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Thread: USCG Crazy Exam question: Sidereal vs Tropical Year
Post: RE: USCG Crazy Exam question: Sideral vs Tropical ...
| Peter,
I'm working on it. Say, that test is very interesting.
Clen |
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c_davidson |
General Topics Here
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3 |
2,460 |
05-04-2023, 01:17 PM |
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Thread: Hello
Post: RE: Hello
| Mike,
If the heavenly body's declination is Contrary name to your DR Latitude enter a negative sign before it.
Pretty easy.
Clen |
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c_davidson |
The Sight Reduction process
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11 |
5,311 |
03-13-2023, 08:10 AM |
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Thread: Hello
Post: RE: Hello
| Mike,
In the formulas above press the Arc Sin key when you see Sin-1 or press the Arc Cosine key when you see Cos-1
Sorry about that.
Clen |
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c_davidson |
The Sight Reduction process
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11 |
5,311 |
03-09-2023, 11:15 AM |
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Thread: Hello
Post: RE: Hello
| Mike,
We are all trying to master this skill and make it as easy as possible and it does get confusing.
Firstly, Chris Nolan is very good at explaining celestial navigation. But sometime there'... |
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c_davidson |
The Sight Reduction process
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11 |
5,311 |
03-08-2023, 10:34 PM |
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Thread: warning - graphic content
Post: RE: warning - graphic content
| The US isn't a model of virtue nor even aspires or attempts any moral purity. What objective standard does that guy use in comparing the US to the Philippines? That Duterte wants to kick the US base... |
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c_davidson |
General Topics Here
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4 |
4,296 |
02-20-2021, 01:32 PM |
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Thread: ARTIFICIAL HORIZON MATH
Post: RE: ARTIFICIAL HORIZON MATH
| Now you fellas have me confused.
To account for IC when using an AH what are we supposed to do?
Thanks,
Clen |
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c_davidson |
The Sight Reduction process
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4 |
4,098 |
02-16-2021, 01:41 AM |
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Thread: Frustration
Post: RE: Frustration
| I love that...."Now that rainy season is over we're getting all the rain we missed during rainy season."
Go to sea?! I'm with you! Not having a boat is a problem. I sold mine this Summer and I s... |
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c_davidson |
General Topics Here
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2 |
2,813 |
12-28-2020, 05:19 PM |
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Thread: New member
Post: RE: New member
| pabrides,
Are you using an AH in your observations above? |
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c_davidson |
General Topics Here
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9 |
7,593 |
12-27-2020, 01:05 AM |
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Thread: 2017 Bowditch- The American Practical Navigator
Post: RE: 2017 Bowditch- The American Practical Navigato...
| Excellent comment!
What about "it"?
I'm tired of looking at the qr codes.
God, bring us back to the days of chairMAN or chairWOMAN.
Bowditch is very helpful and the price is right (fre... |
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c_davidson |
General Topics Here
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3 |
6,238 |
12-23-2020, 12:02 AM |
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Thread: Celestial Nav problem I can't solve
Post: RE: Celestial Nav problem I can't solve
| Ray,
Ok, men. Let's start over. What's the date- the 15th or the 16th?
My date of January 16, 1981 is incorrect. Now I say it's the 15th as the Sun's just rising to your East meaning, using... |
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c_davidson |
General Topics Here
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12 |
13,564 |
04-29-2020, 10:55 PM |
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Thread: Celestial Nav problem I can't solve
Post: RE: Celestial Nav problem I can't solve
| Ray,
I don't know whether they're using Ho-249 or Ho-229 or if they're just using a calculator. The resulting plots will all be close to each other.
Using the time diagram the specifics are as... |
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c_davidson |
General Topics Here
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12 |
13,564 |
04-29-2020, 01:29 PM |
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Thread: The North Pole no longer wanders - it runs
Post: RE: The North Pole no longer wanders - it runs
| Nice work Rumata. Interesting, isn't it, that the magnetic pole is getting closer to Polar North. That the earth is one huge electro-magnet is astounding. |
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c_davidson |
The Sight Reduction process
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7 |
10,696 |
02-19-2019, 01:52 AM |
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Thread: ABC Tables Azimuth Value
Post: RE: ABC Tables Azimuth Value
| Albyreto,
No, I can't help you. It could be that when doing the calculations a negative value must be entered for LHA or use T instead of LHA. I'm no expert in the matter that's for sure.
