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GuLinux

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About GuLinux

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    Star Forming
  • Birthday 02/07/81

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    http://blog.gulinux.net

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  1. Sort of bumping this thread, as I'm very interested as well (I too want to use it on a StarAdventurer, with an ASI1600mm and RGB filters). It seems there are two version of this scope: the INED version, which seems to be the oldest, with FK61 lenses (and can still be found somewhere), and a newer version, with FPL51 (theoretically should give the same colour correction, but who knows?) Anyone tried any of those as AP scopes?
  2. Which given the kind of work that has been done, will likely be quite unstable Just kidding though... I was waiting for this, it will be easier to contribute to the project now
  3. I still have to test this solution, but I'm planning to use hands warmer instead, with an aluminum sheet to spread the heat, and some cloth to insulate it
  4. Skywatcher Star Adventurer

    Yes, what I mean is checking the position with a "polar finder" app. Maybe I'll just write my own version of it, but accepting an "offset" after you rotate the RA axis
  5. Skywatcher Star Adventurer

    Do you mean the locking screw on the wedge? If so, I always tight that one a lot, to avoid any backlash, I always do my adjustment with that tightened up. I need to recheck it, but it was fine last time I looked it. Not 100% accurate, but pretty close. Well, I was hoping to polar align after pointing my cameras, so I'd need to know where on the clock face it should be. But I see your point, I might just polar align before, and then check that polaris is still roughly on the same place. I'm starting to think it might not just be a polar alignment problem, but a balancing issue, affecting tracking speed. 2 degrees is a hell of a misalignment, it's almost the whole field of view of the polar scope!
  6. Skywatcher Star Adventurer

    My major concern right now is polar alignment. With some work, I can get it to align quite precisely, the polar scope is very nice, the knobs are a bit too wobbly, but in the end, it's doable; the problem is that whenever I touch my camera(s), the alignment goes off, sometimes by a lot. Last time I used it, my images had a huge drift, almost 2 degrees over 5/6 hours! I use it with a slighly high focal length (200mm), and I wish to go further in the future, around 300/350mm, but unless I solve the polar alignment issue, it's gonna be tough. I use the L bracket, so you can avoid a few problems (you don't need to mount the cameras after polar alignment), but when I point them it' still the same, I loose much of the polar alignment precision anyway. When using the L bracket you can still look through the polar scope, so I was thinking of a different polar alignment workflow: first a rough polar alignment, then pointing the cameras, then a precise polar alignment, but if you rotate the RA axis, you loose your reference to the exact position of Polaris, and you don't know where it should actually be. Has anyone found out how to improve polar alignment?
  7. I found some unpacking/first light pictures, I forgot they were in my girlfriend's phone
  8. Well, this is a first "preview": telescope close to my luggage and laptop backpack. As you can see, it's just slightly bigger then the latter (although much much heavier... almost breaking my hands... I need to add wheels ) I was expecting troubles at the security checks, but surprisingly they didn't even ask me for further inspection. Ready to go
  9. Thanks for the tip. Fortunately I just found out what was wrong with my thumbscrews: when I first tried the collimation, I probably did tighten one of them too much. As result, the little nut that's between the mirror cell and the support go tighten too much as well, basically creating loads of friction. Just loosening it a bit had a massive improvement.
  10. Will do Well, there are a few airline companies that allow "as much as you can lift" (easyjet) and up to 23 KG (BA). I'm much worried about airport security, though
  11. After a long wait (ordered on May, received it on August) I finally received my new baby The scope is the Sumerian Optics Alkaid, 12 inches version (300mm). http://www.sumerianoptics.com/products-price/ It was ordered from Teleskop Express (DE) It's a bit expensive for a dobsonian telescope, but I was really looking into something very portable. The "fold into a hand-luggage compliant suitcase" feature is really amazing. Not many airline companies do actually allow so much weight (16 KG), but still you can find a few, and I'm gonna see what happens on my next trip in Italy in a couple of days. I haven't yet used it a lot, due to weather, moon, and laziness but these are my first impressions: Unboxing The scope was very well packaged, it was a mess to cleanup the house with all that foam peanuts This of course is all very nice for transport, what was less nice is that all this, and the protective cotton over the mirrors, did create a lot of dust and filaments all over the mirrors. Nothing serious, cleaned most of it with a little air pump, but they might think of a different protection layer for the mirrors. Assembling The first time you read through the provided manual, get it wrong on a few steps, but overall instructions are clear enough, and most of the pieces can be mounted in one way only, so it's quite straightforward. Mounting the suitcase back requires some attention too, but there are instructions for this as well, so it's easy. After doing it a couple of times, you can really assemble and disassemble the whole thing in a matter of 5/10 minutes. Collimation This is where I'm still having some problems. Some of them due to the scope it self, but some might also be because of my inexperience with it, and with the Cheshire tool (I was previously using laser collimators on smaller newtonians). The secondary collimation is quite straightforward. I'm still having some minor issues in aligning it to the focuser, but with more experience it should get better. The primary is what troubles me most. Both the secondary and the primary use a two screws system. The third one is fixed, and you should align it by moving the other two. This in theory should work, but it seems that the two screws don't have enough run to compensate for major misalignments. Also, the screws movement is quite irregular, and after a few tries, one of them became very very hard to move. I will try again using some grease, otherwise I might think of replacing them with some plain old allen keys. Movements and stability Movements seem to be quite smooth. The scope is also provided with a shock cord "counterweight" system for balancing heavier eyepieces. I don't have any (yet), but I'm planning to buy a 1KG ep with a big FOV, so I tested balancing with a 1KG counterweight attached to the focuser, and it seems to hold on quite well. I also bought a third shock cord in addition to the two provided, just in case I need more traction. Red dot finderscope Mixed feelings with this: it certainly looks nice, and it also has a green setting (for daily usage/bright objects I guess?). But to align it you need an allen key (included), which feels a bit uncomfortable, and the window doesn't seem clear enough, blocking too much light, so it's a bit difficult to point at faint objects/stars. The finderscope is also too close to the tube, so it's not very comfortable. I will have a few more runs, and then decide if I want to replace it with a different one (I have a Celestron Starpointer Pro, which I have used with quite some satisfaction). Light shroud There is a little shroud provided, but honestly I haven't even tried it, I really didn't like the idea of an open truss. Instead, I sewed a full length shroud using some lycra cloth. I added some magnets to the top and bottom of the telescope, in order to keep the shroud in place. First light I had a quite unlucky first light, actually. There was too much dew, and the moon rose slightly after 11 pm. I just made it to view a couple of objects (easly resolved polaris b, the ring nebula), but the eyepieces got quickly covered with dew. In a way that was also useful though, since I both tested that my light shroud protected quite well the primary mirror (no sign of dew in there), and the built in anti-dew of the secondary, that in 5 minutes cleared it out. Overall impressions I still have to familiarise with it, particularly with the collimation, but I am really satisfied with this setup. The portability side is quite amazing, I could put it in the back of a quite small car, with lots of room to spare! I'm looking forward to a few more detailed tests over the next few weeks, in a fairly darker spot. I'm a bit worried about the airplane trip, but we'll see about that...
  12. Imaging with the kit lens

