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About jefrs

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    Star Forming

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    West Berkshire, England
  1. If you are considering 4/3 sensors then you might consider getting a Lumix G7 which may go for as little as £200 used, if you don't want to spring £1,000. Pixel size is more important than pixel count in low light. The 16MP sensor has 3.75µ pixels. The Panasonic designed Live-MOS is biased to sweep stray electrons off, unlike Sony CMOS sensors. And it is mounted on a heat sink to keep the temperature stable. The powerful processor has features to further reduce noise as it is designed to shoot movie indefinitely without overheating. Shutter speed down to 1 minute and built in intervalometer. ASCOM drivers are available.
  2. There is the word 'stiction' that aptly describes the problem, yes it is a real word for a real problem - "the friction which tends to prevent stationary surfaces from being set in motion"
  3. Break it down to first principles. You have OTA focal length divided by eyepiece focal length giving the magnification of the telescope. Then your compact will add some magnification factor. For a camera that is the focal length of the lens (not full frame equivalent) divided by the sensor diagonal, aka image circle diameter. Multiply them together. Personally I have never managed to get a compact camera to focus on the eyepiece image, I'm told it has to be set at infinity.
  4. Simple answer (I hope) is divide focal length by the image diameter circle (the diagonal) of the camera sensor. Full frame is 43.3mm and this is the proper length of a prime lens to give 1:1 image although we normally use 50mm or 45mm. For micro four thirds the image circle diameter is 21.6mm so its 'prime' lens is 20-25mm thereabouts, and APS is somewhat variable, nominal 35mm. A typical guide camera might be a 1.2/3 sensor of 7.66mm diagonal. These give the equivalent eyepiece focal lengths when used on prime focus. Magnification is OTA focal length divided by eyepiece focal length. A common misconception is that a larger sensor will see more light than a small one. Both see all the light gathered through the lens/OTA iris (or aperture if closed down). The sensor is at the image focal point and sees all the light. A 130mm reflector is 130mm iris. If 650mm focal length then 650/130 = f/5.
  5. Something I'm always trying to get my head around too. Also complicated by the eyepiece because they can vary in field of view as well as focal length, obviously a long eyepiece will give you a wider FoV than a short one. A camera will also change the FoV, sensor size (crop factor), whether on prime focus or eyepiece projector. This calculator may help https://astronomy.tools/calculators/field_of_view/
  6. The SLT mounts are not strong but with some proper servicing can support and move heavier weights than they were designed for. The bearings need cleaning and a good grease like Castrol used and then set up so they rotate smoothly with a very small end float. If set too tight they bind. The Stifnuts are poor, use Loctite, or they adjust themselves. The Alt clutch can be tightened but must still clutch. The motors like some attention, the muck they put in the gearboxes is not good. Plastic cogs need silicone grease, on the teeth not in a pool on the case floor. The gearboxes are like repairing a clock, and reassembly is a metal puzzle, so if you're not confident, leave it alone. The motors seem to like a drop of Servisol Super 10, an electrical lube. The drive cog onto the platen does need a small amount of play, not forcing the two cogs tight together as it is doubtful the platen is perfectly circular; this does mean some backlash has to be tolerated. The tripod can be adequately braced to reduce vibration with some bungee cord around the legs under the tray.
  7. You will find various illuminator adapters here - http://www.astrokraken.fr/accessories-for-skywatcher-star-adventurer-mount-a184487612 ça plane pour moi I don't have a 3D printer and unlikely to get one. A lens hood can be simply made for the illuminator from a black plastic 35mm film can.
  8. Yes! Once I got the camera refocused it's quite amazing. I set up Thursday night 07/05/20. Of course by the time it dot dark there was solid high thin cloud. I could just visually see Arcturus but little else. So I experimented. There's a LED street lamp over our back room before our patios. Despite that and the cloud and high hedge and fence it still did an Auto Align in under a minute. Adding a star to the calibration makes it want to do another Auto Align. So we did that three or four times. Despite only seeing a few stars, now focused, it competed successfully every time, quickly too. I cannot bend down to use the red dot without pain. Thank you once again.
