Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.



Advanced Members
  • Content count

  • Joined

  • Last visited

Community Reputation

574 Excellent

About Oddsocks

  • Rank
    Proto Star

Profile Information

  • Gender
  • 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. Oddsocks

    Space restricted obsy roof ideas

    Another member of SGL, Skipper Billy, built a micro observatory with a folding roof, website link here: https://sites.google.com/view/astro-imaging/micro-observatory William.
  2. Oddsocks

    problem with tiff file

    PixInsight also has a Batch format conversion tool under Script which will do what you want, I forgot about that when I read your original opening post.
  3. Oddsocks

    problem with tiff file

    I think you had Maxim at one time? if you still have it use the Batch Save and Convert tool.
  4. Oddsocks

    Society Obsy feasability study

    Site liability insurance might be an issue. I used to be a member of a small dinghy sailing club that had to close because we could no longer afford the public liability insurance for the building and grounds. This is essential if you intend to invite members of the public on to your site. Out on the water our own boats, possessions and personal accident insurance were covered by individual policies that were mandatory and part of the clubs rules. These policies were easily affordable costing less than a few hundred pounds per year for small dinghies and day boats but the public liability insurance for guests and public visiting the boat house and club house (sounds impressive but just big sheds in reality) leapt in cost every year and in 2012 we had to close after the annual insurance premium reached £7k. With only room for a dozen boats and eighteen members this was costing each of us nearly £400 on top of our personal policies. Factor in the clubs other costs, rates, water, services, sewage (septic tank), fire and theft insurance, maintenance etc, and we just could not afford to continue as the total membership fees for each of us reached over £1,000 p.a. Being mainly a retired membership and low average disposable income we just could not continue. Personal security and safety have to be considered, phone coverage, land line or good mobile signal to summon help in the case of illness or accident. CCTV provision may be required, it was a condition of our building and contents insurance as we were broken into, or suffered an attempted break-in pretty much once every year, so we needed a high speed broadband connection for the cameras though the thieves used to shin up the telephone pole and cut the telephone and power cables running to the club house quite regularly, one of the problems of having buildings in a remote location. Besides the above, you may find many club members are not physically able to travel safely to and from a remote site late at night and these members will feel excluded from this project unless the faciltiy to access the telescope remotely is included, in which case you are looking at imaging equipment, computers, broadband provision, software, weather station etc etc.
  5. Good to see your redesign has been successful Huw. Have you ‘run-in’ both worms and gears prior to the tests above? Reading the forum posts on the Software Bisque site it seems they run the Paramounts before final adjustment and shipping with an exercise program, slewing the mount in both axis at moderate slew rates for many hours with around 25kg of added weight to simulate an ota, so that the worms and gears bed together accurately. Now that the geometry of your worm brackets has changed significantly I think you would need to carry out something similar. I have no idea whether SB do this with light oil, lapping compound or greased worms, I can imagine it would take a long time to lap the gears with regular grease used as the lubricant. I have read on various engineering forums that chrome metal polish and even toothpaste make good lapping compounds for aluminium gears. It might be worth spending a day just slewing the mount back and forth in both axis at moderate slew rates ‘as-is’ to bed-in the worms and see if the guiding graph improves, if you do this do watch out not to overheat the motors and drive controller though and pause the exercise regularly to allow time for cool-down. William.
  6. Oddsocks

