Sextant...

[SkiprJohn]

I have an Astra IIIB that I bought from a friend who was not going sailing any more. I paid $200 for it and it had one flaw. It had never been used but he had put batteries in it for the illumination and never taken them out therefore there was lots of corrosion in the battery box.
Bargains are out there. Just need to shop around. If the price had been much higher I would not have gotten it and would have just held onto my Davis Mk 25 or one of my old Mk 15s. When new my Mark 25 was $125 so you can estimate in what year I bought it.

[RBEmerson]

At least with a Plath artificial horizon, shooting with a bubble is not something for a small boat under way. Chasing the bubble makes herding cats or nailing jelly to the wall seem easy.

[RBEmerson]

Originally Posted by alan2

RBEmerson:
Wasn't the Navistar a combination sextant/calculator/computer, all in one unit mentioned by the late William Buckley in one of his sailing books? If memory serves, he mentioned the Navistar or something by the Plath people. I think he also made mention of HP software and a navigational calculator with navigation software that loaded into the old HP 65. Fine when it woked, but he supposedly had problems with one he had bought.

I have a copy of "C. Plath - 1837 - 1987" (a company produced history of C. Plath) and the Navistar Professional with a built in calculator (no idea if there were angle sensors or timing functions in it - I suspect not, but that's a guess) is included in the illustrations. However, there was also a "non-calculator" Navistar Professional and that was available for sale. There was one on eBay recently -auction just ended. ( LINK to completed auction) It's worth looking at this sextant in detail and comparing it with the traditional Plath. Check out the filters, for example.

Dunno about WFB and a Navistar. A quick flip through Atlantic High shows him using a traditional sextant but talking about a Plath [sic] Navicomp and there's a photo of same. This appears to be a competitor to the Tamaya NC-77. At any rate, WFB seems to like his HP41C over the Navicomp. A thorough reading of the book may, of course, show otherwise.

You slso noted : I hear you on the artificial horizon issue. And not much call for bringing the sun down to the horizon while rafting down the Monongahela, is there?

Not much call for celestial navigation whilst on the Mon, or likely most other rivers either. As I had mentioned, the artificial horizon is most always a PRACTICE DEVICE, handy for those removed from that sea horizon or largfe laks, which might do too, something with which one might "keep their hand in". If the practice becomes overly complicated, it could become "offputting". I seem to have read something somewhere about the following. During Desert Warfare in WW2, both Rommel and the British, who had units running about in the desert might well have used "Celestial Navigation" , sun and or moon shots, taken with something similar to the Davis apparatus (a dish of liquid, likely oil) to find and chart their locations, for that hoped for return to base. They likely also used "dead reckoning" and 60D=ST too, recording compass headings, speeds and time, woirking with such maps/charts as might have been available.

Mea culpa, mea culpa, mea maxima culpa. I was being facetious in my comments and nothing more - my error for not making that clear.

Agreed that there is real value in using a sextant on land. And, hey, if that's the only option for keeping one's shooting skills from rusting or from learning the skills of shooting in the first place, by all means, go for it!

I will forward my question about the PBH to Celestaire, for their consideration, worst that can happen is they won't bother.

It may be just as effective to call, come to think of it. I suspect they get a host of e-mails of a similar nature; a call's a little harder to lose in the "mail queue".

[RBEmerson]

For anyone interested in the Bobby Schenk books mentioned earlier (Navigation zum Ankommen and Astronavigation), I browsed Amazon and was surprised to see listings for both books, albeit from associated "stores" and not from Amazon directly. Prices run in the low $20 range each. I also tried ABEBooks but found most listings (surprise) were in Germany. I did find Navigation zum Ankommen for $22 from a dealer in San Jose, CA (and someone asking $83!!!) but nothing for his celestial nav books.

[alan2]

SkiprJohn:

Small flashlights and batteries therefore are real cheap, and besides, with sun shots and sometimes moon shots too, you are shooting in daylight. I bought a Davis Mark 15 with the no longer made level device, which eliminates "rocking" the sextant. Paid about $110 including shipping. No problems with the instrument, other than those inherent to plastic sextants, wandering index error. Yes, one can sometimes find a deal.

[alan2]

RBEmerson:

Can you imagine a soldier climbing out of a tank in the middle of the desert, pouring some oil into a small dish and then doing sun shots? One does/did what was necessary and or appropriate.

Re Mea culpa, mea culpa, mea maxima culpa. I was being facetious in my comments and nothing more - my error for not making that clear, no apology necessary, my leg has been pulled before.

Re contacting Celestaire, I spoke with Ken Gephardt Monday morning. Nice of him to take the time to explain the thing, which I believe got through my thick head. I e-mailed him my understanding of his explaination, asking for confirmation, or correction should I have missed anything. The biggest problem with the PBH, as I had mentioned is holding the bubble level with the reference line while bringing the sun down to the "horizon". Ken says it's akin to "getting to Carnegie Hall", practice, practice, practice, which btw seems to be the case.

The following reflects my understanding of Ken's explaination, in case you are interested.


