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Hi Nick,
I successfully use Windows 10 with MaxIm DL, the Sky X and an Astrophysics mount. There are no specific tips I can give other than sometimes things don’t work first time when I change my setup, though with trial and error I’ve always got things working.
Good luck with your changes,
Andy
It is a great publicity idea for the RAS and astronomy.
Anyone involved in publications will know how difficult it is to spot every mistake and it is impossible to please everyone with the layout and language. I know mistakes in our own BAA publications often don’t get picked up until after they have gone to the printers, or been published on the website, even when several people proof read them.
An astronomers telegram has been issued as Betelgeuse started to brighten again in mid February. This appears consistent with the existing variability cycles though a deeper minimum than usual, probably due to overlapping cycles. It is still interesting and useful to observe with both photometry (visual and electronic) and spectroscopy. To verify the brightening continues as expected and to obtain more data on the behaviour on this interesting star.
There is no problem storing the photometry from every exposure, in fact I think that is what the majority of observers do. For faint targets, deciding whether and how many sub-frames to combine is always a tricky choice.
Cheers,
Andy
Hi Paul,
I think I understand what you are saying about the database, but I will just explain what is held to avoid possible confusion, including anyone who may be following this thread. Where the observer provides the instrumental magnitudes and uncertainties/errors of the variable and comparison stars then this data is recorded in the database. Thus, if someone wants to recalculate the magnitude using different reference magnitudes, or to exclude one of more of the comparison stars then this is possible. It does not hold information on non-comparison stars, e.g. every star in an image, nor does it hold data on background counts etc. We only require the Julian Date to be submitted, noting HJD and BJD can be calculated, and as a general rule data that can be calculated from existing data is not stored. The exception to this is the derived magnitude, as different observers could calculate this by different methods, and it is desirable to hold what the observer calculated.
As you are doing, it is a good idea to store images including the calibration frames. Then if a recalculation is required, or there is a query from a researcher, it is possible to delve into the detail.
There is no easy or right/wrong answer on whether to submit individual images or combined images. Individual images allow researchers to choose how to combine data (within the limitation of not having the raw images to hand), while the observer doing this can make life easier for the researcher. Also, the observer will be most familiar with their setup and the images. Personally I would suggest combing images if your results are dominated by the noise.
Cheers,
Andy
Hi Paul,
If I have understood what you are proposing, then it should not be done for submissions to the database as a single same image would contribute to multiple measurements/observations.
My understanding is you would first combine images 1-9 to get a good signal, then images 2-10, and so on up to 9-18. This is of course simplified as you would have many images. Image 9 would be used 9 times, and so the same photons would contribute to 9 observations and that would be wrong.
You can do this kind of thing in an analysis, as long as what has been done is stated. Basically it is a smoothing function. It just should not be used for submitted observations to the database. This leaves the choice of whether or not to smooth with the researcher.
Best wishes,
Andy
Hi Paul,
In my opinion an uncertainty of 0.02 magnitudes is excellent on this target. The uncertainties in the CRTS photometry in the VSS Circular phase diagram and other VSS observers appear to range between roughly 0.03 to 0.15 magnitudes, so you are doing much better.
The lower SNR observations are still useful as statistical data can be extracted from many observations, and they confirm U Leo is not doing anything different. Though as always the higher the SNR the better, so I am sure your efforts will be greatly appreciated.
Andy
Hi Paul,
In answer to your questions.
You should use the “CV” filter where you take unfiltered photometry and calibrate using V filter comparison star magnitudes. This filter is standard in the BAA and AAVSO and is there exactly for this purpose.
It is common to add images if the SNR is very low, or to take longer individual subs.
It appears the AAVSO have a sequence for AT 2019xim. It is fine and common practice to quote AAVSO sequences when submitting to the BAA Photometry database when a BAAVSS sequence is not available or if it is not appropriate for digital photometry. They have far greater resources available to produce sequences. Just quote the chart reference, e.g. AAVSO X25107PN or X25107PN.
Best wishes,
Andy
Hi Robin,
You can still access member pages when not logged in, though you have more buttons and capabilities when logged in. For example, I just logged out, clicked on your name in this post and that took me to your member page.
Best wishes,
Andy
Hi Robin,
The quick posts are just designed to be text. A nice idea but for that kind of featured post I suggest using the forum as you already do.
Best wishes,
Andy
Thanks for sharing this Robin. When I first looked on the AAVSO database there were no recent IR measurements, it is great these have been added.
I agree this implies a cooling rather than a change in total luminosity (bolometric).
It is possible the star may have expanded a little rather than contracted as I have seen some saying, to explain the cooling. Though that is pure speculation on my part. A more detailed analysis of the existing data and ideally additional spectra in the IR would help to tie down the change in bolometric luminosity and temperature, to then understand if it has changed size.