    Lifting the Lid

    Hi Hugh. From my experience with boats, abrasive flap wheels are not the appropriate tool to use on fibreglass for this particular job. You will not have sufficient hand control over the power tool and as the resin surface heats and melts with the friction of the flap wheel the tool will dig itself into the surface and you will end up with a series of concave dips. The trick with sanding fibreglass resin to a flat finish is to keep the surface and the abrading tool cold. When you have the lid raised up on blocks again use a piece of medium grade grit (P160-P180) wet-and-dry abrasive paper wrapped around a small piece of wood block around 4" x 3" x 1" (~100mm x 75mm x 25mm), take a bucket of water with you to the work and dip the wet-and-dry wrapped block into the bucket to wet it, press the block against the surface and make half a dozen passes over the seam then dip the block back into the bucket to cool and re-wet the abrasive plus wash the resin out of the abrasive to keep it cutting. Move to a medium-fine grade grit as the surface becomes flatter (P220-P280) and then finish with fine grade wet-and-dry (~P600) to a polished surface. Be careful not to abrade through the existing gel-coat and expose the inner glass fibre matting, if this happens environmental water will wick along the exposed fibres under the surface over time, freeze in the winter and split the top-coat from the fibre glass mat core. If you do expose the glass fibre core matting you will need to paint over and seal the exposed fibres with a two-part gel-coat mix which you can find in yacht chandlers, car-body repair kits for GRP shells, etc. Resin fibreglass is soft and easy to sand with wet-and-dry paper, used wet, and wrapped around a wood block, each seam should take ten-fifteen minutes or so to flatten by hand and the resulting 'bridge' across the seam will be as flat as you can achieve by any other method. You will need to remove and then replace the drip-strip to gain proper access to the work. The drip-strip is just regular self-stick closed-cell door frame draught excluder for external doors that you can find in most DIY shops. Clean the surface of the fibreglass with acetone before applying the new strip. I had to replace the drip strip on my Pulsar dome after just a few months, I don't think they cleaned all the mould release agent off the dome before sticking the drip-strip on and it fell off in several places allowing rain water to track inside the observatory but a quick clean with acetone and then a new bit of drip-strip fixed that easily and the fresh strip has remained firmly attached. HTH William.
  7. Oddsocks

    Remaining dust bunnies, processing them out

    Looking at the side-by-side image you posted, all the donuts in the master flat have concentric bright rings around them. I thought at first that this might be just a bit of jpeg-ery edge detection enhancement going on with the screen capture but the fact you see these artefacts in the calibrated light suggests it is a real artefact in the flats. Posted screen captures are really much too low quality here on the SGL forum to make an accurate diagnosis and it is always a good idea to post the fits images as well, or a link to a Dropbox or Google Drive folder containing them when asking for help with image artefact or calibration issues. Taking your screen capture and applying curves in PS shows that the darker donuts in the flat master are also present in the calibrated lights, it is not just the bright arc that remains after calibration. There are only two ways to produce bright concentric ring artefacts in the flat masters (using PI) that I am familiar with. First is a change in focus during the time it took to take the flats, i.e, the telescope focus was not consistent across the full sequence of flats used to create the master. Second, either bias frames were not taken and included in the batch processing script (or if using the manual calibration tool in PI, a bias master was included but the tick box 'calibrate' was not ticked in flats selection window), or there is a temperature mismatch between the lights, darks, flats and bias frames, and/or a matching dark frame for the flats was not included in the batch processing script. Because both the bright ring and the dark donuts are present in the calibrated image then it confirms the flat is not calibrated correctly. In PI when calibrating images from a 8300 sensor it is essential that the full set of matching temperature calibration frames are included, if the flats exposure is longer than a few seconds, then matching time and temperature darks are also recommended. If it is simple case that you did not take bias frames, or matching time dark frames for the flats, set the camera to the same temperature as for the lights and take a series of bias frames and matching time flat-dark frames now and rerun the batch processing script with the bias and flat-darks included, that should fix the bright ring artefacts around the dark donuts in the flats and calibrate the lights correctly, if it doesn't, try the manual calibration tool instead as I find it often produces better results than the batch processing tool as you have more control over the fine-tuning characteristics of the calibration procedure. If you did take bias frames and flat-darks and include them in the batch processing script or manual calibration tool check the fits headers for the bias, darks, flats and lights, were they all taken at the same temperature? If these images were taken with the G2-8300 the 8300 chip shows a great variation in dark current with temperature so it is important the temperature is consistent across all the frames used (as I found out with my own QSI 683 that uses the same sensor). I can't offer a post processing solution to fix your current image but maybe going back over the calibration procedure with the full set of matching calibration frames will solve the problem and you won't need to resort to "air-brushing" the final image. HTH.
  8. Oddsocks