I'm ... |
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c_davidson |
The Sight Reduction process
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5 |
10,672 |
11-08-2018, 04:41 PM |
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Thread: Freiberger vs Tamaya
Post: RE: Freiberger vs Tamaya
| Joe,
Most Freiberger's I've seen have a wooden handle mounted on the metal/aluminum frame. It's quite secure- just a nice touch of wood on a possibly cold handle when in the Arctic.
Clen |
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c_davidson |
Equipment- Wanted or for Sale
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4 |
8,054 |
07-05-2018, 01:21 AM |
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Thread: Freiberger vs Tamaya
Post: RE: Freiberger vs Tamaya
| Joe,
Both are made by very good companies. Does the Freiberger has a wooden handle?
If they're both acceptable in terms of condition it's a tough choice. You'll get a good sextant either way... |
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c_davidson |
Equipment- Wanted or for Sale
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4 |
8,054 |
07-04-2018, 10:00 AM |
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Thread: USNO Astronomy site down?
Post: USNO Astronomy site down?
| For the past few days the USNO's Astronomy site, in its entirety, has been unreachable. The links below are examples.
http://aa.usno.navy.mil/data/docs/celnavtable.php
or....
https://aa.us... |
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c_davidson |
General Topics Here
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2 |
5,610 |
04-21-2018, 01:41 AM |
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Thread: AP in the east.
Post: RE: AP in the east.
| Most instructive, Wannathermal.
I had been confused as to whether this discussion was about DR or Ap or plotting an LOP. Now I understand that when determining the Ap longitude for plotting in the E... |
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c_davidson |
The Sight Reduction process
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17 |
19,611 |
03-03-2018, 10:02 PM |
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Thread: Astron Excel sight reduction manual almanac
Post: RE: Astron Excel sight reduction manual almanac
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Rumata Wrote: (10-01-2017, 07:03 AM)
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Gentlemen,
I just tried to use Sight reduction Astron spreadsheet / manual option and can't locate Altitude correction for Sextant sight. Also, Index err... |
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c_davidson |
The Sight Reduction process
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6 |
10,012 |
10-02-2017, 10:36 PM |
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Thread: Sighting the eclipse
Post: RE: Sighting the eclipse
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BigBill Wrote: (08-21-2017, 09:22 PM)
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I was able to see it well.
I wonder if the eclipse bends the light somewhat. I took a number of sun sights during the event but so far have only reduced tw... |
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c_davidson |
General Topics Here
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4 |
7,197 |
08-21-2017, 10:45 PM |
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Thread: Planning for twilight phenomena observation
Post: RE: Planning for twilight phenomena observation
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Rumata Wrote: (07-02-2017, 01:17 AM)
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Gentlemen, I have a question regarding planning for twilight phenomena observation. But before some wordy stuff, sorry.
The situation: In a morning I plan ... |
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c_davidson |
The Sight Reduction process
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5 |
9,254 |
07-03-2017, 12:03 PM |
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Thread: Why Polaris isn't listed?
Post: RE: Why Polaris isn't listed?
| Rumata,
I can't exactly answer your question. However, while Polaris is easily found in the sky, Pub. 249 Vol 1 includes the Polaris tables 6 & 7 on page 353 (the last page of tha volume).
The ... |
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c_davidson |
The Sight Reduction process
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14 |
22,380 |
04-20-2017, 12:32 PM |
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Thread: v for the sun
Post: RE: v for the sun
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albyreto Wrote: (03-30-2017, 07:02 PM)
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hi,
why there's not v correction for the sun GHA?
In italy the "Nautical Almanac" have the v correction for the sun.
Maybe its not important but sometimes... |
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c_davidson |
The Sight Reduction process
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6 |
9,629 |
03-30-2017, 07:50 PM |
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Thread: Which season is it?
Post: Which season is it?
| For those in Southern Latitudes it's now Fall. The Sun in South Lat. is now "Contrary name".
For those in Northern Latitudes it's now Spring. The Sun in North Lat. is now "Same name". |
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c_davidson |
General Topics Here
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2 |
6,587 |
03-21-2017, 03:53 PM |
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Thread: Stellarium- finding stars
Post: RE: Stellarium- finding stars
| BigBill,
I'm getting the same error-
"Sorry! This site is experiencing technical difficulties".
Looks like all of the plugin pages are having trouble.
