Starship Asterisk*

Wolf Kotenberg wrote:Some time ago, quite possibly a few years, prof Lewin issued a challenge to APOD viewers to explain a light issue with a photograph, possibly taken by prof Lewin himself, that had a misterious light source location. I have been following APOD for many things and some of them I have in the back of my mind as " no answer ". Perhaps someone can enlighten the vast audience, namely me, as to the answer to that puzzle.. An ice cold one would be nice for a reward.

Chris Peterson wrote:Here is the APOD in question and here is Lewin's answer. More here.

Wolf Kotenberg wrote:Some time ago, quite possibly a few years, prof Lewin issued a challenge to APOD viewers to explain a light issue with a photograph, possibly taken by prof Lewin himself, that had a misterious light source location. I have been following APOD for many things and some of them I have in the back of my mind as " no answer ". Perhaps someone can enlighten the vast audience, namely me, as to the answer to that puzzle.. An ice cold one would be nice for a reward.

Ayiomamitis wrote:Reading the challenge ad verbatim, one would have to expose for 24 hrs continuously and which is possible quite north (or quite south) where one has continuous darkness for a portion of the year. Given the temperatures involved, my single concern would be the ability of the lens to withstand such extreme elements and especially for 24 hrs.

I do not know if film emulsion has any sort of operating temperature but I suspect it may also respond in a non-orthodox manner in such a harsh environment and especially over the course of 24 hrs.

Rupert wrote:Not sure if some one has tried:

A "single" exposure... Solved by using film (to much noise digitally). Fix the camera pointing in a direction, and only open the shutter for 1/365 of 24hours every day or 1/52 of 24hours once a week. It is only "exposing" 1 frame

Wolf Kotenberg wrote:
Ulysses most likely could

Ayiomamitis wrote:This challenge is something which has crossed my mind a number of times and I believe it is much easier than it may seem.

The suggestion above was my first possible solution to such an image and I believe it would require three strategically selected and dedicated evenings. Let's not forget that winter is approximately twelve hours in duration at its peak which solves one-half of our problem. The balance SHOULD be doable around late spring and early fall.

For something like this to be really pulled off, an area with dark skies would be necessary and where a camera could be left in a permanent setting so that the three exposures I describe above could be pursued.

The more and more I think about this exercise, the more and more convinced I become to (finally) pursue it since fall is not too far away for one of the three desired evenings.

APOD Robot wrote:create a real single-exposure image of a clear night sky that features 360 degree star trails.

GB wrote:I'm wondering... has anyone achieved the same effect at lower latitudes by stitching together a year's worth of circumpolar photos, based on, for example, two hour exposures on the first of every month for a year? Sure beats spending a long day's night in Thule. One could even meet the "single-exposure" criteria for Lewin's Challenge by dedicating a camera for a year, forcing the diaphragm open for the whole year, exposing it to the stars for the twelve two-hour nights, and exposing it to the inside of a light-proof bag the rest of the time.

pitwi wrote:Hello to all!
Thanks to "alter-ego" for showing the stars that made the circles. I'll have a look at the original image tonight to confirm it.
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Ann wrote:Thanks a million, alter-ego!

Thanks in particular for pointing out that the main stars of Cassiopeia lie within a declination of 55 00 00.0. And Alpha, Beta and Gamma Cas are all second magnitude stars. I missed them, because my software presents a rectangular picture which cut Cassiopeia off when I tried to make sense of the neighborhood of Polaris yesterday, and I'm not good at rotating the image. Still, it was a stupid oversight. And - darn it! - I forgot Alderamin, Alpha Cephei, too!

Ann

Ann wrote:So perhaps the circles can't be identified. Perhaps it isn't possible to say which of the bright inner circles was made by red giant Kochab. Perhaps it isn't possible to say which circle is third magnitude Pherkad's, Gamma Ursa Minoris, an interesting and rare A-type giant. Perhaps it isn't possible to say if third magnitude and very blue Beta Cephei, Alfirk, has made its own circle in this image. Perhaps itsn't at all possible to identify the brightest broad whitish circle in today's APOD or the two bright blue circles outside it.

It's just that neufer once told me that it isn't hard to identify star trails if you give it a try. I gave the circles of today's APOD several hours this morning, but I wasn't successful, so I just wondered if someone else could identify the circles for me.

Ann

gv wrote:Let's see: astronomical twilight is when the sun is within eighteen degrees of the horizon. It's called astronomical twilight because there is still too much light for astrophotography. So, since the inclination of the earth's axis is 23.5 degrees, on the day of the solstice (the most favorable day) you still need to be no further than 23.5-18=5.5 degrees from the pole to take that picture.