Do navigation lights move faster when near ? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Skills and Seamanship > Learning to Sail
 Not a Member? 


Reply
 
LinkBack Thread Tools
  #1  
Old 01-07-2011
Senior Member
 
Join Date: Dec 2008
Location: Chesapeake
Posts: 471
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
lapworth is on a distinguished road
Do navigation lights move faster when near ?

I was coming home last night and noticed a plane flying by and he was going fast over the horizon. I know with a motor boat this would make as much sense because they can change there speed. So what I was wondering is could you get a better feel for the distance of a boat from you by how fast they are moving over the water ( I know there not moving faster @ closer distance ).
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 01-07-2011
BubbleheadMd's Avatar
Chastened
 
Join Date: Nov 2009
Location: Edgewater/Annapolis
Posts: 3,021
Thanks: 1
Thanked 59 Times in 55 Posts
Rep Power: 6
BubbleheadMd will become famous soon enough
Send a message via Yahoo to BubbleheadMd
Perception is everything.

The questions that you're trying to answer are:

Is this a small, dimly lit vessel crossing me close by or
Is this a large, brightly lit vessel crossing me far away?

They might look very similar.

Things you can do to help determine this are to observe how high off of the water the lights are. That might indicate a larger vessel if they're high off the water.

Then you observe how fast the lights are moving past fixed points on land (or fixed lights if you can't make out a land feature). Also, if you suspect that the vessel might be close aboard, listen for engine and wake noises (though you might not hear any.)
__________________
S/V Old Shoes
1973 Pearson 30 #255
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 01-07-2011
Bene505's Avatar
Glad I found Sailnet
 
Join Date: Jul 2008
Posts: 3,718
Thanks: 6
Thanked 42 Times in 41 Posts
Rep Power: 8
Bene505 will become famous soon enough Bene505 will become famous soon enough
By "light's moving faster", you might mean changing their relative bearing to you. In other words, you are turning your neck as you watch the lights.

I'd only add that the change in bearing to the light can tell you something, but not enough without BubbleHeads' answers.

A faster bearing change will happen if the boat is
closer
faster
not heading to intercept you (If he's going to hit you there will be no bearing change.)
Also, the perceived height angle (azimuth) could change fast, but by then it's probaly too late.

Regards,
Brad
__________________
.
.
Great minds discuss ideas;
Average minds discuss events;
Small minds discuss people.
.
The best minds discuss sailing. I don't know why. It's a mystery!
.

Last edited by Bene505; 01-07-2011 at 10:13 AM.
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 01-07-2011
Senior Member
 
Join Date: Dec 2008
Location: Chesapeake
Posts: 471
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
lapworth is on a distinguished road
Let me try to word this another way. If I see a sail boats port light cross in front of me over the horizon and it is sailing at 5 knts about a mile away would it take the same amount of time to cross 5 degrees of vision as if the same boat was 2 ml away still doing 5 knts.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 01-07-2011
Member
 
Join Date: Nov 2010
Posts: 42
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
acunningham is on a distinguished road
Quote:
Originally Posted by lapworth View Post
Let me try to word this another way. If I see a sail boats port light cross in front of me over the horizon and it is sailing at 5 knts about a mile away would it take the same amount of time to cross 5 degrees of vision as if the same boat was 2 ml away still doing 5 knts.
No, it would take about half the time.
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 01-07-2011
jrd22's Avatar
Courtney the Dancer
 
Join Date: Nov 2000
Location: San Juan Islands., WA, USA
Posts: 3,841
Thanks: 3
Thanked 16 Times in 16 Posts
Rep Power: 15
jrd22 will become famous soon enough
The lights you see that are "moving" aren't the ones that are the most dangerous to you.
__________________
John
SV Laurie Anne

1988 Brewer 40 Pilothouse

Reply With Quote Quick reply to this message Share with Facebook
  #7  
Old 01-07-2011
Senior Member
 
Join Date: Dec 2008
Location: Chesapeake
Posts: 471
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
lapworth is on a distinguished road
Quote:
Originally Posted by acunningham View Post
No, it would take about half the time.
Then I should be able to make a device that could estimate distance of moving objects. Maybe something similar to the way you use a sextant on a bridge or light house.
Reply With Quote Quick reply to this message Share with Facebook
  #8  
Old 01-07-2011
Member
 
Join Date: Nov 2010
Posts: 42
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
acunningham is on a distinguished road
Quote:
Originally Posted by lapworth View Post
Then I should be able to make a device that could estimate distance of moving objects. Maybe something similar to the way you use a sextant on a bridge or light house.
That would work, as long as you know the speed and angle the object is moving at. Of course, you could ask them via radio :-)
Reply With Quote Quick reply to this message Share with Facebook
  #9  
Old 01-07-2011
Senior Member
 
Join Date: Dec 2008
Location: Chesapeake
Posts: 471
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
lapworth is on a distinguished road
Quote:
Originally Posted by acunningham View Post
That would work, as long as you know the speed and angle the object is moving at. Of course, you could ask them via radio :-)
I could use it other ways. If I know it is in the channel and I know how far away I am then I would be able to calculate there speed.
Reply With Quote Quick reply to this message Share with Facebook
  #10  
Old 01-07-2011
Member
 
Join Date: Nov 2010
Posts: 42
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
acunningham is on a distinguished road
Quote:
Originally Posted by lapworth View Post
I could use it other ways. If I know it is in the channel and I know how far away I am then I would be able to calculate there speed.
Very true! If they're in the channel you can make reasonable estimates of both their distance and their course. Isn't mathematics wonderful?
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
LED Navigation Lights solman55 Gear & Maintenance 14 10-29-2010 10:06 PM
Navigation Lights tager Electronics 42 11-07-2009 09:35 AM
Navigation Lights Guidera48 Gear & Maintenance 10 07-24-2009 06:27 PM
Navigation Lights sailaway21 Seamanship & Navigation 44 06-04-2007 01:46 AM
Navigation Lights 1970Columbia34 Gear & Maintenance 9 02-28-2007 11:29 PM


All times are GMT -4. The time now is 09:54 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.