15-Day Drift Scan at Dec +40 Degrees from my 2.4 m Dish

[Ayushman Tripathi]

Hi,

I managed to resolve the artifacts generated by the baseline correction in my script.

Here are the plots with this week’s data included.

I’ll also adjust some observation settings to evaluate the impact on the results.

Also, for my smaller dish, I’ve added a steel mesh around it and will share its data.

Thanks.

[Alex P]

Excellent results :)

What techniques did you implement ?

Thanks,

Alex

[Ayushman Tripathi]

Hi Alex,

Here's the pipeline method I used:

1. Per-observation calibration. Each 5-minute scan is recorded raw with Airspy Mini (3 MHz span, 1024 FFT bins at 1420.406 MHz). VIRGO processes it against a separate cold-sky calibration scan: it divides the observation by the cold-sky spectrum, then normalizes it by the noise standard deviation in the line-free channels to put everything in signal-to-noise (SNR) units and finally applies a median filter in frequency. The output is one "filtered" spectrum per scan.

2. Wing-linear residual. I measure the remaining slope and offset using only the true line-free wings and then subtract that linear baseline from the whole spectrum.

3. VLSR correction + RA stacking. Each observation is Doppler-shifted onto a common LSR velocity grid, then observations are binned by RA (0.10 h bins) and median-combined across all sidereal loops.

I'm constantly experimenting with these techniques to improve the pipeline.

Thanks.

[b alex pettit jr]

Hello Ayushman,

Sounds very close to my sequence, except I subtract vs divide as the shifts are not gain but environment amplitude shift related.

And I use simple mX+b slope correction ..

I probably will not incorporate VLSR correction in the HL3D code.

Thanks,

Alex

============================================

[Ayushman Tripathi]

Hi Alex,

Yes, I’m still trying to improve it. I can also try HL3D’s plotting on the same collected data later this week and will share the results.

Thanks.

Sent from my iPad

[b alex pettit jr]

Attached is an example of the IFavg format for *.txt Input  and the *.csv output

*.CSV format as required for Rinearn Graphics 2D / 3D .

A1 Blank  

B1 ....  (RA) Time Hrs

ColA = Freq

Ampl Field dB re cold sky

Thanks,

Alex