.
What I would need is a systematic setup starting with a small CO of 0.2 or even smaller with slowly increasing sizes of CO.
To some degree I hope I can this do with an already ordered 8" f/22.5 scope with CO 0.25 but the date of delivery has slipped for several month's.
If this does not bring enough useful data material I may have to buy a ~f/10 Newton but I don't like the idea to have to handle such a large tube - so I would appreciate it very much if somebody with this kind of equipment would contribute limit observations by changing size of CO up (and maybe aperture down as alternative approach) to the limit of resolving doubles with the help of masks.


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overdue analysis of the RoT behavior new [Re: WRAK]
      #6061773 - 09/03/13 10:10 PM

Wilfried, the CO size ties in nicely with the discussion elsewhere about how good are reflectors for double stars. Looking at this graph, I notice bars for 235mm aperture, although CO is given there as 0.38, and Celestron say 0.36 for the C9.25.

But, taking the bars as given - it appears the 235mm SCT is equivalent to a 155mm aperture, in terms presumably of resolving large-delta-m doubles. Yes? Obviously it's not about light gathering, as obstructed 235mm collects more light than unobstructed 155mm; and likewise outperforms it on equal pairs.

As a generalised equivalent I find it interesting because my own comparisons of my two telescopes, unobstructed 140mm, obstructed 235mm, suggests the SCT is slightly better (but only slightly better) for large delta-m pairs, assuming the secondary star does not fall on the first diffraction ring, and if delta-m is very large, that it doesn't fall on the 2nd or 3rd rings.

Your thoughts on whether I'm reading you correctly....


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Overdue analysis of the RoT behavior new [Re: fred1871]
      #6062103 - 09/04/13 03:32 AM

Fred, while your impression that the C925 might be compared with a 155mm refractor in terms of performance for resolving doubles may be correct this relation is not the topic of the graph above. This graph illustrates how utterly wrong the RoT algorithm works for CO 0.35 or larger. In the short term this means that the RoT only works for CO up to 0.35 - this is no problem for most scopes but I will try to correct this if possible.
Regarding obstruction of C925 - specs give 85mm for the secondary mirror but including mounting the CO is exactly 90mm. This means 90/235 = 0.383 CO. But I fear there is more to consider with SCTs (in comparison with other types of reflectors - as for example the Schaefer TML calculator does). Ed Wiley is happy to get with his C11 results down to Rayleigh with video - I assume then this would be impossible for visual observing.
Back to the topic RoT: I have far too few limit observations in this aperture range and it will be difficult to get much more because you can not reduce the aperture without getting absurd high CO - and when you can not reduce the aperture you never know if an observation is actually on the limit.
Only possibility would be a large Newton with small CO as a start and masks for reducing aperture as well as increasing CO to maintain a given ratio - may be a bit cumbersome but it could be done.
Wilfried


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Overall RoT Performance new [Re: WRAK]
      #6062255 - 09/04/13 08:01 AM Attachment (16 downloads)

Trying to get an overall picture I applied die current RoT algorithm on my full data set of ~380 limit observations (excluding all observations with CO larger 0.4 and obviously underperforming ones).
This data set includes also the about 130 ones I used for creating the current RoT algorithm with statistical analysis but ~250 observations are "new" ones.
A small part of the observations is sourced from published papers and books and also from observations posted on this board (thanks to Fred, Norme, Roberto, Mark, Ed, Sasa, Tom, Dave, EdZ ...) but most observations are my own made mostly with refractors using aperture masks or iris diaphragms - so there is a bias towards smaller apertures.
It would certainly be possible to redo the statistical analysis with the now much larger data set to get higher statistical significance for the parameters but I tend to wait until I have more observations with apertures larger than 140mm. I want also to find a solution for the larger CO values.
Meanwhile the results are not this bad as you can see from the graph - the blue line shows the actual reported apertures and the red line shows the proposed aperture calculated with the RoT algorithm.
Wilfried


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Overall RoT Performance new [Re: WRAK]
      #6062268 - 09/04/13 08:15 AM

Excellent work Wilfried and all credit to you! I'm more than happy to keep feeding data to refine the model. Fit looks excellent and aperture coverage is very good for the instruments available to the typical observer. Moreover, if your exercise also leads to better understanding from newbies (like me) to what can be expected from a typical instrument and their local conditions, the exercise is worth while in itself!

Thank you for your efforts and for sharing it with us.

