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About Oddsocks

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    Proto Star

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  • Interests
    Engineering-electronic and mechanical design, development and implementation, Software development, Astronomy, Photography, Hiking, Sailing, Literature, Music, Art, Theatre, Single malt Scotch Whiskey.
  • Location
    Dorset U.K.
  1. Is this a problem with my flat frames

    Hi Billy. Couple of things to look at / clarify... The uneven vignetting pattern may be a poor collimation or the method of collimation used that results in either a centred or off-centred alignment of the secondary. Either method will result in a good apparent collimation but the centred method produces an uneven vignetted field while the off-centred method produces an even vignetted field. Other possibly causes of an uneven vignetted field include optical path tilt due to a loose coupling between camera and flattener, poor coupling between flattener and focuser or focuser draw tube alignment to the focuser body etc. I found Vic Menards booklet 'New Perspectives on Newtonian Collimation', available from FLO, a great help when trying to understand the theory behind Newtonian collimation and tune up a fast (f3.8) Newt' though I never achieved the best the telescope could deliver until I began using an autocollimator eyepiece as described in later chapters of the booklet. https://www.firstlightoptics.com/books/new-perspectives-on-newtonian-collimation-vic-menard.html When using a LED panel for flats, placed directly on the front of the OTA, there is a risk the flats will be contaminated by indirect illumination of the focuser entry port and focuser draw tube as shown below. The light path from flats source to the camera when taking the flats should be identical to the light path taken for the lights, any differences will show up when the flats are used to calibrate the lights with the effects being more or less pronounced depending on the diameter of the OTA, distance the focuser is from the end of the OTA, focuser port diameter, focuser draw tube diameter, type and quality of the matt-black paint or flocking used around the focuser entry port etc. The entry focuser entry port and draw tube must be absolutely black and non-reflective if you wish to avoid this. The focuser entry port and draw tube can be flocked with flocking paper or painted with a pigment based matt black paint such as Matt Black High temperature Barbecue paint from B&Q: https://www.diy.com/departments/rust-oleum-stove-bbq-black-matt-matt-stove-bbq-spray-paint-400-ml/128291_BQ.prd If using the spray paint in the link, spray some of the contents into a glass jar away from the telescope and apply to the focuser entry port with a brush, do not use the spray paint directly from the spray can on the telescope because of the obvious risk to the optics and bearings/bearing surfaces of the focuser mechanism. Or simply take steps to move the LED panel further away from the front of the OTA. A wrap-around matt black dew shield of the kind used by SCT owners can be fitted to the front of the OTA and the LED panel placed on the end of that, or a cardboard packaging tube flocked or painted inside with black-board paint can be used, pointing the telescope into one end of the tube and the LED panel at the other. Obviously, these techniques are more difficult to apply to a Newt with it's long OTA and I still think that sky flats taken either before the session begins during twilight, around half an hour to an hour after the sun dips below the horizon, or pre-dawn flats taken an hour to half an hour before sunrise, will give the best flats. Using a wrap around dew shield on the front of the OTA will help guard against stray light entering the focuser port indirectly even when taking sky flats and is essential when battling nearby sources of light pollution such as street lights and house lights etc that can shine obliquely into the focuser entry port depending on the orientation of the OTA. Flats must be taken at the same focus as the lights so mark the focuser draw tube position against the focuser body with a felt pen or blob of Tippex fluid next time the camera is bought to actual focus on a star and then make sure the focuser is set to the same mark if taking the flats at a different time. I see that you are using Astroart for calibration and having used that myself for several years I know that program can produce excellent calibration results. It does need BIAS frames though and will not produce a correctly calibrated flat if you omitted to take and use them. Missing the BIAS frames does lead to an overcorrection when applying the flats since the BIAS frames contain the cameras pedestal offset value which can not be determined from lights and flats alone. I you missed the BIAS frames then you can take them anytime as long as the BIAS frames are taken in pitch darkness and ideally at the same temperature as the lights though with the new CMOS cameras that seems less important than it once did with their very low dark current. If you did not use BIAS frames originally try taking some now and go back to the original data and recalibrate using the new BIAS frames. You can substitute a master BIAS for a master DARK with these low noise CMOS cameras as long as you use mount dithering combined with a bad pixel map and a sigma reject combination method when combining the LIGHTS. If you can't use mount dithering then stick to using matching exposure time LIGHTS and DARKS and the shortest possible exposure time for the BIAS. For the majority of commercial and free image calibration programs the BIAS frames can not be omitted if calibration is to be correctly applied, for the new breed of CMOS cameras DARKS may be optional. If you look at this recent thread it shows the results of omitting BIAS frames during image calibration: HTH William.
  2. Lifting the Lid

