Equipment: ============ Scope: SkyWatcher Esprit 80 triplet APO Mount: SkyWatcher AZ-EQ6 Field Flatener: SkyWatcher Esprit 80 field flatener Guide Scope: SkyWatcher EvoGuide 50ED Camera: Canon EOS 600D (unmodified) Filters: - Guide Camera: QHY5L-II-C Other Gear: StarSharp Bahtinov mask Pegasus Astro FlatMaster HitecAstro manual 4ch dew controller AstroZap dew straps PowerSonic 69Ah AGM deep cycle battery Orico 4 port powered USB3 hub (accepts 12V input) Unitek Y-3015 active 5m USB3 extension Unitek Y-3015 active 10m USB3 extension Thinkpad T470 with 72Wh+24Wh batteries TEMPer USB temperature sensor (poor accuracy but better than nothing) Software: APT (capture) PHD2 (guiding) SharpCap Pro (polar alignment) DeepSkyStacker (stacking) StarTools (processing) eqmod 2020-08-15 30 good exposures, 6 dark frames, 30 flats 2020-08-17 30 bias frames 2020-09-07 52 good exposures, 16 dark frames, 30 flats 2020-09-08 42 good exposures, 15 dark frames, 30 flats 2020-09-12 28 good exposures, 25 dark frames, 30 flats 2020-09-19 29 good exposures, 27 dark frames, 30 flats 2020-09-20 86 good exposures, 17 dark frames, 30 flats 2020-10-04 7 good exposures, 15 dark frames, 30 flats 2020-10-05 38 good exposures, 15 dark frames, 30 flats Final version: * Total integration time: 10h 24m * Stacked only subs where FWHM was below 4.0 * Processed data is in processing-final directory * File list used for the stack is in final-file-list.txt * Deep Sky Stacker version 4.2.3 * StarTools 1.7.442alpha (Win64 GPU accelerated) Core i7-860, 16GB RAM, Radeon HD 5850 (Cypress, 18 compute units) Notes: * This target was originally attempted on 15-AUG-2020 with 48 minutes of integration time. Result was surprisingly good but quite noisy. In September 2020 the decision was made to try and gather another 9 hours of data to improve the SNR and produce a good quality image. The original attempt is archived here in the [processing-2020-08-15] directory. * Additional revisions are present showing the improving SNR as integration time goes up * Images 2020-09-12 #12 (7:55PM) and 2020-09-12 #20 (8:30PM) have faint satelite trails. Stacking should remove these. * Significant difficulty was encountered trying to stack the 2020-09-12 data alongside previous nights with DeepSkyStacker on the Laptop. Almost seems like alignment was going wrong. Problem wasn't present when done on the desktop so perhaps a DSS bug? When done on the desktop only the best 80% of frames were kept so perhaps one of the rejected frames was really bad? Challenges: * Initially ran into problems slewing to the taret due to mount limits. These were disabled to allow it to reach the target. * On 2020-09-07 APT PointCraft couldn't lock on to M8 for some unknown reason. Plate solving near by and elsewhere in the sky worked fine but when M8 was near the center of the FoV PlateSolve2 would forever and All Sky Plate Solver would terminate with no result after about 130s. So these exposures may not perfectly match up with the framing in the 2020-08-15 set. I suspect similar issues may have been encountered last time too. * Polar alining on 2020-09-08 was time consuming. It was difficult to get SharpCap to settle on a number/rating. * Plate solving continued to be problematic for 2020-09-08 along with some APT and EQMOD stability issues and malfunctions (APT failing to slew the mount seemingly because PHD2 was doing something). * The 2020-09-08 data set has a number of tracking errors. These are discussed in a later section. * 2020-09-19 had significant cloud issues. Ended up leaving the rig running to below 30 degrees but these subs are badly affected by light pollution. * The two october nights had difficulties with light pollution from the near-full moon towards the end of the session. Additionally, the 5 october session had APT/camera connection stability issues early on resulting in starting some 40 minutes later than planned. * The last few sessions didn't were just focused by eye using the bhatinov mask rather than APTs bhatinov mask feature due to it incorrectly detecting the spikes. This needs to be investigated further some time. Issues with this image: * More darks would be good. Current number is initially due to limited battery life (max 75x 2m exposures on a charge after time taken for flats and occasional refocusing) and later due to available time * Brigher stars are blown out. Need to reduce exposure length next time Things to do differently next time: * Check histogram and image max pixel value to ensure nothing is clipping. Reduce exposure time as necessary * More dark frames * Run guiding assistant before starting imaging plan to check seeing and ajust settings as necessary * Longer exposure time in PHD2 to reduce effect of bad seeing (see section below). 2-4s is recommended. * Ensure camera cable loom is tightly fixed to the camera so as to not tug on the guidescope at all. Multiple Processings: After each night of imaging that night has been stacked along with all prior nights and run through startools to observe how the SNR improves with more integration time and also to practice processing in startools. These revisions are stored in the following directories: processing-2020-08-15 Contains: 2020-08-15 processing-2020-09-07 Contains: 2020-08-15, 2020-09-07 processing-2020-09-08 Contains: 2020-08-15, 2020-09-07, 2020-09-08 processing-2020-09-12 Contains: 2020-08-15, 2020-09-07, 2020-09-08, 2020-09-12 processing-2020-09-19 Contains: 2020-08-15, 2020-09-07, 2020-09-08, 2020-09-12, 2020-09-19 processing-final Contains: 2020-08-15, 2020-09-07, 2020-09-08, 2020-09-12 2020-09-19, 2020-10-04, 2020-10-05 Subs with FWHM < 4.0 only Processing-final is the final version of the image uploaded to astrobin. The file-list used to produce this is "final-file-list.txt". File lists for earlier revisions are in the "old" directory. 2020-09-08 tracking issues: A significant number of subs from this data set exhibit tracking errors. In 13 subs it was quite significant - these were shifted to the junk directory and are excluded. The remainder were relatively minor and have been left in on the assumption stacking and binning would overcome the issue. The previous nights data (2020-09-07) does not exhibit any tracking errors at all. The worst of its subs are equal to the best of the 2020-09-08 subs. This depsite it having higher polar alignment error (0.7') than 2020-09-07 (0.4') Guide statistics: 2020-09-08 2020-09-07 RMS Peak RMS Peak RA 1.63" (0.51px) 15.81" (4.94px) 0.96" (0.3px) 25.10" (7.84px) Dec 0.60" (0.19px) -24.80" (-7.75px) 0.95" (0.3px) 14.89" (4.65px) Total 1.73" (0.54px) 1.35 (0.42px) In the graph for 2020-09-07 Dec and RA rarely cross the 2.5" line where as on 2020-09-08 they quite frequently cross 5". Dithering seemed to take much longer on 2020-09-08 with many RA adjustments. Outside of dithering there have been quite significant and prolonged adjustments to the RA axis at times. Possible causes: * Combination of Bad seeing and short exposure time causing PHD2 to chase seeing. This might explain the difficulties polar aligning. * Traffic in the nearby lane. The following car movements were identified on the security camera all of which match up with excursions on the guide graph. This doesn't explain all of them however. 8:48-49 9:10 10:28-29 10:53 * Dragging cables