User`s Manual – G42 Observatory+
Contents
1. 12 Troubleshooting Drive does not start Incorrect polarity insufficient current unstable noisy power broken power cable electronic transient fuse blown Motors vibrate and do not turn the telescope Large unbalanced mass Rebalance the telescope Motor cables broken Repair or replace Cable connector became loose at mount or driver end Motors run but do not turn the telescope Motor worm coupling became loose Tighten setscrews No PEC encoder signal arrives Magnet missing Encoder broken There is backlash in declination The DEC function screw is turned in Read section 6 carefully 13 Options 15 13 1 RA head lock The mounts ordered with the GHS tripod are shipped with the handknob shown in the overview section The mounts ordered for permanent setup are shipped with an M10 allen head screw This version allows more overhang after the meridian has been crossed 13 2 Colour Black mount with red handknobs and elevation adjuster Red mount with black handknobs and elevation adjuster Natural silver mount with black handknobs and elevation adjuster Blue mount with black handknobs and elevation adjuster The base gear covers worm blocks and platform are always black 14 Maintenance Anodised aluminium surfaces must be protected from the UV radiation by silicone or paraffin oil a few times a year or when dry Use a soft cloth to apply the oil to the surface Apply silicone oil aeroso2. DEC gear and microstepped stepper motors are standard The worms are hardened ground steel 18mm diameter lapped in RA Only high grade aluminium alloys brass and stainless steel are used for the machined parts The RA and DEC heads are NC machined from an oversized solid block 2x2pc tapered roller bearings hold the axes 2 Safe use Make sure that the power source used is stable Noisy power will cause malfunctions and may eventually damage the Driver Pulsar FS2 or other Switching Mode e g laptop power supplies may but not necessarily do interfere with the Pulsar driver When rotating the telescope watch the motor cable It should never be stressed Keep the mount away from dust sand and other kinds of dirt Protect it from rain The mount should NEVER rest on the motors when stored or transported Use your transport case During transport the slip clutches should NOT be locked The worm may suffer damage otherwise 3 Overview OTA platform DEC Function screw v DEC clutch f handle Polar finder mounting y Position RA clutch handle Electronic connector Ra head lock Azimuth adjuster Counterweight Shaft hole PEC encoder Staged Elevation adjuster 4 Setup Polar align roughly Connect the mount to the Driver Unit Put the counterweight s on slip clutches released Mount the telescope dec motor towards the sky end Release the slip clutches and balance th
3. Note the FS2 is not a supported driver and while it can drive the mount under most circumstances no responsibility will be accepted for any malfunctioning Please set the parameters in the Mot and Mot2 menu as follows Currl 0 7A F 4 0 Curr2 1 4 A maximum Offset 0 01 Freq1 20 Hz Accel 5 or best value Freq2 0 Hz Clear usually 0 Offset 0 02 A Freq3 40Hz S Rev 200 L R Left Gear 432 EncR none Wave micro EncD none Please set Misc Teeth at 432 Rate 5 which will be used for the GoTo function also depends on the load and the power supply Try 500 and decrease if the drive fails The maximum slewing speed depends also on supply voltage Acceleration Accel should be slow for heavy loads For autoguiding select rate 1 which should be set below 1 siderial to exclude any backlash To use any other controller that can drive bipolar stepper motors with at least 1 A phase you can prepare your cable based on the DB15 connector on the side of the DEC head of the mount pinout below RA _ phasel pins 4 5 phase2 pins 7 8 DEC phase pins 1 2 phase2 pins 9 10 The illustration below shows a typical physical setup of the mount tripod and driver Please note the correct position of the declination motor toward the sky end of the tube 5 Slip Clutch Operation RA and DEC Turn the handle right to lock left to release Do NOT use excessive force on the locking handle Lock it gently The slip clutch may be adjusted by lifting and