1. One takes several sets of sun shots, individual shots spearated by sufficient time to get a decent angle between lop's. This could involve taking sights on 2 consecutive days, depending on time of year, and when one starts..

2. Reduce the sights and plot the lines of position obtained, this mentiond in instructions.

3. Measure the distances between the calculated position plots and plot of Known Position. Take their numerical average. Convert nautical miles to minutes of arc, 1 minute of arc = 1 nautical mile.

4. Subtract the number of minutes obtained from sextant reading.

5. As the PBH has zero magnification, figure that the sun shots you took are mid body. Apply the SD correction, subtracting it from sextant reading after correcting sextant reading using lower limb sun data from table A2 in Nautical Almanac.We will now have subtracted twice from sextant reading, once as per items 2 and 3, the second subtraction as per item 5. Having now obtained the BC, one writes the damned thing down so as not to loose it.

When I clicked on the link you provided, I got the following error message.

Internet Explorer cannot display the webpage


Most likely causes:

• <LI id=causeNotConnected>You are not connected to the Internet. <LI id=causeSiteProblem>The website is encountering problems.
• There might be a typing error in the address.

What you can try:

[IMG]res://ieframe.dll/bullet.png[/IMG] Diagnose Connection Problems

[IMG]res://ieframe.dll/down.png[/IMG] More information


This problem can be caused by a variety of issues, including:

• <LI id=errorExpl2>Internet connectivity has been lost. <LI id=errorExpl3>The website is temporarily unavailable. <LI id=errorExpl4>The Domain Name Server (DNS) is not reachable. <LI id=errorExpl5>The Domain Name Server (DNS) does not have a listing for the website's domain.
• If this is an HTTPS (secure) address, click Tools, click Internet Options, click Advanced, and check to be sure the SSL and TLS protocols are enabled under the security section.

For offline users

You can still view subscribed feeds and some recently viewed webpages.
To view subscribed feeds

1. Click the Favorites Center button [IMG]res://ieframe.dll/favcenter.png[/IMG], click Feeds, and then click the feed you want to view.

To view recently visited webpages (might not work on all pages)

1. <LI id=viewRecentWebpages2>Click Tools [IMG]res://ieframe.dll/tools.png[/IMG], and then click Work Offline.
2. Click the Favorites Center button [IMG]res://ieframe.dll/favcenter.png[/IMG], click History, and then click the page you want to view.

Strange, isn't it?

[RBEmerson]

Originally Posted by alan2

RBEmerson:

Can you imagine a soldier climbing out of a tank in the middle of the desert, pouring some oil into a small dish and then doing sun shots? One does/did what was necessary and or appropriate.

Oy, mate! Keep yer 'ead down!

Re Mea culpa, mea culpa, mea maxima culpa. I was being facetious in my comments and nothing more - my error for not making that clear, no apology necessary, my leg has been pulled before.

Duly noted.

Re contacting Celestaire, I spoke with Ken Gephardt Monday morning. Nice of him to take the time to explain the thing, which I believe got through my thick head. I e-mailed him my understanding of his explaination, asking for confirmation, or correction should I have missed anything. The biggest problem with the PBH, as I had mentioned is holding the bubble level with the reference line while bringing the sun down to the "horizon". Ken says it's akin to "getting to Carnegie Hall", practice, practice, practice, which btw seems to be the case.

The following reflects my understanding of Ken's explaination, in case you are interested.


1. One takes several sets of sun shots, individual shots spearated by sufficient time to get a decent angle between lop's. This could involve taking sights on 2 consecutive days, depending on time of year, and when one starts..

2. Reduce the sights and plot the lines of position obtained, this mentiond in instructions.

3. Measure the distances between the calculated position plots and plot of Known Position. Take their numerical average. Convert nautical miles to minutes of arc, 1 minute of arc = 1 nautical mile.

4. Subtract the number of minutes obtained from sextant reading.

5. As the PBH has zero magnification, figure that the sun shots you took are mid body. Apply the SD correction, subtracting it from sextant reading after correcting sextant reading using lower limb sun data from table A2 in Nautical Almanac.We will now have subtracted twice from sextant reading, once as per items 2 and 3, the second subtraction as per item 5. Having now obtained the BC, one writes the damned thing down so as not to loose it.

Yikes! I think I'd rather do my sights at sea! Er, on point 5., it's not the magnification (or lack thereof) that makes these mid-body sights, it's that the object is centered on the bubble. In effect, by bracketing the sun's image in the middle of the bubble, it's the same as putting the middle of the sun on the horizon. With the sun or moon and a real horizon, putting a limb (upper or lower) on the horizon is more accurate (solid edge of limb on solid edge of horizon). Of course, toss clouds and haze into the picture and... surprise! things get hazy.

When I clicked on the link you provided, I got the following error message.

Um, er, yes, well... I thought I was copying a live eBay link but I guess not. Anyway, use the "advanced search" tool to look for completed auction 280298072915
That should do the trick.

[alan2]

RBEmerson writes:

Yikes! I think I'd rather do my sights at sea!

I'd rather do mine stading on the beach, it's ever so much more stable. Artificial horizons are, as their name states, artificial.

I will try the link to completed auction. It's academic anyhow, as this particular auction is history.

