Markarian's Chain
Started a mult-session collection on 03/26 (52) and continuing on 04/15 (47), 04/16 (109) and 04/19 (~20) against Markarian's chain with the venerable Orion ST80 using the generic dual narrow-band filter, clear Astronomik EOS clip-in filter (for consistent focusing with the EOS CLS clip-in filter) and Canon T3I (astro modded for Ha sensitivity). 180s collections used for each (except for 3/26 at 300s) and flats collected against morning blue sky when needed based on re-focusing (03/26, 04/16). Canon configured with UTC time. Based this collection in Kstars/Ekos/Indi by centering on NGC 4438.
For this processing, utilized both 60x180s and 30x300s darks as well as 130 bias (all at ISO1600) frames for calibration.
Collection notes from 04/19: Ran entirely on the Odroid XU4 via remote desktop protocol (rdesktop client with compression) to simulate a remote location and provide some robustness for network / wifi drop-outs.
PHD2 ran fine on the Odroid and showed a reasonable polar alignment using just leveling and polar scope of about 1.5-2'. KStars/Indi/Ekos ran with only one crash during setup. Plate solving ran successfully once configured. Although ~20 frames were initially collected successfully, issues were found starting at 01:30am and continuing where guiding would calibrate successfully and a frame or two collected... but then guiding would suddenly become erratic and uncorrected. Parked the mount and restarted collection to no avail. Cables were checked and seemed free of strain. Balance had been checked at set up and seemed fine. More investigation needed.
Collection notes from 04/21 (an additional night of collection). Again set up with rdesktop running Kstars / Indi / Ekos directly on the odroid, rather than on the main server connected to indi running on the odroid. Polar aligned with the scope -- did not verify with phd2 drift alignment. Ran the focus tool with Vindemiatrix (etta Virginis) centered. Initial focus number for the main star showed 9.03. Refocused outside (will need new flats) and re-reran the focus tool...which now showed 8.83. Interestingly, the first Ekos tab shows focus results with HFR indicating 5.58px. Ultimately, rdesktop setup failed to work reliably with only a small number of guided frames collected overnight. While working fine initially, when left unattended the system appeared to hang / freeze.
Collection notes from 04/23. Moon nearly 1/2 full...very bright. And very close in the sky to the target :< Initial polar alignment with the polar scope showed great initial alignment with PHD2 drift alignment with the system pointed to NGC 4438 (~0.26' after several minutes). No issues with focus were observed. Running the focus tool in Indi shows 1.82 for the few stars in Markarian's Chain that were measured (so no need for additional flats for this session). After collecting 13 light frames, inspected levels and found the background too high. Reduced exposure times to 160s from 180s and restarted collection. Ultimately, 92 lights collected ... much more successful than running KStars / Ekos /Indi directly on the Odroid (why) via remote desktop where guiding was stalled and few frames collected.
Collection notes from 04/30. Windy with light clouds at 10-ish (clear by 11pm). Moon waning gibbous with 75.9% of the Moon illuminated (moon rise at 12:30am). Polar scope alignment once again dead on with phd2 reporting a drift alignment error of ~2'. Oddly, Indi won't communicate with the Canon on the odroid...with a bug report already noted in the Indi/Ekos forums (for version 1.9... whereas this is version 1.8.9...odd). Tried removing the PPA repository for nightly as well as stable and reverting to stock ubuntu version (which was also 1.8.9)... no impact. Went back to installing the nightly build, no impact. Ultimately used Indi to guide and simply ran and the intervelometer shell script (which calls gphoto2) to collect frames. However, plate solving used the guide camera instead of the main telescope & Canon because of this limitation. A quick check on nova.astrometry.net for frame #10 showed significant error (although focus on the ST80 remains ok...no adjustment appears necessary and exposure looks sane with 180s collection). Adjusted and restarted collection. A second adjustment was needed... which came very close. Then more. Meridian flip complicated the process. Eventually (12:30am) obtained a reasonable framing and started guiding and capturing 180s frames.
Collection notes from 05/01. Tripod left in place since last night. No wind, clear skies early with clouds predicted after midnight. Updates to indi/ekos software fixed the indi_canon_ccd driver...which now works fine. Slewed to the target galaxy (NGC 4438) and performed initial plate solve with the Canon T3i...which worked.
To test if pulse guiding was (remarkably/surprisingly) working (since the ST4 port has been used for many months), tried an initial calibration in phd2 using the hand controller. Oddly, a calibration in phd2 succeeded. Drift alignment indicated good overall polar alignment without any adjustments required. Ultimately, guiding in Indi/Ekos with the internal guider showed a consistent RMS under 3. Collection proceeded normally until NGC 4438 reached the altitude limit of 35 degrees ending collection automatically at approximately 2:45am with approximately 70 lights. Scoped was found in the morning parked correctly.
Collection notes from 05/05. No moon. Some breezes. No clouds. Temps in the low 60's. Seeing described as very poor. Tripod repositioned over previous location (grass marks from vibration pads). Initial polar alignment through the polar scope was a bit difficult... lots of branches. PHD2 drift alignment (with NGC 4438 centered) showed ~2' (3px) error after several minutes of drifting. Once again, polar scope works on the first attempt. First collection with the Zwo Asi 120MC-S following firmware upgrade and the Cosmicar 50mm F1.8 lens was refocused (put the line under the 7). Also readjusted centering using Denebola (also adjusted ST80 focusing w/ the Canon T3I). Was successful in getting alignment between guide camera and Canon to within 128 arcseconds. Two jobs scheduled: NGC 4428 until 03:00 then NGC 6888. Guiding was tough... switch to using ST4 cable and binning (2x). RMS values a bit higher than 5.
To focus the ST80 with the GSO dual-speed Crayford focuser: loosen the top (and only the top) screw.
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| Final focus |
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| Initial focus |
Setup NGC 4438 as the target in the scheduler. Alignment worked without issue with platesolving using the builtin Stellar Solver. Guiding commenced with RMS values of ~2. Capture proceeded with 180s lights @ ISO1600.
Utilized Bayer drizzle with a scale factor of 1.5 within Astro Pixel Processor. Set levels within GIMP.
Results from astrometry showed a scale of 1.47 arcseconds / pixel following this drizzle processing step.
Final result:
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| Initial integration of 3/26 through 4/19. |
HI Fred -- we've been looking at the same targets, I imaged this area in early April! And the Crescent a week after you. Question: You were using a dual-band filter on this -- Isn't it better to view these galactic sources in broadband, or were you looking at something specific?
ReplyDeleteMy stuff is on Telescopius. I'm using the ASIAIR pro to control everthing these days and loving it. Just need more clear nights.
Clear Skies -- Richard
Richard -- My wide field telescope is the cheapest in the world -- the venerable Orion Short Tube 80. As an achromate, it suffers from severe chromatic aberration imaging in wideband. The dual band filter helps limit this problem. Plus, I'm Bottle 9...so filters can be helpful in combatting light pollution. Although there are plenty of posts suggesting the best way to combat light pollution is just average more frames and forget filters. As LEDs begin to dominate, that's likely what we'll be left doing.
DeleteAh, yes you mentioned that to me before. I have a pretty good APO, so I tend to forget about CA. Yes, LP filters don't really do much these days, with all the LED lights. I have a dual-band Optolong L-eNhance I use a lot, especially when the moon is out. I try to save moonless nights in the mountains for braodband targets.
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