David's Astronomy - Notes 2019-02-13 (S00663)

Under automated operation the Shutter was commanded to open at 18:18:37 (this was some 10 minutes before the starting time for the nights Observing Plan). The process of opening the shutter normally takes 45-50s. However upon checking the session over a remote connection at around 19:00 it was noted that the plan session hadn't started the observing plan. Checking showed that the session hadn't progressed through the dome equilibration phase and was seemingly still waiting for the shutter to finish opening. Shutter status field in AstroMain and POTH.HUb showed the shutter was still 'Opening'. The shutter was manually commanded to close which it duly did in a normal time of 45s.

The observatory was visited and the the shutter system observed whilst it was opened. On reaching the Open Limit Switch there seemed to be a bit of hiccup and the motor stopped (I think, but I might have intervened). Checking the wires to the Shutter Drive Unit showed them to be somewhat disturbed and the plug that comes from the upper relay switch was partially pulled out from it's port. The plug was reinserted and the wires tidied up. The observatory dome was then operated ok for the remainder of the session include a further close / open operation and a final close operation at the end of the session.

It would seem that the wires to shutter unit became pulled loose when passing one of the dome clamps during the last session which had pulled the relay plug from its port.

As per a previous incident involving a probable short circuit in wires going to the lower relay switch, the shutter drive motors continue turning as the relay failed to tell the system that the open/close operation has completed. Examining the shutter units battery level records showed that it dropped from 97% down to 85% and voltage dropped from 15.0v down to 14.6v. Temperature Sensor reading jumped from 10° C to 20° C during the incident. 16 hours later the battery has still not started to recharge itself.

It then became clear why there was no recharging ... Upon checking the observatory the following afternoon it was discovered the two- wire charging cable for the shutter drive unit was wrapped around one of the dome clamps, one end had been ripped from its metal male plug (which was still inserted in the shutter drive unit) whilst the other end had been ripped out of the upper induction charging box. There seems to have been no damage to the shutter drive unit or induction charger themselves. It is presumed that the damage was done during the previous session and at the same time that the plug from the upper relay switch was pulled loose. (whilst relay wire & plugs were looked just after the Shutter Opening Issue, it was dark and this probably explains why the broken cable was noticed). After contacting Pulsar Observatories the induction charger box was removed and it and the cable sent to them by mail for repair.

Actions :

Improve the security and fixing of the cabling/wires to Shutter Drive Unit. Need to ensure that cables can't work loose and get snagged or pulled when passing the 4 dome clamps.
Cable/wires reviewed and their fixings were upgraded to try to prevent a re-occurance of the problem.
>> Need to check cables/wires on a regular basis
Check Shutter Chain for possible damage. Also check shutter chain tension.
Done 2019-01-14
Perform realtime checking of Shutter Opening / Shutter Closing times versus expected time.. If shutter opening takes longer than normal, an alert is raised and an interventation made to close the shutter.
Added 2019-01-15 (AstroMain 3.9.2)
Monitor Shutter's Battery charging over the next few days
Done 2019-01-15 (>> Shutter Battery Health Charts)
(as it turned out battery charging became out of action due to damage to the charging cable)
Contact Pulsar Observatories regarding the incident. The firmware show really pick up that motors have been running far longer than a normal operation and should stop.
Email sent to Pulsar Observatories technician
Repair damage & replace charging cable . Induction Charger and its broken cable were sent to Pulsar Observatories on 2019-02-15 for their repair
Induction charger with new wire has come back from Pulsar Observatories and has been refitted in the observatory (2019-03-xx)

Dome Shutter Health Charts showing impact of the incident
(incident time 2018-02-13 18:18 to 19:00)

Selected Focus Profiles from Session

FWHM and HFD V Slope Focusing Compared
a) Case with well performing HFD Method (11 steps different)

Focusing prior to Target 7, GCVS TZ Cas
Focus Star Mag +7.2, Focus Frame Exp. 1s, 1x1 binning, Temp 7.1 C

