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Geoff Lister

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Everything posted by Geoff Lister

  1. I have the same Skymax mount, and my Skyliner Dob mount also has the same Nyloc nut. The difference between a slack axis and a tight one is a fraction of a turn of the nut. I have adjusted the clamping force, so that there is no slip in normal operation, but that it will slip if part of the OTA touches other parts of the mount or tripod. Geoff
  2. I have a 2" 56mm Plossl that I use with my 10" Dob, but it only gets very occasional use. All my other eyepieces and cameras are 1.25", so to use a 2", I have to remove the 1.25" adaptor from the end of the focus draw-tube and replace it with the 2" one, then reverse the process for all the others. I have also found that I need a short extension tube to achieve focus, so adding to a bulky, and heavy, extension at the front of the tube. To compensate for the extra weight, I had to add a balance weight at the primary mirror end. I haven't done the sums, but I would have thought a 32mm 52 1.25 Plossl would do a similar job, in a more user-friendly, and cheaper, package. I normally start my sessions with mine. Geoff
  3. +1 for the 32mm Plossl and 7-21mm zoom. I tend to start a session with my 32mm, and then the zoom. The zoom is particularly useful, with Jupiter & Saturn, for getting the best compromise between magnification and clarity of view. Geoff
  4. Hello Brad, and welcome to SGL. I have the same system, with the older, V3, Synscan handset. Several years ago, I had problems with the azimuth axis control; not exactly your problem, but it would not align or give fine positional control. The problem was inside the azimuth gearbox cover. There is a motor control board, with several ribbon cable connectors going to the motor and the 2 encoders (motor position and, if moved manually, axis position). One of the ribbon connectors was partly disconnected from its pins. It was difficult to see, as it was on the underside of the board, and the ribbon cables have very little slack. I managed to re-seat the connector, (using manual dexterity and a dental mirror!), and the mount has behaved perfectly since. From your description, it looks as though the motor position control loop is not getting the encoder feedback. I have used my mount with 1.5A and 2A plug-top supplies, but the Synscan system is likely to give problems if the internal voltage drops below about 11V when doing a maximum-rate slew in both axes simultaneously, usually during the alignment auto-slew to the 2nd alignment star. This voltage drop is often caused by poor power-connector contact or thin/long (higher resistance) power leads. Geoff
  5. +1 for the standard focuser with the Lacerta dual-speed upgrade. I fitted the upgrade to my Skyliner 250PX and found it easy to fit, and a pleasure to use. Geoff
  6. Hello Chris, welcome to the forum. I have the Skymax 127mm Mak, and I tend to start my observing sessions with my 32mm Plossl. Next, I tend to use a 8-24mm zoom, to get the best magnification/visual clarity compromise, particularly when viewing Jupiter and Saturn. My version came with a 6x30 straight-through finderscope, and I replaced it with a 6x30 RACI version - much easier when aligning on high-altitude stars. Geoff
  7. I used the main objective dust-cap, supplied with the TS70 kit, and part of an A4 sheet of solar film. The main cap has a smaller secondary cap, and if this is removed, it reveals a nice hole, just right for a solar film sandwich. I made up 2 rings of cereal-packet cardboard, and using sticky film made up a solar film sandwich. I then used a bit more sticky film to mount this inside the TS70's cap. I used a bit more of the card and some PVC electrical tape, to lengthen the sides of the cap, so it would not blow off. Geoff
  8. The version of Starsense fitted in the SkyProdigy has 6 possible settings to help the alignment. "Hazy/Urban" seems to be the default. "Full Moon" is probably the best for northern summer. The others are "Suburban", "Dark", "Windy" - to ignore blurred stars, and "Custom" - it may be possible to adjust the settings to get alignment under semi-dark conditions. I have also found that, if the camera is not finding quite enough stars, it is worth doing a power down, rotate by about 20 degrees azimuth, power up and start again. If this fails, or you have obstructed views, there is a manual alignment option so you can point the 'scope towards a few areas of sky with a reasonable number of visible (through a low magnification eyepiece) stars. Geoff
  9. There is an on-line web resource site for this book at https://www.cambridge.org/turnleft Enjoy the Heritage 130P. I have had mine for several years, and it works well for me. Geoff
  10. I have Starsense camera and software built-in to my Celestron SkyProdigy mount. The camera is a 640 x 480 pixel device, similar to a basic webcam, and needs fairly dark skies to "see" enough stars to perform its plate solving. If it cannot "see" several tens of stars, it tries another section of sky, but eventually gives up. I also have the Skywatcher Skymax mount. The Synscan software requires the user to select alignment stars, and manually centre them in the eyepiece. I recon that I can perform a "Brightest Star" 2-star alignment, using bright stars such as Vega, Altair or Capella, a good 45 minutes before it is dark enough for Starsense to work. On a dark night, the Starsense system gets me aligned a couple of minutes faster than I can achieve with the Synscan system. Geoff
  11. Unfortunately, consumer-grade tripod-mounted optical equipment is supplied with an internal 1/4" - 20 UNC thread. It would be a brave manufacturer that used an ISO metric thread form; the returns, under warranty would be huge. I prefer Whitworth, but my tool box contains something suitable for most imperial and metric fastenings; and if necessary, 4 different-sized adjustable spanners, pump pliers, and a Stillson wrench. My "come in handy" box (well lots of boxes and biscuit tins) contains an assortment of nuts, bolts and washers. I also invested in a 1/4" - 20 UNC tap, so I can add tripod threads at various OTA balance points on a dovetail plate. Geoff
  12. Mine came with 20mm, 10mm & 4mm eyepieces. I tend to use a 32mm Plossl and 7-21mm zoom. Geoff
  13. The dovetail bar on my Travelscope 70 fits several of my Skywatcher/Celestron mounts and has a 1/4" -20 UNC internal thread for use with much better photographic tripods (than the one supplied).