    I think the simplest way to do this would be to knock up (or hire) four A-frame trestles and a couple of planks/boards from scrap timber, chopped branches etc, anything that is lying around or inexpensive. With a couple of willing helpers, lift the dome off the walls on a calm day and walk it across to the trestles then lay the dome on a couple of boards or planks placed across the trestles, use a few scrap wood blocks placed on top of the planks to support the dome on the flat part of the dome lip (where the support wheels normally run) to keep the skirt away from the boards, then throw mesh/netting or a tarp over the dome and tie it down with guy ropes and tent pegs. You can crawl under the dome just as easily as if you were entering the observatory normally as the dome will be at the same height as it usually is and you can position/rotate the dome on the trestles/boards so that the dome quadrant joints are all freely accessible to work on. Once the work under the dome is finished for the day and if the repairs need time to set/cure and there is even the remotest chance of windy weather then the dome can be securely pegged down using the mesh tarp and guy ropes. Work on the dome walls can be covered at the end of the day with a waterproof tarp supported wigwam style from the pier and tied down with guy ropes and tent pegs. Doing the job this way would keep the dome unstressed and level. If you have nothing to hand to make your own trestles you could hire the adjustable height steel A-frame trestles and a couple of scaffold planks from most tool hire shops you only need to make up some tent pegs out of scrap timber and supply some guy-rope, mesh/netting and waterproof tarp. Since a sketch paints more than words (if only I could ) see attached:
  3. Flats Help

    Beautiful image Richard. Really makes one feel rather small in the vastness of it. Glad the calibration changes have resolved the problem for you. William.
  4. Lifting the Lid

    Hi Hugh. I helped the Pulsar team lift my 2.2m dome into position, there is a time lapse video of the whole install attached below. (I'm the weedy looking one with the checked shirt). The dome is not heavy, it was just awkward for two people to lift and guide into place at my site because access around the dome walls was so restricted so was I asked if I wouldn't mind helping. The dome is lifted on the walls at around the 5min 38 sec point in the video. Dropping the dome into the walls just needed all three to keep the dome level while lowering it into position and giving a bit of a shove to flex the dome if the skirt caught on any of the lateral guide wheels. The only thing that secures the dome against blowing off in the wind is the short skirt that drops down inside the walls. The lateral guide wheels and support wheels have no adjustments, the wheels just gently push against the dome skirt and underside of the dome lip. When gales are forecast and I am home I manually apply the optional security clamps inside the dome, if I am away A neighbour does this for me. I can't remember how heavy it felt now, certainly not more than my carrier bag of groceries from Sainsbury's, around 10-12Kg perhaps per person. Three people can easily lift the dome, walk it sideways and place it down, four people would make it easier to lift and lower but obviously a fourth person can not walk through the dome when the dome is taken away so a forth pair of hands is just useful for the actual lift but not really essential. The problem you would face with jacks is that once the dome is lifted the wind can get underneath and blow the dome away very easily, it will act just like a yachts spinnaker and be half way up the English channel before you know it. I once tried to work on a water leak on the dome of my old SkyShed POD (shown in stills in the early part of the video) and lifted the dome single handed using wedges and planks to slide the dome of the wall. Needless to say, getting it off the walls was the easy part, getting it back on proved much harder, I just could not slide it back up the planks and manoeuvre it into position, it is just impossible to maintain any sort of control over a heavy round object while pushing and pulling uphill on a pair of planks at a single point on the circumference. I had to recruit a couple of willing helpers from the pub opposite my home (for the price of a pint each) to help lift the SkyShed POD dome back in position. The SkyShed Pod dome was around 25Kg heavier than the Pulsar dome, being filled with insulation, and a few years of water ingress that had soaked into the insulation did not help. While the Skyshed POD is quite tough, being made of polyethylene (disposable milk bottle plastic) and can take a lot of flexing and abuse, the dome of the Pulsar is made of GRP and you risk damaging and cracking the gel coat if the dome is flexed too-much or lifted and lowered crookedly. If using jacks around the edges of the dome you would certainly run the risk of damaging the dome skirt and lip unlesss you could be certain to spread and cushion the weight over a large area and lift the dome equally all around, and to do this the jacks have to be a fair distance from the walls so that the Acrow's lifting collars can spin, this makes it all a little unstable. You would really need to lift the dome first, slide long planks between the dome and the walls and then lift using Acrow's on the ends of the planks to give you room to swing the Acrow's collars and jack up the dome. Now that my dome has settled I too have a few points during dome rotation where the dome catches against the wall joints and gives a loud 'crack' and a lurch as the small moulding imperfections in the dome joints and wall joints brush against each other and catch. The plan I came up with was, because the dome is so light, I would remove the scope and mount from the pier, place a pair of jacks inside the dome strapped to the pier for support and place a piece of circular cut 15mm ply, ~600mm diameter on top of the jacks, padded with foam and securely tied to the jacks and then lift the dome on the jacks centrally until it was clear of the walls and work on realigning and resealing the walls and joints could be done, then lower it back down until the skirt was engaged but not taking the weight of the dome while the joint sealant repairs had time to set. Obviously if lifting the dome internally on a central jack the shutter chain would need to be removed. As long as the skirt is dropped back down inside the walls then the wind can't get back under the dome to lift it and a mesh sheet thrown over the dome and pegged down would keep it stable while any joint sealant used had time to set. You would certainly need help guiding the dome skirt back into the walls as you lowered the jacks because the dome will flex and change it's shape once the forces acting on it change their positions. But then I thought this is an awful lot of faffing around, and will most likely just enlist the help of neighbours, relatives, or hard up pub goers who can spare ten minutes for the price of a pint and just lift the dome off as it was installed, work on the dome while on the ground, cover the dome walls with a tarp while any re-sealing dries and then lift the whole lot back a few days later. Let us know how you get on, I hope to learn a bit from your experience before tackling mine later in the summer. HTH William.
  5. Help! Heq5 making loud noises

