Forum Replies Created
-
Posts
-
In my experience, it is much easier to convert a DSLR image to FITS than it is to persuade Astrometrica to pay any attention to an embedded WCS.
For JPG and PNG files, nova.astrometry.net will convert to FITS and plate-solve for free. There are any number of free apps to convert from RAW format to something more amenable, including FITS. A very quick search on “RAW to FITS converter” dug up several on the first page.
The major problem with Astrometrica, in my experience, is that it runs natively only under Windoze and barely runs under WINE. I don’t trust the photometry very much either. If the source code were available we could check and perhaps enhance, but it isn’t and we can’t.
Other than that, parts of it are excellent and it is likely what I would use, had I not written a script to track on an object moving from frame to frame.
This raises a general point: should we have a playpen sub-forum where would-be posters can check and edit their proposed postings before subsequently copying the final product to its intended place? This facility is quite common on sites which encourage user-generated content.
Such a place would carry a guarantee that nothing placed there would be permanent (admins or a script could periodically flush everything over a certain age, for instance). It would allow people to learn and it would confine (most) uncovered bugs to a harmless place of quarantine.
Mea culpa.
I was trying to find out what may be attached to a post in line with Nick’s earlier attempt.
Pleased to discover a bug, regret having uncovered unfortunate consequences.
Nick and I have recently been discovering what can and can not be attached to forum posts.
The only information provided seems to be that an attachment must not be larger than 4MB.Please could we have a statement of what is allowed and what is not? Experiment seems to show that text files are not permitted.
Thanks,
PaulI have just noticed that cover photo to ‘Atlas if the Moon’ Wood and Collins, shows both the impact crater and the volcano, designated Mairan T, both are shown together with their correct designation. I’m not sure who names features on the Moon, but giving the crater and the volcano much the same name is confusing. I also note the description inside the atlas that refers to the volcano with a crater on top, this could easily lead one to conclude the feature top most on the volcano is an impact crater, but that is not the case.
The Wikipedia article explains that nomenclature is set by the IAU and the convention for naming smaller scale features located close to the principle crater.
Perhaps it might be useful for you to review the article.
Paul, Thank you and I had seen that Wiki reference, but I was after Mairan T, not the lunar impact crater, Mairan, it’s a bit confusing. I’m interested in the lunar volcano, designated as ‘the silicic volcano Mairan’. Interestingly some descriptions give this as an impact crater or crater, but it’s not, more a collapsed volcano caldera.
I quoted the location of Mairan T as given in that article!
The location of Mairan itself is given as 41.6°N 43.4°W in Wikipedia.
Wikipedia to the rescue:
https://en.wikipedia.org/wiki/Mairan_(crater)
has its location as 41.7° N 48.3° W.
Always worth checking with Wikipedia and DuckDuckGo for these sorts of questions.
Apologies for the typo 111.61 when I meant 311.61.
What is that feature and what do you expect to be its coordinates?
Note that 311.61 East is equivalent, in most spherical coordinate systems, to 360-111.61 = 48.39 West.
Trebor
Alas poor Yorlik, I knew him backwards.
Thanks Nick.
Now snaffled. I already have code to do the first two functions and will implement the third based on your suggestion. My version uses Perl and SWarp.
The best compromise, IMAO, is a fork with long enough arms.
Now the disadvantage is that it needs to be much more robust to prevent flexure. I am fairly sure that my fork would be capable with longer arms and is would appear that yours would be too.
All this is way off topic for this place. Perhaps Webmaster could create a new topic in an appropriate place and more the postings there. Please? Pretty please?
Yes, we win some and we lose some. I don’t actually lose very much useful sky as Dec +75 reaches a maximum altitude of 43 degrees and a minimum of 13 degrees from here and I don’t much like doing photometry below 30 degrees altitude unless it is really necessary. I have always really loathed meridian flips.
HL CMa was nice and high in the sky here (just to make you jealous 🙂 — there are advantages to having a low celestial pole — until cloud stopped play. 1 made it V=12.33 tonight.
You guys up in the frozen north have it lucky.
I find it very frustrating that Polaris is only 28 degrees above the horizon from here. Even worse, my fork mount won’t allow pointing at anything above a Declination of 75N or the camera hits the mount. Guess where C/2022 E3 is tonight …
With luck it will be far south enough to give me a chance in a few days but, of course, the moon will then be very near full.
Life, don’t talk to me about life.
Paul
P.S. now the ****ing filter wheel has just packed up and I must go back to the dome to see what needs to be kicked into submission. Almost always a Windoze/USB failure.
Interesting. Radiant sky temperature in La Palma is also about 30C lower than ambient.
I have never seen dew anywhere except inside a SBIG camera after the desiccant needed renewing. That was excusable because it was generally run at -20C.
Perhaps having the scope inside a dome is advantageous from this point of view too.
If the scope or mirror is below the dew point, condensation will form on it, so you either have to warm the scope and mirror or decrease the dew point of the surrounding air. Don’t think there are any other options.
I can think of another, one employed by myself, Kevin Hills and numerous others.
Move your scope to a site where dew never happens. Operate it over the interweb thingy if you don’t fancy moving yourself as well.
Admittedly, not very appealing to some folk.
😎
A slightly more positive view from down south. Two weeks ago I flew to La Palma via Gran Canaria. The final leg was at night and passe the north side of Tenerife.
The two big islands looked much the same as anywhere else in the overdeveloped world with a similar population density.
La Palma from the air was very different. The Santa Cruz, the capital, was visible from the air but very, very much less intrusive than the towns and roads of Gran Canaria and Tenerife.
Yet Santa Cruz de la Palma is just as well lit at ground level at night as is Santa Cruz de Tenerife.
Light pollution is entirely a legal and political problem, not a safety nor an engineering problem.
Prompted by this thread, I just took a look at the sun on the first occasion it has been readily visible for a few days.
The spot wasn’t visible to the eye at first, but was very obvious through 7x50B. Knowing a precise position, I was able to see the spot without the binoculars. My eyesight is not as keen as it used to be.
Before anyone starts panicking, all views of the sun were through aluminized milar film.
Duncan, this is an interesting idea. For the so-called ‘benchmark universe’, matter and lambda, the scale factor, a(t), is proportional to (sinh(t))^(2/3). So let’s try and see what the Friedmann equations look like if we keep this evolution of the scale factor, but restrict it to one component, which I assume is matter.
…
The universe has undoubtedly lost mass-density since the good old days. That is very much not the same as losing mass. And, as I noted, losing matter is not the same as losing mass.
It is extremely important to be precise in one’s terminology when discussing situations in General Relativity. For instance, it is very tricky to determine the mass contained within a region of spacetime other than in the context of an asymptotically flat background.
Stars loose mass processing simple elements into more complex ones. Our Sun loses about 4 million tonnes of mass per second doing this. Multiply by the number of stars in the universe….
The mass is not lost. It is converted into the mass of the photons which are emitted by the Sun.
Photons have no rest mass but they possess relativistic mass according to the famous E=mc²
