michael8554

Generalising here, most mounts costing less than £8K won't track accurately enough to image with long focal lengths such as the LX10 for more than a few minutes, usually much less, without Guiding. Michael

Hi Dave -Dec_backlash.doc There's some confusion in the numbering so read carefully ! Loosen and remove the Dec clutch screw while holding the OTA, and carefully allow the OTA find a balanced position. Remove five screws holding the cover on with a 3/32" Allen key. (Careful when replacing those afterwards, the plastic they screw into can break, they only need to be finger tight to hold the cover.) Screw the Dec Clutch Screw back on with the OTA back in a normal position. Now you can slew Dec and look for the worm jumping, worm gear damage, etc. The worm is spring-loaded onto the worm gear, and there should be a 1/16" minimum clearance at the end of the Allen screw "Rack Swing Limit PIn" when you slew through the normal range of Dec movement. You can reduce that if you see the worm jumping, maybe when making fast reverses, but never have zero clearance. Michael

I've realised that moving the spacers is wrong, it will make it worse ! Yes, you need to get the OAG CLOSER to the Edge HD, is there such a thing as a shorter Edge HD to T2 adapter ?. As you've shown me yours, I'll show you mine....... 😆 Old-style ZWO 120MM, with a Baader MPCC Coma Corrector between the OAG and the Canon T2 connector. The large diameter metal shim near the ZWO is just to get the ZWO rotated parallel to the Canon sensor when it's screwed on. Michael

The Baader Helical Focuser looks shorter and is only £31 :-< you should be able to sell the ZWO one. https://www.rothervalleyoptics.co.uk/baader-125-helical-focusing-eyepiece-holder-t2.html Michael

Here's your first Calibration: Those lines should be straight and at 90 degrees !! I don't have an explanation for that I'm afraid. The red cluster halfway along the line is where the mount is hardly moving in Dec for 20 or so steps. Although the mount is set to 10arcsecs/sec on both axis, RA is Calibrating at that rate, but Dec is actually Calibrating at only half that rate. Here's your second Cal: Now the lines are trying to be 90 degrees apart, what was changed between these two Cals ? These are not normal LX200 GPS behaviour. Again RA is Calibrating correctly in 19 steps, but Dec is taking 47 steps, and again that even bigger cluster of non-movement. Plus those return pulses S0 to S4 that are way off-piste !I Is the Dec clutch tightened ? The mount shouldn't move if you gently pull down on the front of the OTA. Perhaps one of the Dec gears needs tightening on it's shaft, not uncommon, Your 4 second exposures are too long, 1.6 seconds was recommended in one of the Guide Assistant runs. Michael

Some on SGL say you should forget the data, look at the images. Your last two images are very similar in terms of the amount of star elongation, despite our best efforts ! As shown by RA RMS being 50% bigger than Dec. Final adjustment would be your Guide Rate, which is 5 to 6 arcmins/sec on both axis. That's quite low, the PHD2 guys recommend at least 50% to 80% of Sidereal, about 8 to 12 arcsecs/sec, I'd try 12. Your Guide Assistant results would be more consistent if you guided for about 30 seconds until the mount settles down, then hit the Start button on Guide Assistant. Are you sure you're nudging north until you see the guide star moving north, before Calibrating? There were 10 Clearing Backlash steps before Dec Calibration started at 00:39 ? Michael

Well it was worth a look. Did it ever work correctly ? Michael

Looks okay Time Zone ? Do you have to enter leading zeros ? eg 003 12 W For Brightest Star you have to enter a Select Region eg Northern Sky ? For 2 Star, you have to centre the first star with the HBx, so the mount shouldn't be making any vertical moves on its own ? Michael

Hi Dave The LX10 lacks the features to do DSO imaging. I had a LX6 which had a very accurate RA drive system plus PEC plus guiding, but the crude Dec drive, same as yours, made imaging difficult. With Good Polar Alignment a star should remain in the eyepiece in terms of vertical movement, but a basic RA drive with no Periodic Error Correction means the star will drift in RA as I described. You could modify the HBx to allow guiding, but the crude Dec drive would be the limiting factor, as with my LX6. A good Visual and Planetary imaging scope. Michael

The spacers between the ASI 224 and the OAG are to get the 133mm sweet spot I assume ? Depending on how many more mm of inward you need, instead put that thickness of spacers in FRONT of the OAG, then you'll have that amount more in the ASI 120MM light path to play with. I've realised that's wrong, makes it worse - Michael Or dispense with the sexy helical focuser and adjust focus by hand, trickey but you only have to do it once 😆 You mean the ASI 224 ? Can be anything you like - so long as it's 133mm from the Reducer, and isn't vignetting. Michael

Hi Tom USB3 ? Michael

Do focus during the day on a distant object, if both your cameras will work with SharpCap in Video mode on Auto, my 120MM does. Focus the imaging camera first. Then fire up the 120MM and focus on the same distant object. Now both cameras are focused on the same object, now whatever you focus the imaging camera on, the guidecam will be in focus too. So next try the moon. First focus the imaging camera. Then fine-tune the 120MM focus. And finally check both on a star. Michael

Could be Periodic Error. Over a long period of time the speed will appear to be correct, but over a 4 minute period (the worm drive period) the speed will be, for example, fast for 2 minutes, then slow for 2 minutes, in a roughly wave pattern. If it is PE the left to itself the star will drift out and back in to the eyepiece FOV over 4 mins. Michael