    There are just a couple of points left to check/clarify. You said that you adjusted the RA end float ‘till it was tight, turned the RA axis ‘till it became bound and then released the clutch, after which the RA axis end float became loose again. This could just be because the extra loading you place on the taper bearing when you tighten and release the clutch is forcing the taper bearing into alignment. When you tighten the nut to carry out the initial pre-load then the RA clutch must be released, otherwise the brass gear won’t be able slide up the shaft to take up any slack, so you make the initial nut tension adjustment with the worm tension released a liitle and the clutch undone, tighten the nut set-screws and then the correct procedure is to manually rotate the DEC housing around the RA shaft while every 20 deg or so tighten firmly and then release the RA clutch, then release the nut set-screws and adjust the nut tension again. Keep repeating this until the RA pre-load remains constant for whatever angle the RA axis is turned to. Then adjust the RA worm tension with the RA clutch released. Finally power up the mount, engage the clutch just enough to secure the RA axis from slipping and adjust the RA worm tension under motor drive to minimise backlash and ensure the worm does not bind and stall the motor. In normal use the clutches should only be applied with just enough force to prevent the axis slipping, too much force on the clutches will tend to push the brass axis gears out of line and lead to the worm binding at the point on the brass gear exactly opposite to the clutch lever. Adjusting the worm tension is a balancing act. The Synta mounts are not made to a high enough standard that worm mesh will be constant for a complete revolution of the axis so you need to make the worm backlash adjustment to accommodate this non-linearity and adjust for a compromise so that the worm does not bind at the tightest spot and is not too loose everywhere else. Over-tightening the clutches will affect this adjustment by distorting the brass gear so don’t overdo the clutch tension. If you follow the above procedure but every time you make the nut tension adjustment the RA axis becomes loose again and can not retain it’s tightness then there are only three possibilities I can think of, either you are not tightening the set-scews enough in the nut, and the nut is unscrewing it’self from the shaft when you apply load to the RA axis or the threads of the nut are stripped, are not gripping the RA shaft tightly and the nut slips across threads when tightened or the RA shaft is loose in the DEC casting and is unscrewing it’self from the DEC casting (though I do not know how the RA shaft is secured to the DEC casting so this may or may not be a valid surmise). If the RA end-float becomes stable after the above adjustments then drive the RA to the 2 o’clock point where it used to bind. If it still binds in the same point then this can only be a shimming issue where the RA and DEC castings are rubbing together, the brass worm gear is misaligned to the worm, or one or more of the RA axis bearings are defective. A point to check that may shed some light is when the RA axis is disassembled look at the painted surfaces of the DEC casting, RA worm carrier, RA hub casting and the meeting faces of the brass worm gear where it butts up against the DEC casting. Any sign of rubbing away or gouging of the painted surfaces where the various components meet would indicate a problem with insufficient shimming, too much free play in the RA bearings or simply a high point on one of the castings that needs dressing. If you were a bit closer I would have liked to have been able to give the mount a look over, most likely it would have been a simple problem to resolve with the appropriate tools and mechanical experience but a seven hour drive is a little too far far for me these days. Are there no local astronomy groups close to you? Many astronomy clubs will have at least a few mechanics in their membership that would be happy to help. I see you have opened another thread asking for recommended service providers. You could try contacting Peter Drew at the Todmorden Astronomy Centre, you can PM him here on SGL, I believe Peter used to service and repair telescopes and he may be able to suggest a good engineer that is close to you. The only two companies I know of are SCTelescopes in Kent and Dark Frame Optics in Hampshire. SCTelescopes have been around a long time and are well known and respected. Dark Frame Optics appeared out of nowhere a few years ago but apart from the claims on their website I know very little about them. I can’t think of anything else to suggest and will step aside, maybe there is someone else here on SGL, a bit closer to you and better able to offer support, or who can explain how to make these adjustments a little more understandable than I can, sorry I haven’t been able to help you on this occasion
  6. Help! Heq5 making loud noises

