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jambouk

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About jambouk

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    Nottingham
  1. jambouk

    Synscan GoTo issues

    OK. This test can be done in the day time, in a garage etc and doesn't need a clear night. Point the polar axis roughly to the north. Make sure the scope is in the home position. Lock the clutches. Turn the mount on and enter the date and time and location. Do a three star alignment. How far out is the scope roughly (as there are no stars) from the first star? Move the scope with the handset to where you think the first alignment star would be in you could see it. Accept that position. Go to the second star. How far out roughly is the scope now? Again roughly slew to where the second star would be if you could see it. And now the third star, how far out is that roughly? If stars two and three were pretty close to where you think they should have been accept the alignment. Now what happens when you use the GOTO to go back to the first alignment star? James
  2. jambouk

    Synscan GoTo issues

    "It tracks perfectly and I'm convinced mechanically its sound." So the RA motor side of things is fine. "Theres no issue with the setting up , tried one, two and three star alignment, polar accuracy is ok" So communication between handset and motors OK, power must be OK, and Dec motor must be OK too. This doesn't leave a lot else. If you have successfully done a three star alignment, then for this particular use of the mount the date, time and location details are not an issue (these are only needed to help suggest alignment stars, and also useful if you are subsequently parking the scope and then wanting to wake it up again another time without doing any further alignment). Things I'm thinking: If your polar alignment is WAY off, and there is a delay between doing a star alignment and using the GOTO the targets could have moved. What is the focal length of your scope? If it is over 1000mm, and/or you are using a high power eye piece, then it isn't uncommon for the target to be out of the field of view. How accurately are you doing your star alignment? Are you using a high power eye piece to really centre the target stars and ending with an up and right move on the key pad to do the final centering? Are you 100% sure you are centring on the stars the handset is suggesting? How bady off is the GOTO accuracy? Have you turned on the advanced filter on the handset for alignment stars? I would do that and I would only ever do a three star alignment. Are your clutches tight? Is the balance on the kit as good as you can get it? What scope is it? Is there mirror flop? Are you adding any kit to the set up after you have done a star alignment? Daft question, but are you using the same scope to do your alignment and to use your GOTO? We really need to know exactly the issue before we can help further I think. James
  3. jambouk

    Polar alignment accuracy

    I think it would be relatively easy to polar align in the different ways and then just run PHD2 on either the main scope or the smaller guide scope for 30 minutes and look at the errors for each method of polar aligning (and repeat 3-5 times). It would be a time-consuming project and I guess we know roughly what the data would show (PA accuracy in ascending order: by eye with polar scope < handset polar alignment routine < SharpCap < PoleMaster < drift alignment) but the magnitude of the differences between them would be interesting to know from an academic point of view, especially for the middle three methods. If I knew how PHD2 worked I might be tempted to give it a go from my back garden
  4. jambouk

    Polar alignment accuracy

    Ron, do you do a three star alignment with the mount after your eye ball polar alignment, if so what vales for Mel and Maz does the handset typically give you? Using the Polemaster I usually (and reliably) see values of under 3 arcminutes and often nearer 1 arcminute or less if the routine is done very carefully. I just wonder what are the typical values for eye ball method, and following a sharpcap and drift method.
  5. Has anyone done any reliable comparisons of the different methods of polar alignment (polar scope with the eye, polemaster, sharpcap method, drift aligning) and shown the reproducibility of each and the accuracy of the alignment? I'd be interested to see such data. James
  6. Using SharpCap or a PoleMaster etc gives very tight polar alignments, but I do think it is important for people to learn how to polar align with a polar scope to understand the principles polar alignment and it also helps make you think more about the celestial sphere. James
  7. jambouk

    Non-perpendicular error

    Thanks for that. I'd previously thought about the cone with cone error, but not with NPE, so that is useful. Having both errors would be weird, and I guess that links back to my original thoughts of how does the software differentiate the two. Maybe the machining and assembly of modern mounts mean there really is minimal NPE, and that even if a small amount is present it is just so insignificant it probably wouldn't be noticed by the user. Maybe. James
  8. If your mount had useful setting circles you could have used the hour angle option, offered by the handset, but your mount unfortunately has useless setting circles so not worth explaining that procedure here. James
  9. So, if the handset says 08:22, you need to put Polaris at 08:22 (ish) on the circle, irrespective of the numbers or marks on the reticule. This awful drawing shows some of the near infinite position of the reticule and where Polaris should be position. James
  10. Yes, 08:22 will mean you need to put Polaris on the large circle of the polar scope reticule at that position, assuming 12 is at the top, 3 to the right, 6 down and 9 due left. The issue is the reticule in the polar scope won't be aligned correctly to use the markings on it, so you either have to align the reticule first (an utter ball-ache so don't bother), or just be creative about thinking where 08:22 is on the polar scope reticule. I'll try and draw some examples and post them. If you have Polaris roughly between where 8 and 9 should be, that will be sufficient polar alignment for visual and/or basic astrophotography. If you need your polar alignment tighter than this, then you need to be employing another method anyway in my opinion. James
  11. This question does not relate to a problem I am having, I am just interested to know more about it. 1. Is there a way to work out how much NPE there is in a mount? 2. How does a mount differentiate this from cone error during a three star alignment? Or does the mount only work out the cone error during a 3 star alignment and just uses the value of NPE left in the handset? James
  12. I’m actually impressed at how advanced the software was; I’m also impressed at how quickly it computed the positions of the planets for a given date - not a lot slower than my laptop now ... James
  13. Two questions if I may. 1. Can the three screws marked by yellow arrows in the picture below be used to mount a second finder shoe on the C11 EDGE HD scope, permitting both a straight through and a right angle finder to be fitted? 2. The EDGE has field flattening optics inside; is the distance from the visual back to the chip critical, or by making adjustments to the position of the mirror to achieve focus on a chip say 250mm away from the visual back mean the field will still be flat at that distance? Thanks. James
  14. jambouk

    Old Celestron Advanced GT dec motor

    David Hind says the motor is available, but £150. I think this will push my mate even more to buying a new mount. If anyone knows where I can source a cheaper motor from, let me know. James
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