It's a good plugin but sometimes when... |
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c_davidson |
General Topics Here
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11 |
19,651 |
03-13-2017, 11:42 PM |
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Thread: Theodolite
Post: RE: Theodolite
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BigBill Wrote: (03-11-2017, 04:20 AM)
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Hi,
New guy here. I'm more of a land navigator with the sextants and was wondering if anyone had any experience or ideas about a make and model of surveyor... |
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c_davidson |
General Topics Here
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5 |
10,318 |
03-11-2017, 12:16 PM |
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Thread: Buy a sextant
Post: RE: Buy a sextant
| Douglas,
Now that's a handsome photo! Is that a magnifying glass near the index clamp? What is the index vernier scale graduated down to? .2 .4 ,6 .8? Or are there individual lines for ea... |
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c_davidson |
General Topics Here
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14 |
34,442 |
01-19-2017, 01:46 PM |
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Thread: Buy a sextant
Post: RE: Buy a sextant
| Collecting sextants can be an expensive but very satisfying hobby!
I would really love to get an Observator Mark 4.
Here it is- (notice no filters! Some sort of film/filter is inside the telesc... |
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c_davidson |
General Topics Here
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14 |
34,442 |
01-17-2017, 04:23 AM |
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Thread: Close GHA determination using EoT
Post: RE: Close GHA determination using EoT
| Carlos,
For yesterday, January 12, 2017 the EoT for 12h was 08:24.
Is this method correct? If it was GMT 16:00 then the approximate Sun GHA would be-
16-12= 4 hours
4 x 15°= 60°
EoT con... |
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c_davidson |
General Topics Here
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2 |
5,837 |
01-13-2017, 02:32 PM |
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Thread: Landfall procedure?
Post: RE: Landfall procedure?
| Dustin,
That's a pretty good accomplishment- familiar waters or not. A good experience!
These words, "I fly until the sun is where I want it to be..." (understanding you're using a flight simul... |
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c_davidson |
General Topics Here
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10 |
16,249 |
06-03-2016, 04:49 PM |
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Thread: Landfall procedure?
Post: RE: Landfall procedure?
| Baendu,
In the past I've seen the site you have linked but it's too confusing and disjointed to figure anything out.
Your explanation is a lot easier to understand. Tell me if this is correct; ... |
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c_davidson |
General Topics Here
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10 |
16,249 |
06-03-2016, 01:24 PM |
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Thread: Landfall procedure?
Post: RE: Landfall procedure?
| Paul,
I'm no expert of even too knowledgeable about the Landfall procedure.
I read Chichester's method a long time ago but remember very little about it. Pretty sure you calculate Hc and Zn f... |
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c_davidson |
General Topics Here
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10 |
16,249 |
04-18-2016, 08:15 PM |
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Thread: Co-Latitude
Post: Co-Latitude
| Would someone please explain to me what Co-Latitude is?
C. D. |
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c_davidson |
General Topics Here
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2 |
9,357 |
03-24-2016, 01:21 AM |
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Thread: Arrogant mathematicians
Post: Arrogant mathematicians
| Celestial navigation is difficult for a multitude of reasons but I wish to focus upon one particular- the math portion.
Learning celnav was very difficult for me because my skill at math was and isn'... |
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c_davidson |
General Topics Here
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3 |
8,261 |
02-29-2016, 03:01 PM |
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Thread: Does anyone really shoot the Moon?
Post: RE: Does anyone really shoot the Moon?
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jeremyparker Wrote: (02-29-2016, 04:51 AM)
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My follow up question perhaps belongs in a different thread - Who bothers with Noon sights, and why?
I ask because there seems to be an almost religious... |
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c_davidson |
The Sight Reduction process
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8 |
15,897 |
02-29-2016, 02:30 PM |
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Thread: Doniol- Sight reduction
Post: RE: Doniol- Sight reduction
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LouisC Wrote: (01-20-2016, 03:19 AM)
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Here are the haversine tables up to 179° 58'.
I'm working on a Doniol sight reduction form along with CelNav57.
--
Thanks Louis for the tables.
Is th... |
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c_davidson |
The Sight Reduction process
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7 |
13,948 |
02-02-2016, 01:18 PM |
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Thread: Buy a sextant
Post: RE: Buy a sextant
| Albyreto,
Firstly, I have a III-B and really like it and have had no problems with it. The red LED light for night sights is somewhat hard to read on the minutes knob. I use the whole horizon mi... |
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c_davidson |
General Topics Here
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14 |
34,442 |
02-02-2016, 01:09 PM |
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Thread: Jojoba oil- lubricate sextant
Post: Jojoba oil- lubricate sextant
| Bruce Bauer's book, "The Sextant Handbook" mentions that you can use Jojoba oil as a lubricant for your sextant. He says that it has similar characteristics as whale oil which was used in the past.