  9. An older thread but a good one. My StarSense was not seeing stars. I have a lot of light pollution, LED street lamps. Auto align kept failing. I read this thread and spent the night adjusting the StarSense camera focus as described above - thank you people. I found the focus point to be quite critical. I found the focus point between 15 and 24 half turns out and then narrowed it down to to around number 20. Meaning these cameras are not all the same. I then started going in quarter turns in and out and then 1/8 turns until I got maximum star count. Whereupon I lost count of turns and simply went back and forth, I had marked the focus housing. Seeing conditions were variable so I was getting between say 65 and 87 stars at the same place on repeats. Tightening the lock ring moved the focus so the last adjustments were made with the ring locked each time. As I got near to optimum focus the StarSense would 'solve' and complete alignment, which had to be blown away and resume the Manual Align. Once completed I got Auto Align to run complete successfully in about one minute. Quite amazing considering the street lighting, houses and trees in the way. Finding a target is not spot-on but it is nearby. Once again thank you to everyone who posted on this thread - if StarSense Auto Align is not solving, refocus the camera even though it is long winded and boring. I actually had more problems with the dog prancing about and trying to eat large planter pots, which makes a change from destroying lens bags and my gloves.
  10. Using two cables to the computer may well be true with the older Hand Controller and the 'Celestron Programming Cable' with USB/Serial adaptor. The instructions seem to have been written for this older system (pic). With the USB Starsense HC the data is fed through to the camera on the RJ12 cable. I did a little experiment when I had to replace the motor board (which has its own update process) - I updated the camera with the NexStar+ Telcon serial HC attached, this did require the camera USB cable to be used, all devices were updated. The updates are reinstalled if they are already the latest ones. Then repeated with the USB StarSense HC, with one USB cable, and again with two USB cables. With one USB cable to the StarSense HC all devices were seen and updated. One or two USB cables made no difference. You can observe the updating in progress on the CFM - latest updates are reinstalled. fyi the supplied camera to mount RJ12 cable is far too long, a 50cm RJ12 cable is adequate (usual online vendors)
  11. Typing correction fluid (white paint in a pen) or Sharpie Silver make good night-visible marks for alignment and switches etc against dark/black surfaces. Both can be cleaned off if desired.
  12. Celestron mount with StarSense AutoAlign USB handset on Windows 10. The StartSense Camera does not need to be connected to the computer by its USB, indeed the computer and CFM will not see it. I do not know why the camera has an USB port, the computer does not recognise it. If you connect the handset by USB before turning on the telescope, the handset will light up but you will not connect to CFM. Connect Camera and handset to the telescope in usual manner, switch on whilst holding down button 7 and the Celestron key together so handset shows 'BOOTLOADER', then connect handset USB to computer. Start CFM, it should now see both handset and camera, in the info box. Wait for its preamble to complete then hit 'update'. Go and have a cuppa whilst it does its thing. Switch off telescope and disconnect from computer. Sorted.
  13. I have acquired a number of old camera lenses over the years and adapted to modern digital cameras. However long ones can also be adapted as telescopes. The M42 lens thread is M42x1mm, as used by Praktica et al. When we speak of a camera lens with a M42 thread, this is the one it will have. The T2 (or T) thread we are familiar with on telescopes is the M42x0.75mm, also known as the Taisei (the inventor) or Tamron thread. Both are ISO-metric threads, they are not interchangeable. M42x1 to DSLR camera adaptors are readily available, these lenses were mostly for 35mm compact film SLR thus back focus should accommodate a mirror box however using a shorter adaptor will increase focus-turn range at infinity (some old lenses are not right at infinity on full turn). To adapt a M42 camera lens as a telescope to astro cameras or eyepieces we need to convert to T2. The TS-Optics Adapter M42x1 female to T2 male aka "russian adaptor" is available from 365 Astronomy in the UK without the silly shipping charges from abroad. https://www.365astronomy.com/TS-M42x1-female-to-T2-male-adapter-for-Russian-Objectives.html We may need to further reduce from T2 to C mount (CCTV camera) but these adaptors are more readily available.
  14. An altazimuth mount has to be horizontal so it knows where zero degrees 'horizon' is. Use a spirit level but it doesn't have to be perfect. The mount has to be levelled anyway so I have a little spirit level in the toy set. You have to take the lens cap off (always a good one) The StarSense AutoAlign has to go through a rigmarole first calibration set up - read the book, there are some how-to on YouTube. Read The Book https://s3.amazonaws.com/celestron-site-support-files/support_files/94005_starsense_autoalign_manual_february2016.pdf Watch YouTube The set up "Calibrate On A Star" is important and one-off. After that it can do its normal automatic alignment dance Yes the clock and latitude and longitude has to be correct. I use a phone app (PS Align Pro) and it's GPS for time, lat & long (the app is for an Equatorial mount really, does the other thing). Lat & long only needs to be set once for each location, time and date every time. I only use GMT (UCT). Zulu time saves a lot of confusion. No idea why merikans can't use international date format, or metric screws, like something out of the ark. Do they know NASA is all-metric after they nearly mucked up landing on the moon? Have fun.
  15. I am very interested. Newbury Berkshire. Can we Private Message details for payment and posting? TIA. Jeff. PM sent please reply.
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