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butsam
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Reged: 12/28/12

Loc: Ohio
Share your random "rules of thumb" here! new
      #5639526 - 01/23/13 08:25 PM

Last Friday during my viewing session, I realized something pretty interesting.

I saw the GRS on Jupiter again, almost exactly as I had seen it for the first time with my own eyes almost exactly a week before.

So, I pulled up Stellarium, and sure enough, after exactly 1 week, the GRS is in almost exactly the same position on Jupiter.

(I realize Jupiter rotates about once every 9 hours 55 minutes, but that is not as easy a "rule of thumb" to keep in your hip pocket, to get you close for short-term, first-order "mind's eye" filtering of what may be possible again when.)

Some calculations made me realize Jupiter rotates almost exactly 17 times in exactly 1 week. (It is less than 4 minutes from this, as long as my memory on Jupiter's orbit time is correct!)

Anyway, that got me thinking -- what are some of your "rules of thumb" that you use? (For example, for the planetary moon positions, etc?)

EDIT: It looks like once you take into account the Earth & Jupiter going around the Sun, the GRS is in the same spot about once every week and 40 minutes, at least based on Stellarium's depiction; since Earth's motion, and Jupiter's solar motion, wasn't taken into account in the initial calculation, there is a bit of extra error, but it is still easily close enough to make a "rule of thumb" for mental calculation if you know where the GRS was a week ago!)

Edited by butsam (01/23/13 08:39 PM)


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herrointment
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Reged: 03/12/11

Loc: North of Hwy. 64
Re: Share your random "rules of thumb" here! [Re: butsam]
      #5639696 - 01/23/13 10:38 PM

As a saw operator for some decades my rule goes something like.......anything less than two aint good.

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Maverick199
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Re: Share your random "rules of thumb" here! new [Re: butsam]
      #5640010 - 01/24/13 04:41 AM

My rule of thumbs is to post here on Nexstar forums.

Seriously though, I have no rule of thumb and instead just go out and enjoy myself and take in the sights what the night beholds. Or maybe with my limited city viewing, all constellations look the same.


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: Maverick199]
      #5640024 - 01/24/13 05:11 AM

+1 for Haseeb's take on things. Relaxation and enjoyment are my goals when observing.

Regards. Peter.


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Skip
Starlifter Driver
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Reged: 01/23/08

Loc: Fort Worth, Texas, USA
Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5640333 - 01/24/13 10:15 AM

I too do not use rules of thumb. But regarding Jupiter, I do have a little application that will show exactly where the moons and the GRS are at any time during the night. It is called Jupiter 2 and it is freeware. However, I can no longer get to the website unless I go through the link in the app's About tab. Don't know why.

I also, of course, have Stellarium.


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: Skip]
      #5640402 - 01/24/13 10:49 AM

Hi Skip,
If you select Jupiter in SkySafari, center it and use the + to zoom in, it will show you Jupiter's G.R.S, (if visible) and its Moons "as is".

Regards. Peter.


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Arthur Dent
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Reged: 10/23/08

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Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5640455 - 01/24/13 11:16 AM

Here's one for you...

The Moon moves roughly a Moon's width compared to the background stars in around an hour.

(that's roughly 1/2 degree in an hour, so 12 degrees in a day and, 12 x 28 = 336 (so nearly 360 degrees - a complete circle - in 28 days)

Figures aren't spot on, but close enough.

Art


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: Arthur Dent]
      #5640498 - 01/24/13 11:39 AM

Quote:

Here's one for you...

The Moon moves roughly a Moon's width compared to the background stars in around an hour.

(that's roughly 1/2 degree in an hour, so 12 degrees in a day and, 12 x 28 = 336 (so nearly 360 degrees - a complete circle - in 28 days)

Figures aren't spot on, but close enough.

Art





If that ain't "Teaching your Granny to suck eggs" I don't know what is.

Regards. Peter.


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Midnight Dan
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Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5640750 - 01/24/13 01:52 PM

Winter observing rule of thumb: dress like it's 20°F colder than it really is.

-Dan


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Skip
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Reged: 01/23/08

Loc: Fort Worth, Texas, USA
Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5642330 - 01/25/13 10:51 AM

Quote:

If you select Jupiter in SkySafari, center it and use the + to zoom in, it will show you Jupiter's G.R.S, (if visible) and its Moons "as is".