Roberto


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overdue analysis of the RoT behavior new [Re: WRAK]
      #6063476 - 09/04/13 10:20 PM

Quote:

Fred, while your impression that the C925 might be compared with a 155mm refractor in terms of performance for resolving doubles may be correct this relation is not the topic of the graph above. This graph illustrates how utterly wrong the RoT algorithm works for CO 0.35 or larger. In the short term this means that the RoT only works for CO up to 0.35 - this is no problem for most scopes but I will try to correct this if possible.
Regarding obstruction of C925 - specs give 85mm for the secondary mirror but including mounting the CO is exactly 90mm. This means 90/235 = 0.383 CO. But I fear there is more to consider with SCTs (in comparison with other types of reflectors - as for example the Schaefer TML calculator does). Ed Wiley is happy to get with his C11 results down to Rayleigh with video - I assume then this would be impossible for visual observing.
Back to the topic RoT: I have far too few limit observations in this aperture range and it will be difficult to get much more because you can not reduce the aperture without getting absurd high CO - and when you can not reduce the aperture you never know if an observation is actually on the limit.
Only possibility would be a large Newton with small CO as a start and masks for reducing aperture as well as increasing CO to maintain a given ratio - may be a bit cumbersome but it could be done.
Wilfried




Wilfried, thanks for the clarification. And I'll re-measure my SCT obstruction

Limit observations - agreed, difficult without aperture masks or similar. And with an SCT I agree they don't help. Your suggestion about Newtonians with small CO is a good one; and in the case of larger Newtonians, off-axis aperture masks (no CO) could be used to simulate small telescopes. However, even with a fixed aperture, a large enough number of observations of many doubles might approximate to limit observations for some of them.

I've recently made a long list of some of the more difficult doubles that I've successfully observed with the 140mm refractor. Most of these are not "limit" observations; some of them possibly are. A number of patterns emerged. One is, that for 140mm, a pair where the delta-m is twice the separation (say, 4.0 magnitudes at 2.0") is reasonably difficult, and needs fairly good seeing conditions. It might be glimpsed with unsteady seeing, but becomes very certain in steadier conditions.

A small number of very uneven doubles, much more difficult than that, have also been successfully observed. A point of interest is that a subset of these are pairs where the separation numbers cluster around Rayleigh - in other words, where the separation coincides with the first dark interspace between disc and first bright diffraction ring. For the 140mm refractor, that's around 1.0" - separations listed in the range 0.9" to 1.1".

The much-discussed 42 Ori falls into that category. I did manage to see it as double, with 140mm, but it was about as hard as any pair I've succeeded with. The separation at present is likely 1.0" - a slowly closing pair, the last measure some years ago, as I said in a note on CN some time ago. Delta-m is 2.9 magnitudes. With 42 Ori, the separation is near 1/3 rather than 1/2 the delta-m number. I'll put my data list in another note, and also describe pairs where the separation approximates to the first bright ring.


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Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: Overdue analysis of the RoT behavior new [Re: fred1871]
      #6063902 - 09/05/13 08:12 AM

Fred, I always appreciate your expertise. I want to reply, but will be away for a while. More later, would love to continue the discussion and observe as well.

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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overall RoT Performance new [Re: WRAK]
      #6065392 - 09/05/13 11:20 PM

Wilfried, as promised, here are some lists of doubles that I've seen as definite but difficult splits with my 140mm refractor.

The first list, pairs around 1.0" (about Rayleigh for 140mm), are examples of doing better than I'd expected. The delta-m figures for these range from 1.6 to 3.0. And, yes, the dm1.6 pair was the (relatively) easiest; the pairs around dm 2.5-3.0 noticeably a lot harder, even in Pickering 8 (about as good as it got).

55 Leo 6.0, 9.0 1.1" dm3.0
15 Boo (KUI 66) 5.44, 8.43 1.0" dm3.0
BU 13 Ori 7.57, 9.22 1.0" dm1.65
HEI 670 Ori 5.97, 8.36 1.1" dm2.4
BU 314 Lep 5.9, 7.5 0.9" dm1.6
42 Ori (DA 4) 4.6, 7.5 1.0" dm2.9
Upsilon Gru (BU 773) 5.70, 8.24 0.9" dm2.54
BU 603 Leo 5.97, 8.53 1.0" dm2.6

Minimum magnification needed for these was in the 250x-400x range. 250x was enough for BU 314; 400x for certainty with 42 Ori, and Upsilon Gruis. 285x showed various others.

That first list is not a result of deliberately targeting Rayleigh; it showed this pattern when I've later gone through the last couple of years of observing notes. Now, I'll look for other doubles that fit this pattern - larger delta-m, and falling in the first dark space.

