NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Beginner's questions
From: Randall Morrow
Date: 2011 Oct 14, 08:18 -0700
Please help me with some questions I have regarding sights with an a.h.:
1) How much error can be introduced by the sextant NOT being held exactly vertical when doing a sight? I remember one article suggesting a tilt of a couple of degrees could introduce 7 miles of error. Is this a true figure?
2) With and a.h., you do not have the horizontal reference to help see the vertical orientation of the sextant. Also, the edge of the horizon mirror is not clearly visible in the dark so that reference to vertical is gone. Is there a technique to help in holding the sextant vertically that works with an a.h.?
3) Does it matter which eye you use to sight through a sextant? You have to hold the instrument with your right hand but I find I see better with my left eye. Does this affect observations?
4) I have noticed that I usually have to swing the bottom of the sextant to the left to get star reflections to appear as I slide the arm up and down to locate a star. This would be "rocking" in a counterclockwise direction I suppose. Also, when rocked in this manner the images become brighter and clearer, always to that same direction. I have tried moving my body around the a.h. mirror to get better orientation to the reflection but the trend is still the same, swinging the bottom out to the right gives brighter, clearer images that are easier to bring down. Is this related to the choice of eye or the way I am holding the instrument?
Thanks for your help.
Randall F Morrow PT
Senior Physical Therapist
Ergonomics Safety Consultant
Chronic Pain Program
Department of Physical Medicine
Kaiser Permanente - Kern County - Bakersfield
Phone: 661-852-3677 (Tieline - 378)
Fax: 661-852-3516 (Tieline - 378)
NOTICE TO RECIPIENT: If you are not the intended recipient of this e-mail, you are prohibited from sharing, copying, or otherwise using or disclosing its contents. If you have received this e-mail in error, please notify the sender immediately by reply e-mail and permanently delete this e-mail and any attachments without reading, forwarding or saving them. Thank you.
From: Randall Morrow
Date: 2011 Oct 14, 08:18 -0700
Please help me with some questions I have regarding sights with an a.h.:
1) How much error can be introduced by the sextant NOT being held exactly vertical when doing a sight? I remember one article suggesting a tilt of a couple of degrees could introduce 7 miles of error. Is this a true figure?
2) With and a.h., you do not have the horizontal reference to help see the vertical orientation of the sextant. Also, the edge of the horizon mirror is not clearly visible in the dark so that reference to vertical is gone. Is there a technique to help in holding the sextant vertically that works with an a.h.?
3) Does it matter which eye you use to sight through a sextant? You have to hold the instrument with your right hand but I find I see better with my left eye. Does this affect observations?
4) I have noticed that I usually have to swing the bottom of the sextant to the left to get star reflections to appear as I slide the arm up and down to locate a star. This would be "rocking" in a counterclockwise direction I suppose. Also, when rocked in this manner the images become brighter and clearer, always to that same direction. I have tried moving my body around the a.h. mirror to get better orientation to the reflection but the trend is still the same, swinging the bottom out to the right gives brighter, clearer images that are easier to bring down. Is this related to the choice of eye or the way I am holding the instrument?
Thanks for your help.
Randall F Morrow PT
Senior Physical Therapist
Ergonomics Safety Consultant
Chronic Pain Program
Department of Physical Medicine
Kaiser Permanente - Kern County - Bakersfield
Phone: 661-852-3677 (Tieline - 378)
Fax: 661-852-3516 (Tieline - 378)
NOTICE TO RECIPIENT: If you are not the intended recipient of this e-mail, you are prohibited from sharing, copying, or otherwise using or disclosing its contents. If you have received this e-mail in error, please notify the sender immediately by reply e-mail and permanently delete this e-mail and any attachments without reading, forwarding or saving them. Thank you.
