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Pompey Monkey

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Everything posted by Pompey Monkey

  1. Pompey Monkey
    OK. From a few years back, the Rosette in HaLRGB with a 150PDS, STF8300M and Baader filters. All on a AZEQ6 from a fairly (Bortle 5/6)* light polluted site: Edit: Not "(Bortle 3/4/5)" as I originally wrote.
  2. Pompey Monkey
    You can make one for a third of the cost of a pre-made cable (sorry FLO!). The most important thing is to get a genuine FTDI USB to RS232 serial adapter. Also, as said above by @dunc check the TTL voltage against the mount specs. BTW, APT is a very good piece of software. @Yoddha puts a lot of work into it and listens to all the user feedback!
  3. Pompey Monkey
    Seconded!
  4. Pompey Monkey
    Well I haven't posted an image for a long time, sometimes because I am not satisfied with the end results but, more often, because I give up half-way through. Ii's a character trait of mine that I have to keep fighting! Anyway, I've paid a deposit for remote hosting (with a friend) at E-Eye, so thought I'd better start finishing stuff... Here is my take on M45 from the beautiful Bortle 2/3/4 skies over Portsmouth. I don't have the raw data to hand, but it's probably around 10 hrs of LRGB. Equipment as in the signature. Hope you like it.
  5. Pompey Monkey
    I've seen this before and I think that it was a around the time that I was fiddling with back focus distance on my Esprit 880ED. Have you allowed for the increased optical path length due to the filters? This is usually approximately 1/3 of the thickness of the filters. See here http://www.qsimaging.com/downloads/QSI-500-600-Series-Back-Focus.pdf Also, are the bananas oriented the same all over the FOV, or do they gradually change curvature over the image? If they change, it might be another indication of incorrect spacing between the comma corrector and the imaging plane. Can you post the whole image?
  6. Pompey Monkey
    Are you sure it did not actually brush against the mount at some point? The other thing that comes to mind is a less than perfect PA - this is another source of cone error. However, given the quality of your images, I suspect that your alignment is rather better than +- 3/4 of a degree!
  7. Pompey Monkey
    PI works on Linux
  8. Pompey Monkey
    I gave this post a "like" because it's obviously well informed. However, everything I've highlighted in red illustrates why the mainstream user does not understand and does not adopt Linux: I know what an "ISO" is, but many wouldn't and I have no idea what the other highlighted terms mean, and I'm an engineer who's been on a Unix administration course! I know that GIYF, but it takes time I want to adopt Linux, but the learning curve is steep and, to be honest, puts me off somwhat. I will, however, persevere. One thing that came to mind to me is to get a secondary system running with mount/camera/obsy simulators until I'm confident that I can diagnose problems and find solutions without wasting night upon night of clear skies before going "live"....
  9. Pompey Monkey
    This is a good idea - adding the missing, but necessary, quality assurance. I hope that everyone buying one of these "budget" 'scopes will seriously consider the small extra cost to be a good investment.
  10. Pompey Monkey
    Patent pending? ;)
  11. Pompey Monkey
    Yes! Even more remarkably, I already have the correct spacers for my SBIG CCD/ SX FW combo! That's why I'm buying new: peace of mind. You may, or may not, have seen my thread in "whole scopes" about the second hand Star 71 that I bought a couple of months ago. To my mind it's a write off. Actually, it's worse than that as I've wasted every clear night since the middle of February faffing about with it. Particularly galling as the weather was soooo bad through out autumn... One more question: Do I need a metric or imperial ADM dovetail kit? I'm specifically thinking of the threads on the scope bracket for the low-profile screws. Cheers!
  12. Pompey Monkey
    Well that was fourteen long pages.... ....with no conclusion! I have a SW Esprit 80 ED, flattener and extra dovetail (for balancing my filter wheel and CCD) in the basket at FLO. I'm just itching to pull the trigger but have yet, despite numerous excellent astrobin images, to be convinced of Skywatcher's QC... Anyone? FLO?
  13. Pompey Monkey
    Or you could draw some fine lines on white tape
  14. Pompey Monkey
    I know this post is straight out of the morgue, but it just saved my afternoon!
  15. Pompey Monkey
    Lovely - understanding what you are taking pictures of is sadly missing in too many examples nowadays - you have an excellent appreciation of the "bigger picture" as they say.
  16. Pompey Monkey
    Hi, and welcome to SGL! Your set-up looks fine. The position that your DSLR finished in is actually a very logical one for balancing and works very well, even if it looks counter-intuitive to the inexperienced. Also, APT is my capturing software of choice and will see you a long way into your imaging career. As you are using a DSLR, I'll add one more thing: dither, dither, dither. Dithering is the best DSLR noise reduction strategy (in conjunction with taking more subs) there is. Dithering works great with APT and PHD
  17. Pompey Monkey
    You'll end up either needing or wanting a coma corrector for sure A lot of posters don't mention camera speeds because they use CCDs... Awww - what the heck - it's only 20 mm more - here's my Rosette with the 150 PDS and Skywatcher CC
  18. Pompey Monkey
    I was. But now I had a chance to look at the full size image, I agree with you that it looks like a touch of coma. Sorry about that. Have you got the spacing between the CC and the sensor correct?
  19. Pompey Monkey
    That looks more like internal reflections than coma to me. Welcome to the world of worrying about second-order effects
  20. Pompey Monkey
    Morning Richie, Funnily enough, I only posted about this in another thread just last night: "15 mm movement on a 750 mm focal length telescope is a 2% radius = 4% loss of light due to spillage past the secondary, assuming it was fully illuminated in the first place. I can live with that As for vignetting, I would hope the telescope manufacturers would design for none with the focuser fully extended. I certainly don't see evidence for extra vignetting on my flats. In summary, a small longitudinal movement of the primary is unlikely to have a critical effect on the optical path." I do have the 150 PDS, but the principle is be the same. It's all just triangles. As for the scooping out of the focuser tube.. Well you could always try it and report back your results...
  21. Pompey Monkey
    Good old engineering judgement: I'd read that 10 mm off the focuser would fix the "bitten" star feature. Another 5 mm made sure* I'd also picked up my 150 PDS OTA from Astroboot for £113.50, including postage (Brand new, with just a tiny scratch on the tube). So it would only be a little bit painful if it all went wrong. But how could it go wrong? It's just metal tube and some mirrors! *Of course I checked that I would still be able to reach focus first!
  22. Pompey Monkey
    You missed one, but it still involves the hack-saw: I chopped 15 mm off of my OTA at the primary end and re-drilled the four cell mounting holes in my 150 PDS for the same reason. The advantage of this over the focuser hack is that I could use the tripod to hold the tube while I did the dirty deed. The whole job took less than two hours.
  23. Pompey Monkey
    Odd. That's just the point of doing the flats in the first place. As I posted before, because the correction is normalised and multiplicative, as long as the sensor is reasonably linear and the flat is not clipped at either end, it should not matter... But obviously the range does matter, and your images are a testament to your experience
  24. Pompey Monkey
    Kudos to doing the hacksawing, Rob - I chickened out at this point, although I did hacksaw off 15 mm from the OTA at the primary end of my 150 PDS to stop the focuser causing the odd star shapes! Believe me, I was sweating over that one But why the 16,000 to 20,000 max ADU for the KAF 8300 flats? I've not come across a compelling reason for this in my 'net travels. I'm sure that your experience shows this to be correct, but is there an engineering explanation? Cheers, Paul
  25. Pompey Monkey
    I only do it up finger tight! As tempting as it is to use an allen key, the coma corrector is a delicate optical assembly
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