... |
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c_davidson |
General Topics Here
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0 |
4,876 |
01-07-2016, 01:22 PM |
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Thread: shooting a star
Post: RE: shooting a star
|
Lipr Wrote: (12-28-2015, 01:30 PM)
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stargazer Wrote: (12-27-2015, 01:09 PM)
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LiprThe stop watch that I couldn't remember the name of was "Sight Time" model 911" I can't find it anywhere so it m... |
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c_davidson |
The Sight Reduction process
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6 |
14,499 |
12-31-2015, 01:20 PM |
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Thread: Full UPS or small sheet
Post: RE: Full UPS or small sheet
| Ed,
Trig tables are but a memory. Machinery's Handbook, of which I have a 1943 edition, has them in it. For interest I perused them and was happy to see that it might be a good idea to print them... |
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c_davidson |
General Topics Here
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2 |
6,388 |
12-28-2015, 09:56 PM |
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Thread: Alain Kalita- solo around the world- Sun sight
Post: Alain Kalita- solo around the world- Sun sight
| This doesn't directly have much to do with the process of sun sights but it's a small portion of a video about Alain Kalita sailing solo non-stop around the world.
Here's a portion of the video w... |
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c_davidson |
General Topics Here
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1 |
4,523 |
12-23-2015, 11:35 PM |
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Thread: CelNav- no batteries, no electronics but...
Post: RE: CelNav- no batteries, no electronics but...
| Most likely the best approach lacking accurate time is to refer to the DR Log book that was being kept and make an assumption from the last accurately known time and position (assumed position or fix)... |
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c_davidson |
The Sight Reduction process
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3 |
7,496 |
12-21-2015, 02:18 PM |
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Thread: Pub. No. 249
Post: RE: HO-249
| Heard of R. Doniol method? Yes, a long time ago and even tried it a few times. It's one of the countless methods to arrive at the two precious calculated figures.
"Why not give it a try....again"... |
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c_davidson |
General Topics Here
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3 |
7,415 |
12-16-2015, 10:55 PM |
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Thread: Stellarium- finding stars
Post: RE: Stellarium- finding stars
| Got it. Excellent program.
Clendon |
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c_davidson |
General Topics Here
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11 |
19,651 |
12-16-2015, 01:28 AM |
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Thread: Cleaning shades and mirror?
Post: RE: Cleaning shades and mirror?
| That was an interesting from your youth up- you've lived the name you use. You father did make a wise decision.
Will take your advice about the cotton balls. It looks like the resilvering of Inde... |
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c_davidson |
General Topics Here
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6 |
16,556 |
12-16-2015, 01:26 AM |
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Thread: Pub. No. 249
Post: RE: HO-249
| Celestaire should fix that messy looking Vol. 1.
The only pages I print out are the Latitudes I'm usually in.
You sail during the Summer (in your hemisphere)! Right?
Did you ever use the Do... |
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c_davidson |
General Topics Here
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3 |
7,415 |
12-15-2015, 10:19 PM |
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Thread: Cleaning shades and mirror?
Post: RE: Cleaning shades and mirror?
| That was a good video and the men were very careful in handling and cleaning the mirror.
Those are good ideas for cleaning the first surface mirror on my Astra III-B. When I clean the index mirror... |
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c_davidson |
General Topics Here
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6 |
16,556 |
12-15-2015, 10:14 PM |
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Thread: Pub. No. 249 Vol. 1 Stars
Post: Pub. No. 249 Vol. 1 Stars
| It would be nice if Pub. No. 249 Vol. 1 could be compiled for the Sun too. Man, you could do a sight reduction in a couple of minutes!
Clendon D. |
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c_davidson |
The Sight Reduction process
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3 |
7,128 |
12-15-2015, 12:46 PM |
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Thread: Cleaning shades and mirror?
Post: Cleaning shades and mirror?
| The filters on my sextant are getting dirty/salty. What should I do to clean them?
How about cleaning the index mirror?
Is there any concern about scratching the filters or the mirror?
Clen... |
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c_davidson |
General Topics Here
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6 |
16,556 |
12-14-2015, 03:45 PM |
