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kens

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About kens

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    Star Forming
  • Birthday 08/05/61

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    Male
  • Interests
    Deep sky, fly fishing, cycling
  • Location
    Melbourne, Australia
  1. PHD guiding

    PHD does indeed enable automatic guiding (or auto-guiding). Back in the olden days we used to guide manually using a separate telescope and crosshair eyepiece focussed on a guide star centred on the cross hairs. When the guide star moved from the crosshairs you would make small corrections on the hand controller to recentre it. Autoguiding replaces the eyepiece and manual corrections with a camera and software connected electronically to the mount. PHD is the software in this case and it sends commands to the mount to make the necessary corrections that keep the guide star centred. Most people use a second telescope as a guide scope but if weight is a problem you can use an off axis guider (OAG) which attaches to your imaging scope and sends a small part of the field of view (which is not seen by the imaging camera anyway) to the guide camera. So the only additional weight is the OAG which is quite light) and the guide camera. However they are a bit fiddly to set up and finding a suitable star to guide on is more difficult.
  2. Heres the drawin for the ultra slim: http://www.qhyccd.com/files/QHYCFW2-M-US drawings.PDF Looks much the same but slimmer A T-thread (or T2 thread) is M42/0.75 - be careful with the term M42 as it is also used to refer to the Pentax M42/1.0 thread which has a different thread pitch. In fact, be careful with M54 as well as I just saw one adapter for M54/1.0 so it might be best if you measure the pitch to be sure. By the way, a very useful tool to have is vernier calipers to mesaure threads, spacings etc...
  3. I'm assuming you have the Standard filter wheel in which case here are the mechanical drawings: http://www.qhyccd.com/files/QHYCFW2-M-SR drawings.PDF The drawings show that the threads on both sides are M54 /0.75 (54mm diameter with 0.75mm thread pitch) Which flattener do you have? Is it a 2 inch/ M48 type? If so you'll need a M54 to M48 adapter and maybe some M48 spacers.
  4. Would EQMOD affect PHD?

    I used my DBK21 for some time with PHD2 with long exposures. To get it to work try the following: set the exposure time to your desired value - say 2 seconds. In the camera settings next to the brain set the exposure to the equivalent. Note that the exposure numbers there are not in seconds but some sort of log scale. If it is less than the amount on the main exposure setting you'll get multiple frames per exposure. If it's too much you'll get a blank screen between exposures. When it's just right you get one frame per exposure. Youll get much better support with PHD2
  5. Using the Polemaster

    If you have the Polemaster mounted on the RA axis (some people mount them on their OTA or elsewhere on their mount) and after alignment the NCP is not centred that means the camera is not exactly aligned with he polar axis. In effect it has "cone error". Maybe the Polemaster mount is not squarely fitted or the hole where it goes it not made square. Changing the tripod legs wont change it. The alignment should still be ok
  6. Given that you already have a focal reducer, it sounds like you may be better off getting a good 135mm or 200mm lens for a wider FOV.
  7. Also check out the ASI1600MM-Cool, QHY163M and Atik Horizon. All use the same CMOS sensor which is around the same size as the 383. Lower read noise allows shorter exposures but conversely requires more subs for a given integration time. There's a whole thread on the ASI1600.
  8. Potential Upgrade Solutions

    OP was wanting to go deeper field so longer focal length was implied but it is not necessarily the right approach. The Canon 550D has 4.3um pixels and the 150pds has 750mm FL giving a pixel scale of 1.18"/pixel. So there's little to be gained by going to a smaller pixel scale. What's needed to go deeper is better focus, longer integration time, tighter guiding and lower camera noise for faint objects.
  9. With an Atik 460EX at 1200mm your pixel scale at 4x4 binning is still only 3" per pixel. But seeing as it is "only" 2749 pixels across you would only need to bin 2x2. And in any case, SPA takes into account the pixel scale when it calculates how much to rotate in order to detect the deviation of the arc from a straight line. Smaller pixels need less rotation and speed up the process. But they can have their own problems as poor seeing and errors in the mount have a greater relative impact.
  10. Thats a good question. I've recently installed an OAG but haven't tried SPA with it. The distortion near the edge of the field may cause inaccuracy. You could of course use the imaging cam if its a probem. You'd need to set up a new profile in PHD2 and calibrate it first. I've used my ASI1600 cam for that purpose. I also bin the camera 4x4 as otherwise PHD2 has trouble processing the large number of pixels.
  11. Potential Upgrade Solutions

