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drjolo last won the day on July 23 2018

drjolo had the most liked content!

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About drjolo

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    Star Forming

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    Nieborowice, Poland
  1. Thanks Jim! I will do some final tweaks and clean up, and also need to add some small diffuser to Relco starter to make calibration more reliable. Then I will post or link whole project here. At this moment I am very happy with LowSpec results. Resolution is pretty high (over 1500 at the red part with 600 lpmm gratning), it is fairly easy to setup and calibrate. I use QHY163M as main camera, ASI290MM as guider, all is attached to 10" SCT and there is IMX224 camera with 50mm guider as electronic viewfinder. One tricky part (for me at least) was to align guiding optical path. Guiding lens is fast and needs to be set very precisely to avoid coma and/or astigmatism. Now it is time for me to decide what kind of work it should do. I am not yet 100% sure, but I ordered 1800 lpmm grating to check it out I already had few nights with LowSpec (with and without Moon), and my almost all spectra are at my blog https://astrojolo.com/spectra/
  2. Yeah, I already have problems with such solution - I wrote about it at separate thread https://stargazerslounge.com/topic/348122-relco-sc480-starter-lines-position-depends-on-bulb-orientation/ . I need to redesign it to use some diffuser.
  3. I use LowSpec spectrometer in the (mostly) remotely controlled roll-off shed and also I plan to use 1800 lpmm grating, so I decided to automate the device. The automation covers such functions: moving Relco starter in and out of optical train adjusting grating angle adjusting focus switching on/off Relco starter regulating 0-100% slit LED iluminator perform all the tasks above from the dedicated small software The components that were used: three small 12V BYJ28 stepper motors with integrated gear box Arduino Nano two ULN2803 universal drivers universal PCB, two 5.5/2.1 DC sockets, 5 and 2 pin JST XH connectors, some cables and wires 5mm red LED with 15 degree light angle as slit iluminator M5x100 bolt that replaces M5X80 bolt in focuser M6x40 bolt with M6x20 cylindrical nut that replaces micrometer screw to regulate grating angle 3D printed elements - casing, gears, etc All gears and software were developed and assembled step by step, so actually there was no serious problems during whole process. Currently Relco starter is controlled with small relay, but it will be replaced with 12V inverter, so no 230V will be supplied to spectrometer. After one and half night session all worked well, and I didn't need to visit my shed to refocus or change spectrum range. And that was the idea behind it If someone is interested in this solution please let me know, so I clean up all files and share STL objects to print, schematic, Arduino sketch and control panel software. Panel is for windows system only, but the communication protocol with Arduino is pretty simple, so it can be rewritten to other systems as well. Or it can also be controlled using serial port terminal as well. RR Her spectrum below - captured already with modified LowSpec spectroscope:
  4. Thanks for quick response - I didn't realize that I would need RV standard stars for high accuracy RV measurements. There is whole lot of things to learn. I will check again if that shifts in my setup are caused only by bulb rotation and if they are repeatable. I will fix that bulb in the holder so it will not rotate, add some small diffuser and then maybe the line shift will be more stable, so it can be measured with RV standard stars.
  5. In my LowSpec spectroscope I placed Relco SC480 starter bulb to be able to do absolute spectrum calibration. Last night I made some first tests and tries to measure Doppler shift one of the fast stars http://simbad.u-strasbg.fr/simbad/sim-id?Ident=hd237090&submit=submit+id - 120km/s. Hovewer the results I achieved were far from true (about +30km/s when velocity correction was applied). I eliminated few possible error sources and noticed, that position of emission lines recorded from Relco starter depends on the bulb orientation (rotation along vertical axis). Starter is placed about 25mm in front of the slit, and is oriented parallel to the slit direction: I recorded three test starter spectra after rotating it 90 degrees in the mouting hole. The lines are significantly shifted depending on the starter orientation: This is screenshot from BASS Project software. All images were tilt and slant corrected in the same way and active region is the same for each image. Lines are shifted by several pixels (dispersion is 0.61A/px). I do not think I will be able to do proper calibration in such configuration. Am I doing something wrong? There must be a way to do proper calibration with starter bulb in front of the slit - many commercial devices work that way.
  6. I have ordered two small Nixie tube regulated converters, once they arrive I will let you know. https://pl.aliexpress.com/item/32926216972.html https://pl.aliexpress.com/item/32986857367.html
  7. It may be a good idea. My current setup is 2500mm focal length SCT as main scope, and I use ASI290 mono camera as guiding camera, QHY163M as main camera. Additionally I have 50/180 finderscope with AltairAstro IMX224 camera as electronic viewfinder. After three sessions I use this flow (finderscope and slit area are already aligned during daylight at distant object, and also main camera is focused to spectrum, and main telescope is focused to slit) : I connect QHY163M as main camera and IMX224 EV as second camera to Maxim. Then I do plate solve / pin point using finderscope and IMX224 , and manual slew to point telescope to the star (like Aldebaran) using EV crosshairs I connect ASI290 to PHD2, and the star should be already in the FOV (it is 8x5 arc minutes for my setup) I light the slit back and check if slit frame preview in PHD is in the right place I use 0.5x slew rates in RA in Dec to put star somewhere closer to the slit. Now you may start PHD calibration if you want to. Then I use 0.5x slew rate to put star on the slit. Set proper PHD exposure time to see some star in the FOV and start guide Once you start guide, you can still move the star precisely to the slit, there is a proper menu option in PHD You may now take spectrum, for bright star few seconds is enough. And check focus - if the spectrum is a single thin line It took me like 3-4 hours at the first session to get it all sorted out. But last time it was much quicker, like maybe 30 mins to get first spectrum. One of the last session capture - YY Gem (Castor C) - unusual for M dwarfs emission lines:
