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Thanks Nick, this sounds very much like what I’m looking for. As for using the CLI, that’s what I generally do anyway.
This morning I kludged up a Perl script to modify the CRVAL[12] cards in the FITS headers in attempt to persuade SWarp to stack the images with an offset. Not very successful though. Ether I screwed up the code or the total exposure just wasn’t long enough because I can’t see anything circular on the stacked image — just lots of trailed stars.
1/32K difference in flux corresponds to a roughly 1/32 millimag dip in brightness. Either I’m missing something important, which I do quite often, or I’d change “tough” into “a chance somewhere between nil and negligible”. That said, I’m a great fan of understatement.
In the ARPS meeting today we were advised, correctly in my opinion, to concentrate on objects with a transit depth of at least 10 millimags. Three hundred times deeper, in other words.
My experience is that good observations of a transit depth of, say, 5 millimags is achievable but not entirely trivial. I couldn’t manage one millimag.
The optical variability is measurable by amateurs. I was paying attention to your “visual or CCD” request, honest!
See http://www.threehillsobservatory.co.uk/astro/astro_image_33.htm for instance, where Robin Leadbetter presents his images and http://www.threehillsobservatory.co.uk/astro/pulsar_detection_1.htm where the technique is described.
I’d expect more to come from the hemisphere around the solar apex but we’re going to be in the small number statistics regime for a long time yet. Even if interstellar objects are found annually it will be a few decades before the statistics are good enough to make a definitive statement.
I see very little chance of determining their original star. Unless they were ejected very recently from a very close neighbour the perturbations from other stars will make the trajectory very curvy. It takes a long time to travel anywhere at only 30km/s (chosen because it make the arithmetic easier — it is 0.0001c). At that speed it takes over 3 million years to travel 100 parsecs — close by in galactic terms.
Standard false alarm. Happens all the time. Nothing to see here, move along please.
This is one reason why I run local astronomy.net servers on my TCS, laptop and two main analysis machines. If you can spare a few gigabytes of disk space I strongly recommend that you do so as well.
I can now give some limitations for my site. The fork mount on the main scope won’t allow pointing south of -47.5 degrees. In the other direction, the limitation is about +77 degrees, which means I can’t observe some of the BAA-VSS program.
The on-site images of ω Centauri were taken by Kevin Hills some years back. His observatory is a few metres away from mine and his GEM is nowhere near as fussy. It will quite happily point his OTA very close to the nadir, as we discovered some weeks back.
Perhaps I should take a tripod, DSLR and telephoto lens down to Fuencaliente for an uninterrupted southern horizon where -60 declination should be a real possibility. A nice target at this time of the year might be ε Indi which culminates at about 5 degrees altitude.
“I’ve got some commercialy produced Kodak slides that (since 1973) have realy shifted, to the extent that I would not show them again.”
As long as at least some of each of the RGB response is still there they can be restored. Digitize them now while you still can and restore them at your leisure.
Repeated copying is the way to go.
I still have the machine-readable data I took for my DPhil research in 1982. The original 8″ floppy disks are (probably) unreadable but the raw data is still usable. That said, I still have the disks and a couple of drives up in the attic…
MS Office has had the ability to save and load Open Document Format files for many years now, as does free software such as Libre Office …
Looks like shadows cast by some objects (clouds near or below apparent horizon perhaps) on the regular forward-scattered sunlight.
Thanks. I may well add it to my program later this year once the imaging problems are worked out. Just found https://arxiv.org/abs/1607.08082 which contains a finder chart and a comparison sequence. I will investigate further.
Do you have any recent literature references to hand?
A round tuit arrived today so I uploaded the two nights of THL data to the CalTech periodogram engine. The results are (to me at least) are interesting. Several methods of period searching were used. All gave peaks at close to 0.0281 days and twice that (0.0562 days). The former is 40.3 minutes, which seems rather short. Twice that, 80.6 minutes, is absolutely typical of CV binaries. Perhaps a little on the short side but not exceptionally so — that of WZ Sge is 0.05671 days. The 40.3m light curve shows only a single dip. The other, of course, shows two which if real suggests eclipses of two stars of fairly similar magnitudes.
Another period which comes up strongly is at 0.08 days — 2 hours or so — or perhaps twice that. This is doubtless the 0.1 variation mentioned in the earlier post.
Only two nights and 359 measurements were analysed. Time for me to download more of the BAA-VSS database and see whether the patterns hold up.
I don’t know of any reported variability of Sk -69 202. I’d be mildly surprised if it wasn’t variable.
A good number of LBVs are accessible to amateur observation. AE And and AF And are on my observing program. Eventually I’ll take a look at others in M31 and make start on those in M33. It’s a shame that the LMC and SMC never rise here.
Your mission, Robin, should you choose to accept it, is to take spectra of AE & AF And. This post will self-destruct in five seconds.
😉
Are you sure that the same star was involved?
My understanding, which may well be wrong, is that the objects concerned were very close together on the sky but it’s far from certain that they were identically the same object.
A better example, perhaps, might by SN 1987A, aka Sanduleak -69 202. There is absolutely no doubt there that the SN precursor had been studied by Sanduleak.
“It was a test of how deep I could go with my first astro camera,”
I’ll take that as a challenge. The old camera could reach 22.0 Gaia -g, a good approximation to the SBIG’s unfiltered spectral response, with a reasonable exposure time. When all the niggles have been worked out I’ll try for the H-II regions in IC 1296 and a better view of the more distant galaxy.
You are almost certainly correct. SWarp was used to co-add a number of subs. As the intention was to acquire an image, any image, no biases, darks, flats, bad pixel masks or anything else were used. The filter wheel was playing up and I can no longer remember what, if any, filter was used. The FITS headers claim no filter, which seems plausible, but I wouldn’t swear to it.
The SBIG died unpleasantly and after some deliberation I purchased a Trius 814 from Starlight Xpress. There were many many teething problems but first light came last night. Images are still not as pretty as I would like but one, of a beautiful face-on barred spiral in Lyra called IC 1296, appears below. The bright nucleus is over-exposed to bring out the detail in the spiral arms. I’m certain much better images can be obtained after more tweaking the configuration of various bits of hardware. In particular, I don’t understand what generates the dotty artefacts visible in the image, and there’s some trailing, possibly because the OAG and AO units are not working properly (or at all).
According to a local installation of astrometry.net the plate scale is 0.292 as/pix which matches the theoretical resolution nicely and at 2×2 binning (0.584 as/pix) a typical 2-3as seeing disk is 4-5 pixels across. Just what I wanted.
(OK, I confess to being mischievous. The large blobby thing at the lower-left is M57. I happen to think the 15th magnitude galaxy is prettier.)
Added in edit: I just spotted 2MASX J18530959+3305385, the faint fuzzy just to the left of the top-most star on the right edge of the image. According to SIMBAD it is 10as across and rather red; I can’t find a V magnitude but guess it’s around 16-17.
