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False alarms

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False alarms

Hi all,

In this topic I would like to propose a series of replies to serve as information on what can constitute a false alarm when searching for novae and how to avoid reporting such objects.

False alarms can be:

  1. Asteroids (especially when searching close to the ecliptic) - these can best be detected by entering their coordinates in Minor Planet Checker which should identify all known asteroids. Of course if it's not listed you may have discovered a new asteroid instead. In such cases it's best to retake an image after a few hours at a longer focal length to see if there is any motion.  One can also check against a star catalogue such as DSS-2 red - it would be good if a step by step procedure could be made available for this type of check.  On multiple images median stacking will eliminate a moving asteroid from the final stacked image.
  2. Cosmic  Ray hits (hitting the CCD chip) are common as well. These often look like a hot pixel. Shooting multiple images of the same field will also enable their elimination.
  3. Variable stars - there is no 100% certainty test for these as many new vs are detected. It is best to check with AAVSO's VSX at entering coordinates and a search radius.  GCVS is another resource.
  4. Noise - this can resemble faint stars, shooting a second or third subframe will help to eliminate these too.

The above are just the most common 'culprits', and the ways of elimination are by no means the best so I invite you all to share your views and post additional information.

CdC software can display Tycho-2, GCVS and UCAC4 star catalogues.

FRF's picture
re: fals alarms - VaST helps you

VaST - the sofware  mentioned another thread tonight - detects all know variables listed in the GCVS and VSX, reducing this way of the fals alarms. You can also check know minor planet via VaST: you just need to clink on the "MPchecker" button.

Clear skies,


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