Die "Jet Stream" beïnvloed jou waarnemingsomstandighede!

 Kliek om te vergroot

 Die Suidelike "Jet stream" soos op 4 Junie 2011 besig om oor Suidelike Afrika te beweeg. Tog as jy na die Wolkekaart van Kobus Botha (hieronder) kyk is dit oopgetrek oor Suid-Afrika.  

Kliek om te vergroot

Hoe gaan die "seeing" vanaand by Boyden wees? Waarskynlik onstabiel. Is dit nie `n nfaktor wat ons amateurs nie in gedagte hou as ons observasieaande beplan nie. Agterna kla ons oor die voorwerpe wat rondspring.

Lees gerus die artikel hieronder wat ek op `n webtuiste raak ge-google het.  Onderaan is 'n paar skakels.

How the Jet Stream impacts astronomical "seeing" 

Source: Astronomy Club of Asheville

"Seeing" refers to the the amount of "blurring" caused by the earth's atmosphere -- most apparent in a telescope using higher magnifications.  Astronomers refer to this atmospheric turmoil as "bad seeing".  Seeing well at high magnifications is only possible when the air is steady.

Excellent seeing means, at high magnification, you will see fine detail on planets.  In bad seeing, planets might look like they are under a layer of rippling water and show little detail at any magnification, but the view of galaxies is probably undiminished.

Bad seeing is caused by turbulence combined with temperature differences in the atmosphere.  The turbulence may be caused by ground level winds as well as higher level air movements created by the jet stream. When the jet stream is overhead, seeing is generally poor.

Bad seeing can occur during perfectly clear weather.  Often good seeing occurs during poor transparency.  It's because seeing is not very related to the water vapor content (transparency) of the air. 

Skakels

- Stel animasie op van Suidelike "Jet Stream" 

-  Grafika van vandag se Suidelike "Jet Stream" 

-  The Atmosphere and Observing - A guide to Astronomical seeing.

-  Predicting the seeing (over Holland) is that possible?! 

-  Chapter 8 -- "Astronomical Seeing"

Deep Space Atlas - Father's day Special

FATHER'S DAY SPECIAL!
Father's Day special of R299 for the Deep Space Atlas for the
month of June. (Usual price R399)
Postage: R45
To order, please use the following email address: wayne.mitchell@penbogroupe.com

For more info about the book visit blog article: Deep Space Atlas

Kom bou jou eie teleskoop!

 Inligtingsessie:  Kom bou jou eie teleskoop! 

Datum: 4 Junie 2011 (Saterdag)
Tyd:  18:00
Plek: Boyden-sterrewag

Aangebied deur die Bloemfontein Sterrekundevereniging

Thinus van der Merwe, `n gesoute teleskoopbouer van die vereniging, met `n hele paar teleskope op sy kerfstok, gaan ons meer oor die projek vertel.

• Hy gaan ook vir ons `n praktiese demonstrasie gee van die stappe om `n spieël te slyp.
  

Vir wie:  Almal wat belangstel om sy eie teleskoop te bou.  `n Lekker gesinsprojek.

Nee, dit is nie net `n projek vir die manne nie. Mia Zeelie, van die vereniging het vroeër haar eie teleskoop gebou.

Waaroor gaan ons praat?

- Koste van so `n projek.
- Hoe gaan ons die projek aanpak?
- Is dit goedkoper as om `n teleskoop te koop?
- Hoe maklik is dit om dit self te doen?
- Wat het jy alles nodig om so `n projek aan te pak?
- Waar kry jy al die benodigdhede vir so `n projek?
- Hoe slyp mens self die spieël?
- Het jy duur toerusting nodig om die voetstuk/basis te maak?
- Wie gaan help as jy vashaak?
- Hoe lank gaan die projek neem?
- Is `n selfgemaakte teleskoop beter as `n gekoopte teleskoop?

• As daar nog vrae is kan jy dit gerus vir ons stuur. e-pos aan: assabfn@gmail.com  Die kundige ouens sal dit Saterdagaand beantwoord.

Besoek ons 2007 webblad toe ons `n soortgelyke projek aangepak het en loer na die teleskope wat gebou is.

• Kliek hier
  

Daar is ook `n paar kort videos oor die slyp en bouproses van `n teleskoop.
Ons sal ook van die selfgeboude teleskope by Boyden hê, sodat jy kan sien hoe dit lyk. 
As die weer saamspeel sal ons ook deur `n selfgeboude teleskoop kan kyk.
Die kanse is goed dat jy al so `n teleskoop by Boyden op die platform gesien het.

