Theoretically - could you do narrowband imaging during the day?

[ian_bird]

Hi

As the subject says - Theoretically - could you do narrowband imaging during the day?

Assume you have a mount that could do 15 minute unguided subs. And say a top notch CCD with a 3nm HaII filter.

Could you image during the day?

The SR-71 Blackbird had a Star Tracking Navigation system using a telescope in the aircraft. It could lock on and track stars on the runway before takeoff in broad daylight.

Possible? Theoretically?

Cheers

Ian

[msh1]

good question

[billhinge]

Don't know but I used a big remote telescope with a NABG camera in australia several times, I try to do narrowband during a full moon since telescope time is half price under a full moon.

Often it isn't a problem but a couple of times the full moon was too close to the target and the image wash washed out - I got a refund

With my full spectrum dslr and a 950nm filter I'm still picking up enough light during daylight to take hand held images at low iso so I guess there is an awful lot of solar radiation covering the UV to Ha bands and above to compete with. Maybe if you could shield the solar glare somehow, I'm sure people on here have imaged planets during the day?

[kirkster501]

I assume you are in an observatory? If not how would you polar align etc?

[Gina]

I suppose if you had a very very narrowband filter it may be possible but you certainly can't with 3nm filters, It has to get quite dark before 3nm filters keep out enough daylight to show stars, let alone nebulosity.

[haitch]

Narrowband Ha of the Sun?

[ollypenrice]

There is no longer the slightest diffiuclty so far as the mount is concerned, if you can run to a 10 Micron. You could use an ASA mount as well if you could make it work. As for how narrow the narrowband would have to be, who knows? Food for thought; the professionals don't do it! (Do they???)

Olly

[ronin]

Suppose yes if the object were pushing out more of the wavelength(s) then is present in the scattered light in the atmosphere. That way the peak for the object would be greater then the sky background and so appear on whatever sensor is used. If I recall they say when Betelgeuese goes pop it will be visible during the day so stick a narrow band filter on a scope and there you have it. If you have a method for getting Betelgeuse to go pop let me know so I can be watching, don't keep it to yourself.

Trouble is the sun is a bit closer and so is throwing out a light of wavelengths a lot more intense.

You can do radio astronomy during the day and that is just another part of the EM spectrum. So I assume the principle is the same or very similar.

[Ben Ritchie]

As for how narrow the narrowband would have to be, who knows? Food for thought; the professionals don't do it! (Do they???)

The H-alpha filter on VLT/FORS is 0.6nm, and I think that's fairly typical for service mode filter on a professional instrument - that allows you to split H-alpha from the [N II] doublet at 6548/6582 angstroms, whereas even a very good 3nm filter will blend them.

[TrickySpot]

If you know the theory behind H-Alpha light emissions, you'll see that its the same process that makes stars/the sun work.....hydrogen atoms get ionized to such a point that energy is released as photos etc etc, so basically the sun is a giant h-alpha light emitter. Hence why stars are still very visible through a h-alpha filter, but streetlights aren't :-) So, I'd love to know how the Blackbird did it, its just not possible IMHO

[ian_bird]

The SR-71 Blackbird had a Star Tracking Navigation system using a telescope in the aircraft. It could lock on and track stars on the runway before takeoff in broad daylight.

"So, I'd love to know how the Blackbird did it,"

Me too! It's described in some detail in books written by the guys who flew it.

Cheers

Ian

PS - Or was it disinformation?

[dph1nm]

If you know the theory behind H-Alpha light emissions, you'll see that its the same process that makes stars/the sun work.....hydrogen atoms get ionized to such a point that energy is released as photos etc etc, so basically the sun is a giant h-alpha light emitter.

G-type stars like the sun have very little Halpha emission. In fact most stars (including the sun) show H-alpha in absorption.

NigelM

[TrickySpot]

G-type stars like the sun have very little Halpha emission. In fact most stars (including the sun) show H-alpha in absorption.

NigelM

G-type stars like the sun have very little Halpha emission. In fact most stars (including the sun) show H-alpha in absorption.

NigelM

Only in absorption relative to the rest of the spectrum, it's still an overall h-alpha emitter. The band-pass of Ha emission is wider than the absorption. Even if a filter existed that found the Goldilocks zone that blocked out all the sun's Ha, it would be useless for even stars that have less Ha absorption (K+M), as it would certainly render them invisible.

[Earl]

The SR-71 Blackbird had a Star Tracking Navigation system using a telescope in the aircraft. It could lock on and track stars on the runway before takeoff in broad daylight.

"So, I'd love to know how the Blackbird did it,"

Me too! It's described in some detail in books written by the guys who flew it.

Cheers

Ian

PS - Or was it disinformation?

Carrots.

[Superdavo]

Surely it would be easier in the day to take lots of 2-minute subs than a few 15-minute subs during the day?

[nytecam]

Hi As the subject says - Theoretically - could you do narrowband imaging during the day? Assume you have a mount that could do 15 minute unguided subs. And say a top notch CCD with a 3nm HaII filter. Could you image during the day? The SR-71 Blackbird had a Star Tracking Navigation system using a telescope in the aircraft. It could lock on and track stars on the runway before takeoff in broad daylight. Possible? Theoretically? Cheers Ian

I think the recent Comet Panstarrs before perihelion was recorded in full daylight by a French amateur using very brief stacked exposures and IR transmitting filter - the daytime sky is darker in IR. Don't think NB Ha is much help as the sun, and therefore sunlight, are strong in Ha. Hope that helps.

