Science topic

Optical Astronomy - Science topic

Explore the latest questions and answers in Optical Astronomy, and find Optical Astronomy experts.
Questions related to Optical Astronomy
  • asked a question related to Optical Astronomy
Question
4 answers
I am wondering if it is possible to measure mode-locked laser stability (timing jitter, Noise) with an oscilloscope if the pulse duration is in the femtoseconds regime (lets say 150fs). If so, what type of measurement on an oscilloscope would quantify laser stability. What should be the bandwidth of the photodetector and oscilloscope?
Relevant answer
Answer
I concur with Ahmad Adel Alsakati
  • asked a question related to Optical Astronomy
Question
7 answers
Can any one help me how to find a detailed information about several radio telescopes: VLA, VLBA etc? I am interested mainly in spacial resolution, working frequency and sensitivity - minimum detectable values in Jy.
Relevant answer
Answer
Thanks dear Alvaro :)
  • asked a question related to Optical Astronomy
Question
2 answers
What are the advantages of using the michelson interferometer ? 
What are the disadvantages of using other interferometers ?
What are the trade-offs ?
Relevant answer
Answer
Arms of LIGO are physically 4 KM long. However, in each arm the laser beam moves to and fro 280 times. That is, in effect the beam travels 4x280=1120 KM in each arm. This is achieved by a Fabry-Pe'rot cavity placed in each arm of LIGO. Notice that near the beam splitter there is a mirror and also at the end of the arm there is a second mirror. These two mirrors together form a Fabry-Pe'rot cavity. Due to the presence of this optical cavity, the effect of a passing gravitational wave on the light phase is enhanced by a factor of 300.
LIGO interferometer is thus a basic Michelson interferometer with enhancements. Following are some enhancements,
  1. Each arm contains resonant optical cavity
  2. 20 watt laser input is increased to 700 watt at the beam splitter and 100 KW circulating in each arm cavity.
  3. Partially transmissive mirror at the output broadens the bandwidth of the arm cavities.
  • asked a question related to Optical Astronomy
Question
129 answers
The energy of a CMB photon when released is given by Planck constant times frequency; and also at arrival. Therefore, as frequency decreases with expansion, the energy at reception is S times lower, being S the space expansion since then. As S is around 1000, the CMB photons arrive with an energy that is only 1/1000 of their original energy; where is this huge missing energy?
Reasoning in a different way, the energy density of a black body radiation is proportional to the 4th power of temperature, which shifts inversely to space expansion; so the energy density decreases with the 4th power but space expansion only accounts for the 3rd power decrease.
What happens here? Is this a problem of missing energy? Or is this evidence that there is no conservation of energy over time?
Energy conservation is a property of mechanical interactions that was assumed as a fundamental law; truly, we only have evidences of this law in interactions, but not through time with the accuracy required for applying it at cosmic scale.
Conservation laws presume and imply an invariant, static, universe; but the universe is not static.
What do you think? Is energy missing in cosmic radiation or the validity of conservation laws over time needs to be analyzed?
Relevant answer
Answer
A Few Things You Need to Know to Tell if a Mathematical Physicist is Talking Nonsense: the Black Hole - a Case Study, 29 July, 2015
  • asked a question related to Optical Astronomy
Question
8 answers
The review can be numerical, analytic or observational in nature.
Relevant answer
Answer
You can read these reports
1. A panchromatic view of AGN (Risaliti) http://arxiv.org/abs/astro-ph/0403618
2. Seyfert galaxies in the local Universe (z≤ 0.1): the average X-ray spectrum as seen by BeppoSAX (Dadina) http://arxiv.org/abs/0801.4338
3. Revisiting the Unified Model of Active Galactic Nuclei (Netzer) http://arxiv.org/abs/1505.00811v1
  • asked a question related to Optical Astronomy
Question
2 answers
I am trying to study the IR spectrum of hot water in the waveno. range 4000 to 400 cm (inverse). If any published data is available, that will help me a lot! This is in turn an attempt to study the hot water spectrums obtained from the sun (sunspots).
Relevant answer
Answer
There is another way to find IR spectrum of hot water  by yourself through the well-known software LBLRTM (one software for atmosphere). It is not difficult to run the software LBLRTM.
  • asked a question related to Optical Astronomy
Question
12 answers
I am currently writing software to control a small refractor (125 mm). Drive motors are brushed DC, encoders are 10 000 ppr mounted on the motors, gearbox has 1:8000 ratio. The German equatorial mount is well built and solid. The observer's software has a GUI and writes directly to Excel spreadsheet using dynamic data exchange (DDE). Another program communicates with the servo drives, and receives pointing information and other instructions from the GUI, via Excel spreadsheet. So both the GUI and servo control software can exchange data via DDE and both can read and write to Excel spreadsheets, allowing data plots, simple statistics etc. Currently the software has a fair number of GUI accessible functions. What would you expect a telescope control program to have as a must, and what would you like if you could choose features?
Relevant answer
Answer
Telescope/mount control is fairly simple - namely "point at this!". Users will generally specify "this" in J2000 coordinates, not current epoch, so you should do the conversion for them. I've never had a need for lunar or other exotic tracking variants. You may want to support "tracking off" for TDI or imaging geostationary satellites (which is fun). Because my mount is so poor, I've automated taking a pointing image, computing a plate solution and sending a correction to the scope, so it's genuinely pointing at the target before taking the "science" image. You can probably use a TPoint model instead. If you have an automated focuser, you could implement your own temperature and filter compensation. Camera control is the real challenge. Useful parameters to expose to users include binning, filter, subframe, exposure, raw/dark/reduced (ie. do you want image calibrated or not). I've gone a bit further to automate stacking and tiling of images. I also compute a plate solution and embed it in the final FITS image.