Second list, doubles where the 2ndry star falls on or about the first bright ring. Again, culled after the event from a couple of years' observing. The standout here is a dm 2.85 pair (BU 1190); otherwise, dm is generally 2.0 to 2.5. Without the diffraction ring I'd expect to have found doubles split with dm 3.5 to 4 at this separation, because these are wider (1.3"-1.6") than the first list (0.9"-1.1").

near or on 1st bright ring
BU 1190 Ori 6.95, 9.81 1.4" dm2.85
STT 145 Gem 7.3, 9.9 1.5" dm2.6
BU 91 Tau 8.1, 10.6 1.5" dm2.5
47 Tau (BU 547) 5.05, 7.32 1.2" dm2.27
Theta Gru 4.45, 6.60 1.5" dm2.15
BU 281 Psc 7.4, 9.4 1.6" dm2.0
BAS 3 Tau 6.16, 8.2 1.3" dm2.0
BU 1089 Oph 6.57, 8.98 1.5" dm2.4

The easiest of these were, unsurprisingly, BAS 3 and BU 281 (160x); the hardest was BU 1190 (285x).
I now plan to try various pairs around 1.3"-1.4" with larger delta-m. One I did attempt, unsuccesfully the first time (I'll get back to it), was HO 389 Boo - 1.6" at delta-m of 3.5 (mags 7.0, 10.5).

I also have examples of pairs wider than the first diffraction ring, with larger delta-m. The second dark interspace for 140mm is ~1.83"; the 2nd bright diffraction ring centred at 2.2". Here are some pairs separated 1.7" to 2.0", with delta-m of 3 or more.

A 146 Vir 7.31, 10.77 1.7" dm3.5
RST 690 Cir 6.7, 9.8 2.0" dm3.1
BU 15 Ori 7.44, 11.6 2.0" dm4.15
Kui 17 Tau 4.26, 7.85 1.8" dm3.6
STF 562 Tau 6.82, 9.94 1.9" dm3.1

These required varying magnifications, typically 230x-285x, though when seeing was best some were visible at 160x.

I should mention that the magnifications are only indicative. I don't always work through a full series of magnifications to discover the minimum required; and seeing conditions affect that as well - some pairs are not possible in less good seeing; some require less power in better seeing. The toughest ones, such as 42 Ori, did require higher powers, after trying less; usually 400x was needed there.

Anyway, I thought this emerging pattern might be of some general interest, as well as providing some more data points for the RoT endeavours.


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Overall RoT Performance new [Re: fred1871]
      #6065537 - 09/06/13 02:50 AM

Thanks Fred, will go through your list for inclusion in my data set and give you feedback with calculated RoT values.
42 Ori was also for me one of the most difficult observations with 140mm but I go never above x280 magnification because the seeing in my location is rarely better than Pickering ~7 - so all I got was a very pointed elongation with a clear indication of separation and position.
Wilfried


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overall RoT Performance new [Re: WRAK]
      #6066803 - 09/06/13 08:32 PM

Wilfried, part of my intention in providing the lists (above) was to document finding that the first bright diffraction ring does appear to have a noticeable effect on pairs of larger delta-m. This is a long-attested belief among observers; and I was not surprised to find my data collection confirming it.

But it does suggest certain complications in developing an RoT. In particular, that the delta-m versus separation factors are bumpy rather than smooth, as a result of diffraction ring interference with visibility at certain light levels. It's one of several matters I plan to look at further while I'm collecting data on difficult doubles. And for enhanced ring effects, I have an SCT of large CO. I'll have to use it more often.


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overdue analysis of the RoT behavior new [Re: Asbytec]
      #6066807 - 09/06/13 08:33 PM

Norme, will be glad to see you return when you can. Useful thoughts you offer.

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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Overall RoT Performance new [Re: fred1871]
      #6068940 - 09/08/13 05:53 AM

Quote:

...

The first list, pairs around 1.0" (about Rayleigh for 140mm), are examples of doing better than I'd expected. The delta-m figures for these range from 1.6 to 3.0. And, yes, the dm1.6 pair was the (relatively) easiest; the pairs around dm 2.5-3.0 noticeably a lot harder, even in Pickering 8 (about as good as it got).