4. focus the reticle remove the eyepiece but mark the position first with a piece of tape You must put it back exactly where it was otherwise the starts Polaris and the two companions will not match the circles on the reticle To focus the polar scope release the counterlock nut and rotate the objective lens 10 9 2 Collimating the Polar Scope field of wiev Polaris wanders on this circle Polaris centered gt Sight Polaris through the Hour Axis bore Attach the Polar Scope with the off axis plate 1 Center Polaris and focus the polar scope by rotating the objective lens Use the elevation and azimuth controls only see fig above left Fix the objective lens counternut Rotate the Hour Axis cca 180 degrees Stop where Polaris goes farthest from the center 2 Move Polaris halfway towards the center as shown above right Use only the Polar Scope collimation thumbscrews now 3 Repeat from 1 except focusing until Polaris stays in the center when the Hour axis is rotated 180 degrees Until now you have been collimating the Polar Scope 5 Rotate and adjust in Az and Elev the Hour Axis until Polaris is in the large circle and the two fainter stars around are in the smaller circles Pay particular attention to the correct position of the far off the pole star Note you can go through steps 1 4 in daytime using a terrestrial object a few hundred meters away Do NOT remove or rotate the polar finder s ey
5. Gemini G 42 Manual Table of Contents Rev 02 June 2009 1 Main features and parameters cccccccesscceceenceceeneeceeseeeeceeneeeeenseeessteeeeeens 2 2 Safe USE anientada aaia iE SARS sania facta emer SE EAE 2 3 Over Vie Weires iaae AERE ENEE EEN E ee ees 3 ASEP ee e E E E E EE 4 4 1 Pulsar Controller Setup ss essnseenseeesseessesseessesseesssssesssessressessressressesseesseesses 4 4 2 Boxd rfer Dynostar Controller Setup wiicsicceascdsssetesisiives cosencavaticerciadentadvatenenasauneves 4 4 3 FSZ Controller Set Hseresnrnniee Lanne abatadiavadaananiotedannareatanes 4 5 Slip Clutch Operation a5 ssccsnsurirnnsavcndesite caeinesy saesnenasdeenearandnasaeoiveeaveacatameisannunes 6 6 DEC function Screw 55s gecencrictissesietiart tends Sees 7 7 PEC WU AUD a siassiuccst tc sar escent ea Oana acces iad aeseuwsaancsousemmaancoiees eam iauoicum enone 7 8 Polar AN NO sas sauce cecaraectosearicnanedimea tials tadeaoa ae aka exe eaten ene 8 9 Polar Scope Open scs cccn cienuwsinuusiusnier aaa mame 9 9 1 Getting to know your Polar Scope cccccecccceeeseeeceeeeeceeneecessneeeeeeneeees 10 9 2 Collimating the Polar Scope i cccccsccsscsiessiescsassedsasearscvesstsarssnesamessrcessderaesatoanys 11 10 Notes on the pointing accuracy of the MOUNT ccc ceeeteeeeeeeeeees 12 11 Gemini GHS 140 MkII tripod 0 cc cccceeneeceeeneeeceeeeeeseeeeeneeneees 13 12 VG les OOO 8 asses sens zeececivenssncnnrasocnignts Wethedesedenteiea
6. alignment use the screw pitch values given in the first paragraph To use the mount in the Low range the RA head must be reversed in the base The elevation scale will not work in this position unless the mount was ordered for low elevation originally 9 Polar Scope optional The G 42 can be equipped with an optional high precision bright field Polar scope This 12x30 finder uses a 20mm Pl ssl eyepiece and offers a smaller than usual field but provides better precision than most other models The large objective permits seeing faint stars that make the alignment very accurate The first time the mount is used the Polar scope should be collimated with the Hour Axis using the 3 small thumbscrews M4 in its adapter Off axis plate The 3 allen screws 1 spring loaded hold the polar scope centered in the adapter the 3 thumbscrews are for collimation The 2 handknobs of the off axis plate should be turned a small amount at a time one ofter the other to avoid seizing of the positioning pin 9 1 Getting to know your Polar Scope To take advantage of the GoTo function of a transportable mount Gemini have developed a high precision Polar Scope HP2 Compared to the previous model it has better eye relief and two concentric circles in the center to make the collimation easier When used with care this product gives results comparable to a good drift alignment Counterlock Objective lens Eyepiece locking setscrew To
7. driver only The PEC encoder is wired internally to the electronic connector there is no need to plug any cable in it To program PEC use a high magnification crosshair eyepiece 600x 800x or a CCD autoguider with about 1sec integration time PEC can also be programmed using PemPro CCDSoft For more details on programming see the Pulsar manual Once programmed the PEC is kept accurate by the encoder which uses a magnet glued to the RA coupling 8 Polar alignment Elevation can be adjusted after slightly releasing the two handknobs one on either side locking the polar or RA head The elevation of the polar shaft can be adjusted by the rigt left handed screw mechanism To adjust azimuth the central on pier or tripod locking screw and the lateral ones when fitted must be slightly released Tip Adjust slightly above the pole and fine adjust after loading OTA and counterweight Lock the hand knobs firmly Do not use tools other than your hands on the handknob There are three elevation ranges of the mount The difference is in the length of the longer right hand screw Attention the lower elevation screw safety mark indicates 8mm safety margin Turning it more out risks failure of the support mechanism and a serious injury Standard 35 57 degrees latitude shipped unless specified otherwise Low 0 35 degrees latitude the RA head must be reversed in the fork base High 45 70 degrees latitude To make a drift
