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Hello Benji,

Many thanks for the description, it is good to know you address the same problem!
I have started learning spcAudace now.

Peter

James, Thank you for sharing your method, good to see you also care with the shifts - at least the in case of high-res H-alpha region! If I'm right, you don't have any tellurics for the CaII region (not even for H-beta), so you can't check for any shift. In case with fiber fed eShels, you won't meet...

Tonis, I do around R~3000 and R~17000, with only a 0.3m scope. Tellurics are either blended (R~3000) or very noisy, and only a few of them (R~17000: only 100A coverage so have very few tellurics - sometimes in middle of emission -, e.g. 6510-6605A in case of H-alpha). Toward H-beta, tellurics just n...

Tonis, By practice, we use tellurics only for checking spectra, mostly in case of high SNR + smooth continuum (cooler stars have spikes everywhere, rendering it unuseable). They are too low by SNR for a general use, and dependent on sky quality. However, DIB and tellurics certainly useable at low re...

Thank you Jack for describing your experience! I never intended to fix the skew itself, and the method 2.c.ii) that I'm doing for a while is already treating that error sufficiently for my needs - reducing the resolution drop to a single exposure's timeframe. My main problem left here, is only the a...

Dear LHires III/L200 owners, I am opening this topic to discuss how to process calibration shifts of long (multiple hours, e.g. 12 x 10 minutes) of exposures. As I have experienced so far, many of us approaching it several different ways, with no mainstream resolution I'm aware of (whilst we produce...

Good catch of this event, Woody! Looking at your flux graph, my result suggests a tendency H-alpha is shrinking day by day very quickly: Ha_flux.png I've used wide slit (1 x 600 sec) for flux calibration. At OI 7772 region, I've got only very low signal (SNR~10, no flux calibration): OI_7772.png Not...

Thank you for the APM 2.7x Barlow test, Christian! So the 65mm backfocus (yellow arrows in the picture) is your modified recommendation in order to achieve 2x rather than 2.67x ? (APM specs saying "Backfocus: 105 mm from Center last Lens" and "Resulting focal length: - 62.9 mm") ...

Tom, I am using the Alpy at f/4 without any lens, and LHires III with an APM Barlow 2.67x (designed for f/4) from the very beginning. I am unable to distinguish the well known aberrations of LHires internral dublet from this APM barlow, seeing also in the IR with 600/mm grating but less severe than ...

Comparing my result from yesterday to previous (2020.09.12 and 18), in the IR it looks like the N I emissions got stronger - relatively to all other lines: novacas2020_20200918_765.png novacas2020_20200918_866.png It is causing the rightmost Ca II 8662 blending with the neighbour N I emission. Peter