David's Astronomy Pages Notes - Session 610.5  (2018-05-13, Observatory Commissioning)

Notes (S610.4)

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Notes (S610)

	Session Aims & Highlights
	Operational Issues
	- Critical Issues (0),  Major Issues (0),  Minor Issues (2),  Small Defects (0),  Continuous Improvement (0)
	Polar Alignment
	Periodic Error Assessment
	No images from this session  >>

Session Aims & Highlights (2018-05-13)

This was a night-time session to continue formal commissioning of the new Dome Observatory including :

1. Polar Alignment. Check/refine Polar Alignment using PemPro2 Polar Align Wizard
2. Periodic Error. Create periodic error curve and upload correction curve to scope.
3. System Stability. Continue check stability of POTH.Hub and Observatory Control Software

Equipment & Software

• 12" LX200 and ST-10XME
• CCDApp2, TheSky6, CCDSoft 5, POTH Hub

Highlights

• PemPro.  Pempro's Polar Align Wizard worked better in this session (improved familarity with the software)
• Polar Alignment.  Polar alignment further refined with an alignment estimated to be within 1.5 arc min of north celestrial pole (results >>)
• Periodic Error.  RA tracking measured across 2 x 24 minute cycles. Data again shows a normal' Periodic Error trace  (results >>). 
    Results again confirm that the repair to RA drive has been successful . Key lesson learnt over the need to re-synchronise PemPro's PE Counter after moving the telescope.
  
• System Stability.  POTH.Hub / system was stable through the whole session (though not pushed that hard in this session)

Notes

Summary Plots & Logs

Night Sky Summary Plot - 2018-05-13 Not applicable for this daytime session

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Operational Issues (2018-05-13, S610.5)

• Critical Issues (0)
• Major Issues (0)
• Minor Issues (2)
• Small Defects (0)
• Continuous Improvement (0)

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Critical Issues

• None

Major Issues

• None

Minor Issues

• Polar Alignment process again took longer than it should. Althrough improvements were made from the previous session time taken was longer than ideal. This doesn't effect normal observing sessions. so it is not critical.
  Closed (Polar Alignment, PemPro)
  
• RA tracking wasn't improved (and indeed made worse) after uploading PE Correction curve to the mount. This happened because the telescope was moved between synchronising PEMPro and acquiring RA tracking data, which meant that the acquired PE curve was not correctly synchronised with the scope, with the result that corrections were not being applied at the correct times.  PemPro Help system gives an important warning regarding this (Fig 1). An attempt to correct the PE Curve by shifting it to align with a 2018-05-10 dataset will be tested at the start of the next session.
  Closed (LX200,  PemPro)

Small Defects

• None

Continuous Improvement

• None

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Polar Alignment  (2018-05-13)

Polar Alignment (2018-05-13) (Polar Alignment using PemPro Polar Align Wizard (PAW) Note: An incorrect plate scale was used on 2018-05-10 (2x2 one instead of 1x1) and the real errors are believed to be 50% of those shown in the graphs for this date.

Azimuth Adjustment / South Sky Point Initial Plot (2018-05-10)

Post Azim Adjustment (2018-05-10)

Azim Check (2018-05-13)

Post Azim Adjustment (2018-05-13)

Final Azim Check, Post Alt Adjustment (2018-05-13)

Altitude Adjustment / West Sky Point  (40 degs) Altitude axis raised by temporaily easing two side bolts with Allen Key and then rotating the Altitude Knob in an anticlockwise direction. (anticlockwise when looking at the wedge from the south) Initial Azim Check (2018-05-10)

Post Azim Adjustment (2018-05-10)

Alt Check, Post Azim Adjustment (2018-05-13)

Post Alt Adjustment (2018-05-13)

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Periodic Error Assessment (2018-05-13)

Periodic Error Asssement / RA Tracking (2018-05-13) (Star close to Dec 0, tracked with 2x2 binning, image scale 0.884 arc sec/pixel)

Plot after Initial 29 minutes (RA drift is noticeable, this may be a result of mis-polar alignment, an imperfect tracking rate, or mount/OTA flexure, but does not effect the generation of a Periodic Error Curve)

Earlier Periodic Error Asssement Plot (2018-05-10) (22 minute run. Similar graph shape, but worm phase is offset by around 5.3 minutes = 132 cells)

Plot after full 50 minute run (2018-05-13), drift corrected

RA Tracking Graph

Fitted PE Curve (Periodic Error +/- 18.2)

Calculated PE Curve (Peak to Peak Periodic Error 36.5 arc secs)

Uploaded PEC Curve 1

Periodic Error Assessment with PEC On (Run 1a) (run halted after it was clear that the uploaded PEC Curve wasn't producing the expected improvement in RA Tracking)

Periodic Error Assessment with PEC On (Run 1b) (again run halted after it was clear that the uploaded PEC Curve wasn't producing the expected improvement in RA Tracking)

Periodic Error Assessment with PEC On (Run 2) (again run halted after it was clear that the uploaded PEC Curve wasn't producing the expected improvement in RA Tracking)

Uploaded PEC Curve 3 (scaled by 50%) (working on hypothesis is that Image Scale needs to be for 1x1 binning, even though Binning of Tracked Star Image is 2x2)

Periodic Error Assessment with PEC On (Run 3) , using Uploaded PEC Curve 3 ('scaled by 50%') (first 3 minutes where encouraging but the following deflection shows Pec Curve 3 isn't producing the expected improvement in RA Tracking,  perhaps curve needs to be inverted)

Uploaded PEC Curve 4 (scaled by 200%) (test to see that PEC is being applied by the LX200 mount)

Periodic Error Assessment with PEC On (Run 4) , using Uploaded PEC Curve 4 ('scaled by 200%') (this was a test to see that PEC is being applied by the LX200 Mount. The artifically 'inflated' corrections produce large deflections in RA tracking suggesting that PEC values are being applied)

Periodic Error Conclusion Whilst PEC is working it is evidentally not delivering appropriate corrections to improve RA tracking. After examining PE data collected and the associated log files it is concluded that after using 'Sync PE' to synchronise PemPro to the LX200's RA Pec Segment Counter, the scope was moved to access a brighter star and PE data was acquired without doing the necessary 'ReSync'. By shifting the PE Curve left by 132 cells the RA worm phase of the Two Cycle PE Curve can be matched to that of the One (90%) Cycle Curve created from data collected on 2018-05-10

Periodic Error Curve to be uploaded at next session This shifted PE curve might still be usefully used without collecting another 60 minute worth of PE data and will be uploaded at start of next session and  'PEC On' RA tracking examined

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