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To be quite honest, I don’t know. I’ve not tried to find out. It would not surprise me to find a few in the 19-20 range but fainter than 20 are likely to be more common.
That said, I can take measurable images at magnitude 20.5 unfiltered in 51.5 minutes (see https://britastro.org/observations/observation.php?id=20181108_230500_5f60877f698839f2 for an example) and 22.2 in 178 minutes (see https://britastro.org/observations/observation.php?id=20200113_230000_a5cc9ad9ed617011) with a 0.4m on a decent night.
Owners of smaller scopes need to multiply by the square of the aperture ratio. A 30cm, say, takes (0.4/0.3)^2 as long — 92 minutes and 316 minutes (5h16m) respectively. The figures for a C14 (0.356m) are 65 minutes and 225 minutes, or 3h45m.
I accept that over five hours is almost certainly too long for most people. Nonetheless observers equipped with telescopes in the 30-40cm class should be able to do useful research by measuring objects which are significantly below mag 21.
I measured it at V=11.016 ± 0.005 at JD 2459431.4507
It’s been cloudy ever since. Unusual in these parts for this time of year.
Perhaps tonight …
The resolution of the naked eye is roughly 1 arc minute and the diameter of the sun at 1 AU is roughly 30 times larger. Simple arithmetic suggests that beyond 30 AU looking directly at the Sun might be dazzling but likely not otherwise harmful. The blink reflex will protect you long before retinal burns occur, though there will be localized bleaching which will fix itself within a few minutes.
I mailed her and received no reply.
Could you ask her to mail me (paul dot leyland (at) gmail dot com) please? If she contacts me we both know that we each have the other’s address.
Thanks.
Nights are moderately long (though dusty and/or smoky) in these parts.
The orbital period of 0.18864 days according to AAVSO appears well determined. What is the value of further lengthy observation runs? Is there a suggestion that the period may be changing or are we looking for flickering in the accretion disk?
I am prepared to spend some telescope time if it is worth my while but there other calls on it too.
(Added in edit: not that it makes any difference tonight. Complete cloud cover as of about 45 minutes ago.)
=for comment
Parsing comments is a non-starter for all practical purposes.
They are free text, of zero or more characters, and all you can assume in FITS is US-ASCII.
=cut
; I would be quite within my rights to create this informative FITS header:
DATE-OBS= ‘2021-07-26T22:03:10’ /Ad ultimum diem et ad tempus.
// which tells you everything you need to know.
% I am with Nick on this one.
# Sorry, I couldn’t work out how to put a Perl or bash single-line comment into the subject as well.
<!–You have to make do with Fortran, Algol68, and C.–>
“Good” software includes Maxim DL. It even explains the data format and specifies the time zone.
DATE-OBS= ‘2021-07-15T23:30:15’ /YYYY-MM-DDThh:mm:ss observation start, UT
EXPTIME = 30.000000000000000 /Exposure time in seconds
EXPOSURE= 30.000000000000000 /Exposure time in secondsI could make a strong case for either end or the mid-exposure DATE-OBS. Perhaps the strongest is for the mid-point.
In practice it doesn’t really matter as (a) you are paying attention and (b) EXPTIME or EXPOSURE is also present and correct.
Andy has already addressed your second issue.
As for the first: the impact wasn’t big enough to destroy the Earth but was big enough to cause fatal damage to the significantly smaller impactor. What makes you think that the Earth’s orbit wasn’t changed by the collision from what it was into what it is now?
There is stuff here in La Palma called “No mas clavos” made by an outfit named Pattex. Literally translated this is “No more nails” and a quick web search suggests that it is the same as the UK product.
Regardless, it sticks almost everything to almost everything, is flexible and waterproof. I used it to get an extra 3 months wear out of a pair of sandals when their soles became unbonded, so I can testify to its strength and flexibility.
A 250g tube cost only a few Euros a couple of years back.
Might be worth investigating.
Have you thought about mounting a camera at the prime focus and doing away with the secondary altogether?
No worries about light-loss from multiple reflections.
Might not work, but if you are experimenting anyway, perhaps this might be worth a try.
I observed some targets from Roger’s most recent alert list. There were a few issues which I believe are now mostly sorted. In particular, Astrometrica would not play ball so I used my regular BAA-VSS pipeline. To do that, I had to build my own comparison star photometry file from the APASS catalogue, itself downloaded from a link provided by Roger. The script to make that file is available on request.
First result: at 2021-07-07 23:00, Gaia21au was CV=16.72 ± 0.05 and V=17.00 ±0.10
Some of the fields are very crowded and aperture photometry likely won’t be sufficient. PSF fitting, e.g. by DAOPHOT should work but that will be another can of worms to explore.
Anyone in the VSS wish to comment? In particular, should these observations be uploaded to the database?
“Yes, I can print pages from that though I still get the encrypted message if I download and use Acrobat DC (Win 10).” Aah, that suggests that your browser will print anything it is displaying but that Acrobat is honouring the content creator’s wishes. I will try to look into it.
Good to see you have an effective if possibly crude work-around.
Added in edit:
A very quick search on “printing password protected pdf” turned up numerous sites, such as these two. https://passper.imyfone.com/pdf/how-to-print-password-protected-pdf/ & https://www.maketecheasier.com/recover-lost-pdf-passwords-linux/
I can’t vouch for either of them.
Thanks. I will give that one a try when we have a decent night here. A calima has filled the sky with very fine dust 8-(
Would an off-axis stop help for bright objects, do you think? It would reduce the sensitivity and I generally dislike throwing away photons.
If I get anywhere I may consider using a more conventional spectrograph, but that is serious money to spend on a whim, hence the SA.
Thanks, Robin, for getting back to me so quickly.
I used the calculator to determine that with my equipment the SA200 was the better bet. Your advice: “On telescopes with a larger aperture and a longer focal length, the dispersion of the SA100 can be insufficient to achieve the best results.” tallied well with my set-up — a 0.4m f/6.5 Dilworth with a SX imaging train. Plugging the relevant numbers into the calculator seemed to bear out that advice.
I will check out the other links too.
My first scientific observation since returning to La Palma and to a whole host of instrumental and computer problems.
V=16.85 ± 0.04 at JD 2459400.480961
There seems to be another wrong-link misfeature.
Creating a new forum topic and clicking preview works fine. However, then clicking on the “Read more” link took me to the page “Filters for visual observing of the Moon and planets”.
Thanks, Paul.
We agree that a line needs to be drawn. We agree that additions to the tag table, if any, should be as easy to do as possible.
I could very easily write a sequence of SQL statements similar to “INSERT INTO tags VALUES (DEFAULT, ‘name’)” if the database schema were available to me, not least because I have exactly that kind of list in the code which creates my own image database. Your work would then consist solely of eyeballing it for structural correctness and then running the SQL on the database.
Thanks. Now updated that one using the date of the last image. The time was left at 00:00:00 UTC to indicate that any greater precision is unjustified for an observation which took 349 days to complete. (Incidentally, should the time of observation field be pre-filled with that value? It seems to make more sense to me than to have it set to the time of uploading.)
Would you consider running the suggested SQL query to see how many other examples exist? If there are only a (relatively) few perhaps a web page could be created with a list of (username, url) pairs. It would then be up to individuals to update their own observations and would require no further action on you part except, perhaps, re-creating the table every few months.