55 Leo 6.0, 9.0 1.1" dm3.0 -> pA 158mm
15 Boo (KUI 66) 5.44, 8.43 1.0" dm3.0 -> pA 169mm
BU 13 Ori 7.57, 9.22 1.0" dm1.65 -> pA 149mm
HEI 670 Ori 5.97, 8.36 1.1" dm2.4 -> pA 137mm
BU 314 Lep 5.9, 7.5 0.9" dm1.6 -> pA 145mm
42 Ori (DA 4) 4.6, 7.5 1.0" dm2.9 -> pA 152mm
Upsilon Gru (BU 773) 5.70, 8.24 0.9" dm2.54 -> pA 170mm
BU 603 Leo 5.97, 8.53 1.0" dm2.6 -> pA 155mm

-> According to the pA numbers 15 Boo and Ups Gru should have been the most difficult but all observations are within a reasonable pA range

...
Second list, doubles where the 2ndry star falls on or about the first bright ring. Again, culled after the event from a couple of years' observing. The standout here is a dm 2.85 pair (BU 1190); otherwise, dm is generally 2.0 to 2.5. Without the diffraction ring I'd expect to have found doubles split with dm 3.5 to 4 at this separation, because these are wider (1.3"-1.6") than the first list (0.9"-1.1").

near or on 1st bright ring
BU 1190 Ori 6.95, 9.81 1.4" dm2.85 -> pA 148mm
STT 145 Gem 7.3, 9.9 1.5" dm2.6 -> pA 138mm
BU 91 Tau 8.1, 10.6 1.5" dm2.5 -> pA 150mm
47 Tau (BU 547) 5.05, 7.32 1.2" dm2.27 -> pA 124mm
Theta Gru 4.45, 6.60 1.5" dm2.15 -> pA 99mm
BU 281 Psc 7.4, 9.4 1.6" dm2.0 -> 110mm
BAS 3 Tau 6.16, 8.2 1.3" dm2.0 -> 120mm
BU 1089 Oph 6.57, 8.98 1.5" dm2.4 -> 116mm

-> most of these pairs should have been rather easy and be possible with smaller apertures

The easiest of these were, unsurprisingly, BAS 3 and BU 281 (160x); the hardest was BU 1190 (285x).
...
I also have examples of pairs wider than the first diffraction ring, with larger delta-m. The second dark interspace for 140mm is ~1.83"; the 2nd bright diffraction ring centred at 2.2". Here are some pairs separated 1.7" to 2.0", with delta-m of 3 or more.

A 146 Vir 7.31, 10.77 1.7" dm3.5 -> pA 164mm
RST 690 Cir 6.7, 9.8 2.0" dm3.1 -> pA 121mm
BU 15 Ori 7.44, 11.6 2.0" dm4.15 -> pA 188mm
Kui 17 Tau 4.26, 7.85 1.8" dm3.6 -> pA 118mm
STF 562 Tau 6.82, 9.94 1.9" dm3.1 -> pA 129mm

-> A146 might have been a bit of a challenge but certainly doable and BU15 is an extraordinary observation with 140mm - congratulation. The other pairs should have been rather easy

These required varying magnifications, typically 230x-285x, though when seeing was best some were visible at 160x.

...




Fred, thanks for these report - I have added all these observations to my data set. Interesting the range from pA 99mm to pA 188mm given your impression that all of these doubles were on the 140mm limit. May be you can revisit some of these doubles with seemingly extreme low or high values if you find a difference how difficult resolution is.
Wilfried


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overall RoT Performance new [Re: WRAK]
      #6070466 - 09/08/13 11:47 PM

Wilfried, thanks for running the RoT numbers on these doubles. More of a mix than I'd originally thought, although I could see that some were less difficult than others at the time of observation. In particular, some of the "1st bright ring" pairs I suspected were very much subject to seeing conditions. There I'll stay with BU 1190 as being of high difficulty; BU 91 on the numbers is similar, but on the night, conditions made it slightly less difficult.

Generally, I thought the first list was a good listing of "limit" observations, though as usual the seeing conditions at the time will affect what happens. However I'll stay with my estimation that 42 Ori and Upsilon Gruis were the two most difficult pairs for 140mm. Both required 8/10 seeing, with any significant unsteadiness they became uncertain. In the case of Upsilon Gru, I had observed it with a 7-inch (178mm) refractor years ago, and thought it fairly difficult then - requiring 330x for certainty on a quite steady night. I was surprised that the 140mm managed it - the same night I had looked at Theta Gruis, and noticed it was straightforward, so I tried nearby Upsilon, knowing it was a lot tighter and had larger delta-m. Theta I agree is not a "limit" example for 140mm.