Cheers,
Andy
Betelgeuse is a cool red star with the majority of its flux in the red and infrared, while the majority of observations are visual or with a V filter. It occurred to me the widely discussed drop in luminosity is based on the assumption that what is happening in the visual represents the total luminosity of the star, and this might not be the case. I decided to do a little investigation using spectra from the BAA Spectroscopy Database and V filter magnitudes from the AAVSO International Database to do a rough flux calibration of the spectra.
My first plot shows what passes through a V filter using James Foster’s spectrum from 9th April 2018. You can see the V filter is most sensitive to wavelengths where Betelgeuse is not at its brightest. The V filter is approximately like human vision, not a perfect match but reasonable. You can also see how the flux continues to rise to shorter wavelengths towards the infrared.
Next I compared James Foster’s spectrum from 9th April 2018 to Robin Leadbeater’s recent spectrum from 30th December 2019. The approximate V magnitudes on these dates are 0.4 and 1.4, though due to difficulties with measuring the luminosity of Betelgeuse it is best to consider these with uncertainties of +/-0.1 magnitudes. A magnitude of 0.4 is fairly typical of Betelgeuse in recent years, noting it regularly varies by nearly a magnitude. I did a flux calibration using the V filter profile rather than any specific representative wavelength. This was to avoid any effects due to individual lines skewing the results. This shows a very marked drop in luminosity to longer wavelengths up to at least 7400 Angstroms.
Their aren’t spectra in the BAA database with longer wavelengths into the infrared due to the difficulty in making these measurements. So instead I then compared Pickles reference spectra for M2 and M4 (both at luminosity class III). These aren’t perfect matches to James and Robin’s spectra but they are good enough for a first approximation (M2 typical and M4 now). It can be seen that a drop in luminosity at shorter wavelengths in the visual region does not necessary continue to longer wavelengths, with the flux being about the same from about 8000 Angstroms. These spectra only go to 10,000 Angstroms, but give a hint of stronger flux deeper into the infrared for the cooler M4 spectrum. So I wonder whether the total luminosity has not dropped by as much as it appears. Perhaps some or most of the flux has shifted from the visual into the infrared?
Comments and criticism welcome 🙂
Congratulations Robin!
It is incredible what has become possible due to advances in technology, though it still requires great skill to reach such faint magnitudes. A very well deserved award.
Andy
Well spotted Ken. This error was pointed out in the early November eNewsletter.
A replacement page is available in the Handbook area of the website, and the online Handbook has the correct phases.
https://britastro.org/handbook
Best wishes,
Andy
Hi Robin,
It is possible and I must admit I have not checked. It would be a useful and interesting experiment.
Cheers,
AndyKevin,
I will just a bit of clarification.
Yes, you can submit clear photometry, though you should probably use CV. This means clear filter (or unfiltered) using V-band comparison stars. The important point here is that while your own observation might be made with a clear filter, the comparison star magnitudes will have been made through a V filter, or at least you should try to obtain V filter magnitudes from the BAA or AAVSO charts.
The full list of filters can be seen near the bottom of the review observations page of the BAA Photometry Database. Note as far as possible we try to stay in-line with the AAVSO on filters and filter codes. This makes life easier when combining data from different databases.
https://britastro.org/photdb/data.php
If you have a spare slot in the filter wheel, it might also be worth trying truly unfiltered observations, as for some targets a slightly higher signal may be preferable to a luminance filter.
Best wishes,
Andy
BAA Photometry Database Manager
I have created an page for the Armagh meeting in the Publications -> Downloads -> Past Talks area of the website.
https://britastro.org/downloads/19324
We have 3 talks thus far, and I shall upload anymore that I receive.
Andy
Hi Martin,
The auto-suggest does not come from the BAA website. It is actually your web browser remembering what you have previously entered into those fields and then suggesting options based on this historic input.
It would be difficult to auto-populate object name and location from the filename as we would need to agree a standard filename layout that everyone would need to use, and otherwise gibberish would appear in those fields. There would also be a reasonable amount of bespoke development by BAA volunteers to write code to extract this information from the filename and populate the fields, assuming it is possible.
Sorry it is not better news.
Best wishes,
Andy
Hi Eric,
I am sorry to read that you are unhappy about your posts being publicly visible. While only BAA members can post to the forum, in common with most internet fora and other astronomy fora the posts are visible to all, e.g. SPA, AAVSO, cloudy nights, stargazers lounge, astrobin, etc. This means internet search engines like Google have access to the content, and this can be helpful when searching on a particular topic.
I would draw your attention to the BAA forum terms of use, in particular:
“We strongly advise that you do not disclose personal information to others. Do remember that the Forum and Member Pages are visible not just to BAA members, but to the whole world. If you wish to exchange contact details with other members, the Forum and Member Pages are not an appropriate place to do it.”
https://britastro.org/forum-terms
Kind regards,
Andy Wilson
BAA Systems Administrator & Web Content Editor
