Abstract

The Transient Double-beam Spectrograph (TDS) is designed for low-spectral-resolution optical observations of nonstationary and extragalactic sources at the 2.5-m telescope of the Caucasus Mountain Observatory (CMO) of SAI MSU. The spectra are recorded simultaneously in two channels, short-wavelength (360–577 nm, reciprocal dispersion 1.21 Å/pixel, resolution \(R=1300\) with a \(1^{\prime\prime}\)-wide working slit) and long-wavelength (567–746 nm, 0.87 Å/pixel, \(R=2500\)) ones, with the light between them being split by a dichroic mirror with a 50\(\%\) transmittance at 574 nm. In the ‘‘blue’’ channel, it is possible to automatically replace the main grating by an additional one with a double resolving power. Two CCD cameras based on E2V 42-10 detectors cooled down to \({-}70^{\circ}\)C with a readout noise of 3 electrons at a readout rate of 50 kHz serve as detectors. The height of the entrance slit is 3 arcmin. The spectrograph incorporates a back-slit viewing camera and a calibration unit to record the line spectrum of a gas-discharge lamp and a continuum LED source (‘‘flat field’’) to take into account the vignetting and slit width nonuniformity. The transmittance of the entire optical path without losses on the slit at the zenith is 20 and 35\(\%\) in the ‘‘blue’’ and ‘‘red’’ channels, respectively. Excluding the atmosphere and the telescope, the efficiency of the TDS itself reaches 47 and 65\(\%\) at maximum, respectively. The spectrograph is permanently mounted at the Cassegrain focus of the 2.5-m CMO SAI MSU telescope together with a wide-field photometric CCD-camera; the light is fed into the spectrograph by a flat diagonal mirror inserted into the optical path. Regular observations of nonstationary stars and extragalactic sources to \({\sim}20^{\textrm{m}}\) with a signal-to-noise ratio above 5 in 2 h of observations have been carried out with the TDS since November 2019.

中文翻译：

---

SAI MSU高加索山天文台2.5米望远镜的瞬态双光束光谱仪

摘要

瞬态双光束光谱仪（TDS）用于在SAI MSU高加索山天文台（CMO）的2.5米望远镜上对非平稳和银河外源进行低光谱分辨率的光学观测。光谱同时记录在两个通道中：短波长（360-577 nm，倒向色散1.21Å/像素，分辨率\（R = 1300 \），具有\（1 ^ {\ prime \ prime} \）宽的工作范围狭缝）和长波长（567-746 nm，0.87Å/ pixel，\（R = 2500 \））的光束，它们之间的光被分光镜以50 \（\％\）分开。574nm处的透射率。在“蓝色”通道中，可以用具有双分辨能力的附加光栅自动替换主光栅。两个基于E2V 42-10探测器的CCD摄像机冷却到\（{-} 70 ^ {\ circ} \） C，并以3个电子的读出噪声以50 kHz的读出速率作为探测器。入口缝的高度为3 arcmin。该光谱仪配有一个后视镜摄像头和一个校准单元，用于记录气体放电灯和连续LED源（“平场”）的线谱，以考虑渐晕和狭缝宽度的不均匀性。整个光路的透光率在天顶处的狭缝上没有损耗，为20和35 \（\％\）分别在“蓝色”和“红色”通道中。不包括大气和望远镜，TDS本身的效率最高分别达到47和65 \（\％\）。该光谱仪与一个宽视场光度CCD相机一起永久安装在2.5米CMO SAI MSU望远镜的Cassegrain焦点上；光线通过插入光路的平斜镜反射进入光谱仪。自11月以来，已经用TDS进行了2小时观测的信噪比大于5的\（{\ sim} 20 ^ {\ textrm {m}} \）的非平稳恒星和河外源的常规观测2019。