Building An Inexpensive Artificial Star

Good collimation is important for getting the best performance from a telescope. I recently installed Bob’s Knobs on my Celestron SCT to help with collimation – mostly to reduce the risk of damaging the corrector lens when fumbling at night with a screwdriver. Unfortunately, installing the knobs put the telescope way out of collimation – it wasn’t just a minor mis-alignment, in-focus stars were comet shaped and the out-of-focus stars appeared as crescents rather than the desired donut pattern. I spent a couple of hours, over two nights, trying to improve the collimation to no avail but some Google searches and building an incredibly simple artificial star helped.

Flashlight with aluminum foil

An Inexpensive Artificial Star from a bike light and aluminum foil.

An artificial star is a small point of light that is used for collimation or optics testing. With an artificial star, collimation can be done during the day and doesn’t require clear skies or good seeing conditions. Artificial stars are available commercially from $25 USD but a precision artificial star is not required for rough collimation so I “built” one for free using a bike light and aluminium foil.

I started by poking four small holes in a piece of aluminium foil with a sewing needle while varying the pressure to produce holes of different sizes. The foil was then wrapped around a bright MEC bike light and secured with a rubber band.

startest_collimation_in_tweaked

The donut pattern on a out-of-focus real star after tweaking collimation.

I set up the telescope on its mount in my yard and aimed it at the artificial star which was placed on on barrel about 20 meters away. The second largest hole produced the best image when viewed through the telescope so I put a bit of tape over the other holes to block them out then followed these instructions to restore rough collimation in about ½ hour. A few minutes of tweaking at night produced a much improved view and the expected donut pattern on an out-of-focus star.

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Perseid Meteor Shower Peak – 2016

This year’s Perseid meteor shower is expected to peak late on Thursday Aug 11 or in the early morning on Friday Aug 12.  Under good dark-sky conditions, you can expect to see 40 to 80 meteors per hours.  Be patient, the Perseids do not create a blizzard of streaksthrough the sky:  60 meteors an hour means an average of just one per minute, and that includes many faint ones.   From locations in the Lower Mainland with moderate light pollution, you are more likely to see one meteor every two or three minutes.

There is often a good show of meteors several days after the peak so the Perseid Meteor Shower Watch event on Saturday at Aldergrove Region Park is great chance to the shower.

PersiedsShower_Chart

Ten Perseid Meteor Facts:

  1. The Perseid Meteor shower has been observed for over 1000 years.  In 33 AD,  a Chinese skywatcher reported that “more than 100 meteors flew thither in the morning” but when the shower first occurred is unknown.
  2. The Perseid meteors are caused by the Earth passing through the debris trail left by Comet Swift-Tuttle which orbits the sun once every 133 years.
  3. The meteors are the pieces of debris,  usually no bigger than a grain of sand, that enter the Earth’s atmosphere.
  4. More meteors are expected this year because the Earth will be moving through a thicker clump of debris from Swift-Tuttle, created partly from the influence of Jupiter’s gravity.
  5. The Perseid meteors strike the atmosphere at a high velocity, about 60 kilometers per second, which tends to produce bright meteors and an unusual number of super-bright meteors, called fireballs.
  6. The Perseid meteors appear to come from the same place: the constellation Perseus, also called the “radiant.” Perseus is found in the northeastern part of the sky.
  7. Light from the moon will interfere somewhat this year but the moon sets at 12:53 AM on August 12.
  8. Observers have photographed Perseids striking the moon.
  9. People have claimed to hear sounds associated with meteor: hissing, sizzling, or pops.  Scientists have recently proposed that that very frequency radio waves created by meteors could vibrate metal objects on the ground.
  10. An astronaut on the International Space Station, Ron Garan, watched the Perseid meteors from space by looking down at the Earth.

Perseid meteor viewed from the ISS

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Space Suite II Launched on BC’s Knowledge Network

BC’s Knowledge Network recently launched a program called “Space Suite II” and it’s a follow-up to their popular series of short films that comprise the original Space Suite.  The video below is one of ten short films that make up Space Suite II. The piece is titled “Clearer From Afar” and explores the context of the planet Earth from those who have been lucky enough to see it in its entirety.

YouTube: https://youtu.be/4F70wwwtY_s
Vimeo: https://vimeo.com/174578034
Facebook: http://bit.ly/29Py1OC

Full Space Suite II: www.knowledge.ca/program/space-suite-ii

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Telescope Sale at Monthly Meeting on Thurs July 14th, 2016

At the next monthly meeting, we will have a silent auction of several old telescopes and accessories that were part of the telescope loan program. We are doing this to clear space in the storage area and to raise funds for some new telescopes and mounts.
Celestron_NexStar_8

Celstron NextStar 8 with a Goto Mount

 

Below is a list of the items we plan to sell.  The show-case item is a Celestron Nexstar 8” with GOTO mount.
In addition to this list there will be several eyepieces and odds-and-ends for sale.

