NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: planned purchase astra IIIB
From: Greg R_
Date: 2007 Jan 28, 11:27 -0800
----- Original Message -----
From: coralline algae
To: NavList@fer3.com
Sent: Sunday, January 28, 2007 10:51 AM
Subject: [NavList 2137] planned purchase astra IIIB
The astra iiib at approx 500 us looks affordable. If I buy from west marine, I will get a discount and can use a gift certificate.
Upon delivery what should I look for to insure that there are no major problems with the instrument.
Also not to start any big discussion but I was reading an article that recommends against
the horizon mirror as being hard to use with stars.
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From: Greg R_
Date: 2007 Jan 28, 11:27 -0800
> Upon delivery what should I look for to
insure that there are no major problems with the instrument.
I would check to make sure it was packaged securely for shipment (i.e. double-boxed, etc.) and that there was no damage to the packaging in transit. Other than that, the Astras are very well-made and about the only other thing to do that I can think of would be to check/adjust the mirrors for perpendicularity, side error and index error. I bought mine used on EBay, and after doing the alignment checks I'm usually getting accuracies around 1-2 NM (against a known GPS position).
> I was reading an article that recommends against
> the horizon mirror as being hard to use with stars.
I would check to make sure it was packaged securely for shipment (i.e. double-boxed, etc.) and that there was no damage to the packaging in transit. Other than that, the Astras are very well-made and about the only other thing to do that I can think of would be to check/adjust the mirrors for perpendicularity, side error and index error. I bought mine used on EBay, and after doing the alignment checks I'm usually getting accuracies around 1-2 NM (against a known GPS position).
> I was reading an article that recommends against
> the horizon mirror as being hard to use with stars.
Assuming you mean "whole horizon mirror", I'd
agree - it's not really "harder" to use with star sights, it's just that the
trade-off with a whole-horizon mirror is that you lose a lot of light through
the beam converger (I heard somewhere that it's about a full f-stop) vs. a
split-mirror, and as the sky gets darker you start to lose the horizon through
the sextant even though you can still see it plainly with your eyes. But you can
always buy a split-mirror from Celestaire and then you'll have the best of both
worlds (changing and aligning the mirrors is really easy - they attach with 2
screws, takes 5 minutes at most).
--
GregR
----- Original Message -----
From: coralline algae
To: NavList@fer3.com
Sent: Sunday, January 28, 2007 10:51 AM
Subject: [NavList 2137] planned purchase astra IIIB
The astra iiib at approx 500 us looks affordable. If I buy from west marine, I will get a discount and can use a gift certificate.
Upon delivery what should I look for to insure that there are no major problems with the instrument.
Also not to start any big discussion but I was reading an article that recommends against
the horizon mirror as being hard to use with stars.
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
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