  8. You were 100% right - guide lens misalignment was the root cause of that. I printed guider lens holder one more time with larger holding ring, put there guiding lens and aligned as good as I was able to, and now all works and looks fine. Stars are round in the FOV centre, so I am able to focus precisely. Star spectrum height is minimal. The star images at the FOV border are still distorted, but PHD handles with it very well. Reflections from brighter stars are still there, but that is not a big issue at all. Images from guider (Meade ACF 10" f/10 + ASI290MM). Eskimo (left) and WR4 star (right) Raw stack of Aldebaran spectrum 10x5s
  9. The lens fit perfectly into the holder inner diameter, so this dimension is okay. But (at least in my case) this protruding edge was too thin, and was not able to stop lens in the stable position. Lens fits tight to the 12.75mm hole, but it tilts and wobbles at this thin edge. I made this edge a little bit larger, so the aperture is now 11mm, printed it with 0.12mm layer height and it seems to be much more stable now.
  10. I have checked yesterday my guiding lense - it was tilted about 1mm (!!) in the holder. The guiding lense holder has very small holding ring (0.2mm), and setting lens position precisely is not an easy task. I redesigned it a little, so holding ring width is now about 1mm. The lens aperture is then little bit lower, so the image may be little bit darker, but also better quality. This lens focal ratio is f/2.4, so it is extreme especially for simple doublet lens. Fraction degree tilt may degrade image significantly. With this new holder I adjusted and checked all using 25um artificial star. Results are promising, of course reflections are still there, but the star image quality was good, and once placed at the slit it almost disappeared - so most of the light was focused well. Now I need to wait for another clear night for real tests.
  11. If you align spectroscope slit along E-W direction, then tracking and guiding errors will move star along slit. You will not loose light then when star moves off the slit, only the spectrum will be little bit higher.
  12. Two days ago I collected night sky spectrum as well, but this time without clouds and without Moon. I estimated NELM to 4.5mag - some haze and high clouds were still present. Hydrogen absorption lines that came from sun light disappeared due to missing Moon. Oxygen glow at 5577A is much more visible. Also I adjusted focus much better, so now Na doublet at 6154A is resolved, and also some peak appeared inside wide Na absorption line at 5890A that comes from high pressure sodium lamps. Small peak around 4500A probably comes from blue part of white LED light https://www.nature.com/articles/lsa2015105/figures/5 .
  13. Ken, thank you for your suggestions. I will review guider path and check guiding mirror and lens once more. I have 25um artificial star that should help to figure this problem out. Despite such poor guiding image PHD did a good job and RMS tracking error was about 0.6" total in both axes. And here is my first star spectrum, calibrated with Relco starter and processed in BASSProject software. I am very happy about it Resolution is quite good, both Na doublet and Mg triplet were separated.
  14. Today some stars appeared at my night sky, so I attached spectroscope to the 10" Meade ACF f/10 telescope and made first light. I was able to obtain first spectra of bright stars, however I am a little bit concerned about the shape of the stars image at the reflective slit. I have slit mounted with reflective surface pointing to the camera. The star (Betelgeuse) image looks like this: These 6 images shows star at different focus positions. Telescope is collimated well, because I checked it before I put spectroscope into the focuser. The resulting spectra is extended vertically (along the slit) and also slanted in different directions at different wavelength: Left image is blue part of the spectrum, right image is red part. This spectrum was done at the focuser position that corresponds to the third image from left in the upper row of focusing images. I wonder if I should reverse the reflecting slit, so its reflective surface points to the telescope.
  15. I was not yet able to point my LowSpec spectroscope to stars, but Saturday evening I pointed it to the cloudy night sky to measure and identify main light pollution sources. LowSpec has 600 l/mm grating, and camera used was QHY163M. Main source of LP at my location are high pressure sodium lamps, that are responsible for emission Na 5688A and wide bell shaped 5890A line with absorption peak. There are also few weaker lines that comes from mercury Hg - these are emitted by different type of street or garden lamps. Natural airglow that comes from oxygen occurs at 5577A and 6300A. First of these lines can be identified, however I was not able to detect anything meaningful at 6300A. There are also two obvious absorption lines at 4861A and 6563A - I quickly identified them as hydrogen beta and alpha. But I had not idea what could be the source of such lines in the spectrum of night sky background. After some time I remembered that night before I admired almost full Moon in the sky. And Moon reflects Sun light, so these two lines comes probably from Sun light reflected from Moon and then dispersed in the cloudy night sky. Barely visible magnesium triplet confirms this. However I plan to take night sky spectrum two more times when Moon will not be visible - with and without clouds.
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