Best Focus 1491 (FWHM), Total Time 2.7 mins (Profile 1)
Best Focus 1480 (HFD), Total Time 1.6 mins (Focus No 1)

FWHM and HFD V Slope Focusing Compared
b) Case with poorly performing HFD Method (189 steps different)

Focusing prior to Target 9, GCVS Z And Tau
Focus Star Mag +xx Focus Frame Exp. 1.5s, 2x2 binning, Temp. 6.6 C

Best Focus 1557 (FWHM) , Total Time 3.0 mins (Profile 2)
Best Focus 1368 (HFD), Total Time 1.9 mins (Focus No 2)

FWHM and HFD V Slope Focusing Compared
c) Case with very poorly performing HFD Method (189 - 872 steps different !)

Focusing prior to Target 9, XO-2
Focus Star Mag +xx Focus Frame Exp. 2s, 2x2 binning, Temp. 6.8 C

Best Focus 1531 (FWHM) , Total Time 3.1 mins (Profile 3)
Best Focus 659 (HFD), Total Time 2.0 mins (Focus No 4) - target before
Best Focus 1102 (HFD), Total Time 1.9 mins (Focus No 5) - target before

FWHM and HFD V Slope Focusing Compared
d) Case with poorly performing HFD Method (183 steps different !)

Focusing prior to Target 16, GCVS SU Tau
Focus Star Mag +xx Focus Frame Exp. 1.5s, 2x2 binning, Temp. 6.6 C

Best Focus 1426 (FWHM) , Total Time 2.8 mins (Profile 4)
Best Focus 1243 (HFD), Total Time 2.0 mins (Focus No 6)

FWHM and HFD V Slope Focusing Compared
e) Case with moderately performing HFD Method (155 steps different !)

Focusing prior to Target 18, GCVS RR Tau
Focus Star Mag +xx Focus Frame Exp. 1s, 2x2 binning, Temp. 7.1 C

Best Focus 1385 (FWHM) , Total Time 2.6 mins (Profile 5)
Best Focus 1230 (HFD), Total Time 1.7 mins (Focus No 7)

FWHM and HFD V Slope Focusing Compared
f) Case with poorly performing HFD Method (202 steps different !)

Focusing prior to Target 23, GCVS FO Ori
Focus Star Mag +xx Focus Frame Exp. 1s, 2x2 binning, Temp. 7.1 C

Best Focus 1219 (FWHM) , Total Time 2.6 mins (Profile 6)
Best Focus 1017 (HFD), Total Time 1.7 mins (Focus No 11)

Focus Offsets for FWHM Profile and HFD- VSlope Methods compared
FWHM measurement are much more consistent and known to be of better quality.

Issues


	Session Aims & Highlights
	- Observing Result - Night Summary Plot - Session Event Log

	Operational Issues
	- Critical Issues (2), Major Issues (1), Minor Issues (1), Continuous Improvement (0)

	Investigation - Shutter Drive Unit didn't detect that Shutter had finished opening
	Autofocussing - FWHM Profile & HFD V-Slope Comparison

	Images from 2019-02-13 >>

This Web Page:	Notes - Session 663 (2019-02-13)
Last Updated :	2023-11-26
Site Owner :	David Richards
Home Page :	David's Astronomy Web Site

David's Astronomy Pages
Notes - Session 663 (2019-02-13)

Session Aims & Highlights (2019-02-13)

Operational Issues (2019-02-13, S663)

Investigation - Shutter Drive Unit didn't detect that Shutter had finished opening (motors ran on for up to 40 minutes)

Autofocussing / HFD Profiles

David's Astronomy Pages Notes - Session 663 (2019-02-13)

Session Aims & Highlights (2019-02-13)

Operational Issues (2019-02-13, S663)

Investigation - Shutter Drive Unit didn't detect that Shutter had finished opening (motors ran on for up to 40 minutes)

Autofocussing / HFD Profiles

David's Astronomy Pages
Notes - Session 663 (2019-02-13)