Wrist watch that calculates DA
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Re: Wrist watch that calculates DA
I've not been able to find one myself.
I need to get a Kestrel I suppose.
I've not been able to find one myself.
I need to get a Kestrel I suppose.
Re: Wrist watch that calculates DA
Even if I knew of one I wouldn't count on it. Units that are close to the body can be effected by the body. Hold a Kestrel for a bit and watch the numbers move.
Id go with a Kestrel IMO.
Even if I knew of one I wouldn't count on it. Units that are close to the body can be effected by the body. Hold a Kestrel for a bit and watch the numbers move.
Id go with a Kestrel IMO.
Re: Wrist watch that calculates DA
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KNIGHT11B4</div><div class="ubbcode-body">Even if I knew of one I wouldn't count on it. Units that are close to the body can be effected by the body. Hold a Kestrel for a bit and watch the numbers move.
Id go with a Kestrel IMO.</div></div> That's definitely correct, watches pick up too much heat (or cooling) from the body. I will usually take my Casio Pathfinder off as soon as I arrive to the range to get an accurate temp. After 15 min it has an accurate temperature. I really need to just buckle down and splurge on a $3 thermometer though.
I don't know of any watch that does the DA calculation internally. However, using the barometer/thermometer in a Pathfinder, then matching it against the charts I keep in the databook it's pretty quick and easy.
For anyone wondering how to do it this way, read Lindy's article here:
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/ManualDA/
For anyone using an iPhone/iTouch, there's an app for that. I use DenAlt.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KNIGHT11B4</div><div class="ubbcode-body">Even if I knew of one I wouldn't count on it. Units that are close to the body can be effected by the body. Hold a Kestrel for a bit and watch the numbers move.
Id go with a Kestrel IMO.</div></div> That's definitely correct, watches pick up too much heat (or cooling) from the body. I will usually take my Casio Pathfinder off as soon as I arrive to the range to get an accurate temp. After 15 min it has an accurate temperature. I really need to just buckle down and splurge on a $3 thermometer though.
I don't know of any watch that does the DA calculation internally. However, using the barometer/thermometer in a Pathfinder, then matching it against the charts I keep in the databook it's pretty quick and easy.
For anyone wondering how to do it this way, read Lindy's article here:
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/ManualDA/
For anyone using an iPhone/iTouch, there's an app for that. I use DenAlt.
Re: Wrist watch that calculates DA
I have a Casio Pro-Trek that keeps a pretty accurate baro and temp providing that you give it a good reference and I use the same charts that Redmanns has. Body temp does affect temp readings but has minimal effect on baro.
I have a Casio Pro-Trek that keeps a pretty accurate baro and temp providing that you give it a good reference and I use the same charts that Redmanns has. Body temp does affect temp readings but has minimal effect on baro.
Re: Wrist watch that calculates DA
Update on this
The casio Pro-trek calculates DA and its pretty accurate for a freakin' watch. The trick is to give it a good standard day reference. A few days ago the baro was 29.90 at 60 degrees. I drove down to the river which is essentially at sea level and referenced the altitude feature to zero and baro, etc. I've checked it several times since then at varying temps and baro's and the altitude feature gives you altitude in DA. I verified this off an Adaptive Comsulting DA calculator and another chart.
You won't find this in the instructions for the watch but an altimeter that gives an altitude reading based solely on temp and baro, has to do so by giving DA, but you must zero the device at a known elevation on Standard day (59 deg @ sea level). I used 29.90 because the watch gives baro in .5 increments (and 60 degrees was close enough too).
I used this watch last weekend and nailed my 850 cold bore (with a rifle I'm not quite dialed in to yet) which is tough this time of year since the temperature/pressure changes are so drastic from early AM to mid-day.
The numbers aren't "NASA accurate" but neither are the existing charts and slide rules. This watch turned out to be a good find.
Update on this
The casio Pro-trek calculates DA and its pretty accurate for a freakin' watch. The trick is to give it a good standard day reference. A few days ago the baro was 29.90 at 60 degrees. I drove down to the river which is essentially at sea level and referenced the altitude feature to zero and baro, etc. I've checked it several times since then at varying temps and baro's and the altitude feature gives you altitude in DA. I verified this off an Adaptive Comsulting DA calculator and another chart.
You won't find this in the instructions for the watch but an altimeter that gives an altitude reading based solely on temp and baro, has to do so by giving DA, but you must zero the device at a known elevation on Standard day (59 deg @ sea level). I used 29.90 because the watch gives baro in .5 increments (and 60 degrees was close enough too).
I used this watch last weekend and nailed my 850 cold bore (with a rifle I'm not quite dialed in to yet) which is tough this time of year since the temperature/pressure changes are so drastic from early AM to mid-day.
The numbers aren't "NASA accurate" but neither are the existing charts and slide rules. This watch turned out to be a good find.
Re: Wrist watch that calculates DA
DA is calculated from: temperature, STATION pressure and humidity. Unless the watch measures humidity, it does not calculate DA.
DA is calculated from: temperature, STATION pressure and humidity. Unless the watch measures humidity, it does not calculate DA.
Re: Wrist watch that calculates DA
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugaboo</div><div class="ubbcode-body">DA is calculated from: temperature, STATION pressure and humidity. Unless the watch measures humidity, it does not calculate DA. </div></div>
I've calculated DA literally tens of thousands of times for 15 years . Before and during every flight (several times) and likely double that on the ground for engine performance runs and instrument calibration and I can assure you that DA can be calculated with a fair degree of accuracy without humidity or dew point in the equation. There are numerous charts that do not even factor in so much as a molecule of moisture.
Going further...the hygrometer in most hand-held devices (including kestral) are made from forged goat cheese in some obsure Chinese village.
