Saturday, 4 June 2011

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.

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. 


Wednesday, 1 June 2011

Deep Space Atlas - 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:

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

Tuesday, 31 May 2011

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:  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.
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:

Monday, 30 May 2011

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

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?”