View Full Version : APOW II: As the world turns...

05-22-2009, 06:48 PM
I finally was able to capture an unbroken sequence of images, one per minute from twilight to dawn. I made a simple heater to keep the lens from fogging and it worked right up to dawn when it was overwhelmed. I was using a couple of resistors under the lens that dissipated about 200 milliwatts from a 12 battery. If I jack that up to 400 it should be able to keep it clear.

It finally stayed completely clear all night with very low sky glow from the town. I also captured two very bright meteors which was something I didn't expect.

The shutter was open for 45 seconds of every minute taking one frame per minute. We have only about three hours of true darkness now and soon that will be less than 1 hour. Astronomical twilight lasts until the sun is 12 degrees below the horizon. Up until then there is still some "daylight" visible in the sky to the camera even though it appears to be completely dark to the eye.

Here are the two meteors I snagged.



Here is the video of the entire night looking north. ( 3.4 MB)


05-22-2009, 06:59 PM
---> Swweet! <---

05-22-2009, 08:54 PM
Very nice Evan, thanks for sharing with us.:)

05-22-2009, 10:55 PM
Always enjoy your pics.
Thank you.

Bill in Ky
05-22-2009, 11:19 PM
Great stuff Evan, keep them coming!!

05-22-2009, 11:24 PM
Very Way Cool Video Evan

Really amazing the rotation up north there. I guess the natural arraingement of planets really does align towards the equator. Can we see another video pointed towards the equator more so we catch a planet or two

05-22-2009, 11:38 PM
Here are the two meteors I snagged.

The meteor traces show the arc of the trajectory, and also the thickening and narrowing of the glowing trace. I assume the trace starts as the glow emanating from the stagnation point; the glow then grows to encompass the whole mass, finally fading to nothing as the mass ablates. Is that how you read this too?

05-23-2009, 04:30 AM
Serious question Evan, What's the red dot at about 40deg inclinaton to the right on the last meteor trace?? Watched the video and thought it was my display showing a rogue cell, but it seems to be on the last still?? It's stationary on the vid and that's what threw me.

Regards Ian.

05-23-2009, 04:41 AM
Here is a close up from the original image that has been slightly adjusted to reveal more of the meteor track.


The amount of glow in part represents the density of the atmosphere the meteor is passing through. This meteor was captured by Earth in the morning at 02:51 local time. Because the back track points away from the direction of the rising sun it was intercepted on the leading side of the planet in it's orbit. This means the orbital velocity of Earth is added to the orbital velocity of the meteor resulting in a very high velocity as it encounters the atmosphere.

The Earth's orbital velocity is about 29 Kilometres Per Second. Add this to the Earth's escape velocity which is 11.2 KPS and the velocity is at least 40 KPS. The escape velocity of Sol at the orbit of Earth is another 42 KPS so the velocity of an object originating in our solar system can be as high as 80 KPS when it enters our atmosphere.

In this instance the meteor abruptly stops glowing shortly after reaching maximum brightness. This is typical of a carbonaceous chondrite which represents 80 to 90 percent of all small debris that we capture. The remaining percentage of meteors are mostly stony iron objects which show a much more extended trace after maximum brightness as they withstand the ablation and aerodynamic forces better. A small percentage are solid nickle-iron-chromium masses and even very small meteors of this material will make it to the surface.

When a meteor large enough to reach the surface enters it actually come to a nearly complete stop at about 30 to 100 km altitude. At that point the meteor goes dark and then begins to accelerate to terminal velocity. Terminal velocity for a small, dense object from that altitude exceeds the speed of sound. This results in a sonic boom as the object falls into the lower atmosphere. Terminal velocity near the surface for an object of less than a kilo or so is subsonic which is why small meteorites don't blast craters in the surface.

05-23-2009, 04:43 AM
What's the red dot at about 40deg inclinaton to the right on the last meteor trace

It's a hot pixel in the sensor. The images were taken at ISO 800 so this exaggerates sensor noise.

tony ennis
05-23-2009, 10:33 AM
Note Ursa Major makes a grand appearance right before dawn :-)

Very cool stuff.

05-23-2009, 09:14 PM
That was real nice. Thanks.

Quetico Bob
05-23-2009, 09:27 PM
Cool pics.
Question, recieved a telescope from Horse Lake for my son. We can't see any stars out of it. Its a Safari 9324 D=60mm F=700mm. has a 2x barlow, 90 degree mirror eyepeice thing and a HI2.5mm eye piece.

We know nothing about this yet, if I point it at a light in the house, well, I can see light but thats it. Just can't seem to figure out how to focus on stars.

Any thoughts?

Cheers, Bob

05-23-2009, 10:30 PM
Well, that sounds like your average department store not good for much type of telescope ( I am being kind...). At the best you should be able to see craters on the moon and maybe pick out a few features on a nearby planet when one presents itself. It has a small objective and a long focal length which means it has a very narrow field of view and is very difficult to aim. Stars are singularly uninteresting since they pretty much look the same no matter what scope you have. A good scope will still show just a fuzzy blob although that fuzzy blob will be a properly coloured and round fuzzy blob with well defined diffraction zones.

[added] That 2.5mm eyepiece is impossible to focus well even on a high quality scope and on that one is far too much magnification to see anything.

Your telescope is exactly the wrong sort of first telescope. If you really want to get off to a good start in astronomy I would suggest something from Meade such as one of their smaller Dobsonian scopes.

Something like this one in the 8" size will knock your socks off the first time you point it at the Orion Nebula or Andromeda. It comes with everything you need and is very portable for a relatively large telescope. The eyepiece that is included has a huge 70 degree apparent field of view. If you can justify the expenditure I can promise you won't be disappointed.


05-23-2009, 10:44 PM
A couple of things to try before spending loot.

Don't use the barlow.
Use an eyepiece with a "higher number" on it.

If you are watching your pennies, you might check out the used market first for a small dob as Evan mentioned.
www.astromart.com (http://www.astromart.com) is a start.
www.cloudynights.com (http://www.cloudynights.com) is another.

Another good place is www.telescope.com (http://www.telescope.com) There is a small table top dob on there for under $200.00.


Quetico Bob
05-24-2009, 05:11 PM
Thanks Lenord, Evan.
Was starting to think I was completely inept instead of just some.

Think the next step for us would be a home made job.

Anybody ever grind a mirror on the lathe? 18-20"

Cheers, Bob

05-24-2009, 09:54 PM
Bob, quick, head back to that Meade link supplied by Evan. Once you start down the "make your own telescope" bit its all down hill from there! :D