    Could be either, it depends which parts of the castings, if any, that you find are rubbing when the the clutch is tightened or the RA axis is rotated past the 2 o'clock position.
  7. RA Motor Guiding Issue

    Or the ST4 cable is a straight-through pin-to-pin when it should be a changeover cable, or vice-versa...
  8. Help! Heq5 making loud noises

    In addition to the text above here are some pictures of my own HEQ5 with the gaps that need checking, if the gaps are smaller than shown, open and close together as the RA axis is rotated or the clutch is tightened and released then as above, the RA axis is missing some shims, the AXIS shaft is bent, or the AXIS bearings have too much slop. My guess is that the RA axis shims are incorrect. If the mount was ever abused and dropped the RA axis shaft may be bent, or, the bearings in the RA axis are simply sub-standard.
  9. Help! Heq5 making loud noises

    Without being able to see the mount it is difficult to make a diagnosis, from the symptoms you describe it suggests the casting of the RA hub, thats the bit bolted to the tripod that doesn't move, and the casting for the DEC axis, thats the bit that moves when you drive in RA or release the clutch and manually turn the RA axis, are rubbing together somewhere. Check the gap between the RA worm housing and the RA Hub, there should be a gap of a least 1.5mm to 2.0mm all the way around and the gap should maintain that distance as you either drive in RA a full rotation or release the clutch and manually turn the RA axis a full rotation. If the gap is less than this the RA axis may bind if the respective castings come together and rub because of any sloppy manufacturing tolerances in the castings, or a bent axis shaft, causing the gap to open or close as the RA axis rotates, or too much free play in the RA main bearings, which you would see if tightening and releasing the clutch causes the gap to open and close. It might just be that the shim washers, used in the RA Axis that we have referred to before are missing, were never there in the firsts place or were lost by a previous owner, I am curious to know if this was a new mount or a second hand purchase? If you find it is simply a case that the gap between the two main castings, where the RA worm casting meets the RA hub casting, is too small, and the castings are rubbing then you can fix this by adding a suitable shim washer to make the gap bigger. If the AXIS shaft is bent, you may still be able to add a shim washer or two to maintain a working separation between the two castings. If this is a new mount I think I would be talking to the supplier by now...
  10. Attached below is a quick process in PixInsight and Photoshop, I have pulled the galaxy as hard as possible, probably a little too far.... Steps taken in PixInsight were: Dynamic Background Extraction, correction by division. Background Neutralisation. Colour Calibration. TGVDenoise. Deconvolution. Apply Inverted Range Mask. HDR Multiscale Transform. ArcSinH Stretch. Remove Range Mask. Masked Stretch. Apply Inverted Star Mask. Colour Saturation, stars. Remove Inverted Star Mask. Apply Inverted Range Mask. Colour Saturation, galaxy. Remove Inverted Range Mask. Histogram Transformation. Save as Jpg. Move to Photoshop for final steps: Crop. Reduce colour saturation in red channel. Reduce Exposure and Gamma across all channels. Save as Jpg. ____________................._________________ There are not too many comments to add. Flats will help with your post processing, leaving you less to try and correct for afterwards, especially since you are using Photoshop where correcting for vignetting is quite time consuming. For the number of exposures you took there is a surprising amount of useable data captured but there is only so far you can go before the inherent noise in the data becomes apparent, for this target with your equipment three hours of data would be a good starting point and that would allow you to stretch the data much harder while leaving the noise behind. When you comment that you are struggling to get rid of the greyish tinge to the image, for the background that is a good position to be in, the trick is to stretch the galaxy while trying to keep the background neutral. In Photoshop you use layers for that and selective reveal, in PixInsight we use masks. I like the way that you have kept the background noise under control in your image and this has allowed you to pull the galaxy above background and just give a hint at the colour in the galaxy. Focus is good for the galaxy, there is some coma around the image