Mini-SONG & Site testing at Delingha

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1 Mini-SONG & Site testing at Delingha
Licai Deng SONG & mini-SONG

2 Primary Science Goals Photometry of a sample (defined later) of open clusters basic physical parameters measured in a uniform way; Time domain study of variable objects in selected clusters: long time based line, high cadence and high duty cycle, high precision photometric observations; A complete survey (defined later) of stellar variabilities along the main sequence ( Scu,  Cep &  Dor etc……) in selected open clusters; A complete survey (defined later) of small and large amplitude red variables along the RGBs of selected open clusters; A complete survey (defined later) of eclipsing binaries in selected clusters; Looking for transit of exoplanet systems; Looking for flare type variabilities in selected clusters; Stellar rotation and spots activities; …… Time domain study of selected field areas;

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4 Secondary science goals:
Immediate follow-up of the optical after glows of GRBs; Follow-up of SNs found in nearby galaxies; Other generic ToO;

5 Fundamental requirements on hardware
To realize long time base line and cadence, a mini-SONG telescope should be attached to each SONG node, at least in SONG-North; To realize our science goals, (simultaneous) 2 color (SDSS g, r) photometry system is needed; To cover large enough cluster and vicinity area of Galactic open clusters, especially the well studied old populations of clusters, such as M67, NGC188, NGC7789 etc., a minimum of 40’x40’ FOV is needed; To reach the lower limit of -Scuti strip of typical open clusters, and to have them observed at 100 level S/N, and 1mm accuracy at a ~300s exposure, a minimum aperture of 50cm is needed (to be determined); To get an ideal sampling, 4kx4k CCD(s) is needed;

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7 Basics of the survey: The sample of clusters are defined in such a way that the size (dynamical radius) ranges in 10’-30’ (to be determined), and the lower limit of -Scuti strip locates at 19m (if exist, for old clusters) or 5m below the MSTO are covered; A pilot general survey for pre-selected sample of clusters, measure the basic physical parameters; Differential photometry will be adopted though out the project, however, calibration should be done from time to time during the survey; The number of clusters eventually to be observed are similar to the number of SONG program stars, so that the cadence and duty cycle keep the same as the SONG;

8 Criteria for target selection
cluster with well determined parameters; cluster with -Scuti members; clusters with populated RGB; clusters with populated HB (RCG); richness in binaries; number of member stars; density of member stars in cluster core (for transit); etc ……

9 大气视宁度测量的两种方法 DIMM： SBIG视宁度仪： 望远镜口径较小； 不受跟踪误差影响； 测量结果有效性高；
以北极星为目标星，无需跟踪； 拖影，CCD单行向下读出； 仪器小巧，自动化程度高； 可实现长期连续监测，取得大量视宁度资料； 实测表明：易受风力影响；

10 德令哈SBIG seeing统计 2010年2月～3月，总数 1168 平均值1.6，权重值1.2 FWHM<1的占 24%
SBIG视宁度仪可以测到小于1 arcsec的seeing值。

11 对比观测概况 2010年3月在青海紫金山天文台德令哈观测站进行了为期一周的对比观测； SBIG视宁度仪与DIMM同时对北极星观测；
取得3个夜晚，871组有效DIMM视宁度数据，662组有效SBIG视宁度数据。 设备参数： SBIG视宁度仪参数 镜头口径 28mm 镜头焦距 150mm 焦比 F5.3 CCD ST-402ME 视场 2.7°x1.6° 曝光 TDI 5ms读出 DIMM参数 望远镜口径 250mm 望远镜焦比 F10 子孔径 50mm 子孔间距 200mm CCD pixel scale 7.4x7.4µm 空间分辨率 0.61 arcsec/pixel

12 DIMM配置

13 观测数据 系统差约为1 arcsec 北极星附近始终有云，风力稍大。

14 观测数据 系统差约为2 有薄云，风力较小

15 观测数据 系统差约为1.8 整夜有薄云，风力不大，前半夜有月亮

16 德令哈视宁度对比观测结果

17 SBIG受风力影响 2007年4月于河北兴隆观测站测得SBIG seeing与风力数据 Seeing与风速正相关； 风向也有相关性

18 SBIG与DIMM的比较初步结论 DIMM seeing与SBIG seeing有一定相关性 SBIG视宁度仪可估计视宁度好坏
趋势一致； 需要考察云和风影响； SBIG视宁度仪可估计视宁度好坏 测量值偏大； 可以测到小于1的seeing数据，尚需进一步校验精度； SBIG更易受到风速的影响； SBIG seeing与风速正相关； SBIG视宁度仪对云层遮蔽更敏感 SBIG视宁度仪口径较小；

19 谢 谢!

20 2007年4月24日DIMM和SBIG视宁度仪 夜间大气视宁度比较观测

21 2007年4月25日DIMM和SBIG视宁度仪 夜间大气视宁度比较观测