8. e telescope Remember that finders guidescopes large focussers may introduce significant unbalanced weight especially with Newtonians Check and adjust polar alignment see section 8 and 9 Adjust the DEC function screw see section 6 8 Check Driver setup please read the Quickstart section of the Pulsar manual The mount is ready for use aA BWN eS NID 4 1 Pulsar Controller Setup Please set the parameters in the Mount Parameters menu as follows For a more complete guide see the Pulsar Manual Total reduction RA DEC 432 Main Gear 432 RA Rotation the correct value is to be found by trial worm rotates clockwise when viewed from motor end TrackCurr 800mA 12V or 950mA 24V GoToCur 1200mA max 1400mA Stop Curr 100 300mA or same as tracking current for autoguiding MotFreq 255 for most quiet operation cca 190 for smoothest tracking These current settings give low noise and consumption 0 5A tracking 0 9A GoTo If you need more torque change the settings 4 2 Boxd6 rfer Dynostar Controller Setup Note the Boxdorfer is not a supported driver and while it can drive the mount under most circumstances no responsibility will be accepted for any malfunctioning Motor Current Slow Dec 0800 Ra 0800 Fast Dec 1000 Ra 1000 Frequency RA Slow 000 200548 Dec Slow 000 200548 Set Gearing RA 005 529 600 if the mount tracks incorrectly please change the sign Dec 005 529 600 4 3 FS2 Controller Setup
9. epiece after the alignment was done You will lose collimation If the polar finder is stored carefully it will keep good collimation for a long period In this case you need to repeat step 5 only during the next setup 11 10 Notes on the pointing accuracy of the mount The pointing accuracy with a given setup is ensured by paying attention to the following 1 Polar alignment The final alignment must be made with the telescope on the mount Otherwise mechanical effects will jeopardise accuracy Polar finders without a collimation feature will not give good results 2 OTA optical axis not mechanical perpendicular to Declination axis It is not always enough to use two identical tube rings With reflecting and catadioptic telescopes you should always make sure that the orthogonality is correct After collimation of the optics it will be necessary to repeat the test To check the orthogonality do the following 1 Collimate your polar scope as described above 2 Center Polaris in the fileld 3 Align the telescope parallel with the Hour axis should point to the Pole or 90deg DEC 4 When you swing the tube in RA Polaris should cross in the center of the field If not adjust the tube on the platform put spacers under one end The DEC head of the G42 is milled from a solid block of aluminium on an NC machine and the axes are perpendicular to each other within a few arcminutes In practice most of the GoTo pointing error comes from the o
10. haurmianseoeodietidaieai eens 15 IREO In CO i C 15 13 1 RA h ad lotK isisisi eserinin tensiden ine eae 16 13 2 OU AE cs erations e a ev bree ae 16 14 Mamten ance iicccisich tase peel aaa SE i 16 Gemini G 42 German Equatorial Telescope Mount User s manual 1 Main features and parameters e Capacity approximately 40 kg depending on tube length e Weight 22 kg without cw shaft e Power 2A 12V or preferably 3A 24V the values represent the recommended power supply rating not the actual consumption e Wide range of polar elevation adjustment 0 70 degree latitude e Adjustable stick free slip clutches e Removable counterweight shaft 30 5mm counterweight bore required e max 7deg sec slewing speed with Pulsar and 24V only e 200 step INm 1 32 Ohm 2A phase stepper motors in both axes e single cable connection from mount to driver e PE of 5 arcseconds without P E C cca 2 total with PEC Pulsar only e Worm rotation period 200 sec e Elevation screw pitch turn 2mm cca 78 turn e Azimuth screw pitch turn 1 25mm radius 60mm cca 72 turn e Mounting OTAs A tube rings attached using the existing platform holes 304mm spacing B tube rings or other hardware attached to the optional universal adapter plate you provide fixing holes C optional Losmandy 3 size adapter fixed to the mount platform A precision drive system comprising ground steel worms large 217 mm brass RA and anodised aluminium