Best.

[Sam Plan B]

I recall the Navistar as a largish pocket calculator with primitive (for its time) memory capabilities. One inserted magnetic plastic strips into it. The navigation data was stored on the plastic strip. Buckley found that the algorithm was not correct and went through some back an forth with the manufacturer. You can probably pick one up for peanuts these days.

[RBEmerson]

The auction link was for the illustration only. The auction was already over by the time I posted the original link.

I don't now about a strip reader for the Navicomp (Navistar is the sextant line - C. Plath had a host of Navi[something]s in the product line, including a Navigat [gyrocompass], Naviglobe, and Navisat [pre-GPS satnav systems] - interestingly, the German colloquial term for a GPS in a car is a "navi" - go figure). At least WFB doesn't mention it although he does go on about the "iron lung" or charger needed for the unit. TI, however, did have a mag strip reader in some of its calculators, and then moved on to chips in the TI-58, etc.

I suspect prices for this gear would surprise you. Although, in digging around, it seems the Tamaya NC77 ephemeris expired in June 2007 (a 30 year run) with no hope of an update. There is the NC-2100G based on an HP iPaq handheld computer/PDA. Celestaire list the 2100E for "under $1K" - kinda spendy, IMHO.

Curiously, Landfall lists the Celesticomp V (Sharp programable calculator) although it's marked as "no longer available". I have one of these and it's generally not a bad device but... it has one programming flaw which at least I find very questionable: it will not advance LOP's from the previous day. I found this out when advancing evening stars from day 1 to morning stars on day 2. If the data from day 1 is over 12 hours old, it's treated as from day 2 without warning. Not Good.

Landfall also lists StarPilot which has been hosted on a number of TI calculators. I recommend taking a look at the original StarPilot site, too (prices are the same, BTW).

DISCLAIMER: I have no connection with Tamaya or Landfall at all. My sole connection with Celesticomp, Celestaire, and Texas Instruments is as a customer. I have done beta testing for StarPilot and have received compensation for that effort, but have no other connection with StarPilot.

[RBEmerson]

Alan2 asked about non-HP RPN calculators (WFB goes on about the HP-41C), trying to recall the name of one tied to a semiconductor maker. In fact, that's half the name: National Semiconductor (AKA Novus). For more non-HP RPN calculators, see this link.

[btrayfors]

Haven't really been following this thread closely, but a couple of things twigged my interest, notably, the mention of HP RPN calculators used for navigation.

I wrote some of the navigation programs for the HP-65 calculator...way back when! This was a marvelous new thing, and cost only about $850!! I bought one of the first ones when I was stationed in Nepal in the early 1970's. Used it for business and for navigation for years. The little magnetic strips containing the programs were always a problem, mainly because they were easily dropped and with repeated use the magnetic strips wore off.

Anyway, the next HP RPN calculator I bought for navigation was the HP-42S. A really big improvement over the HP65. I still have two of them...one at home and one on the boat. I wrote some navigation programs for this calculator, too, including:

NAV-02 Latitude by Meridian Transit (Noon Sight)*
NAV-03 Longitude by Meridian Transit*
NAV-04 Dead Reckoning
NAV-05 Sun: Sight Reduction*
NAV-06 Great Circle Distance
NAV-07 Course Steered
NAV-08 Visibility
NAV-09 Distance by Vertical Angle
NAV-10 Horizontal Angle Fix
NAV-11 Running Fix

Would be happy to share these with anyone interested.

Saw an HP-42S currently on eBay...bidding up to $61 already. Guess they're not giving these away these days :-)

Cheers,

Bill

[alan2]

RBEmerson:

Re your reference to National Semi-Conductor, that sounds very much like the company whose name I coulodn't remember. Thanks

Re the HP-65, one "fed" programs into the thing via plastic strips, of which there was, I believe, a significant library covering various branches of engineering. I would be surprised if they hadn't had something on celestial navigation.

As I recall, I had somewhere seen offered for sale or auction the Celestecomp by Sharp, described as "obsolete" though highily touted by some commentators, possibly they had an interest in the sale.

[RBEmerson]

A friend worked for "NationalSemi" and I remember playing with one of Bruce's RPN calculators (might even have owned one but doubt it). Speaking of which, anybody ever play with an HP-1? I owned one briefly, a couple of years ago, but came to my senses and sold it to someone who didn't care that it was a battery eater that wasn't waterproof and had to be cajoled into showing the time of day.

I'd forgotten about the HP mag strips but you're quite right about them. This was in the era when a decent cassette recorder made an acceptable "tape drive" for a "microprocessor", usually built around a manufacturer's demo system (KIM-1, anybody?).

Aside from that problem with advancing old LOP's (a practice which, in all fairness, is somewhat debatable), the Celesticomp is actually a rather nifty little gizmo. I still have mine and feed it batteries regularly to keep the program alive. If somebody offered me one, I'd be happy to have it.

[alan2]

RBEmerson:

Re the link in your post #56, I had no idea that there were that many RPN calculators, thinking that it was almost exclusively, National Semiconductor being an exception, HP. One lives and one learns.