Self Taught Celestial

[conachair]

A quick go on Opencpn came up with this... look about right from the numbers?

[scimitar]

Originally Posted by PCFithian

Scimitar, I greatly appreciate your work on this. However, I 'm not sure I understand your progression with the the corrections and determinations from there.

Can you explain a bit further?

[PCFithian]

OK, now I understand the corrections that were made in Scimitar's workup. But they should not be necessary, right, since:

1) The sextant was adjusted so that the index errorr was zero at the time of sight

2) There should be no dip correction, since I was using an artificial horizon

3) There should be no altitude correction for semi-diameter, since the sextant image and the artificial horizon image were merged together.

Am I missing something here?

I'm still trying to figure out how to get the Hc from the Kolbe's Long Term Almanac.

Conachair, the LOP near the bottom of Lake Michigan is exactly where I am. The other one is off a bit, but since these were the first two sextant readings I've ever taken, maybe not so bad.

I think I'm going to order one of the Davis Artificial Horizons to prevent wind effects on the surface of the water pan and get more practice at this.

[scimitar]

Originally Posted by PCFithian

OK, now I understand the corrections that were made in Scimitar's workup. But they should not be necessary, right, since:

1) The sextant was adjusted so that the index errorr was zero at the time of sight

2) There should be no dip correction, since I was using an artificial horizon

3) There should be no altitude correction for semi-diameter, since the sextant image and the artificial horizon image were merged together.

Am I missing something here?

I'm still trying to figure out how to get the Hc from the Kolbe's Long Term Almanac.

Conachair, the LOP near the bottom of Lake Michigan is exactly where I am. The other one is off a bit, but since these were the first two sextant readings I've ever taken, maybe not so bad.

I think I'm going to order one of the Davis Artificial Horizons to prevent wind effects on the surface of the water pan and get more practice at this.

I added index error from my sextant and dip is when I stand on deck of my boat ( 2.80m)



http://www.starpath.com/resources2/LTA_Instructions.pdf

Can you take Moon or Jupiter sight this evening and post sextant reading and time, I will do that as well, or star, let say Polaris. It is easy to find.


And why you are using it, download nautical almanac i correction tables from here

http://navsoft.com/downloads.html

download sight reduction tables from here

http://tinyurl.com/avqqnu9

You can print it if you like, I printed it and even made my own sight reduction tables. It cost me £5 in the ink

[SVTatia]

Originally Posted by Celestialsailor

...on second thought...maybe your GPS is not working all that well...You're an aircraft enthusiast that has navigated into a sailing forum.

+1 on that.

It seems fliers never understand the needs of a sailor because their lives depend on an engine being on 100% of the time.

[LJH]

Originally Posted by SVTatia

+1 on that.

It seems fliers never understand the needs of a sailor because their lives depend on an engine being on 100% of the time.

Perhaps you haven't tried gliding!

[Celestialsailor]

Originally Posted by goboatingnow

It took the combined efforts of the NSA, the Israelis and Siemens ( the makers of teh PLC in question) to load a 'virius' into it to shake the centrifuges to bits in Iran, in that they delayed them for about 40 days.

If someone loads a virus into a GPS satellite, firstly a large number of people are going to get fired in a certain underground bunker. and secondly since each satellite is independent they would have to affect all of them ( and then what about GLONASS).

Seriously a bus will drop on you head first, yet I dont see you building battle armour to handle that!!!..

Dave

I think I'll take Dave M's approach of " Wise sailors learn celestial for the same reason parachutists carry a reserve chute and for the same reason we have life rafts",
Than your bus analogy. One is based on fact, the other a hair brained speculation.

[GrowleyMonster]

You shiuld always check the index error and apply it. Many old school navigators set the index a minute off or on, to ensure that they did apply it and rhat it was applied in the right direction. If you check it for a round of sights and it is zero, add zero just to make it part of your routine to consider index error.

[PCFithian]

I found a good training tool for checking manual sight reductions, Sight Calc app for iPhone

[scimitar]

Originally Posted by PCFithian

I found a good training tool for checking manual sight reductions, Sight Calc app for iPhone

check this then...

[PCFithian]

Scimitar, the Sight Calc app on the iPhone yielded essentially the same results as yours.

I've got this pretty much figured out, now I am waiting on the artificial horizon to arrive and the clouds to go away. Good thing my DR position is not changing at this point!

In my opinion, Rodger Farley's treatise is the best resource to get started on this, posted here again for reference: Celestial Navigation

[PCFithian]

I was finally able to take some sights over the weekend, reduce to find Hc and Zn, and plot. I was within ~2 miles of my exact position for 3 sights, good enough for me on my first try. See attached plot sheet.

Another good reference for those learning celestial navigation is the USNO Celestial Navigation Data for Assumed Position and Time, which can confirm the results you develop:

Celestial Navigation Data for Assumed Position and Time

After additional practice with the sextant, including star sightings, I'll try to figure out the sight reduction using the Kolbe Long Term Almanac tables instead of the iPhone Sight Calc app.

[PCFithian]

Here's a sight form I worked out for using the Kolbe LTA and the iPhone app Sight Calc