The third list - BU 15 in Orion was difficult, but I'm wondering if we have a too-faint magnitude for the secondary. And, looking up Burnham's own catalog, I confirmed that he discovered it with his 6-inch refractor; and the separation record suggest it hasn't changed since his time, although the PA is slowly changing. Burnham also lists a mix of magnitude estimates for the secondary star, three of the four being brighter than the number currently listed. So it might be not as tough as the numbers suggest. Maybe 11.6 is a typo for 10.6?
A146 Vir is I'd say pretty much a "limit" observation for 140mm, and there I think the numbers are accurate.

I am planning to re-visit various of these in the future. Some of them I'll try again with 140mm, others I want to attempt with the SCT (235mm) to see how the bigger aperture plus large CO affect the view. I don't have enough comparisons available yet, for doubles that were difficult for 140mm.

I'll add a couple more observation results here. One that surprised me, though the numbers appear to be fine, is BU 1052 Ori - mags 6.68 and 8.22, at 0.6" (!!) - seen elongated at 400x with 140mm in 8/10 seeing.

Another - I've looked at 46 Virginis (AGC 5) with both telescopes, and it was marginal/uncertain in both, not helped by the seeing on those nights. I'm planning to re-visit 46 Vir - mags 6.18, 8.78 at 0.7". Delta-m of 2.6 makes it tough. It appears to be a very long-period binary, that's been closing, more rapidly in recent times. The small number of measures I have on hand give 1.3" in 1876 (discovery), 1.1" in 1970, 0.8" in 1991, 0.7" in 2005. The PA is slowly increasing. So on the measures recorded, it's not likely any wider than 0.7" at present. It's also on the Haas project list, where successful observations with 7-inch and 8-inch scopes are listed.

Overall, one of my intentions for the three lists was to see if there was a pattern that reflected the reduced visibility effect in the area of the first bright ring. Although that shows, I'll need to find some pairs of greater delta-m where the secondary is on the ring. As well, more observations for all three categories would be useful; that means making lists of further unequal doubles at various separations and concentrating on those. And I'll hope that I don't get too many Gamma Equulei type conundrums as a result.

Edited by fred1871 (09/09/13 12:44 AM)


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Overall RoT Performance new [Re: fred1871]
      #6070734 - 09/09/13 06:29 AM