  14. I'm not sure about this particular one, but some handsets have an internal, replacable, button cell to power the real-time clock, when the handset/mount is powered down. Geoff
  15. Hello, and welcome to SGL. If you could tell us the model of the telescope, we should be able to help you. Celestron make a wide range of different telescopes, and the setup instructions are somewhat different for each type. With any new telescope, it is worth setting it up during the day; it's much easier to focus on a distant tree/post/building, than it is a star. Geoff
  16. I have just been viewing the Sun with my SS60 + standard diagonal, Revelation binoviewer and a pair of 32mm Plossls. I could not achieve focus, so I unscrewed the black lens unit from my Celestron X2 Barlow, and screwed it into the nose-piece of the binoviewer, in place of a filter. I then had plenty of focal adjustment range. It was not as easy to get a good inter-pupil adjustment for both eyes as it is during night use, but certainly worth a bit more experimentation. Geoff
  17. A few years ago, I had problems with the azimuth axis on my Skyliner 250PX, particularly jumpy operation at the lower slew rates. The connector on one of the ribbon cables was partly pulled off the pins on the underside of the control board. I think it was from one of the encoders, and it was not obvious without unscrewing the board. It looks as though there was a post-design modification to feed the ribbon cables through some ferrite rings, probably to meet EMC emissions/susceptibility requirements. This makes the cables effectively shorter, and thus a tight fit under the board. I re-seated the connector, and have not had problems since. Geoff
  18. Counterweight Shaft The mount is supplied with a 150mm long by 19mm diameter counterweight shaft, and a 1.4kg counterweight. These feature in some of my earlier photos, and, as also mentioned above, the shaft works fine with the (20mm internal diameter) counterweights from my Skywatcher SkyTee 2. Different OTAs require different counterweight combinations at different distances along the shaft. To avoid having to balance the mount after each change of OTA, particularly for the larger ones, I used my modeler's mini-drill, with a cutting disk, and marked the shaft at (roughly) 1cm intervals along its length, starting at 4cm. I checked balance for my regular OTA's, noting weight used, and particular mark adjacent to the inner face of the weight. I now have a small table of OTAs, with weight(s) and distance(s) for each. Geoff
  19. Most diagonals and Barlows come with dust caps at each end, and most OTAs also have a dust cap at the focuser. I turned one of these into a collimation cap by drilling a 1mm hole in its centre. Geoff
  20. And now for the 8408 handset As I had my screwdriver handy, I thought I would have a look inside the handset. The manual refers to replacement of a 3V lithium button cell, size CR1220, for RTC operation, and it was clear that the system was not retaining, and incrementing time, when the mount was switched off. The nominal capacity of a CR1220 is 36mAh at 100uA. The data sheet for the microcontroller shows a dormant current consumption of 1.4uA at +25degC, with a Vbatt of +3.3v; equating to a useful life of about 3 years. If the cell is discharged, the mount powers up with default time/date and Az/Alt at the zero position of 180 deg. and 90 deg. respectively; with a good cell, the RTC runs, giving reasonable time at restart, and the Az/Alt angles are those displayed at power-down. Handset main board:- Top section with STM32F103 Microcontroller (middle), Winbond serial Flash memory (top) and xtals 32.768kHz (RTC) & 8Mhz (CPU clock) Middle of board with 3V cell and MAX3232 RS232 transceiver. Given the obvious board space available, it's a shame that they could not have fitted a holder for a CR2025 cell, with a capacity of 163mAh. Bottom of board with MC34063 switching regulator and the RJ8 (RS232) & RJ12 (HBX) connectors. The underside of the board forms the keyboard contacts with individual button LEDs, a buzzer (with protective cover still left covering the hole), and the two connectors. I have added some strips of glow-in-the-dark yellow/green strips, to make the handset easier to find in the dark (all the LEDs turn off after a short period of inactivity). Geoff
