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» Online Classroom   »   » Public Discussion of Cel Nav   » Lunar distance using Stark's tables (Page 1)

 
This topic comprises 3 pages: 1  2  3 
 
Author Topic: Lunar distance using Stark's tables
navi


 - posted May 18, 2017 05:04 PM      Profile for navi           Edit/Delete Post 
Hello,

I have tried to calculate UTC using Stark's tables.

In his second work form he has this.

D-D#1 -->table 7 value
D#2-D#2->table 7 -value
and the value above is minus the value below. Finally that difference is put into table 8 to get the minutes which to add to the previous hour.

I made a Jupiter to Moon 13 of May at 4:43 UTC. My D-D#1 is less than D#2-D#2 so that difference getrs to be negative -0.3975 which is about 24 minutes.

If I deduct 24 minutes from 5 I get 4:36 UTC which is not crazy far from the true value 4:43.

Is it ok to do so?

(If D-D#1 would have been larger than D#2-D#2 I should have added according to his work sheet.)

From: Chi
navi


 - posted May 18, 2017 05:29 PM      Profile for navi           Edit/Delete Post 
Hi again,

Revising the sextant distance it seems it should read 64 6' and not close to 65. Uisng those numbers D-D#1 still is smaller than D#2-D#1 taking the difference and going to table 8 I get 42 minutes. If I add those to the previous hour I get 4:42 which is close to 4:43...

Please tell me the rules regarding of to add or subtract and how the D-D#1 and D#2-D#1 works.

Starl's book is not very explanatory.

From: Chi
Capt Steve Miller


 - posted May 18, 2017 08:37 PM      Profile for Capt Steve Miller           Edit/Delete Post 
Hello, I will look into this tomorrow morning.
From: Starpath
Capt Steve Miller


 - posted May 19, 2017 06:08 AM      Profile for Capt Steve Miller           Edit/Delete Post 
I have looked at your posting and what you did is correct.
As you have probably deduced the negative Table 8 result means that the observation occurred earlier than the time you recorded at the observation.
That is the reason you do not have to worry about a negative result.
Good work with your Lunar Distance observation. Your resulting UTC is very reasonable.

From: Starpath
navi


 - posted May 19, 2017 12:31 PM      Profile for navi           Edit/Delete Post 
Hi again,

I am not sure I really got it yet.

So Stark's method on work form two is based on previous hour and folloving hour.

Say I guess the time to be between 4 and 5 UTC -> previous hour is 4 and following hour is 5.

There is then two cases:
1. The situation Stark shows in his book:
D-D#1 -->table 7 value
D#2-D#2->table 7 -value
and the value above is larger than the value below so the differenme is positive. He then adds that the the previous hour, that is in my example I would add to 4 UTC.

The other case is that the difference is negative!

Should that negatoive value be deducted from the previous hour, that is deducted from 4 UTC or deducted from the following hour that is 5 UTC?!

From: Chi
Capt Steve Miller


 - posted May 20, 2017 06:08 AM      Profile for Capt Steve Miller           Edit/Delete Post 
First, I noticed that you have a typo in your post the line containing D#2-D#2->table 7 -value should read D#2-D#1->table 7 -value.
Since, you have set the outer limits of the UTC time when you subtract a negative number you would subtract it from the next hour. Subtracting it from the previous hour would put your resulting UTC outside your limits.
If for some reason your computed UTC is outside your limits you would have to change your limits and redo all your calculations. I have had this happen to me.

From: Starpath
navi


 - posted May 23, 2017 10:13 AM      Profile for navi           Edit/Delete Post 
Cap Steve,

So from what you have written I deduct that if it is:
+ I add to previous hour
- I take away from next hour

You also say that if it is outside the limits I need to recalculate the limits.

Does the amount of minutes indicate the new limits? Say I get + 75 minutes when my hours are 4 UTC - 5 UTC, does that mean I should recalculate with limits UTC 6 - UTC 7 ?

Is there anywhere where I can read about how the lunar method works in general and how Stark's method works in particular? As for now it is very "mechanciacal" for me just filling in numbers with not so much understanding.

From: Chi
David Burch


 - posted May 23, 2017 10:25 AM      Profile for David Burch           Edit/Delete Post 
Regarding the references part of the question:

Here is a discussion of the Stark method

http://www.starpath.com/catalog/books/StarkTables.htm

and here is extended discussion of lunars

http://reednavigation.com/lunars/

From: Starpath, Seattle, WA
Capt Steve Miller


 - posted May 23, 2017 08:44 PM      Profile for Capt Steve Miller           Edit/Delete Post 
You are mostly correct.
In your example of outside the limits with the +75 with 4 and 5 hours then the new limits would be 5 and 6 --- not 6 and 7. Since you have +75 you would add that to the 4 not the 5.

From: Starpath
navi


 - posted May 29, 2017 09:12 PM      Profile for navi           Edit/Delete Post 
Hello,

As you know I am using Stark's book. I am pretty much able to work with the second form, previous hour and following hour.

Still I struggle with his first form. I think he is too vague when it comes to calculated vs measured heights. The discription of the W.W table is minimal.

I am land locked and would like to be able to do Lunars WITHOUT a horizon. So if I have understod it right I can (somehow) calculate the heights and use the W.W table.

Can you please describe how to use W.W.

