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leonardo2012

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About leonardo2012

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    Nebula

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    http://marklimbrick.co.uk

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    Suffolk
  1. Having spent time getting the telescope optics and GSO coma corrector aligned - it may be useful to anyone contemplating a Newtonian plus this corrector for astrophotography to note how it performed in practice. firstly - with the GSO CC in the optical train you have to provide an extra 35mm to reach the new focal plane. The CC itself also shifts the focal plane by its insertion length, about 50mm. I was able to fit longer bolts on the mirror cell to take care of this extra distance. If you just hang extensions on the focuser the secondary mirror size needs checking. secondly - don't expect 'r
  2. Chris - is that a drawtube extension piece - it's difficult to see any change in diameter of the focuser tube and whats added to it? So, the CC is inside that extension? That's what you called a 'holder'. And hence it has the thumbscrews to hold the eyepiece/2" to 1.25" adaptor etc.
  3. Thanks Chris. I meant is the GSO coma corrector inside the focuser drawtube and then the 2" spacer is added by threading it on? The 'eyepiece adaptor' I can see is after that - just ignore the mis-typed wrong label.
  4. I have been building an ultra low profile '~Crayford-style' focuser for imaging only this weekend. Leverage was my main concern with a DSLR. So I did some levering as I assembled. Without resorting to some CAD analysis software, I have to say that the basic design is for smooth movement without precision engineering skills, not holding the drawtube perpendicular (it has a spring in it - surely a big clue!). Or for pulling heavy loads against gravity. A three-legged stool doesn't wobble and can be quickly made by the milkmaids - but is less stable. An engineer care to analyse and confirm this?
  5. No, I have got it wrong! The 45mm 2" adapter referred to in the photos and the spacing distances list by Chris is the GSO 'eyepiece 2" adapter' which is not supplied with the cc from Teleskopexpress? Is that correct? The 2" adapter extender (2" long?)on the focuser drawtube is in place in both photos. The eyepiece shown in the vertical setup thumbnails is a 2"? There seems to be an approx 5mm shoulder sitting on the eyepiece holder WO cc in place and in last pic with cc in place it is also just sitting on the top of the 'eyepiece adaptor'. Can I ignore this as just being part of the eyepiece?
  6. I have looked carefully at the photos posted here with before/after cc and eyepiece. The movement of the focuser 'inwards' towards telescope is given as about 10mm - after 45mm 2" spacer is in place. So about 35mm movement of original, non-CC, focus relative to telescope tube/focuser mount, outwards. Which is what I observed when testing on distant trees. The photo is neccesarily at lo-res - but the 2" spacer looks the same diameter as the focuser drawtube...so it is a 2" drawtube adapter being used as a "spacer" with the CC sitting inside it. Is this understanding correct? I have only 20mm l
  7. Received my GSO corrector - sent from Germany in the middle of the night - excellent service from Telekop-Express! I checked it out this afternoon on some trees about 200m away. I thought I was going to be making up an ultra low profile mount to accomodate this CC - a Crayford with half the bearings inside the telescope tube. But the final focus is not inwards - towards the scope - 'by about 10mm' as read on forums. It was measured as moving outward - by about 35mm. Double checked I had the unit the right way around and spacing to eyepiece field stop was 75mm! This isn't mentioned anywhere on
  8. leonardo2012

    astro

    general astro stuff
  9. I have just ordered a GSO 2" coma corrector from Teleskop-Express and will be interested to see how it performs with my 16cm f3.8/f13.5 scope. Last Autumn I removed the cassegrain secondary and put in a flat to try some photos with a DSLR. Everything I have is home-built, so a quick fixup with an ancient cast-iron stand (1900's?) gave me an image of the Andromeda Galaxy surrounded by lovely 'seagulls'. The GSO should do better both on the image and with the OAG star images. But by how much, will I lose the resolution in the centre of the field that the seeing alone allows? OAG - small mirror r
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