Is it "true" DA without humidity? OK...sure...not.
BUT...Is your "true" DA any more accurate? Unless you can measure the different micro-climate layers present, in 1 foot increments across the ballistic arc of the round from take-off to touchdown...you're likely no closer to accuracy. You have to remember that there is no spoon.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugaboo</div><div class="ubbcode-body">DA is calculated from: temperature, STATION pressure and humidity. Unless the watch measures humidity, it does not calculate DA. </div></div>
I've calculated DA literally tens of thousands of times for 15 years . Before and during every flight (several times) and likely double that on the ground for engine performance runs and instrument calibration and I can assure you that DA can be calculated with a fair degree of accuracy without humidity or dew point in the equation. There are numerous charts that do not even factor in so much as a molecule of moisture.
Going further...the hygrometer in most hand-held devices (including kestral) are made from forged goat cheese in some obsure Chinese village.
Is it "true" DA without humidity? OK...sure...not.
BUT...Is your "true" DA any more accurate? Unless you can measure the different micro-climate layers present, in 1 foot increments across the ballistic arc of the round from take-off to touchdown...you're likely no closer to accuracy. You have to remember that there is no spoon.
Re: Wrist watch that calculates DA
It wasn't meant as an attack, just a side note.
I agree that unless you can get the DA along the entire flight path, you are working with a limited precision. The same is true for wind.
I also admit I never calculated DA by myself.
It wasn't meant as an attack, just a side note.
I agree that unless you can get the DA along the entire flight path, you are working with a limited precision. The same is true for wind.
I also admit I never calculated DA by myself.
Re: Wrist watch that calculates DA
BattleAxe, which model Pro-Trek do you have that calculates actual DA internally? I know they have altimeters, but I didn't know any of the Casio models computed anything other than barometric altitude, not density altitude. I'd definitely be interested in one if it did, but the Casio website makes no mention I could find of density altitude.
As a test I threw my Pathfinder PAW-1300T in the fridge, dropped it 30*F, and the altimeter actually read a 60ft increase in altitude so I know mine doesn't do it. Thanks.
BattleAxe, which model Pro-Trek do you have that calculates actual DA internally? I know they have altimeters, but I didn't know any of the Casio models computed anything other than barometric altitude, not density altitude. I'd definitely be interested in one if it did, but the Casio website makes no mention I could find of density altitude.
As a test I threw my Pathfinder PAW-1300T in the fridge, dropped it 30*F, and the altimeter actually read a 60ft increase in altitude so I know mine doesn't do it. Thanks.
Re: Wrist watch that calculates DA
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugaboo</div><div class="ubbcode-body">It wasn't meant as an attack, just a side note.
I agree that unless you can get the DA along the entire flight path, you are working with a limited precision. The same is true for wind.
I also admit I never calculated DA by myself. </div></div>
I didn't percieve it as an attack...I was just ranting
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugaboo</div><div class="ubbcode-body">It wasn't meant as an attack, just a side note.
I agree that unless you can get the DA along the entire flight path, you are working with a limited precision. The same is true for wind.
I also admit I never calculated DA by myself. </div></div>
I didn't percieve it as an attack...I was just ranting
Re: Wrist watch that calculates DA
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Redmanss</div><div class="ubbcode-body"> BattleAxe, which model Pro-Trek do you have that calculates actual DA internally? I know they have altimeters, but I didn't know any of the Casio models computed anything other than barometric altitude, not density altitude. I'd definitely be interested in one if it did, but the Casio website makes no mention I could find of density altitude.
As a test I threw my Pathfinder PAW-1300T in the fridge, dropped it 30*F, and the altimeter actually read a 60ft increase in altitude so I know mine doesn't do it. Thanks. </div></div>
Technically the Pro-Trek gives you pressure altitude(or absolute pressure/baro), not DA but the only real difference between DA and Pressure alt is humidity correction, which is something you can only measure at one exact altitude. Sounds meaningless but without much effort, particularly during this time of year you can actually see different/varying layers of humidity at ground level, particularly in the morning. Since a projectile travels in an arc that can be as high as 30-ish feet in the case of a .308 at distance, the projectile can travel through several different humidity layers, most of which you're not correcting for.
Putting your watch in a freezer is actually a bad simulation depending on the type of pressure sensor in the watch.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Redmanss</div><div class="ubbcode-body"> BattleAxe, which model Pro-Trek do you have that calculates actual DA internally? I know they have altimeters, but I didn't know any of the Casio models computed anything other than barometric altitude, not density altitude. I'd definitely be interested in one if it did, but the Casio website makes no mention I could find of density altitude.
As a test I threw my Pathfinder PAW-1300T in the fridge, dropped it 30*F, and the altimeter actually read a 60ft increase in altitude so I know mine doesn't do it. Thanks. </div></div>
Technically the Pro-Trek gives you pressure altitude(or absolute pressure/baro), not DA but the only real difference between DA and Pressure alt is humidity correction, which is something you can only measure at one exact altitude. Sounds meaningless but without much effort, particularly during this time of year you can actually see different/varying layers of humidity at ground level, particularly in the morning. Since a projectile travels in an arc that can be as high as 30-ish feet in the case of a .308 at distance, the projectile can travel through several different humidity layers, most of which you're not correcting for.
Putting your watch in a freezer is actually a bad simulation depending on the type of pressure sensor in the watch.
Re: Wrist watch that calculates DA
The key to getting the readings to be accurate is setting them to zero at a known point and good temp. Otherwise these things are way off generally. I have a PRG-50 and love it. I have played with it and check it against my Kestrel 4500nv
The key to getting the readings to be accurate is setting them to zero at a known point and good temp. Otherwise these things are way off generally. I have a PRG-50 and love it. I have played with it and check it against my Kestrel 4500nv
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