Laat weet asseblief of jy die geleentheid gaan bywoon.
e-pos aan: assabfn@gmail.com

A Reminder: Total eclipse of the Moon (Wednesday June 15, 2011)

 

Date: 27 – 28 October 2004

Time: 02:00 – 04:25Place: Back Yard Observatory, Westdene, Bloemfontein

Equipment:  Canon 10; ISO 400 - 1600; Exposure: 1/250 – ¼  sec; Camera attached to Celestron 11GPS telescope; Focal length: 2800mm. Only first half of eclipse was visible. Neighbours roof and sun interfered with last part.

Technique: Shutter release used to prevent movement. Telescope was in Lunar tracking mode.

Image Processing: Photoshop

 Photographer: Hannes Pieterse

On Wednesday evening, June 15, 2011, the Moon will be in line with the Earth and the Sun, and the shadow from our planet will obscure the Moon, turning it a dramatic orangey-red colour.

This beautiful and rare event is inspiring to watch

Click here for the details:

Observing 101: Averted Vision

Averted Vision: Getting The Most From What Nature Gave You

Using averted vision means looking slightly off to one side rather than straight on. It exposes the most sensitive part of your eye and lets you see much fainter objects. If you’ve never tried this before, you’ll be amazed at how much more you can see, with or without a telescope.
The Basics
• The retina of your eye has two types of light-detecting cells: rods and cones.
• Cones detect color under well-lit conditions and are densely packed in the fovea, near the center of your retina. Cones help you see color and fine detail, which is why you look directly at objects you want to see well, like books, movies, and faces.
• Rods are mostly away from the center of your retina. You see less detail and no color with the rods, but they are much more sensitive to light.
• The way your eye is structured means you see the faintest objects if you look 8 to 16 degrees off center. The exact angle is a little different for each person.
• This only works if the object you’re looking at is on the nose-ward side of your eye. So look slightly rightward with your right eye and leftward with your left eye. Do the reverse and you’ll expose the blind spot of your eye and you won’t see a thing.

A cross section of the human retina, showing rod and cone cells.
A Deeper Look
• If you’re using both eyes, as with binoculars, looking only sideways makes one eye more sensitive at the expense of the other. The solution? Look up. That uses another rod-rich part of your retina above the fovea.
• With a little practice, averted vision reveals objects 20-40x fainter than direct vision. That’s a huge difference.
• Rods are most sensitive to blue-green light, but your optics nerve and brain are not wired to detect color when only your rod cells are exposed to light. That’s why faint objects appear grayish-white.

The sensitivity of rods and cones to light across the spectrum
Good To Know
The blinking nebula, NGC 6826, is an object that most dramatically demonstrates averted vision. Stare directly at this blue-green planetary nebula and you see only the dim central star. Look slightly to the side and the faint nebula around the star appears suddenly. When you switch from straight on to averted vision, the nebula appears to blink on and off. It’s darned impressive.
Personal View
I usually begin with a short lesson on averted vision when showing faint objects to beginners. When they try it, they usually gasp at the subtle detail that suddenly appears.

Observing 101: Dark Adaptation

Dark Adaptation: “Looking” Your Best

March 14, 2008
To best see faint deep-sky objects like galaxies and nebulae, you have to make sure your eyes are “dark adapted”. Here’s what you need to know.
The Basics
• The human eye evolved to operate in two modes, photopic for seeing in well-lit conditions and scotopic for seeing faint objects in the dark.
• As you learned earlier, your retina has two types of cells, rods and cones. In photopic mode, the cones detect bright light and colors. But in scotopic mode, the rods detect faint light. Both types of cells contain dyes that undergo a chemical change called “bleaching” when hit by light.
• In light-adapted or photopic mode, the dyes in your rods are fully bleached, so they can’t detect faint light… they’re out of action. Turn the lights off and the rods to return to dark-adapted mode, but it takes a long time, about 20-60 minutes. That’s why astronomers get so angry when someone carelessly shines a white light in their eyes… they have to wait a long time to recover their dark-adapted vision.
• Going from a dark to light adapted state happens much faster, in only a few seconds.
A Deeper Look
• Each eye reacts separately to light, so you can keep one eye dark adapted while using your other eye to read star charts and slew your telescope. An eye patch is ideal.
• You can keep unwanted streetlights out of your eyes by throwing a towel over your head when looking through the eyepiece of your scope with your dark adapted eye.
• You often see astronomers using bright red LED flashlights when looking at star maps and gear around the telescope. That’s because red light cannot bleach the dye in the rods if the wavelength is > 620 nanometers. So the chemical structure of the dye in the rods is completely unaffected, while the dye in the cones still enables scotopic vision.
Good To Know
Your body cannot by itself make the dyes for the rods and cones in your retina. It needs an external chemical-beta carotene-to synthesize the dyes. A good source of beta-cartone? Carrots. So carrots really can be good for your eyesight.
Personal View
You can imagine the reaction I get from the police officers who occasionally find me in the local park wearing an eye patch with a towel over my head to block out the nearby street lights. “Really officer, I’m just trying to see the faint structure in M97. Want a carrot?”