Fred, the first ring for a 140mm scope should be around 1.35". Here is a list with doubles with separations 1.3-1.4" and delta_m's larger 2 up to 4:
ID Name RA Dec M1 M2 Delta_M Con
WDS04209+1352 BAS3, BD+13 00665 04h 20m 52,7s +13:51:52,1 6,16 8,2 2,04 Tau
WDS02037+2556 STF208, IDS01580+2527, BDS1074, ADS1631, BD+25 00341 02h 03m 39,3s +25:56:07,6 5,82 7,87 2,05 Ari
WDS12136-3348 HWE72, IDS12084-3314, CD-33 08257 12h 13m 36,8s -33:47:34,6 6,48 8,55 2,07 Hya
WDS16200-6439 I15, IDS16107-6424, CP-64 03442 16h 20m 00,5s -64:38:55,7 6,84 8,95 2,11 TrA
WDS07310-0210 A1967, IDS07259-0157, ADS6147, BD-01 01745 07h 30m 59,1s -02:09:53,4 7,2 9,33 2,13 Mon
WDS17406-3539 DAW148, IDS17339-3535, CD-35 11803 17h 40m 36,5s -35:38:53,5 7,82 9,96 2,14 Sco
WDS19134-1427 BU138, IDS19078-1437, BDS9106, ADS12168, BD-14 05333 19h 13m 25,8s -14:26:49,3 7,81 9,96 2,15 Sgr
WDS21555+6519 STT457, IDS21529+6450, BDS11391, ADS15467, BD+64 01607 21h 55m 31,0s +65:19:14,9 6,01 8,17 2,16 Cep
WDS04294+2433 LEI4 04h 29m 23,7s +24:32:59,9 7,55 9,77 2,22 Tau
WDS19313-0207 D20, IDS19260-0220, BDS9365, ADS12538, BD-02 05024 19h 31m 15,8s -02:06:36,7 7,22 9,58 2,36 Aql
WDS17557-3034 I1011, IDS17493-3033, CD-30 14939 17h 55m 45,0s -30:34:18,0 7,63 10 2,37 Sco
WDS20229+4259 HO128, IDS20195+4240, BDS10180, ADS13786, BD+42 03721 20h 22m 55,5s +42:59:00,4 6,41 8,82 2,41 Cyg
WDS22139+7228 A895, IDS22119+7158, BDS13616, ADS15781, BD+71 01116 22h 13m 52,3s +72:27:55,2 7,91 10,36 2,45 Cep
WDS16413+3136 STF2084, IDS16375+3147, BDS7717, ADS10157, BD+31 02884 16h 41m 17,5s +31:36:07,0 2,95 5,4 2,45 Her
WDS11073-4238 HJ4409, IDS11027-4206, CD-41 06343 11h 07m 16,7s -42:38:19,3 5,24 7,73 2,49 Cen
WDS05145-1823 B1943, IDS05101-1830, BD-18 01035 05h 14m 29,0s -18:23:06,4 7,86 10,4 2,54 Lep
WDS06344+0318 A2673, IDS06291+0323, ADS5202, BD+03 01304 06h 34m 21,7s +03:18:23,3 7,44 9,99 2,55 Mon
WDS01036+6104 BU396, IDS00575+6032, BDS543, ADS868, BD+60 00157 01h 03m 37,0s +61:04:29,4 6,06 8,62 2,56 Cas
WDS03421-1709 HU436, IDS03375-1728, BDS1830, ADS2706, BD-17 00715 03h 42m 04,1s -17:08:45,3 7,84 10,41 2,57 Eri
WDS23288-0050 A896, IDS23236-0123, BDS13647, ADS16781, BD-01 04440 23h 28m 46,2s -00:50:08,2 7,98 10,59 2,61 Psc
WDS13544+2955 STT272, IDS13499+3024, BDS6671, ADS9051, BD+30 02461 13h 54m 25,5s +29:54:56,3 7,56 10,18 2,62 CVn
WDS07378-0236 A534 07h 37m 48,9s -02:35:49,4 7,94 10,61 2,67 Mon
WDS04312-7838 I472, IDS04364-7850, CP-78 00145 04h 31m 09,9s -78:37:58,6 7,96 10,67 2,71 Men
WDS19535+2405 DJU4, IDS19492+2349, BD+23 03820 19h 53m 27,7s +24:04:46,6 4,63 7,37 2,74 Vul
WDS15166-6054 B1777, IDS15085-6032, CP-60 05698 15h 16m 36,7s -60:54:14,4 5,79 8,55 2,76 Cir
WDS23208-5018 RST5560, IDS23152-5051, CD-50 13948 23h 20m 50,1s -50:18:23,0 6,15 8,93 2,78 Gru
WDS05574+0002 BU1190, IDS05523+0001, BDS3069, ADS4542, BD+00 01227 05h 57m 25,3s +00:01:39,1 6,95 9,81 2,86 Ori
WDS03428+0754 STT61, IDS03374+0735, BDS1828, ADS2709, BD+07 00537 03h 42m 45,9s +07:54:10,6 7,77 10,63 2,86 Tau
WDS05528-3832 I16, IDS05494-3833, CD-38 02270 05h 52m 47,7s -38:31:33,6 6,88 9,76 2,88 Col
WDS01125+0228 STT27, BDS643, BD+01 00223 01h 12m 30,6s +02:28:17,6 6,54 9,5 2,96 Cet
WDS13101+3830 BU608, IDS13051+3904, BDS6410, ADS8805, BD+39 02611 13h 09m 42,0s +38:32:01,9 6,26 9,23 2,97 CVn
WDS23244+1429 BU719, IDS23194+1356, BDS12346, ADS16735, BD+13 05105 23h 24m 23,9s +14:28:44,9 7,65 10,68 3,03 Peg
WDS07059-0101 CRJ1 07h 05m 52,8s -01:01:13,6 5,98 9,11 3,13 Mon
WDS06544+2110 STT160, IDS06484+2117, BDS3681, ADS5553, BD+21 01426 06h 54m 21,3s +21:09:40,8 6,66 9,92 3,26 Gem
WDS17039+1941 BU822, IDS16595+1950, BDS7847, ADS10323, BD+19 03218 17h 03m 52,7s +19:41:25,8 6,58 9,89 3,31 Her
WDS03346-3152 B53, IDS03306-3213, CD-32 01358 03h 34m 33,6s -31:52:29,3 6,6 9,93 3,33 For
WDS19502-1000 RST4643, IDS19447-1016, BD-10 05195 19h 50m 09,8s -10:00:25,7 6,91 10,26 3,35 Aql
WDS04339-0644 BU881, IDS04290-0657, BDS2268, ADS3305, BD-07 00838 04h 33m 54,7s -06:44:20,1 5,72 9,19 3,47 Eri
WDS03027-0741 BU11, IDS02578-0805, BDS1549, ADS2312, BD-08 00568 03h 02m 42,3s -07:41:07,7 5,4 8,9 3,5 Eri
WDS13328+2421 A567, IDS13281+2452, BDS6523, ADS8937, BD+25 02643 13h 32m 48,2s +24:20:48,3 6,21 9,71 3,5 Com
WDS17420+1557 BU1251, IDS17375+1600, BDS8120, ADS10723, BD+16 03256 17h 41m 58,6s +15:57:07,8 5,59 9,38 3,79 Her
WDS09087-0835 KUI38, IDS09038-0811, BD-08 02588 09h 08m 42,2s -08:35:22,2 5,6 9,47 3,87 Hya
WDS23190-0937 HO199, IDS23138-1010, BDS12289, ADS16671, BD-10 06094 23h 18m 57,6s -09:36:38,6 5 9 4 Aqr
All these doubles should be doable with 140mm but some may be already rather difficult (pA up to 180mm).
Wilfried
PS: Did not check if any of these doubles were already in your observation reports


