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FaDG

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About FaDG

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    Star Forming

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    Rome, Italy
  1. I mean that, out of the box, the scope was utterly unusable! As you know, the primary mirror cell is held in place by three couple of screws. But these do not (thank God!) act on the mirror directly, as it is supported by three holders. Well, if these are screwed too tightly, they can deform the mirror, and this can be seen as a pattern diverging from the theoretical circle. In extreme cases (and mine was one of these) the deformation is such that the out of focus pattern acquires an almost triangular (curved, clearly) shape. So I removed the mirror from the cell, let it rest for three days, and reinserted it very carefully. Perfect circle! squinted focuser: the SkyWatcher crayford has a set of screws which allow to tilt it: in my case this was needed because the camera sensor was not orthogonal to the light beam (stars in focus close to the centre and out of focus on the sides, intra on one and extra on the other) Just for sake of completeness: the secondary shadow not being centred in the out of focus pattern is NOT a defect. the fast Newt design needs this for better field illumination.
  2. Yes, you're right. But considering that I fully solved that issue in less than half an hour, I'm now 129 pounds richer! Seriously though: this was a friend's scope and it was a catastrophe, as the secondary was totally uncollimated and almost stuck to the point that one of the spider vanes bent when I tried to get it free, the primary strongly tensioned (almost triangular), the focuser was squinted, so the flare was really only the minor issue! Actually I told him to sell the bloody thing for cheap, but then I tried messing with it and the Ugly Duckling became a wonderful Swan, as it had really great optics, just assembled by the wrong guy! Yet, when it finally was perfect my friend decided that a Newt was too complicated for him (a newbie) and asked me to keep it: I struggled to convince him even to accept some money (what I consider a low price for that value: I've been lucky on that). Hence, you see, there was really no sense in investing on it at the time. Fabio
  3. If you were really happy with the optics, you could have tried a 4cm extension tube between focuser and camera. This way you could have kept the focuser retracted, yet enjoy the optic performance. But now, all the best with your triplet! Fabio
  4. I have a Photoline 72 f5.5 linked above, and I just love it! It's so compact and lightweight that the Star Adventurer perfectly supports it, and using FPL53 it's virtually free from chromatic aberration, even better than my ED80, which is f7.5. I have found enthusiastic reviews of the WO ZS61, yet my view is that, while for photo the aperture difference is negligible (shorter focal length), for visual already 72mm is quite small. I don't want to start the FPL53 vs whatever quarrel, but I think that the SW 72ED is slightly less corrected than the others. Fabio A field flattener is in order for all of them, for astro photo...
  5. Yes, you're fully right. After chopping it off I did not have the hideous flare anymore. And this is what the reworked focuser looked like. Actually, the design is not flawed per se: you REALLY need the extra length in order to use the scope visually, just, when rectracting it all the way in, the end of it enters the light path. It's just another trade-off: to avoid it, Skywatcher should have used a MUCH larger tube for the 6". Hardly a better design choice. Even so, 90% of the users never complain and are super happy of their results. Not me! But now I find it to be a great budget scope. Yet, if you find the root cause of the weird spike, I'll be happy to deal with it too. Fabio
  6. Here you are. It's the only image affected by this artifact, luckily. It's on Electra.
  7. No, not strange at all, actually! If you needed a confirmation that it was a reflection, now you have it. The fan like flare is a reflection of the light cone off the focuser drawtube. To solve it I took a hacksaw and cut about 3 cm off it. Issue solved, but it won't focus with eyepieces anymore: I don't care as i never use it visually. The single stray spike is a reflection off something depending on the specific position of the point light source (star). It seems to be a characteristic of the Skywatcher newts design, as I have the same in my 150 f5
  8. The point there is to clearly separate the sky background from the read noise, as it will improve your SNR We didn't stay long in Adeje, but El Duque was really fun due to the huge waves, and we also loved Medano, my son started surfing there. And my best Milky Way so far was shot from the southern shore of La Gomera: pitch black sky, the closest light in the south being Dakar (Senegal), 1500 km away!
  9. I have used a Y mask and, while letting more light trhrough, this stays in the stars Instead of migrating into the spikes. So, my experience with it wasn't positive and I reverted back to a bathinov. I post a picture of the comparison: the Y mask is the leftmost one, the others are two slightly different bathinovs. Fabio
  10. Your tracker periodic error and RA rate, your polar alignment and balance and light pollution will be the limits, alongside thermal noise for very long exposures in hot climate. This being said, the habit is to avoid very long exposures because you lose a lot due to a plane or a gremlin, and shorter exposures set lower constraint on the mount. Also, few great lenses are really crisp and with flat field when used wide open, so you'll probably want to stop it down a bit to increase image quality. I imagine that with all the above, my suggestioni would be: don't get too analytic, find the best ISO value for your camera and expose in order to have the sky background about 1/4th to 1/3rd of the histogram. And enjoy your time in Tenerife! My family is longing to go back there... Fabio
  11. I'm pretty sure that the additional small spike is due to reflection. I found it in only ONE of my images, namely M45, I acquired with my 150pds. It was on ALL subs in that sessione and NO other. Neither different targets, nor the same target taken with a different FOV. And I'm sure that in my newt the focuser doesn't protrude in the light path, so it must have had a different root cause. Could you try to take a longer exposure of a rich star field, in order to cause spikes around multiple stars around the image? It could help debugging... Fabio
  12. FaDG

    Hi from Italy

    Ciao Luca, benvenuto! Fabio
  13. If the focuser is a good one, normally it shouldn't, at least with a DSLR. For sure threaded connections are sturdier and less subject to sag/flex.
  14. Send us a photo, but simply: do you screw the camera adapter in the focuser thread or do you insert the 2" nose inside the focuser?
  15. I use Canon, so no idea about clip ins for Nikon. For the 2" filter, it depends on your focuser: if your connection is purely screw-in, then I wouldn't venture to screw your camera adapter in the filter and it to the focuser: only a couple of threads would get the full load on them, you can expect flexure at the least... This is why i passed to full clip ins in my setup. But if it's a traditional focuser, you could screw the filter in front of the reducer (i.e. on objective side) thus it would not impact the reducer backfocus. Fabio
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