The Atmosphere and Observing - A guide to Astronomical seeing.

Introduction

An observer, be they at a mountain top observatory, or in their own back yard must, at all times contend with the Earth’s atmosphere. It is a notoriously unpredictable and limiting factor in obtaining fine views of the Planets, and close binary stars. Many often comment, especially here in the UK that seeing is all too often mediocre on most nights, but what are the factors that contribute to this?. Are there ways and signs, which indicate whether the atmosphere, will be stable or turbulent on a given night?.

What is “seeing”?

So what exactly is atmospheric seeing? - it is high frequency temperature fluctuations of the atmosphere, and the mixing of air “parcels” of different temperatures/densities. This behaviour of the atmosphere is seen at the eyepiece as a blurred, moving, or scintillating image. There are roughly 3 main areas where Atmospheric turbulence occurs. Near ground seeing (0 – 100metres or so.) central troposphere (100m – 2km), and High troposphere (6-12km.) Each area exhibits different characteristics, which are explained in more detail below. 

• Read more about "Astronomical seeing"
  
   
• Seeing in Holland  

Beware of the Jetstream

  Clouds along a jet stream over Canada.

Jetstream can influence your "seeing" 

3. High Altitude effects.

Effects at this altitude are caused by fast moving “rivers” of air know as Jet streams. Wind shears at around the 200-300mb altitude level can cause images to appear stable, but very fuzzy, and devoid of fine detail. There isn’t anything the observer can do to prevent these effects, but forecasts are available, to help predict weather a Jet stream is present over your area. Areas of the Northern hemisphere most affected by the Polar jet stream are the Central US, Canada, North Africa, and Northern Japan. The Jet stream’s position varies with the seasons, tending to move further South during the winter and spring months.

Southern hemisphere Jetstream

Africa Jetstream

Source: Wikipedia > Jetstream

Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere (where temperature decreases with altitude) and the stratosphere (where temperature increases with altitude).[1] The major jet streams on Earth are westerly winds (flowing west to east). Their paths typically have a meandering shape; jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including the opposite direction of most of the jet. The strongest jet streams are the polar jets, at around 7–12 km (23,000–39,000 ft) above sea level, and the higher and somewhat weaker subtropical jets at around 10–16 km (33,000–52,000 ft).

• Read more about Jetstreams

Total Lunar Eclipse of June 15 - Also in Bloemfontein

Total Lunar Eclipse of June 15

The first lunar eclipse of 2011 occurs at the Moon's ascending node in southern Ophiuchus about 7° west of the Lagoon Nebula (M8). The Moon passes deeply through Earth's umbral shadow during this rather long event. The total phase itself lasts 100 minutes. The last eclipse to exceed this duration was in July 2000. The Moon's contact times with Earth's umbral and penumbral shadows are listed below.

   Penumbral Eclipse Begins:  17:24:34 UT
   Partial Eclipse Begins:    18:22:56 UT
   Total Eclipse Begins:      19:22:30 UT
   Greatest Eclipse:          20:12:37 UT
   Total Eclipse Ends:        21:02:42 UT
   Partial Eclipse Ends:      22:02:15 UT
   Penumbral Eclipse Ends:    23:00:45 UT

At the instant of greatest eclipse [5] the umbral eclipse magnitude [6] will reach 1.6998 as the Moon's centre passes within 5.3 arc-minutes of the shadow axis. The Moon's southern limb will lay 54.2 arc-minutes from the edge of the umbra while the northern limb will lay 22.3 arc-minutes from the umbra's edge. Thus, the northern regions of the Moon will probably appear brighter than the southern regions that lie deeper in the shadow. Since the Moon samples a large range of umbral depths during totality, its appearance will change dramatically with time. It is difficult to predict the exact brightness distribution in the umbra so observers are encouraged to estimate the Danjon value at different times during totality (see Danjon Scale of Lunar Eclipse Brightness). Note that it may also be necessary to assign different Danjon values to different portions of the Moon (i.e. - north vs. south).