Hi Ryan I think it would help if you posted the actual figures you entered for Lat/Long, Date, Time, Daylight Saving etc. As you've eliminated Runaway due to power problems, it's back to the all too common incorrect data entry. Michael

Hi Philip Good to see you're getting there. Afraid your tiny image is not much help, a guide log would. The image shows two RA spikes, then it settles down. The RMS figures only report on the section of guiding in the window, so if you'd carried on guiding until those spike had left the window, you may well have seen much better RA RMS. Was this guiding based on Guide Assistant recommendations ? Depends on how much it was out, which the guide log will show. After Calibrating you could go to Tools / Review Calibration data and make a judgement before guiding, often that warning can be ignored. 4 Seconds exposure is a bit slow. Michael

Whichever solution you opt for, with the wedge you will reach the zenith in all compass directions - I just tried it (51 degrees north). For visual you don't need anything fancy - plenty of online designs for fixed angle wooden wedges. Michael

The spring is meant to keep the worm on the wormwheel. The Allen screw should be closer, so that the worm can't jump off the wheel during fast reversals of slew. About a 1/16th inch free play at the tightest point of the Dec range. That means, slew the scope between your lowest and highest Dec, looking for where the allen screw gap is smallest. MichaEL

Much better. Calibration was better this time. RA and Dec are now moving about the X axis. PA is still 18arcmins, but Dec is now also moving about the X axis with hardly any correction needed, so good enough. Calibrations would be a lot more accurate for PHD2 to guide with if only you'd nudge Dec north until you see the star move, before you Calibrate. Michael

Your third Cal at 23:50 was getting there, with the axis at 90 degrees to each other. But you didn't nudge the mount north until the star moved, as mandated in the Best Practices PDF, to clear Dec Backlash before Calibrating. So there were 45 Backlash Correction steps that muddied the Calibration So better Cals are possible. Your image results are pleasing, but there are a few problems remaining. Polar Alignment Error wasn't just slightly off, it was 18 arcmins, try to get it down to about 5arcmins. Periodic Error on RA is large, you could investigate Periodic Error Correction for the mount. You can see from this RA trace above that the guiding error was always above the line, with constant guide east corrections, PHD2 never got the guiding to centralise on the zero line. Dec is similar, always below the line. Both these drifts are in part due to the PA and PE errors. Both RA and Dec Aggressions having high settings, but PHD2 isn't managing to totally correct the drifts. PHD2 calculated Guide Rates are still low despite recommendation, increasing both to 0.90/90% of Tracking Rate in the mount, this will allow PHD2 to make bigger corrections. Finally there are some strange movements in Dec that aren't due to PHD2 pulses. Just before points A, B, C, PHD2 has corrected with the PHD2 north pulses, but the mount immediately moves south on its own to where the arrows point, there is a gap in the PHD2 guide pulses where this occurs. This action repeats for a long time. Have you got Backlash Compensation set to ON in the mount? This will fight against PHD2 as you can see, turn it to OFF and use the PHD2 Backlash Compensation offered in the Guide Assistant results. Michael

Post the file not the text, using choose files next to the paperclip icon below this text window, should look like this: PHD2_GuideLog_2020-05-14_223434.txt To Calibrate, PHD2 moves RA, and then Dec, in small steps until it reaches a set total of pixels of movement. The size of those steps is calculated by PHD2, based on the guidecam pixel size, and the guidescope focal length, that you entered in the Profile Wizard. You say your Guidescope is 60mm - that's the aperture, not the focal length, which is probably 200mm to 240mm, I don't know what you have, you'll have to check the manufacturer's specification. So PHD2 is guiding with pulses that are 4 to 5 times too big, which have probably moved the star outside the square surrounding the guidestar, resulting in the "Star Lost" messages. Or you're trying to guide in really unsuitable cloud conditions. Read this PDF, improve the guidecam focus, then try again and post your new guidelog: https://openphdguiding.org/phd2-best-practices/ Michael

Hi Dan The shafts in the gearbox have flats onto which the gear lock-screws are tightened. I imagine some of those screws are easy to get to to tighten, some not: https://www.thefirmament.nl/astro/main_screen.html?https://www.thefirmament.nl/astro/lx200_dec_play.html&2 NOTE - Imperial Allen keys, not metric. Michael

Dec Backlash comp flat out isn't normal. If you take the cover off the side with the Dec motor you will see there's a spring loaded adjustment to the worm mesh, needs to be adjusted to allow the worm to come off the wheel a tiny amount. Slew to high Dec where you were having problems and check if it's binding or unmeshing. If there's damage you could unclutch, slew 180 degrees, reclutch, you're now on a probably unused section. Balancing in Dec with lead fishing weights at the front could help. Michael

The ZWO USB cable looks to be pulling on the camera, I'd rotate the camera so that the connection is underneath, and attach a smooth cable loop to the mount. Have a read about Differential Flexture: http://astronomy.mdodd.com/flexure.html Michael

You should post your PHD2 Guidelog. Michael

Cheer up knobby ! I would no longer worry about the poor Dec in Cal, as actual Dec performance is good because your PA is good. But stop "Piddling About", follow the Guidelines, and in the right order, and you could get Dec Cal better. Michael