There will be minimum bids. We may be able to issue tax receipts if the final bid amount exceeds the item’s value by a certain amount (if 80% of the bid is above the value of the amount, a receipt can be issued for the difference).
 

Item
Description
 Value
1
Skywatcher 90mm refractor with GE mount
$200
2
Orion “Space Explorer” 8” (maybe 6?) Dobsonian
$400
3
Meade ETX-125 Maksutov Cassegrain with mount
$400
4
Small Celestron Tripod
$10
5
Celestron Clock Drive
$20
6
HOC 90mm Refractor (no mount)
$250
7
EQ Mount
$50
8
LDx55 Mount and Tripod
$350
9
LDx55 Mount (no tripod)
$200
10
Celestron Nexstar 8” with GOTO mount
$1000
11
Hand-made 6” Dobsonian (needs work)
$200
12
80mm Celestron Refractor
$150
13
80mm Karl Weser Refractor
$150
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The Twilight Zone

The days are long and the nights are short around the summer solstice that occurred a few days ago at 03:34 PM PDT on June 20th, 2016. How late should one stay up to observe the stars in a dark night sky?

At this time of year, Vancouver resides in a twilight zone where we never reach a fully dark night sky. Instead, we experience different levels of twilight. Twilight occurs when the sun is below the horizon, but there is still light in the sky caused by the refraction and scattering of the sun’s rays in the atmosphere. Astronomers define three different types of twilight depending on how far the sun is below the horizon.

Civil twilight starts when the sun dips below the horizon and ends when the sun is 6 degrees below the horizon. There’s enough light to see, but people turn on their lights to drive a car, and the streetlights are starting to come on.

Types of Twilight

Nautical twilight  begins when civil twilight ends and lasts until the sun is 12 degrees below the horizon. The sky can still be distinguished from the distant horizon when at sea, allowing sailors to take measurements of bright stars (hence the name).

Astronomical twilight ends when the sun moves below 18 degrees from the horizon. Night finally begins and you can observe the stars in a dark sky – assuming that there is no bright moon and there are no clouds are in the way.  

But at Vancouver’s northern latitude (a bit above 49º north), the sun does not make it below 18 degrees from the horizon during June and during good chunks of May and July. We don’t experience night, with fully dark skies, during these months but remain in the twilight zone until sunrise the next day.

Twilight hours at 50 degrees norht

Civil twilight is shown in pink, nautical twilight in dark blue, and astronomical twilight as gray. The horizontal axis represents a full 24 hours, and everything that’s not shaded is daylight. Image credit:  Tony Flanders

 

 

What can observers do? One option is to travel south – traveling a few hours south to Seattle lets you experience close to 1 ½ hours of night according to timeanddate.com. Another option is to observe bright objects that are visible during twilight such as planets, the moon, or bright double stars.

 

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In Transit – June 2016

RASC Vancouver President, Suzanna Nagy, revived the “In Transit” presentation at the June 2016 member’ monthly meeting.  “In Transit” is a short presentation of interesting astronomical events that are visible in the current sky.

Three Bright Planets

Intransit-Jun2016-planets

Three planets – Jupiter, Mars, and Saturn – are bright in the evening sky throughout June 2016.

 

 

 

intransit-Jun2016-Jupiter

TROTTIER OBSERVATORY – NEW PLANETARY CAMERA May 27 – Oleg Mazurenko and Howard Trottier

 

Intransit-Jun2016-mars

Mikhail Chubaret in the Ukraine made this chart. It shows the view of Mars through a telescope in 2016. We pass between Mars and the Sun on May 22. We won’t see Mars as a disk like this with the eye alone. But between the start of 2016 and May, the dot of light that is Mars grows dramatically brighter and redder in our night sky. Watch for it.


The Sun is Getting Less Active

Intransit-Jun2016-sun

 

Spotless Days
Current Stretch: 4 days
2016 total: 4 days (1%)
2015 total: 0 days (0%)
2014 total: 1 day (<1%)
2013 total: 0 days (0%)
2012 total: 0 days (0%)
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
Updated 10 Jun 2016

 

 

 


Open Star Cluster NGC 457

Intransit-Jun2016-ngg457-casseopia

The open star cluster NGC457 is located in Casseopia and has an interesting shape.

 

Intransit-Jun2016-ngc457-#1

Intransit-Jun2016-ngc457-owl

An owl …

Intransit-Jun2016-ngc457-et

or ET!

 

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