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Thats a useful looking book. Will grab a copy off ebay.
The calcs I am doing are based around the standard CCD S/N calculation mentioned by Steve Howell in his “Handbook of CCD Astronomy” – derived from Mortara&Fowler plus Newberry and others
Something like…
SNR=Nstar*t/sqrt(Nstar*t+npix(Nsky*t+Ndark*t+Nread*Nread))
where:
t – exposure length
Nstar – electrons from the star
npix – number of pixels covered by star
Nsky – electrons from sky in each pixel
Ndark – dark current electrons
Nread – read noiseLets be honest. Some people don’t do nice chats.
I had a nearby neighbour with 500W halogens on the back of their house. Eventually I had to try the light nuisance route with the local council. I got a letter suggesting I buy thicker curtains…
Four usable, or part usable nights here, in the last 2 weeks (all night last night) – I know because 2 weeks ago was when a Windows 11 update totalled the network between my house and the dome. Not that I am counting the clear nights since, you realise.
I’m expecting several more clear nights before I manage to mend the network…
I have to do it myself as while Microsoft have admitted some people had probs with a recent update, they are not planning a quick fix. Unfortunately, my full knowledge of networking fits on the back of a stamp – written using a crayon. Its not a fun learning curve.
Ah yes. Have never used one of the duo/tri/quad band pass nebula filters and don’t use OSCs. Agree: one of those filters would require properly corrected optics.
I was just looking at how much a Takahashi 106 costs these days and even a Borg 72mm is no change out of £2.5k – and lets not even mention the TB 203.
I’m probably just mean, but I always think “Ouch” if handing that much money over for something that isn’t necessary. Mortgages and such like taking precedence.
I am impressed that you now see refractors down to f/3.9 but a 72mm isn’t really giving that much light to filter. My approach would be a mono CCD/CMOS, single band filters and a SW 80 achromat and a focal reducer/coma corrector – but, yes, that wouldn’t be running at f/3.9. Can see why the 8″ V2 RASAs are so popular.
Taks and fast EDs are great for those who can afford them.
Reading the JAMA link Nick gave, it looks like they think that you might be somehow taken by surprise by the Sun reappearing and instantly damaged.
Which is kind of weird as the end of totality is always easy to see coming and I must admit I have yet to hear of the Diamond Ring damaging anyone’s eyesight.
I could only imagine a problem for people whose eyes remained fully dilated (for some medical or pharmaceutically induced reasons) or who were using a telescope/binoculars during the Ring or forced themselves to keep staring after the Ring was over. Other than that, it sounds tosh to me. But, as Nick wisely says, your experience may differ*.
*Its a bit frustrating that everyone now needs to protect themselves from the wrath (legal or otherwise) of people not thinking about the potential consequences of their own actions.
Theres some background here: https://en.wikipedia.org/wiki/T_Coronae_Borealis
One of the fora has a latest update by Digital Monk Marketing. But I cannot see it on the list of contributors. Are we being attacked again.?
Fear not. Had my checkup last week.
The corneas yellowing with age is a known thing. The cataracts are of no concern and it will be years before I need an op apparently. Happens to lots of people. Certainly among the oldies of my family. 🙂
I too suspect things are worse than they were, though I also try to bear in mind that my eyes are older too. My corneas will be yellower and the first hints of cataracts are probably appearing.
I certainly notice it takes me longer to light adapt. There are times when the drops used by opticians to dilate the pupils look very attractive.
But I must admit we did have a stonking night here last month when the stars were crystalline jewels, despite the fact few places are more than 25 miles from a significant town.
La Palma remains my favourite place on the planet – I’ve never been to Chile. 🙂
They push back because they are cheaper and the number of lights replaced is bigger if they use the bluer lights. The number of lights replaced is an easy metric for “progress” achieved.
Recently, a sports field I occasionally drive to, to take pictures upgraded their lights. I asked if they would be animal/insect/bird friendly and they said “Yes”. 6 months later I got an email from them apologising that the quotes they got back for animal friendly lighting had proved unaffordable for them – a charity. Happily they usually go off about 10pm.
Will let you know in a few days. Hope to have a play this weekend.
I think I last had a play a year or so back and I did the numpy int16 thing (taking care that the values fit in 65536 bins) and it just wrote out a BITPIX=32. I have a feeling I have to force its hand with BSCALE and BZERO explicitly plus there is some option for in effect, “Don’t mess about with BZERO and BSCALE”. It may be you have to – yourself – make sure the image counts are in the range -32768 to 32767…
If you had code to hand I would be keen to see it.
I recently used VIIRS data taken over the last decade to look at the flux recorded for my area of south Wiltshire and found, as I would expect, massive increases from towns like Amesbury. Looking more generally, even at villages, it appears that these are getting brighter too. The glow from Salisbury is spreading outward.
I tried pointing out to the local lighting officer and my County Councillor that lower colour temperature LEDs were better, as they reduced scattered light in hazy/foggy conditions, but they seemed largely ignorant or believed I was some sort of nut. Plus the manufacturers sell the bluer lights at a lower price.
Consequently, the green areas of the Philips light pollution map in South Wiltshire have extended and blue areas in Witshire, Dorset and Somerset are shrinking.
If you stand in the middle of a roundabout in Wiltshire you will be able to read a newspaper down to the fine print.
I pointed out to a Lighting Engineer that “Guidelines” are only guidelines and not rules. His response was that wouldn’t do him any good if a coroner investigating a road traffic accident asked him why Guidelines were not followed.
Silly thought, is it because the FITS header is rather longer. I think it has to be multiples of 2880 bytes or something. I don’t suppose the author of Vphot could have made the assumption that it was always 2880? Saw that once. But only once and 10 years ago.
I’ve seen FITS format files that were FIT, FITS, FTS and f and lower case variants thereof. Never encountered any that were not processed.
Have once come across software that seemed only equipped for 16 bit data – a histogram of 65536 bins was being used.
Theres some fun for anyone using Python, the Astropy library discourages the writing of 16 bit FITS files and I think it defaults to 32bit.
To see fainter faster and allow a V band filter to be put on the front, thereby supporting photometry.
