ICEINSPACE
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19-02-2008, 11:09 AM
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Sir Post a Lot!
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Join Date: Sep 2004
Location: Gosford, NSW, Australia
Posts: 36,799
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Diffraction spikes for my ED80
Hi all
I'm a fan of diffraction spikes, and would like the option of adding some to my widefield imaging through the ED80/350D.
What's the best way of making some sort of fishing line arrangement that I can put over the objective end of my ED80 to achieve this?
How thick should the fishing line be? What size does the holder need to be to fit around the dew-shield of the Saxon ED80?
Suggestions welcome.
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19-02-2008, 11:18 AM
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Registered User
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Join Date: Oct 2006
Location: Adelaide
Posts: 658
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you could make up the same kind of arrangement as a cardboard solar filter, 20lb fishing line is probably comparable to the thickness of the spider in a gso newt.
since the fishing line is fairly transparent i'd give it a quick rub with wet + dry paper and spray the whole thing black because i've noticed in some of the shots that people have used fishing line it kind of works like a prism making the spikes rainbow coloured
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19-02-2008, 11:20 AM
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Moderator
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Join Date: Aug 2005
Posts: 26,625
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A quick and easy way is to use blu-tack and stretch the ends over the dew shield.
I'd recommend using fine black fishing string to avoid the rainbow effect that clear fishing line creates, unless that effect is desirable.
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19-02-2008, 11:26 AM
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Sir Post a Lot!
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Join Date: Sep 2004
Location: Gosford, NSW, Australia
Posts: 36,799
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.. and a protractor to ensure my angles are 90°
Thanks guys. RB yours sounds quick and easy, might go that route for now. Cheers.
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19-02-2008, 11:31 AM
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Moderator
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Join Date: Aug 2005
Posts: 26,625
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Quote:
Originally Posted by iceman
.. and a protractor to ensure my angles are 90°
Thanks guys. RB yours sounds quick and easy, might go that route for now. Cheers.
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That's what I did since I wanted to try things out first.
It's not to difficult to get them at right angles and it won't show up if they're not perfectly 90'.
This also gives you an easy way to try different thicknesses before committing to a permanent frame later if you want.
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19-02-2008, 03:15 PM
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bewise betold neverbecold
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Join Date: Jan 2006
Location: Terrigal NSW
Posts: 3,828
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you might also try your fishing line and a thick rubberband instead of the blu-tack Mike
geoff
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19-02-2008, 03:53 PM
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Plays well with others!
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Join Date: Nov 2004
Location: Ridgefield CT USA
Posts: 3,535
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Permanent Marker on the glass...
I think the blu tack sounds like the real winner...
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19-02-2008, 04:11 PM
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Amongst the stars
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Join Date: Jun 2006
Location: Glen Innes, N.S.W.
Posts: 2,888
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How about the top cover of a 25 or 50 cd stack for a cap. They already (most) have 4 holes or notches at 90 degrees. Just cut the flat top off and sticky tape your fishing line to the holes. Then you can just drop the hole thing over your dew cap and use a little blu-tack to hold it or just sticky tape?
Maybe something elastic for the difraction spikes like thin black hat elastic would work a treat for this?
cheers Gary
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19-02-2008, 06:19 PM
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Tech Guru
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Join Date: Dec 2005
Location: Sydney
Posts: 2,901
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Or simply use Photoshop CS2 and a astronomy marco to add diffraction spikes!
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19-02-2008, 09:53 PM
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Meteor & fossil collector
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Join Date: Jul 2005
Location: Bentleigh
Posts: 1,386
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I have to admit, I am not a fan of difraction spikes for visual use and find them very annoying....in fact one of the reasons I bought the SCT! But photos without them seem to be lacking something! They seem to add character to star images.
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20-02-2008, 12:31 PM
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Moderator
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Join Date: Aug 2005
Posts: 26,625
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Quote:
Originally Posted by g__day
Or simply use Photoshop CS2 and a astronomy marco to add diffraction spikes!
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I must admit I'm not a fan of software created diff. spikes at all.
If I was to image through a refractor/SCT and wanted to create spikes then I'd use the string method and even then it would depend on the actual object being imaged.
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20-02-2008, 01:34 PM
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PI rules
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Join Date: Jul 2006
Location: Sydney
Posts: 2,631
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Hi Mike
Personally, I think that one of the great things about a refractor is that they don't show diffraction spikes. However, if I was going to put them on stars I'd go the photoshop method. That way you keep your options open and get two pics for the price of one. Noel Carboni has some astroplugins here that will do the job.
Geoff
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20-02-2008, 03:15 PM
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Sir Post a Lot!
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Join Date: Sep 2004
Location: Gosford, NSW, Australia
Posts: 36,799
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I agree that diffraction spikes are not for everyone, and probably not for every object.
But I like them, and on bright stars I think they look great. I'd much prefer to use fishing line method as opposed to the software version - i think they look more natural.
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20-02-2008, 04:31 PM
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lots of eyes on you!
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Join Date: Jun 2005
Location: Launceston Tasmania
Posts: 7,381
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i like the black marker option.........how cool is that??
and then if you make a mistake, just rub it off with your finger.............after you have eaten greasy chicken
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20-02-2008, 09:21 PM
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I HATE COMA!
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Join Date: Jan 2006
Location: Melbourne, Victoria
Posts: 3,208
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Quote:
Originally Posted by davidpretorius
i like the black marker option.........how cool is that??
and then if you make a mistake, just rub it off with your finger.............after you have eaten greasy chicken 
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    hey its permanant
Yes the fishing line does the trick but it makes the diff spikes not as thick as newts.
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21-02-2008, 02:53 PM
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Registered User
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Join Date: Sep 2006
Location: Perth, Australia
Posts: 176
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Just wondering if anyone adds more than the standard 4 spikes? Presumably you could do 6 or 8 for a really funky image.
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