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Hi Darren,
It is truly pleasing to learn of someone who wishes to do science as well as art!
I would strongly recommend getting a Johnson-V filter. It is by far the most used photometric filter and although it is possible to emulate its results by taking images in several other filters at the same time, that process is really not recommended unless you have no choice. It requires more exposure time with complicated calibration and data reduction processes to give inferior results.
Until your filter arrives you can spend your time productively working through the data reduction process on whatever images you have to hand. The results will not be compatible with measurements made in standard pass bands but you will learn much about what needs to be done. There are all sorts of niggles that need to be dealt with, as I have learned the hard way.
The LP weather forecast is also a bit Novemberish, i.e. typical for the rainy season. Tonight is a washout and we will be returning back to the UK on Friday, assuming Iberia doesn’t cancel our flights a third time, but I will see what I can do.
Three possibilities immediately spring to mind, two of which require that the neutron star is on the very brink of collapse anyway.
1) Accretion from the remainder of its earlier circum-stellar planets, dust and gas tip it over the mass limit protecting it from collapse.
2) Its rotational period slows down to the point where centrifugal force no longer keeps its equator far enough away.
3) Merger with an orbiting star tips it over the mass limit.
There could well be other explanations. I do not know enough about the equation of state of neutron-rich matter (who does?) to be able to decide whether cooling (for instance) could also cause a transition.
We may have to agree to disagree. There are quite a few “Paul Leyland”s on the net and finding the right one can be difficult. About once every year or two I receive wrongly addressed mail intended for one new to me. I am currently trying to fight Halifax Bank into accepting that I am not the droid they are looking for.
Accordingly I use two pseudonyms, Xilman and Brnikat, both of which are very unusual and so form excellent terms to feed into a search engine if you wish to find me.
Just finished a 2-hour set of exposures in Johnson-V. Nothing obvious in the quick-look stack and I don’t expect to be able to measure anything when the subs are processed properly. Best guess is <20.5 mag. but all will become clear soon enough.
A real pity conditions were not good enough here the previous couple of nights. Wind is still ferocious but at least the dust and clouds have gone.
Oh well, at least there is a nice GC in the field (at least one, perhaps more) and a whole bunch of supergiant stars resolved in the galaxy. An in-depth examination and comparison with sundry catalogues will doubtless turn up quite a few more interesting objects. I find it fascinating that we amateurs get about as good a view of M31 these days as Galileo did of our own galaxy.
I was observing AF And and AE And last night at about 20201030T2300Z. The full moon was so bright that I had difficulty getting an adequate SNR for them at around V=17 so didn’t even try for the recurrent nova.
It might have been possible, I suppose, but certainly would not have been easy to get an unambiguous re-discovery and almost certainly not decent photometry.
Tonight promises to be clear.
I have found errors in VSP. A few people with whom I have corresponded have also found errors. Some objects are missing from the VSP; some non-existent objects are included.
Unfortunately it appears that it may be difficult to get errors corrected.
How excited to get is a matter for you to decide. What I do is always to check with the MPC asteroid calculator and to compare with the DSS images available through Aladin. If something new passes both those tests, then I get excited and ask for confirmation. The last time this happened it turned out that the suspected transient was actually a ghost of a bright star. The slightly embarrassing details can be found on my personal collection of images here on britastro.org.
Just a reminder: M31N 2008-12a is due to go off any day now. This recurrent nova goes into outburst at roughly 11-monthly intervals and reaches mag 18 or so at maximum. It is visible for only a few days each time and nightly monitoring of the field is recommended.
https://arxiv.org/pdf/1607.08082.pdf contains a finder chart and magnitudes in a number of photometric bands for a number of comparisons.
This might be a completely off-the-wall suggestion but I observe that C-c{l,r}amps are available with a grasp of at least six inches, or 150mm. Almost the first link I found is https://www.yandles.co.uk/tools-machines/clamps-cramps/c604
Not entirely convenient perhaps, but very likely functional.
You reaction is understandable. Clavius is clearly not on the dark side of the moon because I have seen it for myself. Mare Moscoviense is on the dark side of the moon (*)
Anyway, there is no dark side of the moon really. As a matter of fact, it is all dark (+).
* In the same sense as Africa used to be the dark continent.
+ According to Pink Floyd. As the albedo is roughly the same as that of tarmac they make a good case IMO.
00:00 is the first midnight of each day; 12:00 is noon; 24:00 is the second midnight of each day.
00:00, occurring before the sun reaches its highest point the sky (except at the geographic poles), is quite clearly ante meridiem and 24:00 is equally clearly post meridiem.
Yes, I am a pedant. Guilty as charged.
I would recommend doing so in a wavelength which isn’t completely drowned out by man-made pollution …
Although the original data has been withdrawn from its original repository it is still available if you know where to look. If there is any interest I will try to dig it out and let you know where to find it.
I’m trying to find out how Astrometrica estimates the gain, G (e-/ADU)
Ah. The photometry I do, which hardly ever uses Astrometrica, takes the gain as a given constant which I have evaluated for the specific camera which I use.
Just spotted this:
The reason I am doing this is that Astrometrica gets this wrong. In fact it reports two different SNRs in two different places
If by two different places you mean two different positions within the same image, it may not be wrong. As I noted in my earlier response the PSF can be position-dependent. The sky brightness will almost certainly be position-dependent (try measuring LBVs in the Andromeda galaxy!). Anyway, a fainter star (lower signal) will have a lower SNR than a brighter one even if the background is the same.
I am not quite understanding what you mean, in other words. I am but a bear of very little brain.
If you really want to get rid of stars, DAOPHOT does a damn good job in my experience.
The work flow is to identify all the objects, then a set of unsaturated and unblended stars. From the latter you build a model of the point spread function. Note that the PSF may be position-dependent. Fit one or more PSF models to each detected object, removing ones which are “good enough” in some sense as you go. Repeat until you no longer have any “good enough” fits.
Much the same could be said of the usefulness of publishing predicted magnitudes as faint as 15, let alone well below 20.
BAA members can now readily observe things which are significantly fainter than mag. 22.
My dome is controlled by LesveDome and very successfully too.
The major problem, from my POV, is that LesveDome is Windoze only and I want to move to a Linux-based TCS. The only thing stopping me is the lack of an INDI driver for the Velleman K8055 controller board. If anyone knows of one, please let me know.
