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Post by galileo on Mar 6, 2015 12:18:29 GMT -5
Happy to get my lens cell at last from Peak to Valley Instruments at Buxton. No other parts yet purchased, thinking of using some 6" drainage stock for the tube, open to suggestions and advice / help. WIll post as it progresses.
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Post by boomboom on Mar 7, 2015 21:16:37 GMT -5
Whoohoo...best of luck with it. No suggestions for tubes as you have seen my thread. I just used what was locally avaliable. Let the fun begin! Matt
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Post by galileo on Mar 12, 2015 13:30:22 GMT -5
A few more components to report, focusser from a SW Newtonian with the curved bit removed. A diagonal and a rather nice zoom EP.
And a piece of 6" drainage pipe for the tube, bit crude but will do the job admirably I reckon, very rigid if a bit heavier than I wanted. Will buy the carbon fibre tube when I win the lottery.
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Post by galileo on Mar 29, 2015 13:28:32 GMT -5
Some more parts.............
Scope rings from a SW 130p are perfect for the job, big relief there, was worried I'd have to get some made at great expense. Here shown on my HEQ5 and a short length of the drainage tube.
Now don't laugh, a pet bunny tube is perfect for the dew shield in every dep't, perfect diameter, light and cheap. Just need to coat it with something to stop it soaking up moisture. Just working on making a collimation cell out of MDF, just needs a bit of patience, again a big saving on getting one machined from aluminium. Will post pic soon and then hopefully a pic of a complete mock up.
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Post by galileo on Mar 30, 2015 11:01:53 GMT -5
here is a cross section through the business end of the scope
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Post by galileo on Apr 18, 2015 14:18:50 GMT -5
Manufactured some baffles from a craft cutting mat. Ideal combination of rigidity and slightly bendable to fit to the tube. Made a sleeve inside the tube also to give the baffle something solid to locate against. Below are the baffles placed on a 1:1 drawing of the light cone to enable me to locate them correctly in the tube. They aren't exactly state of the art knife edge baffles but they hug the light come quite nicely I think so am optimistic they will do a good enough job. Here's a shot of the lens cell and lens cell attached to the tube. and the 'carbon fibre' dew shield
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Post by galileo on Apr 19, 2015 12:10:05 GMT -5
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Post by astromanuk on Apr 20, 2015 10:55:43 GMT -5
Looking forward to hearing of your first Jupiter and Venus observations. Lovely finish you have achieved there and the whole telescope is a credit to you. Some of my most memorable views of Jupiter have been through 5" & 6" refractors.
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Post by galileo on Apr 27, 2015 10:08:26 GMT -5
Looking forward to hearing of your first Jupiter and Venus observations. Lovely finish you have achieved there and the whole telescope is a credit to you. Some of my most memorable views of Jupiter have been through 5" & 6" refractors. Thank you Ian for you kind words
FIRST LIGHT REPORT
Had first light last night at last after the hours of thought and work, here goes............
First of all I reckon it is collimated spot on with the laser collimator, airy discs were concentric but better defined inside focus, not sure what that indicates if anything?
I was struggling to get a decent reflected beam back from the lens to the collimator so assuming the front face of the lens cell is a reasonably precision machined and parallel to the lens itself, I held a mirror flat against the front face of the cell and got a great reflected beam then and collimated to that, seems to have worked well.
I've looked at some star test examples and think other effects I was seeing were due to air turbulence, ie: some flaring round the edge. I tried to let it cool down for as long as possible and it did improve but I think rooftops radiating heat after a sunny day and quickly dropping temperatures contributed to unsteady air, would you agree?
I've never had a scope of this physical volume before so never had to wait long for cool down and I've no idea what the thermal properties are of the tube are and whether that is a contributing factor. Maybe I should leave the focuser end open during cool down to aid air flow ?
Unfortunately Jupiter had just been obscured from my viewing location by the time I was set up so I got some views of the Moon, very impressed, I tried to be very critical of any CA but it was really negligible on the terminator, very pleased. Details in craters and mountain ranges had me transfixed like never before. Had a look at the great cluster in Hercules (M13), very impressed here too considering the light pollution in my home location, using averted vision it was quite an impressive sight resolving individual stars (at a push) and made a much larger image in the EP than I've been used to. I may try to image M13 with my dslr by doing unguided subs, I can get 120 " unguided with my 800mm fl scope so am reasonably confident of getting 60 " with the Istar. Will keep posting.......
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Post by astromanuk on Apr 27, 2015 14:35:25 GMT -5
You are correct in saying the flaring you see in the out of focus star image can be due to atmospheric turbulence. Another cause can be tube currents. If you get a very bright star or the moon and throw focus way out to get a large bright disk at the eyepiece then often it is easy to see tube currents in motion. I find that leaving the focuser open and with objective pointing at the ground - hot air rises - you can speed up venting of warm air from the tube.
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Post by mikey cee on Apr 27, 2015 14:52:53 GMT -5
As well as sticking a Shop Vac into the drawtube and sucking the hot air out in mere seconds with a short burst of the motor. No waiting around!! Mike
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Post by galileo on Apr 28, 2015 11:43:00 GMT -5
Thanks for your comments Ian and Mike, I've never really experienced this effect before only having small apo's. Need to plan my observing sessions carefully to allow cool down time. Trouble is at this time of year and summer, there is a big difference between day and night temperature so your scope can be playing catch up all night I assume. Found this image which shows quite accurately what I was seeing
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Post by galileo on Apr 29, 2015 11:36:57 GMT -5
And the finishing touch.......
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Post by Viktor Z. on Apr 29, 2015 18:18:24 GMT -5
Woww, Galileo! You did a really nice job! Congratulatiions to your beautiful telescope! Viktor
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Post by galileo on Apr 30, 2015 11:45:43 GMT -5
As well as sticking a Shop Vac into the drawtube and sucking the hot air out in mere seconds with a short burst of the motor. No waiting around!! Mike Make sure it's on suck rather than blow Mike or you'll get the contents of the bag in your scope
Thank you Viktor
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