  21. AlexK has some useful ideas. I noticed that your second photo shows what looks like a clutch adjustment knob on the side of the altitude gearbox. My Skyliner does not have this, and mine (over 10 years old) has the handset cradle mounted across where that knob would be. My Skyliner mount has dual encoders for each axis (1 for the motor and the second for the axis shaft) but uses friction, adjusted by setting 2, big, Nyloc nuts, to move the mount. The nut setting is a compromise between ease of manual pointing and reliable motor drive, and is not easy to adjust during a session. I found that I had to tighten the altitude nut to get reliable operation with a heavy eyepiece/binoviewer/DSLR, and added the rear weight to help the balance. The Skywatcher mounts, also including my Skymax 127 and Virtuoso 90, are essentially "Dumb" when used with the Synscan handset, and the encoders are just clockwise/anticlockwise pulse counters. At power-up, the GoTo software's axis angle registers are set to zero, which equates to OTA horizontal and pointing to celestial North. If you had ended your last session with <Park> <HOME>, and not moved your mount since, then at the next power-up, the mechanical and electronic "model" will be aligned at zero. The alignment process is most accurate if your azimuth axis is perpendicular to the Earth's surface, i.e. the base/mount is level. It is much easier to get the base level to under 1 degree, than it is getting the OTA pointing, with a similar accuracy, towards celestial North. With my mount, when I set up on my patio, I move the bottom part of the base round until the bubble level has its bubble pointing away from one of the feet, and then slide a wedge under that foot until the bubble is central - job done. If you choose your first alignment star close to the horizon, the azimuth alignment will be accurate as soon as you centralise the star, and any small leveling (altitude) error in that direction will be measured. If you choose a second star at 90 degrees in azimuth from the first, the mount will also measure the leveling error at a 90 degree compass direction; so as the mount rotates, the software will add, or subtract, a proportion of these two errors, to give a more accurate GoTo (and also tracking once the target is acquired). Geoff
  22. For a mains supply I use a 12V 1.5A or 2A plug-top supply, the type often sold for use with the LED stick-on lighting strips, external hard drives, or Ethernet switches. Geoff
  23. UPDATE:- I wanted to check on the gearbox lubrication, so unscrewed the covers. The altitude final drive pinion uses the altitude shaft as its bearing, and the clamping knob links the two to provide adjustment and drive. More detail of the worm drive:- Connector side of the main PCB (note RA/DEC, although mount is Az/Alt):- 32-bit ARM micro-controller (top left), quad op-amp, probably for encoder interface [designers seem to like 1 Megohm resistors] (top right), and dual motor driver for brushed DC motors (bottom right). Power input side. The 16V electrolytic is probably the limiting component for maximum input voltage.
  24. Your base looks fine. Initially, I had problems with alignment. Quite often, the suggested second star was behind a roof/tree/fence. I spent some time with the "Stellarium" program, on my PC, and produced a table of 14 of the brightest stars visible from my back garden, and for dusk, at the middle of each month of the year, selected a few, with compass direction and altitude. By aligning at dusk, the bright stars are easier to select - you do a manual slew to the first, and the mount does an automatic slew to the second, and it is usually visible in the finder. By selecting 2 stars with about 90 degrees difference in azimuth, and 20+ degrees difference in altitude, the Synscan software gets the best input conditions to compensate for errors in leveling the base. At the moment (mid March-ish), I usually start with Sirius. I have added a large bubble level to the base, and use a wedge under one of the feet to centralise the bubble. The handset gives altitude and azimuth for the first star, so I set that value on the altitude scale, and then slew in azimuth, standing behind the optical tube, until the tube is pointing towards the star. By aligning at dusk, I can complete alignment, and the mount will continue tracking whilst I go in for a warm drink, and wait for the sky to go properly dark. If I have done my alignment properly, the 2nd star will still be in the field-of-view of my 32mm Plossl eyepiece, when I come out again. Geoff
  25. I enjoy solar viewing with my 127 Mak, with a solar film front filter. The 32mm Plossl eyepiece gives a nice, full view. Geoff
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