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almcl

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About almcl

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    Telford, Shropshire
  1. Ah, yes good point. That could certainly be contributing to the problem, couldn't it?
  2. To interpret the guide logs there is a tool (written by one of the programmers of PHD2) here http://adgsoftware.com/phd2utils I find it very useful for analysing guiding performance. Among other things it reports that your Polar alignment error was less than 1' : There is a brief explanation of its use on that page, but if you want to dig a bit deeper, there's a pdf that can be downloaded here https://openphdguiding.org/tutorial-analyzing-phd2-guiding-results/ Looking at the 4 logs for May, I can't see any reason for the target to drift off the screen. PHD2 is making corrections, albeit of some fairly large excursions, and the guide star is coming back to position, at least as far as the guide camera is concerned. Sample of this below: That suggests that the issue may be flexure between the guide scope and the imaging scope, it doesn't take much movement at all to produce this effect and plastic tipped guidescope ring mounting screws are famous for producing this result, if you have those? That isn't to say that resolving flexure (if that's what the cause is) will completely resolve star trails, the scatter plot suggests there may some more issues to check: I'll disagree slightly with Michael here, updating to the latest version of PHD2 may improve matters slightly, with better guiding assistant analysis and improved calibration algorithms. Finally it may be worth posting guide and debug logs over on the PHD2 Google group https://groups.google.com/forum/#!forum/open-phd-guiding Andy and Bruce are pretty quick to respond and will have much greater insight.
  3. +1 for the 700 (mine is astro modded) and have been imaging with it for just over 4 years. The 750 suffers from an (apparently) uncorrectable banding issue.
  4. Sean If you can post a the guide log from the affected session (PHD2 stores these automatically and the default location is My Documents) it should be possible to see which axis is causing the problem, whether guide pulses are being sent and not responded to and how good the PA and calibration were. This could help show if it's a mount problem or something else.
  5. What happens to the guide star on the PHD2 screen? Does this also move or does it stay in place? You say you took subs while 'PHD was going through its routine', is this while it's calibrating? That would produce star trails for sure, and how was the calibration? Any reported problems?
  6. I used white Hammerite hammered finish, but as I couldn't find it in a spray can had to mix it with thinners and spray it from my air driven spray gun. The result was acceptable rather than wonderful. If you go this route your local automotive paint factor may be able to come up with a very much cheaper alternative to the unbelievably expensive Hammerite thinners. Mine did.
  7. Thanks, Gina. Longer lasting is just what I am looking for!
  8. A little while ago someone posted a link to a higher quality TEC 12706 Peltier cooler. Unfortunately, I can't now find this anywhere, and my first cheap one failed a couple of weeks ago after several months of good service and its Ebay replacement has failed after only a few days, so I think I am ready to try for something a bit more robust, if anyone has the link or a recommendation? On another allied topic, what flexible foam insulation do people use on the cold finger and associated cold parts?
  9. Coming a bit late to this, but I ran your 'before' image through StarTools' lens module and got this result. Not sure how much of an improvement it is? Didn't take more than a minute over it, so better may be possible.
  10. If you have the latest version of PHD2 there are two polar align routines that use the celestial pole: Polar Drift Align and Static Polar Align. PDA works for me as it doesn't require stars to be identified but SPA is said to be more accurate if your guide camera fov will allow it, mine won't.
  11. I cured a similar problem by switching to an OAG. This might be overkill for a ~500 mm focal length imaging rig, but getting rid of any plastic tipped screw mounting guidescope rings and just clamping with solid rings may help?
  12. Unfortunately the guide log only shows two minutes of guiding, which isn't really long enough to make a judgement although PHD2 has reported an issue with guide rates in the calibration, but the images certainly look like flex between guider and imager. Try taking an image of the PHD2 screen at the start of a run (the 'Save image' function on the file menu can do this) and at the end of the run and then compare the two images. If the guide star hasn't moved, it's likely to be flexure.
  13. OK, in which case check to see if there's any possibility of movement between the guidescope and the imaging scope. Do you have the guiding logs for the session in question?
  14. Alternatively, and without knowing what scope, guide camera, mount and guidescope you have it's difficult to give specific advice, it could be differential flexure?
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