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symmetal

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About symmetal

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    Star Forming

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    North Cornwall
  1. symmetal

    Star Halo(s)

    Sorry to hear about your misfortune Kaliska. Hope it can be recovered. I suppose now's not the time to give advice about backup disks. Alan
  2. symmetal

    Tilt Adaptor - Solving the Tilt

    I think it's a law of astrophotography that no matter how many spacers and adapters you have you will always need one more. Good luck with your tape for the moment. Alan
  3. symmetal

    Tilt Adaptor - Solving the Tilt

    Hi Aidi, I found that CCDI gives misleading results regarding tilt and curvature when using a field flattener as it ignores the orientation of the elongated stars. Stars too far from the correct distance are treated the same as stars too close, so a badly tilted sensor where the centre is at the correct distance will be reported as having no tilt but significant field curvature. I gave up on using CCDI to try and correct tilt as it does more harm than good and you end up chasing your tail. I found just looking at the orientation and length of the elongated stars in the image corners is a far better way to see where the errors are. I too resorted to 'jamming' objects in the threads to force a correcting opposite tilt with some success but did end up getting a tilt corrector. Luckily it's fitted far enough away from the camera that adjustments are easy with the allen keys and in an hour or so got it to the best it's ever been and even copes with rotating the camera orientation with very little change in tilt. I'd wasted days before trying to correct it so the tilt adjuster was well worth it for me. I don't know why they can't be made as an option with the adjustment screws on the opposite side so that you can still adjust them easily when it's fitted close to the camera. You also need to know the orientation of the sensor in the camera and whether the camera software automatically rotates it by 180 degrees, in order to work out whether the 'tilt' corner you need to adjust is the same corner as indicated by the image or the diagonally opposite corner. On the ASI1600 it's the opposite corner. On my Atik One it's the same corner. It's easiest to just make a large adjustment in one corner and see where the effect occurs in the image to determine what yours is. Alan
  4. symmetal

    sgp mosaic questions

    There was a discussion between me and somebody on the forum a year or so ago on this very topic and they did ask others who did mosaics how they dealt with this but there was little response. Like you I thought of manually rotating each frame to correct this but as you say it's just too tedious. I think the rotation angle could be the RA offset angle * sin( Declination angle), as at zero Dec there is no rotation but I haven't worked it out to check. If you took a 4 panel mosaic centred on the Pole you would end up with each panel rotated 90 degrees although what SGP would say I'm not sure as the target RA angle is any number you like between 0 and 360 degrees. Ah! Good to see that PinInsight does acknowledge that the problem exists. I my previous post I did say about aligning the camera edge parallel to the RA movement when moving back and forth in RA. In reality the RA movement will describe a segment of a circle so it should be the tangent of the RA movement circle where it crosses the image central vertical axis should be parallel to the image top or bottom, but unless you're near the pole this circle segment can be considered as a straight line.
  5. symmetal

    sgp mosaic questions

    When you click 'Create Sequence' using the mosaic wizard the next window that appears called 'Mosaic Sequence' has a tick box called 'Auto rotate or validate rotation on mosaic start'. By default this is enabled. If you untick this box, you will get a warning that rotation can't be validated but that's ok. You can then run the sequence without it stopping saying a rotator is required. It's easiest for mosaics if you align a camera axis, horizontal or vertical, so that it's parallel with the RA movement of your mount. I normally select horizontal, and check by moving the scope in RA while taking short exposures using 'Frame and Focus'. The stars and/or their trails should move parallel to the top and bottom edge of the image. Keeping this camera alignment setup, which you can repeat easily on other days, you can then do your mosaic. You need to bear in mind that the mosaic panels to the left and right of your centre panel will be rotated compared to the centre panel, depending on the declination of the target. At Dec zero there is no rotation and as the Dec increases the rotation will be larger. The auto rotation (or manual option) in SGP does not take account of this Dec dependant rotation (I don't think other mosaic software does either, unless anyone knows different ). It just ensures the same rotation angle relative to the RA direction for each panel (which you've already done by aligning a camera axis to RA). You may need to increase the overlap between your panels when your imaging a target at higher Dec to account for this. Here's a rough mosaic stitch of the Heart & Soul Nebulas at about 60 degrees declination showing the amount of rotation you will get. Panels in a vertical direction are not rotated with respect to each other. Alan
  6. symmetal

    Meade LX90ACF Problems!!

    The GPS receiver time output is always UTC so does not change with location. There is no timezone information in the GPS receiver messages. It's up to the software which is using the GPS data to add timezone offsets if it wishes. Actually, being pedantic, 'GPS Time' is what the GPS receiver gets from the satellites. It's a count in seconds from 6th Jan 1980. It does not take leap seconds into account so is currently 18 seconds ahead of UTC. The GPS messages do contain this offset so the GPS receiver converts 'GPS Time' to 'UTC'. Alan
  7. Excellent video, well worth the effort. Orion certainly stands out and the clouds scudding by enhance the video. Alan
  8. symmetal

    Win 10 Home to Pro update path

    Yes, you just buy a new licence key either direct from the Microsoft Store or from sellers on Amazon etc. Here's how to do it from the store. If you buy a licence key use the same method but instead of clicking on 'Go to Store' click on 'Change Product Key' instead. RDP is installed on the machine whether you buy the Home or Pro version. The Pro licence just unlocks it to use it fully. Alan
  9. If it was 15 degrees off in RA I would suspect a 1 hour error in the time setting somewhere. Daylight saving time ending perhaps. Alan
  10. symmetal

    Star Halo(s)

    If you're using ZWO narrowband filters then this thread may help you out. OIII seems to be the worst offender. Alan
  11. symmetal

    Pelican Nebula - 8 hours H-alpha

    Ah, I thought this was a colour CCD. What does the CCD image look like without the combined DSLR. The edges of the picture do show the common DSLR blotchy noise and it's probably adding to the noise on the CCD image unless you've masked it off. Alan
  12. symmetal

    Pelican Nebula - 8 hours H-alpha

    For comparison this is 4 hours of 300s subs on an ASI1600MM at unity gain. I just gave it a stretch in Photoshop. No other processing. In your image there are some black clipped areas which makes the noise around them stick out a bit more. You have 4 times the acquisition time of mine which other things being equal would imply a similar amount of data assuming you just used the red channel output. Mine's using a small aperture ZS-61. Alan
  13. symmetal

    Pelican Nebula - 8 hours H-alpha

    Coming along nicely. Not bad at all for not having "essential" cameras You've just caught a mini-orion in the bottom left too. Alan
  14. You're right tooth. 'Essential' was the wrong word. I should have said 'preferred' or 'recommended'. In my defense it was early morning when I wrote it. Alan
  15. Hi Craney, The exposure times would be about the same for all three bandwith filters to record the same Ha component of the image. However with the 35nm the sky background level will be higher for the same exposure time as it's recorded more 'light pollution' too. So the feint areas of Ha will be swamped by the sky background and the image will have less contrast. The 3.5nm will have a much lower sky background level than the 35nm for the same exposure time, so giving more contrast and resolving more feint detail. This means you can actually expose for longer if you wish to get even more detail. The 7nm will be pretty good but wouldn't quite match the 3.5nm. Alan
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