Bottom Timer vs Dive Computer

[inquis]

If I need a redundant source of info to my main computer in case of emergency.

If within NDL, just end the dive. No second computer needed.

 

[tursiops]

If within NDL, just end the dive. No second computer needed.

The purpose of the 2nd computer is so you can do a repetitive dive afterwards.
If that is not a concern, then nothing is needed.

 

[TimTheDivenchanter]

thanks, all for the input. The consensus seems to be a second computer is better. I currently use GF 40/85 for my peregrine - which is the default. So I think the best way forward is finding a computer with the same algorithm so I don’t have different NDL/deco measurements. Will wait for a sale and maybe get another shearwater. And maybe till then add an analog depth gauge to my SPG.

 

[TimTheDivenchanter]

If within NDL, just end the dive. No second computer needed.

But if the computer failed and I have no way to know my depth then I need at least a depth gauge and maybe a watch?

 

[TimTheDivenchanter]

The purpose of the 2nd computer is so you can do a repetitive dive afterwards.
If that is not a concern, then nothing is needed.

I understand. My concern is. Computer fails and I wanna end the dive. I don’t have an accurate depth. Technically I can use the color shift underwater till I can almost see red. But for a night dive this doesn’t work. So if I need a safety stop I need a way to know depth. Especially at night. So another option is an analog depth gauge attached to my SPG and a watch (which can be also replaced by counting)

 

[inquis]

Computer fails and I wanna end the dive. I don’t have an accurate depth.

1. You're relying on your buddy in case your LP hose blows, right? Therefore, you should be able to rely on them for safety stop depth.
2. Most places you should be able to eyeball 15 ft to the surface. Or eyeball 10 ft. Another option is to tie a knot 15 ft down from your DSMB.
3. The safety stop is OPTIONAL. IF you were separated from buddy and IF vis was that bad and IF you lost your DSMB... a slow ascent (no faster than the tiny bubbles) all the way to the surface is within recreational diving guidelines.

 

[tursiops]

I understand. My concern is. Computer fails and I wanna end the dive. I don’t have an accurate depth. Technically I can use the color shift underwater till I can almost see red. But for a night dive this doesn’t work. So if I need a safety stop I need a way to know depth. Especially at night. So another option is an analog depth gauge attached to my SPG and a watch (which can be also replaced by counting)

The safety stop -- if you do one -- can be anywhere from 10-30 ft; it is not a fig deal. Shine your light up at the surface; your guess will be good enough. Tracking psi used is also a way to judge time; again, exactly 3 minutes is not critical. Spend 100 psi at your safety stop. Or, put up a DSMB with a marker (knot?) on the line at 20 ft. The point is in the very rare circumstance that your compuer fails on a night dive, you have perfectly doable alternatives.
But a spare computer is better....
The Deep6 Excursion might be your cheapest GF-settable backup.

 

[TimTheDivenchanter]

1. You're relying on your buddy in case your LP hose blows, right? Therefore, you should be able to rely on them for safety stop depth.
2. Most places you should be able to eyeball 15 ft to the surface. Or eyeball 10 ft. Another option is to tie a knot 15 ft down from your DSMB.
3. The safety stop is OPTIONAL. IF you were separated from buddy and IF vis was that bad and IF you lost your DSMB... a slow ascent (no faster than the tiny bubbles) all the way to the surface is within recreational diving guidelines.

These are great suggestions. The SMB one specifically. I will tie a knot at 15ft

 

[TimTheDivenchanter]

The safety stop -- if you do one -- can be anywhere from 10-30 ft; it is not a fig deal. Shine your light up at the surface; your guess will be good enough. Tracking psi used is also a way to judge time; again, exactly 3 minutes is not critical. Spend 100 psi at your safety stop. Or, put up a DSMB with a marker (knot?) on the line at 20 ft. The point is in the very rare circumstance that your compuer fails on a night dive, you have perfectly doable alternatives.
But a spare computer is better....
The Deep6 Excursion might be your cheapest GF-settable backup.

Yeah. Great suggestions. Thanks

 

[mrdee]

I understand. My concern is. Computer fails and I wanna end the dive. I don’t have an accurate depth. Technically I can use the color shift underwater till I can almost see red. But for a night dive this doesn’t work. So if I need a safety stop I need a way to know depth. Especially at night. So another option is an analog depth gauge attached to my SPG and a watch (which can be also replaced by counting)

Another option is any of the current crop of smart watches with dive functions. Take your pick from Suunto, Apple and Garmin.

The Apple Watch Ultra is unique in requiring a subscription to the oceanic app to function as a fully fledged drive computer with Buhlmann ZHL-16C algorithm. Otherwise it functions as a depth gauge/timer out of the box