Daylight photometry

[andrew s]

Maybe worth a try?

https://arxiv.org/abs/2112.12673

Daylight Photometry of Bright Stars -- Observations of Betelgeuse at Solar Conjunction

Regards Andrew 

Edited December 24, 2021 by andrew s

[vlaiv]

There is interesting account that I heard.

Apparently, at the bottom of a very deep well - you can see stars during the daylight.

Maybe very long and carefully crafted dew shield that will act as baffle tube would help with daylight observations to minimize stay light?

I just found small text that puts estimate on daytime sky brightness at about 1.5 to 3 magnitudes per arc second squared. I guess that with careful dialing in of resolution - go with as high resolution as possible while keeping star disk as small as possible - it can be done.

[lukebl]

6 hours ago, vlaiv said:

Apparently, at the bottom of a very deep well - you can see stars during the daylight.

Slightly off-topic, but I remember this oft-quoted claim from decades ago, and it's always bothered me. As I've got older, I've realised that it must be an urban myth or even a wind-up.

• Firstly, if you were at the bottom of a very deep well,  the field of view (i.e the opening at the top of the well) would be absolutely tiny. After all, you're at the bottom of a very deep well! If you're, say, 100m down a 2 metre-wide well, the field of view would only be just over a degree.
• Secondly, wells are (presumably) vertical so you'd only be able to see stars exactly at the zenith.
• Thirdly, the chances of there being a star bright enough for you to see, and precisely in a narrow field of view at the zenith when you were viewing, seem pretty remote!
• Fourthly, it seems a pretty pointless exercise!

 

Edited December 26, 2021 by lukebl

[vlaiv]

5 hours ago, lukebl said:

Slightly off-topic, but I remember this oft-quoted claim from decades ago, and it's always bothered me. As I've got older, I've realised that it must by an urban myth or even a wind-up.

• Firstly, if you were at the bottom of a very deep well,  the field of view (i.e the opening at the top of the well) would be absolutely tiny. After all, you're at the bottom of a very deep well! If you're, say, 100m down a 2 metre-wide well, the field of view would only be just over a degree.
• Secondly, wells are (presumably) vertical so you'd only be able to see stars exactly at the zenith.
• Thirdly, the chances of there being a star bright enough for you to see, and precisely in a narrow field of view at the zenith when you were viewing, seem pretty remote!
• Fourthly, it seems a pretty pointless exercise!

 

I think that it is one of those things that happened to someone and is therefore perpetuated in "folklore", and if it is true that sky has brightness of about 1.5-3 magnitudes, then I can see it happening for mag0 star for example?

 

[JeremyS]

This chestnut was addressed by David Hughes in his 1983 paper: https://adsabs.harvard.edu/full/1983QJRAS..24..246H

[lukebl]

1 hour ago, JeremyS said:

This chestnut was addressed by David Hughes in his 1983 paper: https://adsabs.harvard.edu/full/1983QJRAS..24..246H

Interesting. Like I said. A pointless exercise!

[Xilman]

On 24/12/2021 at 10:22, andrew s said:

Maybe worth a try?

https://arxiv.org/abs/2112.12673

Daylight Photometry of Bright Stars -- Observations of Betelgeuse at Solar Conjunction

Regards Andrew 

I'm tempted.

I have managed to image a 12th magnitude star with a 2-second exposure through a Sloan i' filter only 36 minutes after sunset. Not measurable and no comparisons in the FOV, other than Venus and Neptune, the conjunction of which was the point of taking the image.

Most everything brighter than, perhaps, 10th magnitude, should be measurable in full daylight with a little care.  I can manage 19th after dark.

Edited December 26, 2021 by Xilman