Friday, July 1, 2011

A Beautiful Generally Clear Night

We have had perhaps a dozen reasonably clear nights this year--a year that was beginning to look like it was not having to have a summer.  I have been too busy with going through an online class in how to teach online classes to take advantage of any of these evenings--and many of these were only somewhat clear nights.  Even tonight, there was enough moisture in the air that viewing conditions were not ideal. 

Nonetheless, I am working on a new product for ScopeRoller to make it easier for my customers to repeatably align their mounts on the North Celestial Pole, and this was a clear enough night for testing the device.  Since my existing customer base includes more than 300 customers, if I can come up with something very profitable to sell to even 25% of those customers, it is worth some development effort.

I have forgotten how dark a sky I have here in Horseshoe Bend--and it is getting darker.  The neighbor down the hill who had a relatively bright exterior garage light has moved out, and the house is now vacant and dark.  No one is moving in, either.  What a glorious sky!  I was able to find The Ring Nebula almost immediately, and I was able to align my mount on NCP well enough to track the Ring Nebula manually by just advancing the mount.

If you don't know what I am talking about, all the objects in the sky move across the sky in circles around the North Celestial Pole, which is approximately where Polaris, the North Star, is located.  The NCP is the height above the horizon that is your latitude.  If you are at 44 degrees N. latitude (as I am), then NCP is 44 degrees above the horizon, due north.  If you are in Los Angeles, at 33 degrees N. latitutde, then NCP is 33 degrees above the horizon, due north.

An equatorial telescope mount has two axes.  If the polar axis is pointed at the NCP, rotating the mount around the polar axis will cause your telescope to track an object across the sky.  The more precisely you point the polar axis at the NCP, the more accurately your telescope will stay pointing at the object.  This is very important if you are doing long exposure astrophotography, like this picture


taken by one of my customers. (Note the wheels under the telescope.)


Anyway, getting an equatorial mount lined up on NCP good enough for visual use is pretty easy.  If you get within a degree of NCP, you generally won't notice that you are off except if you are tracking an object at very high power (250x or more).  You just make little adjustments along the way, no problem.

For astrophotography, it really does matter, and to do an adequate job of lining the mount up on NCP can take 20-30 minutes.  I'm working a way to make it fast and easy for customers to roll their telescopes out and be immediately lined up on NCP.  At least, they will be lined up accurately enough for all but the most demanding long exposure photos.

6 comments:

rmunn said...

The human brain's ability to pick out patterns, even when they aren't there, is truly interesting. My brain insists that I'm seeing a picture in that photo of M16HA: a skeleton dancing a jig. The darker V shape is the rib cage; the two straight lines below are the legs. (The pelvis is missing but my brain fills it in just fine). One leg is bent at a 45 degree angle, hence the "dancing a jig" part of my comment. Two tiny bright spots above the V-shaped ribcage provide the neckbones, and the head (or skull), turned so it's "facing" the left, is the brighter spot above the neckbones with a darker patch on its left-hand side.

When you look at clouds and say "that one kind of looks like a ship/a whale/a tree", you generally have to force yourself to see the resemblance. But the "hey, there's a skeleton dancing a jig" pattern popped into my head the instant I saw this picture, and I can't make myself not see it. Really fascinating how that works.

Epsilon Given said...

You're making it too easy to be accurate: you're taking the fun out of it!

(I have never had the opportunity to try to calibrate a telescope, but if it's anything like calibrating a mill before machining a piece of aluminum, I would certainly be in favor of taking the "fun" out of it! ;-)

Mauser said...

I thought one did it by putting a special spotting scope through the mount and lining it up on Polaris.

Roy said...

I have just about given up on serious astrophotography. When I first moved into this house, you could go outside on a clear moonless night and you could barely see your hand in front of your face. The skies were magnificent. Now, just 12 short years later, there are so many of those damn security lights on everyone's house and garage, I might as well be downtown in the city.

Roy said...

...oh yeah, rumnn. Now that you have pointed it out, I can definitely see the dancing skeleton.

Clayton said...

Yes, there is a polar alignment scope in my mount, but it is so inadequate that I am glad that I didn't pay anything extra for it. Worse, these alignment scopes are merely a step towards the more precise alignment required for long-exposure astrophotography.