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pipnina

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About pipnina

  • Rank
    Sub Dwarf
  • Birthday 15/02/1998

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    Male
  • Location
    Devon, England.
  1. M 16 Ha

    That sounds pretty similar to where I am. Except my dark and bright patches are the other way around (the light dome for me is north and I get somewhat better southern sky.) Gives me some hope if I eventually get into telescopic AP.
  2. M 16 Ha

    Very nice image What's your bortle/SQM? (roughly)
  3. Yep that's my scope. That's also a very narrow focusing margin! Unfortunately I only have a single-speed focuser fitted. It seems to manage about 12 mm of travel per turn. So that would be 0.01~mm of travel per mm of focus dial rotation (measuring the dial as 21mm radius). So I would have to get the focus to within 5mm rotation if I've measured everything correctly (which I probably haven't).
  4. I could attempt video capture, but my camera is limited to 1920x1080 @ 24fps. The frame rate isn't so bad but the 3x shrinking of resolution would be a killer. I used some scale-aware contrast boosts on the jupiter image (it basically just brought the bands out a bit better) i think this is somewhat similar to wavelets. Hmm, It's one thing to be able to focus on stars (there are tools I could use, though bahtinov masks are a bit confusing.) but focusing on the tower proved rather difficult. I kept moving the focus back and forth past where it appeared to become most sharp, but it never got any better than the images attached. I'm not sure if the Mizar and Algieba shots are out of focus or not. What tips you off to it being a focus problem and not just turbulence?
  5. I'm using a T2 adaptor for my camera's mount that screws in to the base of my 2" to 1.25" adapter. So it's Nikon D3200 -> T2 adaptor -> 2"/1.25" adaptor base -> focusser. I have excess focus inwards and outwards. I've noticed my focusing not being perfect. I took a 30-second exposure of polaris which showed two diffraction spikes per side instead of one but I focused individually for Algieba, Mizar and Jupiter. With bad wobble one night I took a 1/3 second exposure of M42. It wobbled and made a very long spaghetti star trail. Dividing that length by nearly 100 might be close to that level of clarity, but even zoomed in through live view on the communications tower showed the same blur, with little wind and no visible wobble.
  6. I've been taking snaps with my 250PX recently and found that the telescope is possibly not as sharp as the rayleigh criterion would have me believe. At 254mm and a 6000x4000 APS-C sized sensor I have a pixel scale of 0.69" and a rayleigh criterion of 0.66" (at hydrogen alpha line, to give a pessimistic estimate, 0.44" at far blue for optimistic estimate). I have found that the camera is observing a rather large blur around objects (not the somewhat sharp (or possibly under-sampled) image I was expecting. This image was taken from the top of my driveway, it shows the top of a communications mast some miles away. There is a rather large level of "blur". The telescope was stable and I used 1/250th shutter so I doubt that it is wobble. I spent some time trying to focus. It also shows the center of the frame, with the telescope collimated (primary only) before hand. Bottom of the frame (below) seems to show yet more blur (i think) possibly coma or perhaps mis-aligned secondary? On astronomical terms, this image is of Mizar A&B: Some clear atmospheric effects seem to be at play, making it hard to identify whether it is the same problem as before or just turbulence. 1/6th of a second exposure. [EDIT: It is 1/60th not 1/6th] And Algieba: same exposure Finally Jupiter. I think the atmosphere's effect is easily visible here but still hard to assess for me. Do you guys think these images look right considering the telescope's properties? I'm not using a coma corrector but these photos all show roughly the center of the frame. There are rather large "blurs" around objects which is my main concern. Cheers,
  7. The reflective 45-degree surface serves as an entrance for light (I shine a small red torch on that surface when it's too dark to do it without additional light). The light reflected from that surface is what can be seen in the secondary mirror. The black dot which can be seen when looking through the cheshire at the primary mirror is actually the hole you look through. Once you have adjusted the primary mirror so that the hole is in the middle of the primary mirror's black ring your primary mirror is properly aligned These telescopes can be mind-bending sometimes. I spent a good 3 minutes looking through the bare focuser of mine the other night before realizing I was actually able to see the edges of the secondary mirror and the light from my ceiling reflecting on the tube wall I suppose this is why they recommend the paper Hope this cleared thing up. Happy collimating!
  8. Does only pixel scale matter for guidescopes, or is a guidescope of certain size relative to main telescope aperture also required?
  9. Help me with observing nebulas

