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I call the AAVSO API to get me the VS data and the candidate comparison stars in a requested mag. range and chart width. I use the B-V from SIMBAD to give me a guide to any major differences that there might be in the B-V values of the comparison stars. It’s more of a sanity check
So there is a Sanity Clause after all!
I use it to get the B-V of the target star. I couldn’t find that in the AAVSO data.
Ah.
When I add a new star to my program, I go to https://app.aavso.org/vsp/ and fill in the appropriate fields (Star, FOV, orientation, limiting magnitude, and more) and first get a finder chart, which I print for use at the telescope.
Next the photometry for the sequence in the filters required is downloaded. The B-V values and their errors are provided whether you want them or not, in line with the bottom of the VSP page where we find the words: “V and (B-V) magnitudes are always displayed. Select any other bands you wish displayed below.” A Perl script subsequent mungs the photometry data into a format useful for my current processing pipeline.
I never take a given B-V of the target star as gospel because it can itself vary as the brightness changes. If I want to know a colour index of a VS at a particular epoch I measure it for myself.
Paul,
The sequences for the BAAVSS visual charts have all been entered into the database. When you try to upload a visual observation, it’s checked against the sequence.
[Deletia
If you use an AAVSO chart, our DB doesn’t have any sequence information for these charts.Ah, there’s a thing.
In principle the AAVSO sequences could also be added to the BAAVSS database (assumng they are not there already – I don’t know). Those of us doing ensemble photometry generally include the (instrumental,catalogued) values for the (magnitude, error) of those sequence members which are measurable.
In principle, the BAA database could run sanity checks using those sequences too. Either that, or I am missing something.
Further, the AAVSO database could be scraped occasionally (once a year perhaps) to see what comparison stars have changed. What to do after a change should be obvious — pretty much what happens for BAA sequence changes.
Personally I like the AAVSO charts and lists of comparison stars because it’s easy to query via my Python code via the AAVSO API. I combine that with SIMBAD/VIZIER data to get other parameters of the target star and I can then create a good list comparison stars for ensemble photometry.
That is essentially what I do, though my code is wrotten in Perl rather than in Python.
By and large I download only the V photometry but include B and R as required. B-V, which is provided regardless, give B magnitudes but not, alas, their errors. My ensemble photometry code does The Right Thing with reported errors, which is to add in quadrature.
Out of interest, what SIMBAD/VIZIER data do you use? For my purposes all that is required is the magnitudes and the coordinates, all of which is provided in a single download from AAVSO.
My concern is that perfectly good data elicits a warning. I freely accept that the important stuff (magnitudes and their errors, star ids, date-time. filter, explen) goes through after checking. It’s the appearance and untidiness of an essentially useless warning that irritates me.
Perhaps if the chart ID was in a standard format (/^AAVSO X.+$/ for those who recognize Perl-style regexps, the database checking software could avoid issuing a warning.
Paul
Sure.
I mentioned it because I am thoroughly sick of being admonished by the VSS database for using non-kosher chart IDs.
Big hint there 😉
No thanks are due to me!
I never met Bob, sadly, but have visited the Hacienda San Jorge many times. I was hoping to jog memories of people who were on that expedition.
I think Charles’ Wain predates our monarchs of that name but it’s most appropriate for this weekend.
It undoubtedly does so. The Wikipedia article goes into at least as much detail as you are likely to want. In particular, it has the same name in essentially all Germanic languages.
I think Charles’ Wain predates our monarchs of that name but it’s most appropriate for this weekend.
It undoubtedly does so. The Wikipedia article goes into at least as much detail as you are likely to want. In particular, it has the same name in a number of North Germanic languages.
…and there is Cor Caroli…
https://earthsky.org/brightest-stars/cor-caroli-heart-of-charles/
Now well-placed for images of the starfield.
Tucked inside the handles of Charles’ Wain. You can’t miss it.An equivalent way of saying this, though it needs considerably deeper understanding of QM, is that the uncertainty principle follows inexorably from the properties of the Fourier Transform.
The linkage is that a quantum state is fundamentally a function of complex numbers, whereas in classical mechanics everything is purely real.
Some of you may know why that the question of the existence of uncertainty principle relating energy to time, and why it has the same value as position-momentuum relation is very far from obvious, largely because time is not a quantum operator. A fascinating journey down a rabbit hole finally gives a good answer to that question, but the reasoning is very far from obvious.
Hacienda San Jorge in Los Concajos perhaps?
The architecture and colour scheme look rather familiar.
On my last trip to La Palma I took some images in Sloan i’, r’ and Johnson V (I don’t have any other JC filters nor Sloan g’) of the M67 Landolt field. The primary interest is photometry calibration but I also realised that tri-colour images should be possible, even though they may look odd.
The images have not yet been processed but I will report back later.
Paul
Now you mention it, iota Cancri is my favourite double star. Similar to Albireo but rather prettier IMAO.
Pi Cephei is was double star of the month according to https://www.webbdeepsky.com/double-stars/object/pi%20Cep
Pi Gruis is, by all accounts a fine double, but too far south at -46 Dec for UK-based telescopes. I may give it a try when I return to La Palma.
Pi Sco is visible from most of the world. The primary is a spectroscopic binary and the secondary is rather difficult (though well separated) at mag 12.2. The primary does show eclispes, but with a depth of only 30mmag it likely presents a worthy challenge to photometrists willing to stretch themselves. The period is 1.57 days. Anyone up to it this summer?
Sounds good. Often thought I should attend.
The event is always fully booked before I receive my supply of round tuits and generally before I know whether I will be in the country at the time it is held.
