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dph1nm

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About dph1nm

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    Sub Dwarf

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    http://www.dur.ac.uk/nigel.metcalfe/astro/

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    Durham
  1. Looks more like fringing to me. NIgelM
  2. dph1nm

    Synguider help

    I think mine did that when I tried to run it off 6V. In the end I used 9V and it was much happier. NIgelM
  3. The 12S Quattro comes with a Losmandy dovetail - so it is obviously possible for Skywatcher to produce suitable rings. NIgelM
  4. dph1nm

    EQ8 and Focal Length

    I have successfully imaged unguided for 2mins at 0.6"/pix with my EQ8 (with PPEC turned on). NIgelM
  5. dph1nm

    How to Get Less Noise

    There seems to be some confusion in this thread. So the only real difference between ISO400 and ISO1600 is that the read noise is lower at ISO1600 (for the Canon 1000D) and the dynamic range is greater at ISO400. The amount of light you collect is the same at either ISO. So to overcome read noise you will need somewhat longer subs at ISO400 than at ISO1600. However, If your subs are already long enough to overcome read noise then you may as well use ISO400 to get the higher dynamic range - but the final signal to noise will be the same for either ISO, if your total exposure time is the same. NIgelM
  6. I don't think DSS will stack images (whether flats or lights) of different exposure times. You can get round this by editing the images' properties in DSS and setting them all to the same exposure time (might have to be 1 sec, as I could never get the editor to accept shorter times). NIgelM
  7. I believe that if you do a 3 star align these numbers are re-calculated. Previous values are only applied to 1 and 2 star alignment. NigelM
  8. dph1nm

    SkyProdigy is slowly dying

    Yes, my SLT (which I have had for many years) did/does this. Still works though - even though it slows it still gets the coordinates right! I believe I read somewhere that the problem is the brushes on the motor getting dirty, but I have never tried to clean mine, so I cannot verify this. It does sometimes help if you run it round and round at the highest speed for several minutes though. NigelM
  9. You can safely ignore the NPE (and CE) messages. They shouldn't happen if you do a three star align anyway (as they are calculated afresh when you do one), only for 1 and 2 star (as you need at least 3 stars to calculate NPE and CE). NPE shouldn't change anyway, as it is the orthogonality of the mounts axes. CE is the cone error, which depends on how the scope is fastened to the mount, but I don't image that will alter unless you change the scope. However 39' is quite an offset for the polar alignment, especially if you are trying to image. NigelM
  10. dph1nm

    DSS trails

    Using the superpixel debayering mode in DSS might fix the problem (which is almost certainly due to the stars being out of focus). Nigel M
  11. How? These mounts do not have encoders so cannot know where they are when you first switch them on. The only possibility I guess is that they have a home switches on the axes, but my (admittedly old) HEQ5 doesn't (although my EQ8 does). NIgelM
  12. dph1nm

    NB filters reduce skyglow!

    Hmm - not sure this makes much sense. As I understand it the SQM already has a 'visual' broad-band filter, and the results are calibrated to work for that. So if you stick another filter in front surely the calibration will not be right? I mean I could stick a neutral density filter in front and get as faint a sky as I liked. NIgelM
  13. Don't guide with mine, I just use (P)PEC - the P is in brackets because it doesn't seem very permanent to me. All I can say is when it is good it is very good (I have done 2mins unguided at 2000mm focal length - 0.6"/pixel - with perfectly round stars), and when it is bad it is really bad (messes up even 30sec shots at 1"/pixel). It seems to go from one extreme to the other randomly, although to be fair it is mostly in the good mode. NIgelM
  14. dph1nm

    Synscan and the 'Home" setting

    Yes, I am sure the alignment routine assumes you are polar aligned and in the home position. It then just needs to know the difference between the RA of the alignment star and the current sidereal time, which it can calculate from the clock time etc. But should Show Position work at this stage? - I would have thought that would depend on whoever wrote the software. My suspicion would be that as there is no sky model yet Show Position would not work - I have never found synscan very sophisticated. I have never checked though, nor, to be honest, felt the need to. NIgelM
  15. dph1nm

    Synscan and the 'Home" setting

    "Home" is not necessarily RA=0 - I suspect in practice it should be more like the current sidereal time. However, when you first power on the mount it has not done an alignment, so I am not sure whether you would expect "show position" to return anything useful (I have never looked). It is also not necessary to start from the exact home position (or to be level) - you can just unclamp the axes and move manually to the first star (by doing this you are, in effect, refining your home position and clock time). Don't do this with subsequent stars in a 2 or 3 star alignment though! The real question is why are your star alignments failing - a 1-star alignment should never fail, so I assume you are talking about 2 or 3 star alignments. With the original firmware in my HEQ5 (3.2 something I think) 3-star alignments would often fail for no apparent reason, but this seemed to be fixed with the later firmware updates. I think to get a 2-star alignment to fail you would either have to have your polar alignment, or some of the initial handset settings, wrong, or to have aligned on one or more wrong stars (or to have some mechanical/software fault of course). NigelM
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