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About jACK101

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    South West Scotland
  1. I am building an observatory and I am at the stage of test fitting my CPC925 and HD Wedge to my pier which is topped with a car brake disc.. I have a print off which I think is a Celestron product which says that the hinge on the wedge should be pointing to the North. Is this correct? I am trying to understand the whole idea of Polar Alignment. I have attached a very rough sketch which looks at different positions at different latitudes. At the equator no wedge is required, I believe. My sketch shows the various orientations of the wedge at different latitudes and with the hinge pointing to the South. In each case, by setting the wedge to the local latitude the mounting plate then becomes parallel to that at the equator. This seems to me to be logical. If the hinge points North as shown in the 60 degree latitude example the mounting plate is at a totally different angle. Can anyone please explain where I may be going wrong? Thank you Jack
  2. Peter, I think that the working load would be in the vertical direction in my application. My idea is to screw or bolt a substantial upstand to the brackets and then build the roof on top of the upstand. All of the load would then be vertically downwards. In addition, I think it might also be possible to add a section of hardwood behind the bracket to stop the roof being lifted. There would have to be additional methods to stop the roof being blown off. Thanks for the replies Jack
  3. I have found an item 252826831189 on Ebay which I think could be modified for an observatory sliding roof. It is a sliding door gear and the maximum door weight is 200 pounds. Clearly 2 tracks would be required, so total safe load would be 400 pounds or roughly 180KGS. This would be strong enough to allow me to work on top of the roof to felt it. Any comments? Jack
  4. Housing a big SCT - and a question.

    Olly, I have just completed a similar exercise. I am using a car brake disc, Mercedes no less. Not because it was Mercedes, but because I needed a 300mm diameter disc. (£20 on Ebay) I drilled out the five existing holes to 16mmm to match the screwed rod I was planning to use, (screwfix) then used that as a template to make 2 identical plates in plywood. I bolted one plate to the bottom of the five rods and the other near the top, but below the finished level. I dropped this assembly into the shuttering for my concrete and poured the concrete. The plywood kept the bars parallel and all I had to do as the concrete was being poured was to ensure that the rods remained as vertical as I could manage. In any case I can adjust the brake disc later to make it as horizontal as possible. The nuts on the immersed plywood templates I think will also make it more difficult for the rods to be pulled out of the concrete. I hope this helps. Jack That is as far as I have progressed, the rest of the obsy has still to be built.
  5. Solar Probe.

    I believe they are sending it at night to get over the temperature problems.
  6. Nikon D3100

    Hi, I use a Nikon D3200 which is very similar to your camera. I use the viewfinder when hooked up to my telescope and it works OK. What shutter speed are you using. It is possible that what you are seeing is movement of your telescope set up resulting in a fuzzy image. Note that the D3200 and probably also your 3100 cannot use liveview when the lens is detached. The camera does not recognise my telescope and this can be a nuisance. Try as high a shutter speed as you can and if the result is in sharp focus you will have identified the reason. Try also to use an electronic release instead of pressing the shutter. The moon is an excellent subject to practise on, particularly when at half moon when you get sharp definition over the boundary between light and dark areas. Jack
  7. I haven't tried a 32mm EP. My problem was using my Nikon in prime focus mode. I have managed to get what I need from Peter's suggestion, see above. Thanks for your help. Jack
  8. Peter, Another one from an earlier sequence. Thanks again Jack
  9. Peter, Thanks very much for that, you have solved my problem. The programme is easy to use and also very quick. See attached result.
  10. I have taken a number of shots using my Celestron CPC925 with my Nikon D3200. These are reasonably OK but I cannot get all of the moon into the frame. I bought a very cheap 0.5 focal reducer on Ebay This screws into the short 1 1/4" stub mounted on the camera. When I use this I cannot get the moon into focus and all I can see is a fuzzy "Polo Mint". I have tried a longer tube on the camera, about 2 - 2 1/2", and this allows me to get the focus but the "Polo Mint" is still very dominant. Is it possible to make this or some similar arrangement work or should I buy the Celestron focal reducer, which mounts directly onto the end of the telescope? Thanks
  11. How to start? Color or mono

    I have read this thread in bemusement. I have also read a few books on Astrophotography and none of them go into this level of detail. Can you recommend a book which goes step by step through the theory you have been describing, or do you have to gain this experience by making possibly expensive mistakes? Thanks
  12. Short Exposure DSO Imaging

    I am puzzled by this discussion. I am coming at this issue after a lifetime as an amateur photographer. In conventional photography, let's say landscape, the exposure would be a simple function of aperture, shutter speed and film speed, or nowadays sensor ISO setting. I cannot think of any situation where many hundreds of grossly underexposed frames when added together could give an acceptable result because the information would not be there on the film or sensor. I can understand the need to have different exposures for different brightness levels which when stacked give an acceptable result, but why does astrophotography seem to work to different rules? Jack
  13. Moon on 1st March

    It is a single image. I am starting to set up an observatory and I have bought the Celestron HD Pro Wedge. I intend to install that on a concrete pier. I therefore did not use tracking, the telescope was on its tripod. I have been a keen amateur photographer for around 60 years so I am more familiar with photographic processing rather that astro. I used Lightroom, adjusting for exposure and contrast then making fine adjustments in Curves followed by a touch of Clarity. Exposure was 1/4 sec at ISO 800. I was using only the telescope lens, the camera lens being removed. I was surprised at how rapidly the image moved out of frame. Thanks Jack
  14. Moon on 1st March

    Hi, I am a relative newcomer to astro photography. This is my attempt at the moon on 1st Mar. I had difficulty getting it in frame and by the time I fitted a focal reducer my front lens had misted up. Celestron CPC925 with Nikon D3200 Any suggestions for improvement welcome.