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WRAK
scholastic sledgehammer


Reged: 02/18/12

RoT Gracious Behavior Analysis new [Re: WRAK]
      #6070952 - 09/09/13 10:11 AM Attachment (15 downloads)

I know that there has to be some bumpy behavior of the current algorithm as I use several logical switches to set the different parts of the model in action (for M1>6, M2>9, ...). To check this assumption I made a set of fictive observations with incremental changes for all involved parameters. The result can be seen in the graph with to my surprise only - to my surprise there is only one real bump to see and this occurs when the M1>6 switch gets active. Will have to make this smoother in a next version.
Wilfried


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fred1871
professor emeritus


Reged: 03/22/09

Loc: Australia
Re: Overall RoT Performance new [Re: WRAK]
      #6072480 - 09/10/13 01:17 AM

Wilfried, that's quite a list of doubles around 1.3"-1.4". Some of them I'll ignore - they're too far north to be above my horizon, ever, where I live at present; and some others have declinations that will keep them too low in the sky. That still leaves quite a few.

A comment on two of them. First, RST 5560 in Grus (23208-5018). It's part of the easy pair, DUN 248 - I have notes on the Rossiter pair from 7-inch refractor days; it wasn't too hard with that telescope, seen double at 180x, despite delta-m of 2.8 at 1.3". I'll try it again with the 140mm.

The other, HO 199 (23190-0937) is on my list to observe, and if clouds had stayed away a couple of nights ago I'd have tried it already. The delta-m is 4.0 at a listed 1.4" - problem is it's a 1962 measure, and nothing newer is listed, so this is a neglected pair. The photometry is old as well, single-decimal magnitudes. The WDS summary indicates a changing PA, 57 degrees in 78 years - extrapolating (linear) suggests ~37 degrees less, so ~130; separation may have slightly increased, but the change 0.2" is within possible errors of measurement and rounding. It'll be interesting to check it. Hipparcos appears to list it as single (hence no 1991 measure) and gives ~5.00 as the V magnitude. Because there are 14 measures listed I'd expect this to be a genuine pair. The possibility exists of course that it may have taken to rapid change between 1962 and 1991, but with a parallax of 13mas it'll be 250 ly away, so rapid change is less likely - 1.4" is a big orbit at that distance (projected 100+ AU separation). Not impossible, of course - depends on which part of the orbit it's in, and line of sight angle.

Again, thanks for the list - I can see a few objects not on my current lists, and several others I need to re-visit.


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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: Putting the "Rule of Thumb" to test new [Re: fred1871]
      #6121395 - 10/06/13 10:07 PM

Quote:

I've had the experience of observing a double star that another experienced observer could not see, same time, same telescope, same eyepiece. The two of us looking alternately. To me the companion was fairly obvious; to him it was invisible, then after "look in this position" it was "maybe I can see it". So we have the observer factor as well. Some observers will need a bigger telescope, or higher power, or more practice on doubles.




this is perhaps the most important and fundamental point.

observer aside, wilfried's comment that different rules have to be applied in different contexts (the rayleigh criterion with this pair, some other criterion with that pair) is just a statement of the blind man and elephant problem: there's a complex landscape of visual targets, which present very different resolution problems to the eye. one size rule can't fit all.

i have never understood the claim that a resolution rule or resolution limit of any kind can "tell me whether i can resolve a binary or not", when the only way to know if you can resolve a binary or not is to try.

one way to understand the problem is that any "rule of thumb" is actually going to suggest to you *how to look*. an experienced observer uses different observing strategies or tricks depending on the visual challenge, and presumably the quality and degree of the challenge is all that a rule of thumb can tell you. thus, a rule such as "in this situation, use the rayleigh criterion" is not how observers think: the operative rule is more like "in this situation, use averted vision" or "move attention around the object, and let seeing help your acuity" or "pile on the magnification". experienced observers don't really need these kinds of rules, because judgment integrates rules into insight.

