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Posts posted by AlanK

  1. My 12 inch dob has been kept in an unheated garage with an old duvet cover thrown over it (the telescope) for 12 years with no ill effects. I have to drag it through the house to get to a dark site, so if it is covered in dew after a session I tend to leave it in the house for a few hours to dry out before putting it back in the garage. Must get a shed in the back garden sometime.

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  2. Hi Jason

    just been out and tried a star test. Seeing is very poor with a lot of high level cloud around, but think the alignment is pretty good - dark spot looks central in the blurry moving image.  It will be good enough for my purposes I think (visual obs only). Probably need to get my specs upgraded now!

    Thanks for your assistance


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  3. Well I spent most of the morning trying to collimate using the cap.

    The initial lining up of the secondary ended like this -



    And the final collimation of the primary looks like that (sorry about the state of the primary)

    I dont know why the focusser tube will not line up central but as it is all reflected back on the secondary I assume there will be no light loss. (maybe the tube is not quite square or the primary mirror is not exactly 45 degrees - I dont know).

    IN any case I will try a star test the next time a clear night appears. It seems the fine weather has now broken and we are back to normal - cloud rain and fog)

    Thanks for all the advice.  Clear skies to you all whereever you are


  4. Thanks Jason. So my understanding is that the mirror frame needs to be moved, but not the plane/angle of the mirror? Otherwise the beam from the laser glasses will be reflected away from the target.. So I will try moving the secondary up or down and see what happens. Weather forecast for today is only poor so will give it a go later.


  5. Thanks for the input.  I'm sure the laser is correctly collimated so presumably the height of the secondary might be the problem. As near as I can tell the secondary is centred in the tube. I'll allocate a half day sometime to try and get sorted.

    im happy enough with the view of DSOs, doubles etc. But I have always been disappointed with planets. From what I read, short focal length light buckets require accurate collomation for decent views of planets.

  6. Hi folks

    Help required re collimating my 12” dob please.

    I have used a collimated laser collimator for years, and the scope appeared to be well collimated (the laser reflects back to its source).  But I have recently acquired a collimator cap and expected the view through it to show perfectly concentric circles. As the image through the cap shows this is far from the case…

    20180722_134340.thumb.jpg.7517cd448308c23eb899c0994a149b83.jpgI am at a loss to know what adjustments are required, but I would guess the secondary is out of position.  However the laser hits the centre of the primary and I am feeling hard of adjusting it as any change in angle will mean the laser will be well out of line with the centre of the primary.

    Any thoughts would be appreciated (other than the primary mirror needs a good cleaning)



  7. Just been out looking at the GRS tonight. It is neither great nor red, but is exactly as shown in the drawing above, which is excellent. Mind you the seeing is only poor here tonight with features drifting in and out of focus. Watched Io disappear behind Jupiter and now wondering whether to wait another couple of hours and try to spot the moment it reappears at around 11:15

  8. Just come in for a break and dry as a bone! Even had the Nortons star atlas outside (paper version) and not even damp. Nice and warm out. Better make the most of it, but can't help wishing all obesrving nights could be like this. Have a cuppa now than back out for another couple of hours.

  9. :hello2:The clear skies have finally reached the Isle of Man! Just put the 12"out in the back garden to get acclimatised and working out an obs plan forthe night. Dew will be a massive problem, but hopefully only on the tube and the Telrad screen, which if I remember to keep covered when not being used should be OK. Weather forecast is for cloud shortly after midnght so need to make the most of the clear skies. Hopefully Chelsea will win the match early so that I can concenrate on observing after half time:D

  10. its just a peice of plastic over the lense if im right. and they want 20 odd quid for it im building one. cheers ill keep checking astro boot tho looks quite good

    You do need something to keep the dew off.I use a simple piece of plastic stuck down on one side with sticky tape. Works a treat as long as you remember to flip it back over when not using the telrad.

  11. With the telrad you still need to look along the direction of the tube, but it is much easier to use to quickly get the tube pointed to the right area of the sky. I rarely use the finder now. I still get neck ache though....

  12. HI

    I've decided to get my 12" mirror and secondary recoated as they are both tarnished.

    I have removed the primary (having had to cut through double sided sticky pads using dental floss) but I am having trouble with the removal of the secondary from its plastic holder. I am guessing it is also held in place with double sided sticky pads inside the holder, but I am at a loss how to remove it without doing any damage.;)

    If anyone out there has had a similar experience I would be grateful for guidance.

  13. Job done.Lovely sunny day today and had a quick peek this morning. The 2" aperture seems to be sufficient and the sunspots were obvious. It was surprisingly difficult to line the scope up on the sun (using the scope's shadow as a guide - the telrad was not much use!)

    May use the remaining film to make a mask for the 6" scope which doesn't get much use these days.

  14. been cloudy all day here today so not had an opportunity to try out the solar filter. I'm certain (well 99.999% certain) there will be no 'danger' in using it otherwise it would not have been on the market for so long. As said above, commonsense precautions should make it safe. Looking forward to a bit of sunshine tomorrow and 'first light'. If the 2" aperture provides inadequate illunimation I can go up to about 4.5" avoiding any obstructions (spiders and secondary mirror holder). Will see how it goes.

  15. HI

    I have just made a cardboard holder to place this film over the 2" offset cutout in the 12" dob tube cover. This will effectively give a 2" aperture at f30 by my reckoning. I'm quite glad that the sun has now set and the forecast for tomorrow is not the best for observing as I find I have now become nervous at the thought of putting my eye to the eyepiece.

    Is there any way to test the light (heat I suppose is the problem) coming through the eyepiece before putting my eye up to it, other than the recommended checking the film for obvious holes and scratches? What do others do?

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