edges. If you are not using a coma corrector this is normal, if you are using a coma corrector check that the spacing to the camera sensor is correct and that there is no tilt in the optical path. The image has some horizontal banding, typical of some Canon Cameras. If you intend to stay with Photoshop and are using the full photoshop program then have a look at adding a set of action plug-ins specifically developed for astrophotography such as Noel Carboni's Astronomy Tools Action Set, or Annies Astro Actions. Noels Tools contains a nice horizontal and vertical de-banding action and several other useful tools such as light pollution gradient removal, star colour boost and background noise reduction amongst others. http://www.prodigitalsoftware.com/Astronomy_Tools_For_Full_Version.html http://www.eprisephoto.com/astro-actions Action set plug-ins don't offer anything you can't do yourself, it just speeds up the process, and they won't run on many of the versions of Photoshop essentials, you have to have a full version of Photoshop to install and run actions so if you intend to buy them make sure your version of Photoshop is compatible. Once you understand how actions work you can easily make your own though I have to confess I still find still Photoshop a bit of a dark art, despite using it for many years. As an engineer I prefer PixInsight because I am more comfortable with numbers and maths, horses-for-courses...... You can find Steve's book that @Adreneline referred to here: https://www.firstlightoptics.com/books/dark-art-or-magic-bullet-steve-richards.html
  11. Maxim DL and dithering

    There isn’t a simple, user selectable option for this in the current release of Maxim DL. It is possible via the scripting interface but would require you to write a script for each target. This kind of fuction is really something that is best handled by an observatory automation program. Previously, I ran an observatory using CCDCommander. Working together with, and commanding Maxim DL via it’s scripting interface, this offers dither options including dithering after every sub or after ‘x’ subs as well as dither magnitude. An automation program like CCDCommander gives you access to the power of Maxim’s scripting interface but without you having to write your own scripts. Being just a regular Windows type GUI program with tabbed pages it is easy to navigate and quick to set up for an evenings imaging. Even if you don't have a bricks and mortar, physical observatory, an observatory automation program will connect to your mount, camera, guide camera, focuser, rotator etc and give you a fairly simple user interface to define a target, an acquisition sequence, including pointing refinement via plate solving, automatic or scheduled refocusing and bespoke dithering. You don’t need to use all the automation facilities, just the ones you need for a particular operation. CCDCommander offers a 45 day free trial period, give it a go and see if it offers what you need. http://ccdcommander.com/index.html
  12. Focuser colour

    For a standard LED flats panel varying the brightness has no effect on the distribution of photons leaving the panel, only the rate at which they leave. Increase the brightness and the rate of photons per second increases, lower the brightness and the rate of photons per second decreases. When you take your flats you still need the same number of photons to reach the camera, if you decrease the brightness the camera exposure time has to be longer, if you increase the brightness the camera exposure time has to be shorter. So far as the distribution of photons entering the OTA is concerned there is no difference. Exactly the same number of unwanted scattered photons will enter the focuser port during a long exposure with a low brightness setting as they would for short exposure with a high brightness setting. Things would be little different if we were to change the energy of the photons leaving the flats panel (such as shifting the colour between the red and blue ends of the energy spectrum) but in this case we don't do that, we just alter the rate at which the photons are produced. Flocking or painting the focuser entry port at the side wall of the OTA as well as the inside of the focuser draw tube should help enormously. Be careful not to be tempted to increase the exposure time for the flats to too long a time, if you do this you will need to start taking matching time dark frames for the flats and then the whole business of image calibration becomes a lot more complicated. HTH. William.
  13. QHY5Lii - guidecam image problem