From: Chi
Capt Steve Miller


 - posted May 30, 2017 12:48 PM      Profile for Capt Steve Miller           Edit/Delete Post 
First of all I notice that you keep referring to the Stark Forms which I agree are a bit hard to follow.
It leads me to wonder if you have seen the article that I wrote for David's Blog (on the StarPath Home Page). I can be found by going to Previous Blogs and then Guest Blogs. I posted the article on 3 June 2014. In that article I explain line/box by line/box how to fill out my modified Stark Forms. The article has each cell in the Excel spread sheet numbered and those numbers are referenced in the explanation for filling out the Form. At the end of the blog there is an opportunity to download a copy of my Excel Spreadsheet.
This spreadsheet IS NOT INTENDED TO AUTOMATICALLY CALCULATE EVERYTHING. It is intended to be filled out using the Stark Tables. If you do allow edits on the Form you can fill it out on a computer and save the file. There are some cells in the spreadsheet that will automatically fill in data BUT it is data that has already been entered on the spreadsheet. In some cases the number in the cell may automatically be negative. This situation may be due to a value being subtracted from a smaller value. Thus the cell should be fixed so the value being subtracted is smaller that the value it is being subtracted from (ie. switch the order of the cells in the cell being calculated).
I think I have explained everything in the article. If you still have questions posting on this Forum will get an answer from me.

From: Starpath
navi


 - posted May 30, 2017 01:33 PM      Profile for navi           Edit/Delete Post 
Capt Miller,

I have seen those Excel sheets, they are probably good if you like that kind of electronic aid. Since I am doing celestial for "old school reasons" I do not like to use Excel (I even feel reluctant to an electronic calculator) and actually got a hand wound mechanical watch with watch error and all. If it is about efficiency I can buy a GPS and I do not need more than push a button or two.

I know this might sound weird but to even consider finding the time by Lunars some weirdness is needed.

I will prepare calculated heights using the Starfinder and the Almanac (USNO is kind of cheating since it is electronical )and the instructions from your article.

When I have the data filled in I will scan (Stark's first) form and post it here, so you can tell me if I am going the right way.

From: Chi
Capt Steve Miller


 - posted May 30, 2017 01:40 PM      Profile for Capt Steve Miller           Edit/Delete Post 
As I tried to indicated in my last posting the excel spreadsheet is not intended to be used as a spreadsheet. Simply print out copies of the Form and fill it out using my instructions. This should be easier to follow step by step than the Stark Forms.
You will not need to use the Stark Forms just use the printed Miller Modified Stark Form.

From: Starpath
navi


 - posted May 30, 2017 02:30 PM      Profile for navi           Edit/Delete Post 
Hi,

Just printed the form will go through your form and Starks form and get back to you.

From: Chi
navi


 - posted June 02, 2017 12:18 AM      Profile for navi           Edit/Delete Post 
Hello,

I have continued with the Lunars using Stark's forms as well as looked into your text describing your adaption as well as looked into Reeds online clearing method. I have several questions marked (A-E)

I made a measurement at DR 41deg 51' N, 87deg 39' W (Chicago) Between Jupiter and the far side of the Moon.

Using Stark's second from I get D#1 = 24deg 55.9' at 2h00m00s Reed at 2 UTC gives the true LD 24deg 55.9' i.e. the same (previous hour)

Using Starks form I get D#2= 24 deg 23.9' at 3h00m00s UTC and the true LD with Reeds online is also get 24 deg 23.9'.

I would then assume I have calculated D#1 and D#2 right. I.e D#1 and D#2 are true LD at 2 and 3 UTC respectively.

Question A: so it seems I got previous hour and following hour right, ok?

I measured at UTC 02h55m47s and I got DS= sextant angle= 24 deg 53' Since I have no horison I used Jupiter Hc, and Moon Hc at UTC 2 worked through Stark's first work form and got D= 24deg 36.3' so D-D#1 = - 19.6
D#2-D#1= -32.0

The negative signs appear because the distance is closing with increasing time. How should one handle this ?! I just took the minus sign away is that ok, that is question B? Any rules for this?
D-D#1= 19.6- table 7-> 1.0880
D#2-D#1= 32- table 7-Z 0.8751
subtraction--> 0.2129 then table 8 gives me 36 min 47 sec which is FAR from 55m 47s

If I key in just the UTC 2h55m47s and 24deg 53' in Reed's calculator and let it calculate the heights automatically I get true LD 24 deg 26.2' and cleared 24 deg 27.9' saying I am 1.7' in error meaning longitude error 51.1' (Capten Cook wrote one should be within 30' but that was Capten Cook!), That is the measurement is cleared in Reed's from 24 deg 53' all the way down to 24deg 27.9' so it gets close to true LD. Not only to 36.3 as when I do it manually using the Hc's. Question C: here seems to be the problem, ok?

Finally I key in the Sa and Ma (I use Hc Jupiter and applying W.W. ref from Stark's to get Sa ) and the Moon Ma (I use Hc Moon and using W.W. Moon and W.W. ref to get Ma ) both at UTC 2h00m00s in Reed's online form then I get from Reed's a cleared distance D of 24deg 36.1' which is far from the true LD but close to what I get using Stark's form number one for clearing namely 24deg 36.3! The error seems to come from the clearing using the Hc's! Reed also writes out a large height error for the Moon, about 7 degrees.

Question D: it seems tha Reed's online somehow calculates the heights right but using Stark and manually calculating heights at the previous hour introduces a large error when the measurement is closer to the following error, ok?

Question E: It seems like it is not possible to accurately calculate UTC without a true horizon or an artifical horizon since one need the correct Sa and Ma, correct?

From: Chi


All times are Pacific
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