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Form- Longitude- meridian by equal altitudes

Hi

I have a Mark 15 plastic sextant and I want to buy a better one.. 
I've heard about Astra IIIb and Astra Professional... differences? what is the best?

Other tips are welcome!!!

Thank you
Alberto

We were sent a spreadsheet that's both an electronic ephemeris (the "Daily Pages" from the Nautical Almanac) and a sight reduction tool. 

It covers all navigational bodies and is very easy to use.  It even has the nice ° symbol.

There are 2 spreadsheet based versions;

- Excel in xlsx format

- Ods format- typically used with LibreOffice Calc

If you can't use either of those formats the excel file can be converted using this website- File conversion service


Complete Celestial Sight Reduction Excel Spreadsheet

Complete Celestial Sight Reduction Spreadsheet in ODS format



Clear skies,

CelNav57

Anybody want to talk about their experience in doing a Doniol sight reduction?

Do you HAV your Haversine tables?

Louis

Much to my delight I noticed Venus this morning at UTC 07:00

Rather than freezing outside a dish of water was placed on the window sill and I got 3 good sights of Venus.

Now if I had referred to this-

PHENOMENA, 2016- VISIBILITY OF PLANETS

...then I wouldn't have forgotten Venus was out there!


Louis

Remember ebook readers?  I've found that my old Kindle Wifi is perfect for putting The Nautical Almanac on.  Since the file is a PDF zoom in is necessary.  The advantage of using the Kindle (old clunker I guess you could call it) is that cold boot up time is about 5 seconds.  Just to "wake it up" takes about 2 seconds.  Battery drain is extremely low.  Using it for a few minutes per day the Kindle has enough power for several months of use.  It'll do a good job- until the batteries are now longer available.  Then we'll have to go back to...what?....paper and pencil?  What's that?

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.

Jojoba oil can be found in health food stores or fancier super markets.
An eye dropper can be used to apply the oil.  It seems to be pretty good and doesn't make the index arm stiff in the cold (below freezing).

(I've used WD-40 on a micrometer years ago and regretted it- it seized up after many months of non-use so I'm not taking any chances with my Astra III-B).

The Sextant handbook is a good book and I got it at our local library.

Clendon

TheNauticalAlmanac.com now has sight sight reduction forms for;

The Sun- using the ocean horizon

The Sun- using an artificial horizon

Stars- using the ocean horizon

Stars- using an artificial horizon

Stars- "quick method" using an artificial horizon based on HO-249 Vol. 1

Planets- using an artificial horizon

You can get them here;

Sight Reduction Forms

Please make suggestions or modifications to the forms that you might have.

The sun has a large apparent disc covering a big area. The lower limb has more atmospheric refractive bending than the upper limb. By the way, the bent light makes it look high, just like shooting at a fish with an arrow. With the lower limb appearing a bigger percentage higher than the upper limb, it makes the sun look flattened as it approaches the horizon.

So how have others been adjusting for the centerline of the apparent disc? Somewhere  between the upper limb and lower limb tabulated amounts, but not exactly half way which would not allow for the increased effect on the lower limb?

Heck, I'm not even sure how to figure the halfway point, which would at least be fairly close to correct. I added the two corrections, one is a negative number so I got a smaller negative number. Appears sensible but seems awfully easy, so I fear it may be wrong.

Anyone have any ideas or good/bad experiences?

Edit: I should have mentioned that I'm using a reflective artificial horizon.

We've just added the procedure for carrying out a Sun sight reduction while using the horizon. 

It is thorough with step-by-step instructions and plenty of pictures and examples. 

A Sun sight reduction form is included which is used in the described process.

The procedure also includes the plotting of the LOP.

This is perfect for the beginner who is having difficulty understanding how to carry out a Sun sight reduction, what documents are needed, where to get them.


Complete Sun Sight Reduction Procedure



CelNav57