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Stub Mandrel

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Everything posted by Stub Mandrel

  1. Stub Mandrel
    Which is which Nige - the second one has excellent colour, the first is 'sharper'. If the first is modded, try manipulating the histogram or curve for the red channel alone.
  2. Stub Mandrel
    I recently ordered one of these: No I'm not insane... I swapped a fully coated 150mm x 50mm lens 2-element achro into an old one and fitted the EP out of a small finder to make a decent finderscope. Now I need a guide scope and I dug out the old lens, which is a 2-element achro but only coated on the front element (360mm fl). I made a new scope body but fitted the lens the wrong way round and chipped it getting it out :-( I have a cheap but reasonable 1.25" focuser lined up so I decided £16 for a reasonable lens fitted in a lens cell, hood, aluminium body and an adaptor so it will go straight onto a pan tilt head is worth the punt! The rest will go in the bits box.
  3. Stub Mandrel
    I can trump that, I've just managed to snap this image with my Nokia. Uranus AND Neptune in the same frame - and look how much detail there is of the cloud formations. Forget StuPOD I think this is one for APOD. Just to confirm, that mottling in the background is the integrated flux nebula, not a doggy bag.
  4. Stub Mandrel
    Here's one of the moon... And does this count, I took the photo (of the computer) with my phone...?
  5. Stub Mandrel
    No I'm saying that bigger pixels are more forgiving of misalignment.
  6. Stub Mandrel
    If your pixels are twice as big you can expose for twice as long, choose bigger targets! Worng.. forgot the issue was rotation..
  7. Stub Mandrel
    A cunning ploy to invalidate my daughter's entry! The whole things rigged!
  8. Stub Mandrel
    You can sort that with Pixinsight's 'Tree Removal Filter' or the 'Chainsaw Tool' in Photoshop.
  9. Stub Mandrel
    Here are a few pics of the lunar eclipse, taken by my daughter, Amelia, using her iphone with my Bresser 76mm Lidl Special. As you can see the event kept her interest for a few hours!
  10. Stub Mandrel
    Wim is right (and I'm wrong) the conic section is an ellipse - but the 'centre' does not lie on the axis of the cone. This is the displacement required. But looking at the links and various diagrams, if the view of the mirror looks right then the displacement is right.
  11. Stub Mandrel
    Great, I've linked to your post in the thread where someone is asking if modding a camera is worth it.
  12. Stub Mandrel
    Presumably because the light cone is wider where it hits the lower side of the secondary, but I don't understand the diagram. If 1 & 2 are the focusser, they should align with the direction of displacement.
  13. Stub Mandrel
    This is what I mean - exaggerated of course - if every time you collimate you tend to tighten the screws the mirror will 'creep' down the tube, and even if you still line up on the centre of the secondary you will have to tilt it backwards to keep collimation. That means the centre point will move back and forth as the focuser moves up and down. Hmm; it will also affect sharpness of focus across the image so worth correcting.
  14. Stub Mandrel
    Ha! My 150PL is doing exactly the same at the moment. As said above, tilt in the focuser movement relative to the alignment with the centreline through the secondary mirror. If the tube and focuser are truly at right angles then the secondary may have moved too far down or up the tube with repeated collimation (if you're like me and you always adjust in the same direction...)
  15. Stub Mandrel
    This is interesting: https://courses.cs.washington.edu/courses/cse467/08au/pdfs/lectures/07-cmos-ccd-imagers.pdf
  16. Stub Mandrel
    Surely reflected or not, it's going to be lost light anyway as it's only photons that miss the light-wells. You can't ARE coat the wells themselves without stopping them working.
  17. Stub Mandrel
    That's the problem with the latest kit, people drool over it...
  18. Stub Mandrel
    That's excellent Nige. Why not split it? Keep the existing version as the lower colour layer, so you don't risk losing it, and create another version focusing on getting detail without over-sharpening paying no attention to the colour at all. Put this second version on top of the first one, but set it to 'luminance'. I do this with most of my images as it means you only have to worry about one thing at a time.
  19. Stub Mandrel
    if you search eBay for "Zeiss 135 3.5 m42" you will find old lenses listed that will give brilliant results (we're talking pin-sharp across the field at f3.5, and effectively apo so the only CA issue is that if you don't block UV you may need to correct small violet halos) and leave you £££ for another new one.
  20. Stub Mandrel
    At the risk of teaching granny to suck eggs, did you realign the secondary and re-collimate the scope afterwards?
  21. Stub Mandrel
    :-) I have a hood for a 400mm lens made out of the body of an aluminium fire extinguisher! Flocked too :-)
  22. Stub Mandrel
    Excuse the double posting (I gave this its own thread), this is the best 60% of 100 x 120s at ISO800:
  23. Stub Mandrel
    A really good image. It seems to be possible to get almost ANY colours out of M42 except the ones you want!
  24. Stub Mandrel
    At this time of year it's vital to keep your equipment warm when out in sub-zero temperatures
  25. Stub Mandrel
    Hmm . .. I had an extra spike on Monday, turned out to be the clothesline... DOH!
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