Wednesday, July 4, 2018

Planets

Last night,  I stayed up late enough to see Saturn.  What a glorious dark sky.   Saturn is still a bit low to get a decent image.   I can see the Rings well enough,  but Cassini's Division is not visible.   Above 333x was not useful.  (It might be I need to recollimate.)  I was too tired to go galaxy hunting.  Maybe tonight.

Just after I rolled Big Bertha back in,  Mars rose red and huge over Bogus Basin.  We are coming up on a perihelion opposition.   Mars has a,very eccentric orbit, and when it comes opposite us at perihelion it is very close and bright.

UPDATE: I checked and the collimation was off.  Rolling across the rough surface probably shook it out of collimation.  Part of why I need to finish resurfacing that area in front of the telescope garage after my surgery is done and healed.

UPDATE 2: Recollimating always misaligns the optical axis of the scope from the finder.  I always forget this.  Unless you have a Moon for realigning, this is a laborious task.  Fortunately, I have an 85mm eyepiece (an extreme outlier among telescope eyepieces) which is 23x, and about 1.5 degrees of field, so it makes an almost adequate substitute for a finder.

Some of you have trouble identifying planets.  Tricks:

1. Unless it is very low in the sky, or you are having a very turbulent night, stars twinkle, planets do not.  Why?  Stars are so very far away that they are less than an arc-second wide.  It takes very little atmospheric disturbance to make their light twinkle.  Planets (at least the ones the ancients knew about; Saturn and inward) are all at least an arc-second wide.  Many, like Jupiter, Saturn, Venus, and currently Mars are at least an arc-minute or close, so the atmosphere has a hard time doing bad things to their light.  Some way even appear as tiny discs to those with good eyesight.  (Usually, it takes 3 arc-minutes for most people to distinguish disc from point.)  Mercury is an exception: it is a very tiny disc and you only see it at sunrise and sunset within an hour of either event.  It is therefore low in the sky, and I have never seen it not twinkle.

2. Brightness: Venus at sunset or sunrise is bright, you can see why fighter pilots during World War II opened fire on it.  Jupiter is often brighter than any other star in the sky.  Saturn not as bright.  At perihelionic opposition, Mars can be overpoweringly bright.

3. Color: Venus is a brilliant white; Jupiter is white; Saturn is often a yellowish white; Mars is red enough to make you think of blood: the war god!  Of course, many stars are colored as well: Antares (rival of Ares or Mars) is red.  Sirius is blue-white.  There are a number of others, although most are white to the unaided eye because it takes a lot of light to excite the retina's cones, which distinguish colors.

Learning constellations requires a reasonably dark sky; Democrats are usually a contraindicator for dark sky.  It also helps to have a guide, at first.  Once you recognize Lyra (just about at the zenith last night at 11:30) and the Big Dipper, and Orion, filling the rest in on your sky map gets easier.

1 comment:

Jerry The Geek said...

I've tried to identify the individual planets and stars whe I go onto my smoking orchem, almost every night. But I can get no further than to admire the plethora of lights in the skyl I have no idea even after I've downloaded the star maps.

I envy your understanding and familiarity of the stars. It doesn't comfort me that SOMEONE has the skill and knowledge to pick them out of the sky.

But it does comfort me that I'm not the only one who thinks that the stars and planets are important.

Jerry the Geek