Pegasus Power Box Advance - can it power my mount?

[Richard_]

I had often read that during a slew, the mount will draw more current than when tracking and if the mount is powered by devices such as the ASI Air and Pegasus Power Boxes with an inadequate power supply, that the voltage would drop and lead to issues such as devices disconnecting or dropping frames from the camera. I decided to test this for myself using data recorded by the Pegasus Power Box and thought I would share my testing and results in case this helps others who may have the same question.

My Pegasus Power Box Advance (PPBA) v2 is powered using Pegasus' recommended power supply (10A @ 12V DC) which is a good quality power supply that provides current in excess of my requirements. The following devices were connected to the PPBA:

• QHY268M -> cooling set to -5C (~24% power usage to reduce from ambiet temperature 11C)
• OTA dew heater -> set to max in Pegasus Unity app
• Guide scope dew heater -> set to max in Pegasus Unity app
• Beelink U59 mini-PC powered and switched on
• EQ6-R pro powered on

I allowed sufficient time for the camera to achieve the desired cooling setpoint and stabilise, and for the dew heaters to reach temperature. I did not include filter changes (QHYCFW3) or focus adjustments (Pegasus Focus Cube v2) during my testing as these are normally performed when the telescope is tracking and not during a slew, and these are expected to draw far less current than a telescope slew. I tested the mount in different phases (parking, tracking, slewing in DEC, RA and then parking by slewing both) to see what happened to the voltage and current, as recorded by the PPBA and exported from the Pegasus Unity software. These phases are colour coded and annotated in the graph below which records voltage (V) and current (A) each second. The key observations were:

• Voltage remained constant at 12.8V, it did not drop at all
• Peak current was measured as 5.3A

In summary, having a good quality power supply which provides current in excess of your requirements is essential for avoiding voltage dips. Furthermore, you should be able to safely power and use a mount from a PPBA if you use a good quality power supply. Testing was performed during ambient daytime conditions (11C) as I've not yet had the chance to verify this over a full imaging session or in the cold. However, if my voltage did not drop under the worst case current draw, I don't know if I'd expect to see anything different during an imaging session.

Questions, comments and your experience are welcome!

 

 

Edited February 5 by Richard_
Correct typos

[PhilB61]

Good information and interesting, I wonder how much additional current is drawn in warmer ambient temps or if cooling to a lower temperature, I guess the CMOS cooler could be the highest current drain.

[SteveNickolls]

Hi, thanks for posting your observations using the Pegasus unit. I have the smaller brother unit the Pocket Box Micro which has powered the whole rig-the GEM28, main camera (ASI533MM-Pro), two dew heaters (for Samyang lens and guide scope) and StarTech USB over Ethernet hub. The unit is powered by the Pegasus mains adapter that you also use. I check and record the number of Watt hours and Amp hours drawn during sessions and while obviously the amount of electricity used varies mainly due to the weather conditions the greatest draw I have recorded was of 114 WHr/8Ahr when the outside temperature was -2.3C this winter. You do see a slight increase in output during slewing but that is very a small part of a multi-hour imaging session. The Pegasus unit copes very well and is rock solid in output.

Cheers,
Steve

[KevinM]

Hi Richard, 

Just checking, are you using the genuine Pegasus PEG-PSU-21 Power supply unit?

Cheers,

KevinM (Perth)

[Richard_]

21 minutes ago, KevinM said:

Hi Richard, 

Just checking, are you using the genuine Pegasus PEG-PSU-21 Power supply unit?

Cheers,

KevinM (Perth)

Correct

https://www.rothervalleyoptics.co.uk/pegasus-12v-mains-10ah-power-supplies.html