David's Astronomy Pages Notes - Session 610  (2018-05-16)

Notes (S610.5)

Notes Main

Home Page

Notes (S611)

	Session Aims & Highlights
	- Night Summary Plot
	Operational Issues
	- Critical Issues (0),  Major Issues (1),  Minor Issues (4),  Small Defects (0),  Continuous Improvement (0)
	Periodic Error Correction
	Flat Frames
	Images from 2018-05-16  >>

Session Aims & Highlights (2018-05-16)

Main Aims

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

1. Periodic Error. Upload periodic error correction curve(s) to LX200 mount and refine
2. Non-Guided Images. Acquire some non-guided image subs of up to 180s exposure to confirm the overall fitness of Polar Alignment and PEC
3. Targets. Acquire images of some selected deep sky objects
4. Target Centering. Identify any issues relating to target centering
5. Target Imaging. Identify any issues relating to target image acquisition
6. System Stability. Continue checking stability of POTH.Hub (Telescope + Dome) & Observatory Control Software
7. Flat Frames. Acquire set of Flat frames for Clear (C) Filter 

Equipment & Software

•  12" LX200 and ST-10XME
• CCDApp2, TheSky6, CCDSoft 5, POTH Hub, PemPro V2.8 Build 138

Highlights

• Periodic Error. PEC curves successfully uploaded to LX200 and confirmed to significantly reduce Periodic Error.
   PEC curves successfully refined and used to further reduce  PE to around +/-2 arc seconds
• Unguided Images. 180s unguided 3x3 binned subs produce acceptable images at plate scale of 1.3 arc sec/pixel
• Targets. Images of a number of deep sky targets were successfully acquired   (first bit of real observing since January ! )
• Target Centering. No issues with target centering
• Target Imaging. A critical bug in the Target Acqusition routines was identified
• System Stability. POTH.Hub / system was stable through the whole session
• Flat Frames. A set of Flat Frames acquired to enable reduction of images acquired during session (flat frames)

Observatory Status Viewer (snapshot taken at 02:53h LT, observatory running smoothly)

Back to Top

Operational Issues (2018-05-16, S610)

• Critical Issues (0)
• Major Issues (1)
• Minor Issues (4)
• Small Defects (0)
• Continuous Improvement (0)

[ Prev | Next ]

Critical Issues

• None

Major Issues

• Target Acqusition routines had a critical bug that prevented automated fine centering of targets. Targets entered with  '-2' (fine centering) pointing mode repeatedly dropped back to '-1' mode (no locate images). Fortunately semi-automated backup routines worked ok and allowed the acquistion of the night's primary target (NGC 6166) and some deep sky targets. Job Executor code has undergone recent modifications to incorporate target specifications driven of a SQLite database and the code for the live program had accidently included a uncommented scenario test line which had effectively disabled fine centering.  Bug identified and quickly fixed.
  Fixed 2018-05-17 (CCDApp2/AstroMain)

Minor Issues

• Camera leads accidently knocked causing the telescope to be knocked off target.  Telescope was busy acquiring PE data (small 100x100 pixel box) for a final check (Fig 1) when the camera leads were accidently knocked whilst finding my way from the observatory door around to the observing desk on the opposite side of the telescope pier.   The run was aborted (fortunately it was just a final check in the PEC process and a full cycle was not critical).  The relatively small size of the observatory, necessary camera leads at the back of the scope and user movements are ongoing components to this hazard.  More awareness of the hazard presented by the camera leads and risk of affecting the telescope pointing are needed. The planned semi-automated / automated operation of the observatory reduces the risk frequency moving forward.  A red-light may have been helpful in this situation as movement in the observatory at the time was my means of the light from laptop screen alone.
  Closed (Observatory)
   
