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Curved vane secondary supports


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thats weired see this stu, its shanes report

http://stargazerslounge.com/topic/201988-diffraction-spikes/

Thanks faulksy, I did post in that one before starting this :-).

I think Shane went for the 3 curved vane version, but haven't seen any results or that he has fitted it yet. Will check with him.

I think the three vane has more total length to it, so as long as the single 180 degree 'arc' is not too thick I think it may be better.

Stu

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I have also been having a look at different spider designs, although I have not changed my standard four vane unit yet. When the scope arrived I did not really notice these (diffraction spikes) even on Jupiter, which is probably the most demanding target when it comes to spike generation? After flocking and baffling the scope it seems to have thrown the spikes into prominence. I think doing a side by side comparison with a c11 did not help either :smiley: although contrast on the Planet was noticeably higher with the newt the c11's dark background does make Jupiter jump out more and 'seem' brighter and more contrasty. So over Christmas I asked my brother to produce a few simulations, fourier transform models, of spider designs and although we did not test a huge number of types there did seem to be an obvious design pop out. This was a single curved vane using the tubes existing curve. Below is the spider model diagram and resulting diffraction patterns.  

Four vane

post-30467-0-92421200-1391447428_thumb.j

Diffraction pattern

post-30467-0-86745400-1391447501_thumb.j

Curved design  

post-30467-0-09255600-1391447538_thumb.j

Diffraction pattern  

post-30467-0-07642800-1391447598_thumb.j

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I ordered one from the US, this one: http://www.1800destiny.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=1D&Product_Code=MCVS&Category_Code=CVS

 with the optional upgrade for dew heater wiring.  It worked out pricy and the upgrade meant it took longer to dispatch but overall happy with it.  It was for a ATM project so it wasn't replacing an existing one though.  It was easy to mount and works well as far as I can tell.

That site also has a discussion of different styles of spiders but they're not independent so could be biased.

http://www.1800destiny.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=1D&Category_Code=cvss

this is where I got mine Stu. It has 'cleaned up' the planetary images superbly. previously there was a planet width (approx) diffraction spike on all four vanes but now it's basically 'refractor-like' with amost no visible diffraction once cooled. I have not yet tested on double stars but suspect it will be very good too, although it always was on doubles. I don't think in truth there's any more detail visible but the view is aesthetically much nocer. also, the view of the sun seems sharper to me for some reason (with film).

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  • 2 months later...

Here you go , I finially got my A into G and dug out the photos of my sweet 5 inch f13.3 newt , built by me , everything , she has the  curved secondary holder .

I cant remember where I read the diameter of the spider but mine works excellently .

With only a 19mm secondary , low profile focuser it gives awesome lunar/planetary views above 300x on good nights , she is a planet killer .

Star testing shows a perfect aeiry disc with one faint ring at 500x , its a nice scope to view thru and use .

Here is a photo .

Brian .

post-18525-0-90818700-1398441723_thumb.j

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