Lists of doubles for seeing quality estimates
Posted 01 March 2013 - 03:16 PM
Posted 01 March 2013 - 04:56 PM
Posted 01 March 2013 - 06:17 PM
I can see where the OP is coming from, have also used close double stars to ascertain the seeing, For example, If I can clearly split an equal brightness pair at 1 arc second separation...yada yada yada.
Both methods rely in PART of a subject evaluation of the stability of their respective image. Over the years, I have gravitated to using the diffraction pattern.
To the OP,
Posted 01 March 2013 - 07:31 PM
I'll say the same as Wilfried and Tom and Beth - the diffraction pattern of a single star is your best way of evaluating seeing. That's why the standard scales, developed over the years, are based on a single star. Single star or double, there's a subjective element in it.
Star-hopping? Works fine, if your charts go deep enough. The First edition Uranometria is good for that (more stars than 2nd edition, and printed with better visibility under a red light).
You could also download the Tri-Atlas -
The B and C charts series go plenty faint enough for finding 9th mag stars, and at a sufficient scale. B goes to mag 11, C to 13, for stars. And plenty of doubles are identified, not just marked, so you can look up current data in the WDS.
You could print off the B charts, for example, to have hard copy for use under the stars. My own preference is the C charts, mostly used at 200-400% to make reading easy.
Posted 02 March 2013 - 06:15 PM
To WRAK, Tom & Beth, the problem with using diff rings when citing seeing conditions in an observing report is that the brightness and width of the rings differ by aperture and individual scope optical quality. Additionally, the air column gets more turbulent as aperture goes up and exit pupil goes down, so tolerable seeing in a 80mm can be just awful in a 200mm. Citing the Pickering or other Airy disk scale is subjective. My optical image at Pick 5 may not be your mental image of Pick 5. If one cites "seeing Pickering 6 to 7", readers can't get a solid handle on how that relates to magnitude depth on a globular or what H2 knots on a galaxy arm look like. I want to cite arcsecs because a GC in 2.5" seeing shows noticeably fewer faint stars than the same GC in 1.5" seeing. The ephemeral contrasts that make galaxies so exciting on a good night are the first thing to vanish if upper altitude seeing goes to hooey.
I'll annotate the doubles on the atlas as I go, so eventually there's be a useful selection on the pages most often used.
Posted 03 March 2013 - 04:22 AM
...the problem with using diff rings when citing seeing conditions in an observing report is that the brightness and width of the rings differ by aperture and individual scope optical quality. Additionally, the air column gets more turbulent as aperture goes up and exit pupil goes down, so tolerable seeing in a 80mm can be just awful in a 200mm...
Certainly true, another factor is also the altitude - near zenith the seeing can be quite good and at 30° altitude awful. But what you are looking for is the given seeing for your given conditions and therefore it is no longer this subjective.
Nice description of the Pickering seeing scale with relation to double stars: http://www.carbonar....ting-seeing.htm
Really good pictures for the Pickering seeing scale: http://www.damianpea...m/pickering.htm
Posted 04 March 2013 - 08:58 PM
Posted 08 March 2013 - 10:15 PM
The C chart showed more doubles marked, and more doubles labelled, without going fainter than 10th magnitude, even though both charts show stars below 10th magnitude. The difference in scale between B and C is certainly one factor in this, as there's less space for labels on B charts.
So for the "find every double you can" observer (and some others of us ) there's a benefit to using C charts.
Posted 07 May 2013 - 05:50 PM
You can export in excel or print the list.