spikes

[Bungielad]

Hi all,

Could someone please explain how you get spikes on stars when taking pictures?

Cheers,

Bungielad

[Scott]

the diffraction spikes are caused by the secondary spider on a newtonian such as your explorer 130p 

[sandyshaw]

Stop down your camera aperture OR put some spider vains on your objective if there is none.

[DaveS]

Use any telescope with a secondary supported by vanes. Diffraction gives spikes.

I understand that some people actually *add* them to otherwise spikeless images taken with refractors.

For the life of my I don't know why.

[RikM]

They are a diffraction effect caused by the spider vanes holding your secondary mirror. They are more obvious and nicer if your star is bright and your collimation is good.

[Bungielad]

Cheers guys,

No way did I think it was the vanes, ya live and learn eh!

Personally I think they look dead good jotted around here and there.

Bungielad.

[PeterCPC]

Hi

You can add your own during processing if you get a piece of software called starspikes pro3. Then you can add as many as you want and stipulate length/intensity etc. It's a plug in for Photoshop/Paintshop etc

Peter

[Bungielad]

Thanks for that peter.

Bungielad

[DaveS]

* shakes head in bafflement *

Still, as I said in another thread, De gustibus etc..

[Bungielad]

As said DaveS......De gustibus etc....

Bungielad.

[Astrosurf]

I, too, like the diffraction spikes!

Alexxx

[knobby]

Diffraction spikes ...

Astro photography marmite :-)

[RobH]

I like spikes, which is a good thing as my RC produces them. Astro 'fairy dust'

Another way to get them if you want them and have a refractor is to tape some thin cotton or fishing line across your objective to simulate a 4 vaned spider.

[Zakalwe]

I like spikes, which is a good thing as my RC produces them. Astro 'fairy dust'

Another way to get them if you want them and have a refractor is to tape some thin cotton or fishing line across your objective to simulate a 4 vaned spider.

Hehe...so we spent £thousands trying to get equipment that delivers light in the most accurate fashion possible, and then go and introduce something that causes on optical aberration...

[RobH]

Indeed we do......if we were doing science, then that would be bad, but most of us are doing technical art :-)

[mrjolly]

As I found out to my expense a short while ago, a good way to get a star spike with a refractor is to forget to move the washing line out of the way when you're down the bottom of the garden... 

[glowingturnip]

as a newt user, I too am duty bound to love spikes 

don't think I'd ever add them manually though

[DaveS]

Diffraction spikes ...

Astro photography marmite :-)

He he..

I like marmite, but don't like (Artificial) diffraction spikes

Go figure, as our American friends say.

[mitchelln]

The need for pretty spikes bred in from birth. Twinkle twinkle little star!

[Alien 13]

As I found out to my expense a short while ago, a good way to get a star spike with a refractor is to forget to move the washing line out of the way when you're down the bottom of the garden... 

Same thing happened to me i spent ages trying to figure what had gone wrong then i noticed the washing line on the second session  what a relief.

Alan

[Mr TamiyaCowboy]

With your telescope and as others before me have mentioned, the spider vanes in telescope make them. 

BUT !!!! 

in photograpghy, we cheat. with a dslr and lens , we run a very long shutter speed 

and have a fairly high F number ( F11 and upwards ). this combination give car light

trail photographs star spikes on the streetlamps and likes. 

photography stores sell filters , 4 star -6 star - 8 star , when fitted this double triple/trebble 

the spikes.  next time its overcast, throw on a camera lens set the dslr up for long exposure

and high F number  pint at street lights and see the effect the settings have. 

[Zakalwe]

The spikes seen with a DSLR and lens are caused by the blades of the iris. A high f-number means the lens is stopped down, so the blades intrude into the light-path. You can normally tell how many blades are in the lens by counting the spikes.

A similar effect is seen when shooting with the lens wide open. The background is blurred into bokeh due to the shallow depth of filed. Cheaper 5-bladed lenses gives a pentagonal shape. More expensive lenses gives a smoother bokeh.

[Mr TamiyaCowboy]

Bokeh, yep i must say bokeh can give some nice effects , 

have to say i like my stars nice and sharp, minimal spiking,

but camera and lens i like to introduce some spiking when possible.

[lensman57]

Hi all,

Could someone please explain how you get spikes on stars when taking pictures?

Cheers,

Bungielad

You can get diffraction spikes even with a super expensive Apos depending on the brightness and type of the stars and close or at the point of correct focus, the design of the lens cell, the type of spacing between the elements can also have an effect.

A.G

[RobH]

The need for pretty spikes bred in from birth. Twinkle twinkle little star!

Very true. Joe Public thinks that stars look like that.

A colleague of mine, who was around when I was processing an image, actually asked me why the stars didn't look like stars....the image was with a refractor and had no spikes. I added some and showed her, and she said that they looked much better!