What star brightness is visible in broad daylight?

How bright does a star have to be to be visible with a small telescope in
broad daylight?

Regards,
-- Mark

Mark Lepkowski
http://www.mcltunes.com

On Sat, 05 Jun 2004 04:33:47 GMT, "Mark Lepkowski" wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

About magnitude 1 (Antares) in broad daylight with my 12" LX200. A polarizing
filter can help improve contrast. You need accurate goto or you probably won't
find any stars.

I've seen Vega, Sirius, Saturn with just binoculars, and Jupiter and Venus naked
eye.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

How bright does a star have to be to be visible with a small telescope in
broad daylight?

Well, it depends on how clear the sky is and how far away from the bright sky
near the sun the star is. I have seen Sirius (magnitude -1.44) in the 8x50
finder of my Nexstar 9.25GPS during the late afternoon, and have seen a few
stars down to nearly 3rd magnitude with the scope itself, although they were
not all that easy to see somtimes. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Mark Lepkowski wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

Regards,
-- Mark

Mark Lepkowski
http://www.mcltunes.com

Related URLs:

http://www.jesus.cam.ac.uk/college/flamsteed.htm
http://www.weatherman.com/wxastro6.htm

"Exactly what magnitude stars can be seen by day? Apparently the limit
runs from 1st to 4th magnitude, depending on the brightness of the sky.
The closer to sunrise, and sunset, the dimmer the stars that can be
detected. Indeed, several minutes before sunset [last fall, you could]
see many of Jupiter's moons through your scope! Can you see a shadow
crossing as well? I haven't tried it, but I bet you could!"

http://www.google.com/search?q=observing+stars+daytime

"Chris L Peterson" wrote in message
...
On Sat, 05 Jun 2004 04:33:47 GMT, "Mark Lepkowski" wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

About magnitude 1 (Antares) in broad daylight with my 12" LX200. A
polarizing
filter can help improve contrast. You need accurate goto or you probably
won't
find any stars.

I've seen Vega, Sirius, Saturn with just binoculars, and Jupiter and Venus
naked
eye.

I've done Satrun naked eye. As Chris says, there is not much contrast with
the background sky. It helps to get it when it is very close to the moon
(for reference). This past summer Mars was also seen naked eye in daylight
(albeit just before sunset) by several observers.

On Sat, 05 Jun 2004 04:33:47 GMT, "Mark Lepkowski" wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

Regards,
-- Mark

Mark Lepkowski
http://www.mcltunes.com

I've got to mag 3 in favourable conditions via my 12" LX200 goto in
mid afternoon. Much depends on sky clarity .

Maurice Gavin - Worcester Park Ob - UK

"Mark Lepkowski wrote in message
How bright does a star have to be to be visible with a small telescope in
broad daylight?

Polaris ( alpha ursae minoris ) I find easy at any time of day or night
throughout the year from near London ( given a clear patch of sky in that
direction. A 2 inch aperture refractor is usually sufficient. It's
certainly very prominent in my 6 inch aperture scope without any special
filters needed.

Gamma Andromedae ( magnitudes approx 2.3 and 5.1 at 9.8 seconds separation )
I have easily observed as a double star in my F8 150mm aperture refractor,
even when the sun was shining directly onto my face during observing !

Anthony

I've gotten down to 4th magnitude without difficulty in an average southern
california sky using my 11'' f/16 and about 150x. This was several hours
before sunset, using no filters. With the wilson 100" (JPL optical comm
experiment) a1064nm infrared filter and CCd camera, we got down to below 6th
at four in the afternoon. As I mentioned in an earlier thread, it was weird
to be observing stars in a dark field with sunlight pouring through the dome
slit! (I know these aren't really small scopes, but thought it might be
interesting)

Jeff


"Mark Lepkowski" wrote in message
...
How bright does a star have to be to be visible with a small telescope in
broad daylight?

Regards,
-- Mark

Mark Lepkowski
http://www.mcltunes.com

Paul Lawler wrote:

"Chris L Peterson" wrote in message
...
On Sat, 05 Jun 2004 04:33:47 GMT, "Mark Lepkowski" wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

About magnitude 1 (Antares) in broad daylight with my 12" LX200. A
polarizing
filter can help improve contrast. You need accurate goto or you probably
won't
find any stars.

I've seen Vega, Sirius, Saturn with just binoculars, and Jupiter and Venus
naked
eye.

I've done Satrun naked eye. As Chris says, there is not much contrast with
the background sky. It helps to get it when it is very close to the moon
(for reference). This past summer Mars was also seen naked eye in daylight
(albeit just before sunset) by several observers.

I saw Mars for about an hour after sunrise following last years
occultation.


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

On Sat, 05 Jun 2004 04:33:47 GMT, Mark Lepkowski wrote:

How bright does a star have to be to be visible with a small telescope in
broad daylight?

Well, let's assume 80mm is what you mean by small.

Stars will be roughly 130 times brighter through such a telescope than to
the naked eye.

Let's say 100 times brighter for simplicity, because that's an even five
magnitude difference.

The day sky varies in brightness, but a rough figure of mag -3 will do.
That means a star needs to be brighter than mag -3 to be visible.

Assuming a pupillary aperture of about 3mm (it's daytime, after all), the
minimum useful magnification of that 80mm telescope is 80/3 = ~26x. At
that magnification, the sky will look just about as bright in the
telescope as to the naked eye, because the additional light collected by
the telescope is spread over a larger area. Stars, however, are point
sources, so the extra light collected is all sent to basically the same
point in the image plane.

So, the sky remains unchanged, but stars brighten by our
chosen-for-simplicity factor of 100, or by five magnitudes.

So, to become brighter than the sky (at about mag -3), a star would have
to be brighter than mag 2.

If you increase the magnification, the sky will become darker, because the
light collected is spread over an even larger area, and the exit pupil
becomes smaller than the eye's pupil. The change in brightness of the
stars, however, remains the same (mostly). So, as magnification goes up,
the magnitude ceiling for stars to be visible goes up. Eventually, of
course, the diffraction pattern becomes more like an extended image than a
point image, after which additional magnification will not reveal more
stars (quite the opposite).

Basically, you can create a night sky through magnification. The larger
the aperture, the more magnification you can use before the size of
diffraction images becomes an issue.

Of course, the higher the magnification, the smaller the field of view,
and the more difficult it is to locate any stars at all (even at night).


--
- Mike

Remove 'spambegone.net' and reverse to send e-mail.