    Actually I have the same problem with my liveview (EOS 700d): with the "standard" 18-55mm canon lens I can only see very bright stars, and only when zoomed at least 5x. I also tried the same camera with a different lens (Samyang 85mm), and the situation is much better. I suspect it has something to do with the stars being too small, or the lens being too slow (f3.5 at best), in fact it's quite annoying!
  13. Raspberry Pi Zero SQM

    Yes, of course But my problem right now is more "theorethical": before calibrating, I need to understand the right formula, and where to apply the calibration factors in the formula (wether they are constant, linear, logarithmic, etc). Good point about the temperature... luckly I have the temp sensor in there, might be useful!
  14. Raspberry Pi Zero SQM

    I've started this little project, using the TSL2591 Adafruit sensor, which seems to have an adequate dynamic range for SQM readings. I finished putting the hardware back together, and hacked a "quick&dirty" software to get the readings and showing them to an OLED display. I also added a temperature/humidity and atmospheric pressure sensor, and the ability to log the readings to a file for future reference. On the hardware side it miss refinings, but not big things: a lens for the light sensor, a decent case (3d printing would be perfect, if only I had a printer..), add a button for the readings and turning everything off (right now it's on a loop, every 2 mins), and maybe redo some solderings. But the software, that's where it gets a bit messy. This is my current implementation: https://github.com/GuLinux/raspi-sqm-weather/blob/master/sqm.py I found only one other project using the same sensor, and this is the associated code: https://github.com/jvoight0205/SQM/blob/master/SQM/SQM.ino The line doing the calculations is quite misterious: mag = -1.085736205*log(.925925925 * pow(10,-5.)*adjustedVisible); It's not clear where the numbers come from, how could I change them for calibration, and of course, I'm not even 100% sure that the formula is correct at all. I saw a similar formula in the Arduino SQM thread on this forum using the TSL237, where the starting point is a frequency. But at a guess, to reuse the same formula, I'd have to know: 1) if the readings I have from the TSL2591 output is a frequency as well (I suspect so, but I can't be 100% sure... the specification document doesn't mention frequencies, but "counts": https://cdn-shop.adafruit.com/datasheets/TSL25911_Datasheet_EN_v1.pdf ) 2) If I should subtract the IR value from the Visible as shown in the other project 3) How to properly scale the values to apply the same formula as the TSL237. Any ideas? Cheers, Marco
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