ARAS Spectroscopy Forum
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I decided to calculate the noise contribution from each source (EDIT Aaargh! why does the forum software remove the spaces in the tableRobin Leadbeater wrote: Yes 1200s exposures might have helped a bit with such a weak signal.
)Hi Robin,Robin Leadbeater wrote:Hi RainerI use the goto controls (eqascom + Cartes de Ciel) to go to the coordinates published for the discovery. I check that I am in the right place by comparing the star field in the spectrograph guider image with DSS images and sometimes also by checking using astrometry.netRainer Ehlert wrote: Is it visible through the imaging camera or the guide camera ? or do we have to find it using the coordinates and pointing at all the bright dots until we see a similar spectrum like you posted.
I then take a series of 10 second exposures from the guider image and add them to identify the "new star" target. (see attached image)
With a target this faint, I cannot see it in short exposures while guiding so I choose another star in the field bright enough to guide on and measure the offset of that guide star from the target.
I then calculate where I need to place the guide star so that the target will be on the slit and start guiding with the guide star at that position. (It is always a relief when the first spectrum appears 10 minutes later !)
Cheers
Robin
Actually that calculation is wrong. I only included 1 pixel of read and thermal noise instead of the full height of the binning zone so the contribution of read noise is more like 60%. This means taking only 1 exposure instead of 16 would have improved the SNR per bin significantly from ~5.9 to ~9.3Robin Leadbeater wrote:
I decided to calculate the noise contribution from each source