    Filters with mono cam

    When imaging with a refractor or a reflector that incorporates a glass element of some sort it is likely that not all the wavelengths of light are bought to focus at the same point on the camera sensor. Infrared and ultraviolet are particularly difficult to control and though we can’t see these wavelengths with our eyes the camera does record them. In practice these wavelengths appear outside of focus at the sensor plane and cause stars to become bloated and fine detail to be lost. Most red, green and blue filters incorporate infrared and ultraviolet blocking as standard, you wont need to use a separate IR/UV blocker with them. If you want to construct full colour images with a mono camera you will need red green and blue filters working in tri-colour mode but to gain the full advantage of the sensitivity of a mono camera you would need to work in L-RGB mode where you construct the image using the three colour filters plus a clear filter, the luminance channel, and you could use your existing IR-UV blocking filter for that provided it will fit the filter wheel and is ideally the same thickness as the RGB filters otherwise you will need to substantially re-focus the camera when swapping between the colour filters and the luminance filter. I’m not sure why people would use a red filter alone for astro imaging and have not read that anywhere myself. A red filter is used with daytime terrestrial imaging and monochrome film to increase contrast but I can’t see a particular use in astrophotography except perhaps planetary imaging. Since I only use a colour camera for planetary perhaps a planetary imager would be the best person to answer that question. Narrow band filters such as Ha, SII and OIII allow you to target particular wavelegths of light from emission objects while controlling light pollution and to some extent moon-glow, giving you a slightly longer imaging window during each lunar cycle. Substituting a light pollution filter for the luminance filter brings some benefit in city or suburban locations where sodium or mercury lighting is still in use though as LED lighting is progressively rolled out in these areas dedicated light pollution filters will become less useful. HTH.
  9. The marks on the inside of the corrector are most likely vapour deposits left by volatiles that evaporate from the grease on the moving mirror support or the paint and glues used for internal flocking. It is common with enclosed OTA’s such as SCT’s and Mak’s that are stored indoors in warm conditions or are used in the daytime for solar observing. The few marks visible on the outside look like acid etch spots left by pollen, I can’t see any external streaky marks in the image but maybe they are too faint to show. The corrector is multicoated to reduce reflections and improve light transmission, if the coating is carried out poorly this can also leave the corrector with ‘streaky’ looking marks. In use, vapour marks have little impact on the views for most objects though very bright objects such as the moon may show a little reduction in contrast. Vapour deposits left behind by volatiles are very tenacious and difficult to remove without solvents once dried and unless you know the chemical make up of the deposit many solvents won’t work while some solvents may damage the optical coating. To clean the inside of the corrector would need it to be removed from the OTA and the rotational relationship between the corrector, primary and secondary mirrors are tuned in the factory to minimize aberration so if you did remove the corrector for cleaning you would need to mark it’s position relative to the tube and other optical components and ensure it went back with exactly the same orientation. If you can see vapour deposits on the corrector glass they will almost certainly be on the secondary and primary mirror too so once you begin a cleaning task like this you may end up having to clean all the components as you chase the contaminants around the optical surfaces. If you are determined to attempt a clean of the optical surfaces then a long soak of many hours in a bath of warm water and detergent followed by a clean using isopropanol alcohol, following general guidlines for cleaning newtonian reflectors, should remove any volatile grease deposits however if the deposits are from paint or glue volatiles it is unlikely this treatment would have much effect. HTH.