• Telescope pointing shows small gradual drift over the course of several minutes. This occurs in both RA and Dec, and introduces trailing on long unguided 3x3 binned exposures or a shorter 1x1 & 2x2 binned images.  Telescope slewing is reasonable k, but it would be beneficial if slewing got the telescope closer to the target center first time.  Scope is probably still slightly misaligned.  RA tracking speed might be slightly off. RA tracking might be getting to the limits of a Meade LX200GPS scope.  Polar Alignment will be measured and refined in upcoming session using TPoint mapping & modelling. The TS80 Guidescope + ZWO 178MC camera will also be installed shortly and automated guiding with PHD2 will be resumed (using procedures & control software developed in 2017).
  Closed (LX200 Telescope)
   
• Connection with Optec TCF-S focuser was lost around 1 hour into the session Focus Position and Tube Temperature both begin showing 0 in CCDSoft & CCDApp2. This issue has now occurred during several  sessions. In the past the connection had worked fine when tested the next day making problem solving difficult. (it is critical to get to the bottom of this issue, and either solve it for good and/or put in monitoring with means to alert to the observatory manager routine and the user.  A reliable workaround is needed to get the connection restarted mid-session).  Eventually fixed by updating TCF-S software/drivers and by connecting to the TCF-S focuser using ASCOM connection rather via CCDSoft5, and also by adding a backdoor facility 'Restart TCF-S Focuser' that quickly resolves any new cases.
  Resolved (TCF-S Focuser, AstroMain)
   
• Condensation formed on front of 12" LX200 Scope, Condensation on the corrector lens at the front of telescope degraded image quality towards the end of the 4.5 hour session.  The Dew Heater Band for 12" scope may be insufficient to keep condensation/dew totally at bay. An extra heater band has been ordered with intention of incorporated into dew shield in some way.  Issue largely resolved in Nov 2018. Dewing tendancy significantly reduced since powering the heater bands from a Pegasus UBP Powerbox and later by adding software control of dew heater to always maintain the OTA tube temperature at a level which is no less than 2°C above ambient (outdoor) temperature (24x7).
  Resolved Nov 2018 (Session, LX200, Dew Heater)

Small Defects

• None

Continuous Improvement

• None

[ Prev | Next ]

Back to Top

Periodic Error Correction (2018-05-16)

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

Earlier RA Tracking Data (2018-05-13) (PEC Off, drift corrected)

PE Curve calculated from above data (Periodic Error 36.5 arc secs, peak to peak)

Shifted PE Curve PE Curve shifted left by 132 cells so that the RA worm phase of the unsynchronised Two Cycle PE Curve can be matched to that of the synchronised One Cycle Curve (~90%) created from data collected on 2018-05-10

PEC Curve uploaded to mount (1) (original PE Curve has been shifted to correctly synchronise it with telescope's Segment Counter)

RA Tracking Data with PEC On  (1) (LX200 mount using PEC Curve 1 to successfully correct the majority of original Periodic Error, however a residual error still exists

Residual PE Curve calculated from above data  (1) (periodic error 7.6 arc-secs, peak to peak)

Building Revised PE Curve  (2) (Revised Curve created by summing above residual PE curve with the initial PE Curve)

Uploaded PEC Curve  (2)

RA Tracking Data with PEC On  (2) (LX200 mount using PEC Curve 2 to correct 'second order' Periodic Error)

Residual PE Curve calculated from above data  (2) (periodic error 7.9 arc-secs, peak to peak)

RA Tracking Data with PEC On  (3) (LX200 mount using PEC Curve 3 to correct Periodic Error)

Data and Fitted Residual PE Curve   (3) (high-frequency jitter in the data is almost certainly 'seeing' rather than periodic error in the RA drive)

Residual PE Curve calculated from above data  (3) (periodic error 4.7 arc-secs, peak to peak)

Building Revised PE Curve  (4) (Revised Curve created by summing above residual PE curve with the previous PE Curve)

Final PEC Curve (4) (Final PEC Curve uploaded to LX200 Mount)

Final RA Tracking Check (run aborted when telescope was accidently knocked but before this the tracking looks pretty good)

RA Tracking Graph

Back to Top

Flat Frames (2018-05-16)

Back to Top