[Gina]

Clearly the sun is an Ha emitter or all these Ha solar imaging scopes wouldn't work!

[gkec]

Hi

As the subject says - Theoretically - could you do narrowband imaging during the day?

Assume you have a mount that could do 15 minute unguided subs. And say a top notch CCD with a 3nm HaII filter.

Could you image during the day?

The SR-71 Blackbird had a Star Tracking Navigation system using a telescope in the aircraft. It could lock on and track stars on the runway before takeoff in broad daylight.

Possible? Theoretically?

Cheers

Ian

Interesting point about SR-71.

Reading this

http://en.citizendium.org/wiki/SR-71_Blackbird#Astro-Inertial_Navigation_System_.28ANS.29

it refers to a "blue light" source. This puzzled me as I thought that as blue light scattered more it would be more difficult.

Then I came across this.

http://frank.pocnet.net/other/ITT/ITT_ImgDis-DSA.pdf

It says that filters are counter productive, also the photon detectors were more sensitive to blue, because blue photons are more energetic maybe?

[haitch]

Would the blackbird have little enough atmosphere above it when flying at altitude to darken the sky?

What we need is a column of vacuum over us right up through the atmosphere .

Sent from my iPhone using Tapatalk

[dph1nm]

Clearly the sun is an Ha emitter or all these Ha solar imaging scopes wouldn't work!

You do get Halpha emission lines from the chromosphere and from prominences. But if you take an integrated spectrum of the whole sun (or a sun-like star, given the original question) you will see absorption in the continuum at the wavelength of H-alpha . So it wouldn't help increase the visibility.

NigelM

[ian_bird]

Would the blackbird have little enough atmosphere above it when flying at altitude to darken the sky?

Apparently it would work on the runway before takeoff.

Cheers

Ian

[TrickySpot]

I did have an odd thought when looking at a Baader filter cover....the cover has a spectrum showing the areas that various elements cover. What would happen if you used a filter like Sodium or Calcium, elements that aren't in abundance in the sun? Or is this contra-intuitive....

Also, if you blow up or see the full absorption map of the spectrum wrt the sun, there are lots of well defined absorption areas. Yeah they are probably only a few 1/10ths of a nm wide, but the US military surely has the money to develop a filter that uses on of these gaps to cut through sunlight, and then I guess its a case of seeing what shines through. If GPS needs three satellites to lock your position (I'm guessing), surely the blackbird wouldn't need hundreds of stars....maybe those that do show up through the hypothetical filter are enough

Martin

[gkec]

I did have an odd thought when looking at a Baader filter cover....the cover has a spectrum showing the areas that various elements cover. What would happen if you used a filter like Sodium or Calcium, elements that aren't in abundance in the sun? Or is this contra-intuitive....

Also, if you blow up or see the full absorption map of the spectrum wrt the sun, there are lots of well defined absorption areas. Yeah they are probably only a few 1/10ths of a nm wide, but the US military surely has the money to develop a filter that uses on of these gaps to cut through sunlight, and then I guess its a case of seeing what shines through. If GPS needs three satellites to lock your position (I'm guessing), surely the blackbird wouldn't need hundreds of stars....maybe those that do show up through the hypothetical filter are enough

Martin

Filters were not used, the only reason blue was mentioned was because the sensors were blue sensitive.

[jezhughes]

I saw a Tom Lowe video a year or so ago and noticed he had daytime star scapes in some of his time lapses, suggesting that for sure, its possible to do something close to what's suggested.

Personally i have no idea how he exposed that many stars in daytime, the most i've managed to image in the day is Venus.

This is the video, the bits i'm referring to is from 1:20 onward.

[FraserClarke]

It's pretty easy to image stars during the day -- the daytime sky isn't all that bright; it's about 3--4 mag/sq-arcsecond (assuming it's reasonably clear without much haze). The moon has a surface brightness of about 3 mag/sq-arcsec, and you can see that pretty easily on a clear day. The reason you can't see stars is because your eye has a resolution of image about 1-arcminute across, and integrated over that area the sky is much brighter than any stars. Bright planets (Jupiter and Venus) are on the limit, and you can often see them if you know where to look (e.g. by sighting along a telescope). Try it sometime

So all you have to do to see fainter objects is have a telescope with decent resolution. Then you put the same amount of starlight into a smaller area on the sky, and hence improve the contrast between the sky and the star. If you can generate an image of ~2-arcsec (i.e. a ~4" telescope with good optics), you'll be able to see stars down to ~ mag 2.5 in a normal daytime sky. That gives you access to a few hundred stars -- more than enough to build a star tracking system. No idea how that compares to the SR71 system, but at least it doesn't seem like unobtanium... Certainly an easy experiment to try for anyone who has an observatory mounted scope that can point to objects without needing to be aligned first.

How far would you get with narrowband imaging... too tired to think about that just now! :-\