Hi Peter,

Yep and I do use SkySafari all the time in the field. I was thinking more of during the day while I'm planning my observing for the night (when I do any planning - HA!). Of course one could use Sky Safari for that as well, but I like to use the bigger screen whenever I can. The old eyeballs, ya know!


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Skip
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Reged: 01/23/08

Loc: Fort Worth, Texas, USA
Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5642333 - 01/25/13 10:55 AM

Quote:

If you select Jupiter in SkySafari, center it and use the + to zoom in, it will show you Jupiter's G.R.S, (if visible) and its Moons "as is".




Hi Peter,

Yep and I do use SkySafari all the time in the field. I was thinking more of during the day while I'm planning my observing for the night (when I do any planning - HA!). Og course one could use Sky Safari for that as well, but I like to use the bigger screen whenever I can. The old eyeballs, ya know!


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: Skip]
      #5642483 - 01/25/13 12:26 PM

Fully understood Skip.

I RESEMBLE your remarks.

Regards. Peter.


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sonny.barile
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Reged: 10/19/10

Loc: In the middle of the glow.
Re: Share your random "rules of thumb" here! new [Re: Peter9]
      #5646829 - 01/27/13 08:02 PM

I have a rule of thumb for observing sessions.

"Never put a black towel over your head to block stray light when skunks frequent your yard."
This probably isnt what you had in mind but believe me I do follow this rule religiously.

Regards
Sonny


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: sonny.barile]
      #5647479 - 01/28/13 06:44 AM

Quote:

I have a rule of thumb for observing sessions.

"Never put a black towel over your head to block stray light when skunks frequent your yard."
This probably isnt what you had in mind but believe me I do follow this rule religiously.

Regards
Sonny





"WHY" ???

Regards. Peter.


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Chris J
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Reged: 05/21/12

Loc: Dartmoor, Devon, England
Re: Share your random "rules of thumb" here! new [Re: butsam]
      #5648288 - 01/28/13 02:06 PM

Rule 1 - the better the seeing/transparency the less time you will have for observing.

Rule 2 - the usefullness of equipment is inversely proportional to its cost cf planisphere vs filar micrometer.


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WaterMasterAdministrator
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Re: Share your random "rules of thumb" here! new [Re: herrointment]
      #5650100 - 01/29/13 11:31 AM

Quote:

As a saw operator for some decades my rule goes something like.......anything less than two aint good.






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coutleef
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Re: Share your random "rules of thumb" here! new [Re: Midnight Dan]
      #5650113 - 01/29/13 11:39 AM

Quote:

Winter observing rule of thumb: dress like it's 20°F colder than it really is.

-Dan




and when this means you have to dress as if it was -60F, just stay indoors to plan your next session


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Peter9
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Re: Share your random "rules of thumb" here! new [Re: WaterMaster]
      #5650206 - 01/29/13 12:29 PM

Quote:

Quote:

As a saw operator for some decades my rule goes something like.......anything less than two aint good.










I hear that many ex saw operators make very good "short hand" typists.


Regards. Peter.


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Skip
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Reged: 01/23/08

Loc: Fort Worth, Texas, USA
Re: Share your random "rules of thumb" here! new [Re: coutleef]
      #5650211 - 01/29/13 12:30 PM

Quote:

when this means you have to dress as if it was -60F, just stay indoors to plan your next session




Hi François ,

You tough Canadians crack me up! I think I would have stated that as "...when this means you have to dress as if it was 20F [positive 20] just stay indoors to plan your next session ..."

But I to your toughness.


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sonny.barile
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Reged: 10/19/10

Loc: In the middle of the glow.
Re: Share your random "rules of thumb" here! new [Re: Skip]
      #5651181 - 01/29/13 09:16 PM

Peter, One evening last fall I was using a towel to block out a light in the next yard. When I took it off of my head to take a break there was a pair of little stinky eyes looking up at me. It was right there at my feet. I stayed motionless until he left but that was as close as I ever want to get. There are plenty of them around here. Now I dont cover my head and I try not to get to engrossed in what Im doing because i am paranoid.

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