  10. Hi Huw. Attached are a couple of suggested sketches for a worm carrier backstop and side thrust stops, both are adjusted just to touch and limit movement of the carrier but not to fully prevent clearance movement in the required directions. Hollow tipping the nose of the side thrust stops and dropping in a single ball just before tightening up would reduce vertical drag on the worm carrier and allow a tighter adjustment than would otherwise be possible with a simple friction mating. Regarding jerkiness of the drive, this could still be improper alignment of the worm and gear, have you tried bluing the gear and checking for correct contact between worm and gear? Clean and degrease the worm and gear and apply fresh engineers micrometer blue paste, reassemble the worm and gear, load up the mount and drive the dec through one or two rotations. Look at the wear displacement pattern in the blue paste remaining on the gear using a loupe or magnifying glass, the point of contact between worm and gear will push away the blue grease revealing the shiny aluminium below. If the point of contact is not central between worm and gear add/remove shims as necessary to bring the worm and gear into alignment, re-apply or re-spread the blue past around a little and repeat until the central axis of the worm is perfectly aligned to the central axis of the dec gear (when I was a young engineer, just starting out, we used to mix chimney soot from the factory foundry, pounded in a mortar and pestle and mixed with regular grease to make our own 'micrometer blue', the boss certainly didn't like to spend out on 'luxuries'....). http://www.arceurotrade.co.uk/Catalogue/Protection-Grease-Adhesives/Engineers-Blue Another possibility for the jerkiness is that the mesh pressure is too high leading to friction lifting of the carrier. A lower mesh pressure and carrier backstop to limit lift may be all that is required to smooth the drive. William.
  11. Were the mods successful Huw? I see you have opened a new thread asking about opinions of the EQ8 as a possible replacement so I’m guessing the star test showed DEC problems have not been solved. Having reviewed both this thread and the original build thread the only design weakness that stands out is long hinge arm for the worm carrier. For the hinge to allow the worm to swing in and out of mesh must mean there is some lateral movement in the hinge and a very small lateral movement in the hinge would translate to a large backlash at the wheel. A possible solution would be to drill a pair of tapped holes in the mount frame, either side of worm carrier. After adjusting the worm mesh use a pair of bolts in the newly tapped holes to press lightly against the sides of the worm carrier and this will prevent any lateral movement of the worm carrier, in theory this would remove any backlash contributed by movement in the hinge. The bolt face should be machined slightly domed where it presses against the worm carrirer and greased so that the carrier can still lift and fall in response to mesh variations. If this were sucessful then the domed bolt could be replaced with a hollow nosed bolt fitted with a single ball to give reduced friction and wear. I’ll add a sketch to the post later this morning when I get a minute or two spare. Given the large mass and moment of inertia that the heavy mount and OTA generates on the worm carrier the spring used to press the worm into mesh would need to be very strong to prevent the worm being pushed away from the gear during drive reversals. Increasing the spring tension would increase wear and drag considerably but a possible solution is to add backstop adjuster screw to the worm carrier so that the principle adjustment and mesh pressure is still taken by the spring but once the spring tension is set then a backstop screw is bought to lightly bear against the worm carrier to limit lift of the carrier during drive reversals. Obviously, a backstop only works if the gear is perfectly centred to the axle and the carrier does not lift and fall by very much during a normal rotation of the axis. In the assembly of the dec axis I notice there are only two mounting bolts and spacers used to fix the hub axle to the frame, this may allow a little twisting of the gear as the direction of rotation changes, I would add a third spacer and bolt to stiffen up the mounting of the axle but I doubt this is where the backlash is coming from. William.
  12. Oddsocks

