The night before last night I have carefully setup my new CEM40EC with AsiAir control WiFi device since it is also PHD2 guiding in basic, but much more easier to adjust and to control.
The scope-imaging includes 115mm apo triplet with reducer/flattener (effective focal length = 644 mm), ASI1600MM Pro cooled to -15 Celsius Degrees, OAG with ASI174MM Mini and ZWO EFW with LRGB and SHO filters.
The seeing was not very good for imaging with intermittent clouds, moderate wind gusts and Moon illumination 82%.
After one-star alignment, I oriented the scope due to East at Dec less than 20 Degrees for guiding calibration (PHD2 calculated step duration 550 ms).
This calibration was used for different targets in opposite celestial location and different latitudes, which is important for this topics.
Due to the file size restriction, I will submit the PHD2 (AsiAir) guiding log as attachment in a separate post immediately after I post this one.
AsiAir sometimes don't record calibration log, but it does the guiding sessions (a total of 4):
1. first was only a minute after the guiding and it shown calm and stable curves, so I stopped it in order to chose the first imaging target;
2. the second last for a continuous 2h 4m 45s during which IC1396 was imaged (located app. RA 21h, Dec app 57 Degrees). The guiding log was depicted in the attached screenshot , as well as the PHD2 Log Viewer screenshot of the entire session. Not only the guiding was very calm with global RMS 0.86" (0.46 pix), but even the clouds (especially the second cloud passage around 1 h of guiding that leads to complete star SNR loss) does not disturbed the guiding
A total of 12 lights with exposure duration of 600 seconds each were imaged (4 of each SII, Ha and OIII filters).
3. third guiding session was only 21 s since I forgot to click the guiding flip button since the scope moved to the opposite meridian position.
4. the last session includes 1h 32m 27s uninterrupted guiding for imaging of M16 positioned app at RA 18h, Dec -13 Degrees. A total of 9 600-seconds exposures were captured (3 of each filter).
The analysis of images in PixInsight revealed that all 21 exposures of 600 seconds each were with better properties (lower FWHM and Eccentricity values) than I have ever recorded before using the previous GEM (Meade LX85). None of the images shown star trails or other guiding-related problems).
I will attach the Ha image (only 3 integrated lights) in a new post just to show the successfulness of the ultimate, real-world test of star size. Please keep in mind that no deconvolution, morphological transformation or any other star-reduction algorithm were included in extremely minimalistic PixInsight processing (only MLT, delinearization by Histogram transformation and Curve transformation were performed for post-processing).
In conclusion, apart from proper gudang calibration, I suspect the the choice of 0.5x sideral as a guiding speed was crucial for resolving of the issue with RA spikes that occured previous nights.
I would like to thank to all of you that had a patience and time to analyze my submitted logs and screenshot. Without your help, suggestions and sympathy, I was completely disappointed.
Now I am very happy with my new CEM40EC.
Best to all,