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(incidentally, I tried to type it in directly using UTF-8 characters but the web server threw a wobbly.)
The original to which I responded contained three characters, each of which were a sexadecimal digit. It read 2-30-2. For some reason I do not presently understand, two different representations of ‘2’ were used. Converting to decimal, 2*60*60 + 30 * 60 +2 = 9002, the number of images uploaded at the time of posting.
My response was in Sumerian because I barely know Akkadian and so didn’t try to push my luck.
The first character is niĝ which means “thing”. The second is “maḥ” which translates as “magnificent” or “great”. In Sumerian the adjective follows the noun. So, a colloquial translation would be “great work!” or perhaps just “great!”.
The final characters form my signature in syllabic characters. PA UL LE LA AN. The terminal ‘D’ is omitted because Sumerian doesn’t have consonantal clusters and a scribe (DUB SAR) would not have transliterated it. It is moderately conventional to add DUB SAR (i.e. “written by”) to a text one has written but I decided not to on this occasion.
Here endeth the first lesson.
Definitely time I started learning Akkadian properly because almost all Babylonian astronomical texts are in that language.
If I understand you correctly, the dewing is occurring between the objective and the camera.
If so, would it be possible to cut a hole in the OTA and fit a dessicator (and possibly a circulation fan to be powered up only outside observing sessions to avoid tube currents)?
Sounds brutal, I know, but that would appear to be from where you need the water removed.
These may be too young for your kids, but <foo> For Babies is a wonderful series. I loved Bayesian Probability for Babies and General Relativity for Babies. Astrophysics for Babies is probably the closest in line with your request but many others are worth considering, including the GR title mentioned and There Was a Black Hole that Swallowed the Universe.
See https://www.goodreads.com/author/list/7438442.Chris_Ferrie for more info.
You give the accurate (and correct) procedure. For a decent approximation I just divide 140 by the aperture in mm, which gives an answer which is “good enough”. In your case 140/102 = 1.37.
Easy to remember.
Far too early to spend time on this now, but would it be possible to add a zoom in/out button to the sky maps, ala google maps?
The sky map feature is really nice!
But (you knew there would be a but, didn’t you) it doesn’t work as I expected. In particular, there is only one image noted as being in Sculptor, and that is not mine of the globular NGC288.
Fair enough, the plate solve didn’t work well enough.
However, discovering that Jupiter was to be found on the Pavo-Indus border came as quite a shock!
I took an image on the Tel-Ind border a while ago, but that is not the one indicated on the map. Indeed, it is not indicated at all.
I suspect that some hand annotation might be required. I will offer my services if desired.
Seconded.
I hadn’t noticed this effect, so have little idea whether it affects any of my uploads.
Can it be made explicit that times should always be entered in UTC, please, regardless of local time zone, daylight saving, etc, and the web site software never changes what is entered regardless what time it might be for itself? The old “you asked for it, you got it” approach.
A special case of “short focal length refractor” is a lens specifically designed for the camera in question. Telephoto lenses are especially flexible in what they can be used for. I’ve taken snapshots with a 80-300mm telephoto of star fields which look quite nice. Never had the skill or patience to do it properly though. Those who do learn the technique have produced some amazingly good work. You may like to try this approach to cut your teeth before spending serious money on a telescope. Invest in a good mount first.
At least one animated GIF works.
https://britastro.org/observations/observation.php?id=20200911_170000_2e604aed4f94042d
Works for me, anyway.
I seem to remember commenting on
https://britastro.org/observations/observation.php?id=20201122_230000_68e4171212c0b467
and Martina responding to my comment. Neither comments appear to have survived the transition to the new regime.
No big deal but perhaps it is indicative of something that might be?
OTOH, perhaps advancing senility has damaged my memory.
It doesn’t seem to matter much whether you use a Newtonian or a Cassegrain. That from personal experience and from reading the metadata attached to many images on the web.
What is by far the most important is that the telescope tracks the sky properly. Getting everything mechanically balanced makes the mount’s job much simpler!
Having an autoguider is not essential but certainly makes life immensely easier. Without it you need to have a very well set up and high quality mount and/or take lots of short exposure subs then throw away any which show unacceptable trailing.
A few glitches. In another tab right now I have https://britastro.org/observations/user.php open. It shows me “Showing images 1 to 40 of 8972” rather than just my own uploaded images. Curiously enough, when I first went there after logging on it did as I expected.Although it is clear how to filter by object name, it is not at all apparent to me on how to search by username.
Next was an attempt to find my Barnard’s star upload to see whether animated GIFs work. Setting the search to “Stars” and Library to “Member Images” resulted in a different set being displayed, some of which were tagged as stars. The majority (an image of the “Copernicus area” for instance) did not. Adding “Barnard’s Star” into the object box did not change the results found.
Logging out and logging in again fixed the first problem. I then went to the Barnard’s Star image and found that the animated GIF now works perfectly. Brilliant! However, the comment is now incorrect but if I try to remove it an error response is given
Papers exist on how to convert between the Gaia G, RP and BP measurements to other wide-band systems such as Johnson-Cousins. For example, see Appendix C and its two tables from https://arxiv.org/pdf/2012.01916.pdf for a detailed account.
I have a large number of unfiltered images with stars between 8th and 22nd magnitude, taken with two different CCD cameras. Perhaps I should measure them and see how well they correlated with DR3 values.
What is your budget, roughly?
Are you wedded to any particular optical design (Newtonian, CDK, etc) and any particular mount (alt-az, GEM, fork …)?
Why does it have to be a closed tube? I used a Beacon Hill 18″ Dob very successfully back in the late 80s with a fabric shroud to keep out background light. It had the advantage of no tube currents.
http://beaconhilltelescopes.org.uk/ are still in business and they still ship up to 12″ with a solid tube. You could ask about larger ones.
(though the need to include a decimal point when defining well known lines is ugly)
I know what you mean. It is so much prettier to write 5889.950Å and 5895.924Å than 588.9950nm and 589.5924nm. It means you get to use a non-ASCII character. 😉
To be serious now: my work was done with a spectrograph with a resolution in excess of 300,000. The sodium D lines were separated by about a centimetre at the focal plane. Decimal points were essential, even when using wavenumbers (cm^-1) because the centroids of narrow lines could often be measured to better than 0.01cm^-1.