11. le to the rubber grommets of the tripod regularly Avoid prolonged exposure to direct sunlight Acknowledgements Special thanks to Dr Dietmar Hager Eiji Mori and Maarten Vanleenhove for their valuable advice on the details of this manual 16
12. mings I have developed the GHS Gemini High Stability design which does not save on material where there is need for it the legs and the column have 5mm wall but is still easily transportable 15 5kg This design uses the weight you put on it to stabilize itself due to a favorable geometry It is constructed out of 13 aluminium and stainless steel and resists the test of time I have left an example outside for 2 years and had to change the rubber grommets only which are not UV resistant The tripod is in folded position for transport Release all handles 2 black 1 red at the collar and 3 black handknobs at the limiters The collar on the column and the legs are free now To adjust height slide the column in the collar To do so grab and fix one leg between your thighs To compensate ground slope adjust leg angle and or length one by one Put the mount on the head so that the azimuth adjusters meet the azimuth pin Rotate the Qlock handknob to the right until the central screw holds the mount firmly The red handle has double function locks the collar on the column and a leg also Do not release the red handle when the mount is on the tripod Adjus lock handle of GHS Release for adjustment Lock for use The limiters stabilize the tripod Release 1 2 turn for adjustment and lock for use Release for adjustment Lock for use 14 The above photos illustrate the high left and low position of the GHS 140 tripod
13. ptical axis misalignment Inaccurate coordinate databases are also to blame sometimes Rotating a diagonal mirror after a GoTo for comfortable viewing can also push the object off center Alternative method without touching the polar alignment 1 Center a bright star near the Meridian and preferably between 40 60 deg DEC 2 Now slew to the North until you cross the Pole then start to slew in RA towards the Meridian yes about 12h in RA 3 when you are close to the target make a GoTo to the same star or slew manually to the coordinates noted before so that the OTA is on the other side of the meridian Steps 2 3 can be done by activating a meridian flip with the Pulsar controller Read the relevant section of the Pulsar manual before proceeding 4 Ideally the star should be in the center of the field again no star diagonals please If it is not correct half of the error in RA with spacers under the tube rings adapter plate Note it is important to have a good polar alignment when doing this test 12 11 Gemini GHS 140 MkII tripod lt lt GHS MkII Qlock handknob as cool as Ice This tripod was designed using my experience with several traditional models pier with legs at the bottom surveyor s type tripod SC field tripods etc The most common problems of these designs are backlash at leg junctions weak legs small resistance to torsion difficult setup interference with long OTAs To overcome all these shortco
14. turning the handle Please remember that the slip clutch is also a protection feature that prevents excessive force from acting on the worm and gear When the clutch is too tight and the telescope cannot slip when accidentally bumped the worm and gear will sufffer damage 6 DEC function screw To obtain the highest precision in autoguiding you can adjust the DEC function screw that acts against the worm tensioning spring To have no lost motion in DEC during guiding 1 center your guidestar 2 start with turning the screw out until it is definitely not acting against the spring Now turn the screw in about 1 4 turn after you feel resistance when the screw touches the worm bearing OR watch the guidestar on the computer display while turning the screw in and stop after the star moves a few arcseconds The second method is more sensitive 3 Now the drive will respond instantly to changes in direction it is necessary to slightly unbalance the OTA in dec to obtain the best result Please note 1 each time you change the position of the telescope the function screw has to be withdrawn several turns and the above procedure repeated 2 For visual observing and GoTo the screw should be withdrawn 2 3 turns Explanation lost motion is the amount of rotation eaten up by small flextures in a mechanical system It is not backlash Backlash is when there is play between two parts 7 PEC operation The PEC function is available with the Pulsar
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