Nearly 30 years ago (1982 Jul 06), the author watched another total lunar eclipse with the Moon in the same part of the sky. I was amazed at how brilliantly the summer Milky Way glowed since it was all but invisible during the partial phases. Observers will have a similar opportunity during June's eclipse. In this case, the totally eclipsed Moon will lie in southern Ophiuchus just 8° northwest of the brightest Sagittarian star clouds. The summer constellations are well placed for viewing so a number of bright stars can be used for magnitude comparisons with the totally eclipsed Moon.

Antares (mv = +0.92v) is 15° to the west, Shaula (mv = +1.63) is 14° south, Epsilon Sgr (mv = +1.85) is 15° southeast, Arcturus (mv = -0.05) stands 55° to the northwest, and Altair (mv = +0.77) is 46° northeast of the Moon.

Figure 3 shows the path of the Moon through the penumbra and umbra as well as a map of Earth showing the regions of eclipse visibility. The entire event will be seen from the eastern half of Africa, the Middle East, central Asia and western Australia. Observers throughout Europe will miss the early stages of the eclipse because they occur before moonrise. Fortunately, totality will be seen throughout the continent except for northern Scotland and northern Scandinavia. Eastern Asia, eastern Australia, and New Zealand will miss the last stages of eclipse because they occur after moonset. Again, the total phase will be seen from most of these regions. Even observers in eastern Brazil, Uruguay and Argentina will witness totality. However, none of the eclipse will be visible from North America. At mid-eclipse, the Moon is near the zenith for observers from Reunion and Mauritius.

Table 3 lists predicted umbral immersion and emersion times for 20 well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see Crater Timings During Lunar Eclipses).

The June 15 total lunar eclipse is the 34th member of Saros 130, a series of 71 eclipses occurring in the following order: 8 penumbral, 20 partial, 14 total, 22 partial, and 7 penumbral lunar eclipses (Espenak and Meeus, 2009a) spanning 1262 years. Complete details for Saros 130 can be found at:

eclipse.gsfc.nasa.gov/LEsaros/LEsaros130.html

ISS & Endeavour visible from Bloemfontein

Watch out for the International Space Station and the space shuttle Endeavour passing over this evening (Tuesday).  Not sure how far apart they'll be - could be a minute or two - but they should both look like bright stars moving upwards from the north-western horizon at 6:57pm.  Both will "disappear" about halfway up the sky as they pass into the shadow of the Earth.

Endeavour launched Monday, and will dock with the ISS just after midday Wednesday.  The "crew hatch opening" at around 2:30pm (and other mission events) can be watched live at www.nasa.gov/multimedia/nasatv
This is the last flight of Endeavour.

For sightings of the Space Station from Southern Africa later this week, go to www.planetarium.co.za  click on "In the Sky" and then "Satellites", and follow the instructions

Source:  

Claire Flanagan

Wits Planetarium

011-717-1390

086-521-4273 (fax)

www.planetarium.co.za

Info for Bloemfontein from Heavens Above
 

ISS - Visible Passes

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Observer's location:	Bloemfontein, 29.1330°S, 26.2000°E
Local time zone:	Universal Coordinated Time -2 (UTC + 2:00)
Orbit:	343 x 346 km, 51.6° (Epoch May 16)

Date	Mag	Starts			Max. altitude			Ends
		Time	Alt.	Az.	Time	Alt.	Az.	Time	Alt.	Az.
17 May	-1.8	18:58:03	10	NNW	18:59:32	23	N	18:59:32	23	N
18 May	-1.2	19:21:31	10	WNW	19:22:57	24	WNW	19:22:57	24	WNW
19 May	-2.8	18:10:11	10	NNW	18:12:52	34	NE	18:14:47	16	ESE
20 May	-2.6	18:33:35	10	WNW	18:36:22	42	SW	18:37:56	21	SSE
21 May	-0.7	18:58:46	10	WSW	19:00:06	12	SW	19:00:56	11	SSW
22 May	-2.6	17:45:30	10	WNW	17:48:17	42	SW	17:51:06	10	SSE
23 May	-0.7	18:10:36	10	WSW	18:11:56	12	SW	18:13:15	10	S