if i remember correctly, this thread began from a "rule of thumb" that i suggested, and if i remember correctly it was just the resolution limit (whichever of the many resolution limits you prefer) multiplied by any magnitude difference greater than 1. (the various studies i have looked at suggest a better rule is the resolution limit multiplied by half the magnitude difference; a magnitude difference of 3.0 means resolution should be expected at 1.5 times the resolution limit of a matched pair.) in practice, i use rules such as this basically to interpret catalog data and decide how long i will persist in the attempt.

the underlying problem is that the catalog data are variously unreliable, especially for the infrequently measured ("neglected") doubles. that embarks us on the search for a rule of thumb for when to use the rule of thumb.


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Putting the "Rule of Thumb" to test new [Re: drollere]
      #6121787 - 10/07/13 06:54 AM

Bruce, nice to hear from you again.
Since this thread started we have discussed most of the existing concepts for a RoT for resolving unequal binaries - and more or less dismissed all of them, especially the deterministic ones for reasons you mention and others as well.

The current state of affairs is a probability model based on statistical analysis (least square nonlinear regression) of a data set of limit observations.
The current model uses the following parameters: separation, delta_m, magnitude of primary, magnitude of secondary, central obstruction, degree of light pollution in terms of Naked Eye Magnitude Limit and a final check against Telescope Magnitude Limit.

Result is a proposed aperture for a fair 50% chance for resolution with the assumption of reasonable good seeing and average personal acuity.
The advantage of this approach is then a known standard deviation allowing calculation of probabilities for smaller or larger apertures.

This approach allows to cover all other factors not included in the algorithm per probability - errors in advertised data, variations of seeing, acuity, experience and so an. So far the results are promising especially in the aperture range from 30 to 140mm I could cover with my own equipment using iris diaphragms.
Current weak points are larger apertures and larger values of CO but I have plans to cover at least the range up to 200mm also myself soon.
Wilfried


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WRAK
scholastic sledgehammer


Reged: 02/18/12

RoT and glare new [Re: WRAK]
      #6188005 - 11/11/13 04:45 AM

My recent attention to the topic of aerosol diffusion (low transparency due to haze) with the effect of enhancing the halo around brighter stars made me aware that I have so far ignored the effect of glare on resolving unequal doubles. This was more or less intentional as I think the number of doubles in this category is rather small and resolving of such doubles is less a question of aperture but used methods like for example occultation.
A minimum size of aperture is certainly needed depending on the usual parameters like separation, magnitude of the secondary and delta_m but may be some extra mm in aperture are needed to have a better chance seeing the companion through the halo. Only if the companion is fainter than the halo even with perfect transparency then resolution with direct vision might be impossible.
Will consider to add a glare module to the RoT algorithm.
Wilfried


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WRAK
scholastic sledgehammer


Reged: 02/18/12

RoT Field Test new [Re: WRAK]
      #6249496 - 12/12/13 04:59 PM Attachment (10 downloads)

The recent RoT "discussion" with Bruce motivated me to post my current set of limit observations to make it public use for RoT field tests.

In total there are now about 300 observations made by me with an iris on my 140mm refractor to be able to change the aperture on the fly. To this set I added about 150 observations found in books and on this board (observer given in parantheses after the name of the object) with fixed apertures but with descriptions proposing limit or near limit observations.

As benchmark I added the results of my current RoT algorithm based on statistical analysis of a small subset (about 20%) of the current base plus a number of observations listed by Lord in his paper on resolving unequal binaries meanwhile eliminated from the data set because considered not this reliable for my purpose.

With the small data set my RoT had a correlation coefficient of 0.932 and a standard deviation of ~14mm and as we have now a much larger data set we can consider this also as good field test for it - with the full current data set the correlation coefficient is 0.913 and standard deviation is ~19mm. This means that there is some degradation to notice indicating that there is room for improvement but this I knew from the very beginning as the first data set for statistical analysis was far too small and the model itself contains some known shortcomings.

I intend to do statistical analysis again with the meanwhile much larger data set but want also to wait for another scope giving me the opportunity to cover the range of apertures up to 200mm myself also with variable aperture.

Finally I want to stress the fact that this data set (while it may include some errors unavoidable with such a number of observations) is the only one I know consisting mainly of "real" limit observations done with variable aperture and is thus a perfect base for field tests for any other RoT concepts. Feel free to do your own calculations.
Wilfried


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