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About D4N

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    Brown Dwarf
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    Northern Sweden

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  1. I like number 3, you can clearly see the double class star and M31, M33 is just about visible too.
  2. Whether you need IR block to get good images will depend on the colour correction in your optics. If you just have mirrors it should be fine but if you have lenses then the different wavelengths of light can end up at different focal points. Since the colour correction is mainly aimed at visible light you get get blue bloat from UV and red bloat from IR. On a mono camera this would just appear as a fuzzy image which is not possible to achieve perfect focus. The focal ratio also comes into play here, on a fast scope the sweet spot for focus is very small so exacerbates the problem. Using IR pass as mentioned above gets around the problem in the other direction by blocking everything else so you are just focusing on the IR.
  3. Ah yes that looks like it will work, I'm sure I can knock something up that will draw the air through the tube. Since I sit it on the primary end when it is cooling down I think I'll make something that either goes into the focuser or into the tube cap. I learnt with my imaging obsy that to leave things setup outside I need the provide constant heat to stop it being destroyed, everything freezes up otherwise. It isn't a problem heating a little frac' but it's impractical to heat a big dob. The advantage of living so far north is that the skies can get incredibly clear when it gets so cold, which is great provided you eyes don't freeze
  4. I'm not sure if it would, I think the problem is the air inside the tube so the fan would need to change this out and not just blow air onto the back of the primary.
  5. I have noticed that when I take my scope out to cool down (12" dob) I get frost on the primary mirror. I assume that this is because the air in my house contains a lot more moisture than outside and reaches dewpoint as it cools down. How do others deal with this? I don't really want to heat the primary as this defeats the point of cooling it down. I also don't really want to leave the tube open as that would be an open invitation for creatures to go inside. I've considered giving it a quick blast with a hairdryer to change out the air once it is outside or fitting a small fan to draw air through the OTA, this would also reduce cooldown time.
  6. I think this is purely to pull out fine Nebulosity without blowing out brights stars or if struggling with light pollution. If the sky is too bright you may only be able to get 5-10 mins R sub but the Ha could be 30 mins easily. I think in some locations collecting L data is totally out of the question so HaRGB would be a substitute for LRGB.
  7. I would suggest using software to help you manage the mosaic as well, nothing worse than spending hours building a huge mosaic only to realise that you missed a bit.
  8. Nice, it looks like you have the 2" adaptor in the focuser so be sure to remove that before you fit the 1.25" adaptor or you won't get focus. Hope you get some clear skies to try it out with.
  9. I guess it depends if it is too much flex to throw the goto accuracy out. The best way to know is to try it. I use mine at ground level with an adjustable observing stool.
  10. The important thing with galaxies is to be somewhere dark, light pollution ruins them. Andromeda is great to view at low magnification, a common mistake is to increase the magnification too much on it so you only see the core.
  11. The spacing has to be exactly right or you will get that sort of thing.
  12. Ah well I removed the mirror from my DSLR anyway so no problems there
  13. The noise on the DSLR will be significantly reduced at that temperature but the battery life will also be reduced as well. My CCD seems to handle low temps fine it is the mount I worry about as mechanical components can easily get stuck in the cold.
  14. One minute isn't bad unguided at 1.5m focal length, I know I've had much longer subs unguided but always at shorter focal lengths. Guiding takes the limit off of it and you can continue to expose until the background gets too bright or highlights over expose. Another option for brightening your image is using a reducer, your scope is f10 which is quite slow for imaging. The apparent reduction in focal length will also allow you to expose for longer before trails appear.
  15. Have you considered guiding? Small PA errors are of less concern when guiding as they help keep the gears meshed anyway.