    Are you sure you have the mono version of the QHY5l-ii, your images look typical for a colour camera, the checkerboard pattern simply being the bayer colour matrix. When you guide with a colour camera you don't debayer the incoming image as it takes too long and would reduce your guiding rate (images per minute) considerably, the guide software should still be able to find the centroid for any suitable guide star in the non-debayered image. If your guiding software supports the use of calibration frames for the guide camera then use a flat at least as this will help reduce any density differences between adjacent colour pixels of a colour camera. Using calibration frames will slow down the frame rate a little but nothing like as much as debayering would. While a colour camera can be used for guiding you do pay a price in reduced sensitivity overall plus some bright guide stars become unsuitable if they have a strong red or blue colour since only a single pixel in each group of four will actually record them. Mono camera is always a better choice for a guide camera in that respect. For your relative alignment question in your other thread, so far as matching the alignment of the guide camera to the axis of the mount and the main imaging camera, most guiding software won’t care. When it calibrates the mount it simply compares where the star moves to in the guide image for a given direction input to the mount motors, once it has calculated that then it will guide just as well if the mount to camera axis are coincident or at any other angle. The main reason to have the guide camera axis parallel to the mount axis is simply to help determine guiding problems, being a lot easier to match guide images to mount movements if the two have an apparent logical connection. But that is just for us humans, the software won’t care. If you really must have both main and guide cameras aligned then it is ok to add a shim spacer under the guide camera connection, a little defocusing wont hurt, in some circumstances defocusing the guide camera is a good thing as it spreads the stars disk over a greater number of pixels and makes it easier for the guide software to determine the guide star centroid. HTH
  14. Help! Heq5 making loud noises

    The bits of thread to concentrate on are the lead-ins, the first few mm of thread at the beginning of each threaded section, that is most likely where you will find a damaged piece and this will most likely be on the shaft. Temporarily reversing the orientation of the nut and screwing it on the shaft would realign a small damaged section on the aluminium nut as it is softer than the shaft but a damaged section of the harder shaft thread would not be restored doing this. A short damaged section of shaft thread can only be repaired by carefully dressing any damaged section with a fine file, running a die over it, or carefully prising away any broken section. The gap in the thread on the shaft is where the set-screws in the nut are supposed to tighten on the shaft. When the factory assemble the RA axis they should ensure that when the axis pre-load is correctly adjusted then the set-screws are aligned with the middle of the gap, if they do not align then they would add one or two shim washers beneath the nut until the set-screws and gap in the thread were aligned. If you tighten the set-screws when they are not central to the gap then the shaft threads would be damaged. (If you find you are missing some shims then you can make your own by cutting one from the wall of an aluminium drinks can using a pair of tough scissors, it needs to be the same diameter as the nut and the central hole needs to be a tight fit on the shaft to prevent it sliding about as the nut is tightened). If you are unable to repair the thread after an hour or so then don’t waste any more time but look in your local area for any small workshops or independent car repairers and they should be able to run a standard metric thread tap and die over the nut and shaft in a few minutes to restore the thread. If you had really broken all that thread away you would have had a great pile of broken bits on the floor when the nut finally came off! ———————————++++++++++++++++++————————————- As an aside, we had a conversation at one of the clubs I belong to a little while back about the lack of engineering skills in the general population with, it seems, the majority of people born from the late sixties, early sevetnties onwards having no affinity towards engineering of any sort, so don’t beat yourself up, you are not alone!
  15. Help! Heq5 making loud noises

    Just had another close look at the images. I can see that the set-screws were not backed out far enough prior to unscrewing the nut from the axis shaft and that is the cause of the damage. Astrobaby’s guide simply says to loosen the set screws before removing the nut but that is a little vague, it would be better if it said unscrew the set-screws ‘x’ turns to clear the thread, or just remove the set-screws completely. As before, when I look at the image of the main axis thread I can’t see anything obviously wrong. I assume you aren’t thinking that the gap in the middle of the thread is damage because that is supposed to be there.