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About Saibot

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    Berlin Mitte
  1. Hi Robin, thanks for your input. For M42 or stars I subtract a spectrum of a nearby sky region taken with the same integration time (60 s). For the moon normalization/response is more tricky. In the literature I find that people sometimes normalized to specific areas on the moon (i.e. Sea of Serenity) in "Lunar Spectral Types" by McCord et al Journal of Geophysical Research, vol 77, p. 1349 (1972). Another option is in principle to construct a sky background model around the moon, or to just obtain the spectral slope with respect to some "average". I am still checking out these different methods. Comparisons can be done to some extent with the Clementine mission data (just 2 points in the visible), or the Moon Mineralogy Mapper (M3) spectral cubes (I still have to see how to process this data better). Cheers, Tobias
  2. Today I took a sequence of spectra across the moon, so far I only extracted the ratio of blueish/reddish color (I averaged across about 40nm around each color), but will look into more detailed analysis to cross correlate for instance with the Clementine mission data. For me it shows that the setup has some spatial resolution on the moon and is working ok! Note the blueish crater on the left side: fresh material). For each spectrum I take also an image with the cold mirror CCD camera (PointGrey Chameleon Mono, USB2), which I then used to determine the location wrt to the spectra taken (I switched off the guiding during the image scan). The Orion nebula M42 image shown in the previous post shows a resolution (full width at half maximum) of around 1nm for the setup.
  3. I took another image yesterday of M42 (Orion nebula) and also of Mirach (Andromeda) to test the fiber spectrometer in combination with the cold mirror (and across the moon, but this requires more processing). In principle the equipment is working fine, I needed to adapt my programming for the readout of the spectrometer after noticing that it takes 1-2 attempts to change the integration time (just to issue a "record spectrum once with 60s" command is not enough. Also as you can see I adjusted the grating to cover blue - red colors. I believe one advantage of the fiber digital spectrometer is that you see the spectrum live on the screen. The post processing is in principle easier, I just subtract a "dark" frame, no need to rotate images etc etc. For the moon there is enough light to cut down the integration time to 100 ms and this should enable me to study the lunar reflectance quite nicely. Overall I can say it works for me, but it requires to code your own data acquisition and processing pipeline, besides the "output" coupler.
  4. Thanks Robin for the comments and suggestions! Indeed the background "noise" is an issue with additional sky light entering the fiber. The supplied fiber with the Science Surplus Spectrometer is not a bad choice, another fiber I bough induces considerably more losses. I checked the focusing by putting tracing paper on the fiber location for verifying a focused image. I compromised on the equipment cost since I can only put my small telescope on a tiny balcony in downtown and see wanted to keep the budget below USD 500 (so far about USD 250 for the spectrometer and another 250 USD for the remaining parts: flip+cold mirror, fiber adapter). This is at a fraction of the costs of the more advanced setups, but it already allows me to study the brighter light sources in the sky, including the moon - and to become familiar with the spectroscopy setup and calibration. For point sources the star analyzer might provide a much cheaper and simpler solution. Still have to see how much further I can get with the current setup... -Tobias
  5. To revive this thread, I also got one unit and first captured spectra of Vega. Next step was to build a beam splitter to have some light available for positioning the telescope. Inspired by this presentation by Jerry Hubbell https://www.raclub.org/Documents/Programs/Engineering-a-fiber-fed-spectrometer-for-astronomical-use.pdf I built my own cold mirror setup with slightly different components. You can see my setup and parts list here: https://quantumdynamics.wordpress.com/2019/01/11/let-the-starshine-in-the-fiber/ Also two spectra I acquired are shown (Vega and Mirach). With my Skywatcher Heritage Newton 130/650 and from the polluted sky around here I estimate magnitude 2.5 or similar is the limit for stellar spectroscopy (60 s exposure). Some caveats: -the repurposed flip mirror requires a back focus of about 7-8 cm. I can do this since I have a Newton (130mm) with adjustable tube length -I wrote my own software to collect the spectral data (serial port protocol, lots of timings/buffer sizes to get right), and at the same time to show the CCD image from the CCD superimposed -many dry runs required to get everything working and aligned, around xmas distant xmas LEDs are a good target to identify LED colors and check the focusing of spectrometer and at the same time the CCD image I just changed the alignment of the spectrometer. As shipped, the window started in the UV range and ended in orange colors, I red-shifted it. This is a very delicate business and I am not entirely satisfied with my current setup, since it lost intensity compared to the original alignment. However I want to do lunar spectroscopy (in particular of the upcoming eclipse) and for this it should work. The spectrometer instructions focus on how to get the line shapes and spectral window adjusted, but less about how to maximize intensity (which is important for starlight of course). Anybody with more comments about the internal alignment of the Science Surplus Spectrometer besides the instructions? The attached image shows Vega, the red graph is the pickles reference. This was with the original alignment and without the cold-mirror. Best, Tobias
  6. Hi, yesterday I might have had a similar problem with the synscan app (Pro 1.14.0, Android) and the AZ-GTi mount. The phone briefly switched away from the Synscan AP to the home wireless network, I connected it as soon as I saw this back to the Synscan AP. The mount meanwhile was tracking the moon fine, the Synscan App was still running, so I thought I can issue another GoTo to a star. The telescope started to turn upside down, I pressed abort to not have equipment falling out and cables getting tangled. I suspect, the mount controller thought it was not pointing at the moon but back to initial North/horizontal direction and thus started turning completely wrong. This happened after about 1 hour observing time and initial pairing of Smartphone + Mount. So there might be an issue with the Synscan App and (short!) intermittent WiFi interruptions to cause a loss of orientation. Did others experience something similar? I reported it to the local (German) Skywatcher representative through the webform, he was not aware of this problem. I will try two work arounds: -use an older Smartphone which does not do the "Internet not accessible with this WLAN" check (I don't see an option to lock into only one Wireless on Android 8/EMUI -remember to switch off the home wireless router before observing so that the home network is physically not available and the phone maybe will not even try to connect to it Anybody else having this trouble lately? -Tobias
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