    I doubt a new OTA would make much difference. A Celestron 925 may well overload your mount and make things worse. The biggest improvements I got over the years were from getting a better focuser and then a motor focuser and from tuning my mount and then getting a much better mount. These changes give me smaller, sharper stars and pull out more detail from all objects. You could also consider a cooled camera (assuming it isn't already) and maybe try narrow band?
  12. I've been through this recently. In my case I have a reducer rather than a flatteneer but they both increase the difficulty of getting the spacing right. You'll need to make some calculations and be prepared to get spacers and shims to get everything right. You'll need to know the optical distance from the prism to the two camera connections, camera back focus for both cameras and the spacing for the FF/FR in addition to the OAG optical length. Start with the optical path from the FF/FR to the imaging cam to get that right. The use the optical distance of the prism to guide cam and guide cam back-focus to work out where you need to "tap into" that path. To maintain the FF/FR spacing, any spacer you add to the front of the OAG needs to be removed from the back of the OAG for BOTH cameras. Ideally you want the guide cam to be as close as possible to the prism . Given you don't have a filter wheel this should not be an issue. (A filter wheel increases the optical path to the imaging cam and requires the same increase to the guide cam) You may need shims of various sizes to get the camera orientations to your satisfaction. Im a bit OCD and like to have the cameras aligned to RA/Dec. The T threads are 0.75mm pitch so shims of 42mm ID between 0.1mm and 0.5mm give good fine tuning.
  13. Being from Melbourne I can say that Polar Drift and SPA actually work better in the Southern Hemisphere than the north. In the northern hemisphere there is Polaris and not much else near the pole and Polaris is 45' away. Here we have 5 stars brighter than mag 8 within 45' of the pole and 2 of those are within 15'. Polar Drift is most useful is when you dismantle your mount and need to realign it as you can get reasonably close in both axes very quickly. I then use the SPA tool but you could equally use regular drift alignment to get very close. SPA is limited in accuracy by how well your mount tracks and also aligns on the refracted pole. Regular drift alignment is still the gold standard for accuracy
  14. The latest dev5 version of PHD2 now includes two new PA tools: Static PA (SPA) and Polar Drift. The traditional Drift Alignment is the most accurate whilst the Polar Drift is very simple and SPA is fast. The two new ones align in the polar region rather than at the equator so may not be suitable for everyone. SPA has been around for a few dev releases whilst Polar Drift has just been released. Polar Drift is particularly useful if you want to align in the polar region but your polar alignment is a long way off e.g. due to a new setup. I use the tools as follows: Do a rough manual alignment Point the scope near the pole (home position for a GEM) Launch PHD2 and start the Polar Drift tool from Tools > Polar Drift Alignment Select a convenient guide star and click Start Wait until the "lollipop" settles down then click stop You can read the PAE on the status line and adjust the guide star into the circle at the end of the lollipop Once within about 10 arcmin I switch to SPA In SPA it is important for the scope to be pointing accurately at the pole so the alignment stars are visible. For northerners Polaris is normally an easy target. In the south thinags are a bit harder so I proceed as follows: Clear any star alignment/ sky model sync points from the mount - these can throw out the alignment process Start the SPA tool from Tools > Static Polar Alignment If the alignment stars are not visible, I pick any star and start the alignment. Ignore the adjustments and see if the centre of rotation (CoR) is in the FOV. If not, slew carefully in declination only to bring the CoR into the FOV. If the previous Polar Drift was reasonably successful the alignment stars should become visible in the FOV Then I follow the normal SPA process. Select an identified alignment star Start the SPA process. If I have any problems I revert to the manual mode and slew manually Adjust according to the on screen display Once I'm within 5 arc minutes I confirm with a regular drift alignment and fine tune
  15. The latest dev5 version of PHD2 also includes two new PA tools: Static PA (SPA) and Polar Drift. The traditional Drift Alignment is the most accurate whilst the Polar Drift is very simple and SPA is fast. The two new ones align in the polar region rather than at the equator so may not be suitable for everyone.
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