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Secondary Support Issues

Secondary Support Issues. Secondary supports create focal plane flares Field rotates in Alt-Az mount Counter-rotating instrument spreads flares in focal plane. Masking flares in software can reduce impact to 1/n for n independent (no flare overlap) exposures.

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Secondary Support Issues

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  1. Secondary Support Issues • Secondary supports create focal plane flares • Field rotates in Alt-Az mount • Counter-rotating instrument spreads flares in focal plane. • Masking flares in software can reduce impact to 1/n for n independent (no flare overlap) exposures.

  2. Secondary Flares – Single ExposureNo Noise First Focus Second Focus

  3. Secondary Flares – Single Exposure1 Minute Integration, mK= 6 Second Focus – No Sky First Focus - Sky

  4. Secondary Flares – Long exposure 2 Hour exposures across zenith: sky/star split 50:50 Images sky subtracted K Star at dec – 10° Star at dec – 30° First Focus

  5. Secondary Flares – Long exposure K Star at dec – 10° Star at dec – 30° Second Focus

  6. Secondary Flares - Conclusions • Spider Scale Factor of 30 makes NICI observations relatively independent of star’s position and time of observation. • Scale factor of 30 is compromise between tolerancing, throughput, coronagraph performance and manufacturability. • Since spiders occupy about 0.25% of the Gemini Pupil area, spider mask loss is about 6-7%

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