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Ricochet

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About Ricochet

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    Brown Dwarf

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    Hertfordshire
  1. For observing from a balcony I would suggest only considering alt/az, not eq mounts. I would think that the way an eq mount changes the position of a telescope would be a bit of a nightmare on a balcony. I would also consider whether you can construct some sort of pier towards the front of the balcony rather than using a tripod, and fit an alt/az head to that. Moving the telescope forward those couple of feet could make quite a difference from a small balcony. Obviously, this won't work with a Newtonian where you need to stand at the front of the tube, but I think those have been discounted already.
  2. I suppose if you have a particularly sloppy focuser it might be a problem, but in that case you could never collimate accurately. In my dob the results this way are indistinguishable from the result of using a star, and you can see the collimation while you make adjustments.
  3. If you are doing it as in the picture above with the hole at the bottom of the focuser then I think you want it as precise as possible as you will be using the hole to centre the reflection. However, if you have a laser collimator with a 45° angled face there is no need for the cut out. Just angle the face so that you can see it from the primary end and the reflection will show on the face of the collimator, and you can centre on the hole in the centre of the face. This is shown in the image below. In the flesh the shadow is seen as an even circle, but for some reason it did not come out properly in the photo.
  4. It basically turns the laser into a torch which illuminates a patch in the centre of the primary. So long as the secondary collimation is close enough that the doughnut is illuminated, you will see the shadow and be able to use it to collimate. I think because the beam is diverging, small changes in secondary collimation will not alter the angle of the rays hitting the centre of the primary and so the reflected image is the same.
  5. For a standard 8" or 10" dob you need a space about two feet square and four feet high, which is actually less space than for a tripod mounted scope that is stored "assembled".
  6. Whether you can see the edge of the primary and/or clips depends on how far in or out you have the cheshire when you are collimating. Seeing those clips is not essential, the most important part is getting the crosshairs, the doughnut and the reflection of the hole at the top of the cheshire all lined up. For collimation to be absolutely perfect then everything should also look circular and symmetrical either side of a line running in the plane of the focuser as shown in the image below. Your focuser is at the top right, marked by the red F, and the centre line is extended from that point. we can see that the "top left" secondary shadow is slightly larger than the "bottom left" secondary shadow, so there is room for some minor improvement, but I think how you have it now is good enough for use, and I wouldn't worry about trying to improve it.
  7. That presentation is a very good find. I like the idea of the film, as it provides an improvement without adding weight or bulk to the scope. I think that I may have inadvertently done something similar by flocking the inside of my dob. It doesn't prevent the radiative cooling of the tube, but I think that it probably prevents or lessens any conductive exchange between the tube and the air inside of the tube. I've not got any temperature sensors to confirm this, but the flocking feels "warm" and the inside of the tube does not dew up like the outside does. However, there is also a primary fan so the resulting small air current may be helping with respect to dew formation on the inside of the OTA. Now that I have properly isolated the fan from the tube with respect to vibrations, I have not noticed any difference visually between leaving the fan on all night, or turning it off for high power observations (nut perhaps I need to do longer testing on this).
  8. For astrophotography, the only thing I know to suggest is to get yourself a copy of the book Making Every Photon Count. Reading and understanding this book should save a lot of aggravation and money in the long run. If you want to do some visual as well and can spare another £100 then maybe an 18mm Baader Classic Ortho and a 12mm BST Starguider would work well, which with your barlow would effectively give you 6, 9, 12, 18 and 28mm eyepieces (0.8, 1.2, 1.6, 2.4 and 3.7mm exit pupils). You could could choose the 18mm Starguider instead of the BCO, but it doesn't do so well in faster focal ratio scopes and I am not sure at what point the image cleans up. Alternatively, if you don't want to spend that much, perhaps just the 15mm Starguider for £50, so that you have 7.5, 15, and 28mm eyepieces (1, 2 and 3.7mm exit pupils). For visual there is the book Turn Left at Orion, and the accompanying web page. I would also suggest downloading Sky Safari if you have a smartphone or tablet, or Stellarium for a PC.
  9. Your secondary needs adjusting. I think that you should buy a proper Cheshire/sight tube to do this. You need to adjust the secondary so that when you look through the Cheshire the doughnut on the primary mirror coincides with the crosshairs.
  10. Do you have any other eyepieces than the 28mm eyepiece that came with the telescope? The 28mm is a 2" eyepiece but the barlow is 1.25". Only 1.25" eyepieces can be inserted into the barlow. The bottom of these two pieces is a 2"-1.25" reducer. You put this piece into the diagonal, then the barlow lens you have bought fits into the reducer. You can then insert a 1.25" eyepiece into the barlow lens. However, you also mention astrophotography. If you are doing astrophotography then you do not use an eyepiece or diagonal, the camera is attached directly to the back of the telescope, and you would only use a barlow if you are doing planetary photography.
  11. Thanks, John. The cut off age is even higher than I had thought.
  12. One good thing about Bresser is that they have a very good warranty department. I am sure, if your neighbour has the receipt, Bresser will take the telescope back for repair.
  13. The best scope for £100 is the skywatcher heritage 100p, but you would be better off increasing your budget for a heritage 130p, or even doubling it for a 150p. With regards to your granddaughter, I am not sure if 3 will be a little bit young for using a telescope. Others will have experience of children this young looking through telescopes and be better able to advise.
  14. Diffraction spikes are more obvious on brighter objects. If you increase the magnification they will become less obvious.
  15. For the money, extremely good. It isn't perfect, there is a slight distortion of star shapes towards the edge, but I suspect the majority of people wouldn't even notice. It's slight enough that I can't remember off the top of my head which, possibly astigmatism. The face cup means you have to turn your head a bit to look through it but that really doesn't matter. The 31N is probably the only similar eyepiece that is (slightly) better.
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