    There is much debate as to whether zoom eyepieces are worth the cost. Personally I would prefer to get different eyepieces with the properties you desire for different tasks. An important factor when buying an eyepiece is the "exit pupil" which is the size of the beam of light that comes out of the eyepiece. You can work out by taking your aperture (250mm for your telescope) and your magnification (focal length divided by eye piece focal length) and dividing the aperture by magnification. This means if your telescope has 1200mm focal length and 250mm aperture, and your eyepiece has 24mm focal length, you get an exit pupil 5mm wide. The exit pupil is important because it determines the brightness of the image. Bigger exit pupils are brighter and smaller exit pupils are dimmer. The maximum exit pupil you want might be somewhere between 5.5mm and 7mm. This is largely dependent on how large your pupils can dilate to. 5mm-6mm is usually a safe bet, but the maximum dilation decreases slightly as you age. Usually the minimum exit pupil you want will be somewhere in the region of 1mm and 1.25mm I find. I think a 2" eyepiece with a big apparent field of view like the 82 degrees from those skywatcher eyepieces would be ideal for nebula and galaxy viewing. I use a 24mm maxvision 82 for this purpose and the large field of view is always stunning. A 2" focuser is better, however a 1.25" eyepiece can work just the same in a 2" focuser as in a 1.25" focuser. The need for a larger focuser comes from the eyepieces properties. An eyepiece with 24mm of focal length and 82 degrees afov needs the extra size of the 2", as the light cannot fit inside a 1.25" focuser. This is the bottom of my 24mm 82deg maxvision. It is a 2" eyepiece and the bottom lens is almost as big as the 2" space it sits in, this is because of the large field of view it covers. A 12mm 164 degree eyepiece would need the same size glass. Ultimately a 1.25" eyepiece is not necessarily lower quality, but manufacturers do not make eyepieces with 2" size unless it is needed for the eyepiece design to function.
  10. 130pds mirror.

    I believe the nature of parabolic curves is that, irrespective of distance, light from a point source which is on-axis (center frame) will always come to focus. I could be mistaken however. The purple spots do seem strange, but I've not seen anything like it before so I'm afraid I cannot provide any insight
  11. Cheshire eyepieces make the process incredibly easy thankfully Since the 250px has a small black ring on the primary you just have to get the black dot created by the cheshire directly in the middle of the black circle. The secondary mirror is more challenging I feel (mainly because of how tight the skywatcher screws are, I've wanted to adjust my secondary for a long time but I've not been brave enough to loosen the screws )
  12. I would think either collimation or seeing. My 10mm can provide very good views so the magnification probably isn't to blame. (usually people say 1x mag per mm of aperture as an optimistic approach, which this scope is well below. I think 0.75x per mm is more like it but probably down to personal preference.) We can rule collimation out entirely if you have a cheshire collimating eyepiece. If you have no collimation tools I strongly advise putting the cheshire at the top of your list! It's cheap and let's you collimate easily in minutes. At f4.7 collimation is more important than usual as well. If you have a cheshire try taking a photo through it and we can see if collimation is in error instantly
  13. Street Lights can cause cancer?

    You know... If it's 5G microwave signals we're concerned about maybe a tin foil hat would work? First time for everything!
  14. star adventurer

    The diagrams help you get polaris into exactly the right spot, after aligning the mount roughly so that polaris can be seen in through the polar scope. Polaris sits on the ring of the circle, the time of night and the time of year determine where on the circle it should be. I use stellarium to see whereabouts polaris should be on the circle just before setting it up, and tend to get it close enough. I can usually manage 2 minute exposures on my 105mm lens (some get that time with a 300mm lens, but that takes very accurate alignment and I don't have the patience). Over all, I think the diagrams are very useful
  15. I have that exact scope and have loved my explore scientific 24mm-82deg "MaxVision" and my Vixen SLV 10mm. The 24mm hasn't got good enough eye relief for glasses but is very reasonable for the well-sighted. I chose the SLV partially because it touts a comfortable 20mm of eye relief while also having a decently large afov and a sensible magnification for the scope. Based on my use of the 10mm I've found the eye relief to be the closest thing to comfort I've gotten while wearing glasses at the eyepiece. It also provided me some of the best views of jupiter I've had I don't use the 24mm with glasses on most of the time because It's for observing big nebs and galaxies really. I find it good for that but if I wanted what the 24mm has to offer and a sharp view of it I'd get lasik... Clear skies.
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