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Hi James,
Could you report your practical limiting magnitude of your equipment please? For example, what is the faintest you can reliably measure to within 0.1 magnitudes after a 10 minute exposure?
I’m toying with getting a small equatorial mount for a Canon DSLR / telephoto lens combination and your experience will help set expectations for a roughly 50mm aperture.
There are limits to what can reasonably be extrapolated from something approaching two orders of magnitude greater light grasp!
“In my experience, size isn’t everything. it’s how you use it that counts” and “There are a hell of a lot of variables brighter than 16th magnitude.”
Have you thought about monitoring stars for exoplanet transits? Some of their stars are quite bright and within range of a 100mm scope.
Of course, if you send the same amount of money on a reflector as on a refractor you could get a markedly larger aperture … This assumes you haven’t already bought your equipment. If you have, there are still many things you can do with photometry on what you have.
In my experience, size isn’t everything. it’s how you use it that counts. With a 100mm aperture you are not going to be making observations of 20th magnitude stars any more than I am of 23rd targets with my 400mm, which estimate is based on a roughly 3 magnitude difference in light grasp. I can perhaps manage useful observations (an accuracy of 0.1 m) down to mag 20 if I am prepared to spend enough time (hours!) on the exposure. You could manage perhaps mag 17 with a similar commitment but 15 to 16 should be entirely straightforward.
There are a hell of a lot of variables brighter than 16th magnitude. Some are so bright that they will saturate your detector and so are effectively unmeasurable.
What you really need to do, IMAO, is to start observing, learn what your equipment can do and to learn how to analyse your data. Your equipment is capable of producing research quality data far beyond that of any amateur set-up as recently 50 years ago.
I would also recommend contacting the VSS, but I’m biased. I found it extremely helpful.
Go for it!
Thanks for drawing this to my attention. It is fascinating stuff which will require much study to do it justice.
A line which caught my attention comes from the extensive bibliography:
Bruno, G., 1584, ‘De l’infinito, universo e mondi’ (On the Infinite, the Universe, & the Worlds)
Very few scientific papers contain references to work performed before 1800. This one contains several.
Faced with the difficulty of getting to La Palma where my observatory is located, I purchased a 10″ Dobsonian cloud maker on eBay so that I could at least try to do something.
It was dispatched on Friday and will likely arrive just in time for the requested observations.
Sorry folks, but tonight is probably the last clear night until June, by which time it won’t get dark at night anyway.
(Added in edit) It arrived a couple of hours ago, and very effective it is too. Rain has been persisting it down since last night.
I agree, except that long years experience in the field of computer security has taught me that what the organizer may consider “local” is profoundly ambiguous. All too often it is just plain wrong. In the case I noted, the organizer was just plain wrong: she explicitly stated “GMT” but meant “BST”.
There are other considerations. For example, the term “EST” is ambiguous, By and large it means UTC-5 but is very frequently interpreted as UTC+10 in Australia.
That is why CERTs are very strongly advised to use UTC and ISO-standard date formats in their communications.
We are all, notionally at least, astronomers and invariably use UT to report events we have observed. Predictions of future events, such as are published in the BAA Handbook, are invariably given in UT.
Can those who organize events for a future date and time please explicitly specify the time(s) in UT?
I missed an exoclock meeting because the organizers quoted 16:30GMT when they meant 16:30BST. I was not the only person to do so. Had the time been advertised as 15:30UT all would have been unambiguous.
This comet is no more. It has ceased to be. It’s a stiff. Bereft of life, it rests in pieces. It is an ex-comet.
I had similar problems when using the PaleMoon browser (a Firefux derivative). Logging in again fixed it for me.
Seems strange that three separate browsers running on very different hardware should all have the same issue…
“launching astronauts to the International Space Station on Crew Dragon at 21.32 on May 27th”; “The UK has an ISS pass at 21.20,”; “and the[n] go into garden to wave them on there [sic] way.”
Am I missing something? How do I subsequently wave at the crew 12 minutes before they leave the Earth?
“Is anyone else making different observing plans in the current situation?”
Yup, I’m trying to get hold of a telescope to use until I can get back to La Palma. See the “Telescope wanted” thread.
Plans that either come to naught or half a page of scribbled lines.
Hanging on in quiet desperation is the English way.
The time is gone, the song is over, thought I’d something more to say.Funny you should say that…
Already checked before you posted. Nothing there but I placed an ad in the Wanted forum.
My attention has just been drawn to a paper by Jonathon McDowell and available at https://arxiv.org/abs/2003.07446
One of his references is to a paper by Buffon published in 1777.
Actually, gaseous NO_2 is in dynamic equilibrium with its dimer N_2_O_4, aka dinitrogen tetroxide. It is the former which has the characteristic brown colour, the dimer being colourless.
I always knew that A-Level chemistry would come in useful one day.
I may be wrong but I believe the nitrogen-oxygen compound in the lower atmosphere is NO_2 (nitric oxide for old-timers, nitrogen dioxide for those born in the last fifty years) and not N_2O (nitrous oxide / dinitrogen oxide to the IUPAC fans).
Be that as it may, satellite monitoring has shown a truly dramatic decrease in the concentration of nitrogen oxides in mainland China recently. https://earthobservatory.nasa.gov/images/146362/airborne-nitrogen-dioxide-plummets-over-china has more detail. (Incidentally it supports my claim that NO_2 is the compound in question.)
I have been using APT (Aperture Photometry Tool) by Russ Laher for all my VS work. It is free, as in both speech and beer, and platform-neutral because it is wrotten in Java. Russ is on the IPAC team and has produced a very fine program. He is responsive to bug reports and feature requests, a few of which I have made.
APT produces output in its own TBL format (basically TSV with an initial couple of comment lines and another at the end) which it can export to CSV for loading into any standard spreadsheet. One nice feature of APT is that one FITS card can be exported into a CSV column — I use it to record for either JD or HJD according to what is desired for later analysis — as well as the complete FITS header where it is readily available for subsequent processing.
Converting the CSV into a BAA-VSS TSV-format file is easy enough and I will happily provide my script on request. The script uses ensemble photometry to produce an instrumental zero point magnitude from a list of (magnitude, error) pairs for the sequence members and then propagates errors appropriately to the derived magnitude of the VS.
I have another script which take an AAVSO VSP photometry web page and generates the correct source list and sequence data files for APT and the script noted above respectively. Naturally this script is also freely available.