    Laptop Upgrade Options

    If you do this are you certain that.... A: Will the laptop onboard regulated power supply be able to cope with the higher power consumption of the uprated CPU? B: Will the current laptop's CPU cooling be able to keep the processor at a temperature where max performance is possible or will the CPU quickly overheat and the CPU clock slow down to prevent core damage? C: Are the laptops motherboard north and south bridges up to supporting the higher performance CPU or will they become a bottleneck? D. Is the current memory fast enough for a higher performance CPU?
  13. Looking at the wear pattern in the picture of the gear, and assuming it is not just an image artefact, it appears that the worm thread is bottoming in the gear thread and that the worm is not centred to the gear. The mesh wear marks in the photograph of the gear are not central to the width of the gear so that the worm and gear are not meshing at the deepest point. If this is the case when you tighten up the worm-gear mesh all that is happening is the peaks of the worm teeth are pushing against the valley of the gear teeth while still leaving a large gap between the walls of the teeth for backlash to occur. Time to get out the engineers blue and check where the mesh points between worm and gear really are....
  14. Oddsocks

    HEQ5 Power Woes

    The type of mains adaptor you have bought is called a switch mode power supply and it is common that poor quality examples are known to leak a little high voltage mains supply voltage across to the low voltage DC side. There are rules governing just how much leakage current they are allowed to pass and still be deemed safe but it is very difficult to know just what you are buying on-line with so much unregulated foreign-sourced electrical equipment entering the country unchecked by customs, often with fake compliance labels on the product and the auction sites totally unable to police the items they sell. leaving aside the risk to the equipment, if you can feel a shock when touching metal parts of the mount then it is a danger to you, especially when using the mount outdoors where it is likely to be damp. Whilst grounding this leakage current by touching the metal parts of the mount is unlikely to cause damage to the mounts electronics, if you should touch any of the mounts connection sockets and ground those via your body then it is possible the mount electronics could be damaged. For your own safety, and because of the risk to the mount, I would suggest that unless you have access to test equipment to measure its leakage current that you consider it potentially unsafe and bin the power supply immediately. A fully compliant 240v AC to 12V DC 5A double-isolated, plug-in switch-mode power supply that does not leak mains voltage across to the low voltage side, that is from a traceable source and supplied by a reputable UK company such as RS or Farnell would cost around £40, if you paid less than that then you are taking a big risk. Truth is, very few astronomers actually follow safe electrical handling procedures. Whilst builders and general craftsmen working on major government or commercial contracts know they would be thrown off site if caught using mains power tools without a safety isolation transformer it is suprising how many would not bother using one at home when doing something just as dangerous! A bench type regulated linear power supply would be the safest type to use, even so, they are not rated for outdoor use as they are not supplied with waterproof cases. If you do buy one it should be kept indoors and only the low voltage cables run out to the mount. To be fully safe it should be used in conjuction with a 240-240 isolation transformer but I bet if you took a straw poll right now amongst other SGL members you would’t find anyone willing to spend the £120 or so that they cost and are quite happy to ‘take a chance’ each time they connect up their equipment in the garden. In my fixed observatory I have an industrial 25A, 240Vac - 240Vac, 100% duty cycle, operating-theatre isolation transformer, this was something I rescued from the skip at a hospital where I was working on a renovation project. All my observatory equipment and lighting is supplied via the transformer, Last time I looked these were around £800 to buy new and that was a few years ago. A builders type site-safety isolation transformer of approx 6A at 240Vac - 240Vac with a 30% duty cycle costs around £120, I would recommend anyone taking mains connected power supplies outdoors should really be using one. Since this reply has rambled on a bit to sum up.... Do not use the power supply you have, unless you have access to a meter and can measure its leakage current, or have someone with the necessary equipment do this for you then it should be considered potentially unsafe and should be binned. A linear bench type power supply is better but should be kept indoors and only the low voltage cables run out to the mount. Consider using any mains powered device outdoors (or mains power-tools etc indoors), in conjuction with a builders site-safety isolation transformer to fully protect yourself against accidental electrocution. For occasional use, a battery power pack is always going to be the safetest option and modern LiFePO4 power packs provide enough power to supply a mount and ancillaries for a whole night (though at a price!). If your existing dead 12v rechargeable power pack is screwed together consider opening it up and replacing the battery, a good make of battery will last years. I have one here that is still as strong as day one and is now over 25 yrs old. HTH.
  15. Without being able to see the mount first hand I would hazard a guess it would be down to moment of inertia. The moment of inertia on the DEC axis is many magnitudes larger than that of the RA axis so that one possibility is belt stretch or mount flex. It might be that swapping to kevlar or steel cored timing belts will be sufficient to stiffen up the DEC drive, assuming you are using polyester cored belts at present? Are the belts really the right size for the gears? The flat face of belts teeth should not 'bottom' on the motor's gear while still leaving room for individual teeth to slide from front-to-back. Edge faces of the belt teeth need to be firmly pressed up against the "walls' of each motor gear tooth as it meshes with the gear, else the belt can slip a little in the direction of rotation when the direction of rotation changes. Aluminium gears are notorious for belt slip as aluminium wears off the gear with use and leaves a slippery coating of powdered aluminium on the surface of the gear and the belt. If the belt is not a snug mesh with the gear then when the motor changes direction the belt can slip a little within the confines of each individual belt-gear tooth mesh. Another possibility is, if using second hand drives, that there is some wear in the motor reduction gearbox of the DEC drive, if new drives, possibly there is some mis-adjustment of the gearbox and it needs shimming. Check how the motor pinion gear and the worm gear are attached to the shafts. Is it pinned with an expanding dowel, solid dowel, keyed or simply held with a grub screw? Pinion gear fixings that use a simple grub screw against a machined flat on the motor output shaft can allow the pinion to move a little from side to side as direction of rotation changes, a solid dowel or expanding dowel drilled right through the gears hub and the motor output shaft would be a stronger fixing less likely to slippage. If the drives are identical try swapping the drives over and see if the problem moves with them. If the motor control system uses sophisticated DC braking or pulse reverse braking before driving continuously in the reverse direction (or some other method of stopping the armature quickly), is the control system applying this to the RA and the DEC motors? Check for end float in the DEC worm bearings, there should be some method for adding preload to the worm so that the worm can not move axially as the direction of forces change when swapping from forward to reverse drive, you may need to add or remove shim washers between the end of the DEC worm thread and the face of the worm bearings, or the bearing mounts, so that the worm can not move axially. Similarly, check for DEC worm mesh adjustment. As the direction of forces change when you swap rotation direction the DEC worm must not be able to lift away from the DEC gear otherwise the mount will just keep travelling in the same direction for a while as the slack is taken up. Thats about all I can think of 'in the dark' William.

Important Information

By using this site, you agree to our Terms of Use.