Making Refractors Produce Star Diffraction Spikes

[Gib007]

I'm in the process of buying a Skywatcher Evostar 80ED DS-Pro OTA and though this may or may not freak some people out, I would really like to make something to add star diffraction spikes to my images taken through it. I simply love them on my Newtonian Reflector. I know these are caused by the Newtonian Reflector's secondary mirror spider vanes but has somebody ever created something, let's say a spider vane type of metal bracket they attach to the front of their refractor to produce these star diffraction spikes?

I'd like something quite stable that I can perhaps clip on to the end of my OTA to get these in there. I've read about some people attaching strings in the shape of a cross on their dew shield but I'd prefer something more stable than strings - something metallic, for example.

[Digz]

How about adding them in post processing?

[Gib007]

How about adding them in post processing?

Not a bad idea but I'd really like to get them in my raw images. I also only really use PixInsight to post-process, so would be very unsure as to how to do it there.

[Bizibilder]

Make up a ring that fits your dew shield and fix a couple of thin wires across at 90°. Some folk use embriodrey hoop to hold Solar filters - I reckon they would work here as well.

[Digz]

I know what your saying, just wondered if you considered the post processing idea. I know you can get a PS plugin (StarSpikes for example) but I'm not familiar with PI.

I guess you could make something similar to the spider vanes maybe with hacksaw blades? Alternatively maybe with some flat aluminium bars? You just need to be careful of weight.

[ollypenrice]

Horrible things but Roger has given you expert advice on how to vandalize your pictures!! Phoney spikes are not offset but real ones tend to be since spider vanes are often offset.

I very, very seriously doubt that the creators of Pixinsight would have anything to do with fake spikes, ever...

Olly

[Gib007]

Haha to each his own I guess. I love diffraction spikes and will miss them with a refractor so I need to shove them in. I will have a think about making a clip-on metal cross with thin aluminium bars at 90° to each other. Thanks guys!

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[Komet]

Get some monofilament (fishing line) - say 15lb bs .... and tape two length across the aperture using electrical tape.

A good side effect is that they assist focussing. When the spikes are needle sharp your focus will be damn close.

[Gib007]

Get some monofilament (fishing line) - say 15lb bs .... and tape two length across the aperture using electrical tape.

A good side effect is that they assist focussing. When the spikes are needle sharp your focus will be damn close.

This isn't a bad idea at all. Cheap, easy and stable. Thanks!

[swag72]

Putting diffraction spikes on images from a refractor is like buying a Ferrari and changing the engine for a 1.1 British Leyland one

[ollypenrice]

Putting diffraction spikes on images from a refractor is like buying a Ferrari and changing the engine for a 1.1 British Leyland one

...or at least buying one that wasn't red!

Olly

[neil groves]

interesting topic, what is cheating and what is acceptable processing?

I have seen pics of star clusters where the colours of the stars within have obviously been altered, however the result looked superb, could you take a star cluster for instance into photoshop and add nebulosity to it and say it's not cheating, what is the end result we are looking for with astrophotography, a stunning image or accuracy to the original?

Neil.

[lukebl]

.... could you take a star cluster for instance into photoshop and add nebulosity to it and say it's not cheating, .....

That really is a step too far!

Diffraction spikes are an inevitable curse of imaging with a Newtonian, and manipulating the image is just using the data you've already acquired by your hard efforts. But to add stuff that wasn't there? Yes, that's cheating! Big time.

[anthony]

I'm with you here. A couple of bits of fishing line at right angles taped to a collar of card is simple, quick and cheap. It does assist focusing (very useful on the guide scope focussing too). As for appearance I think they're fine, but would avoid if there are too many bright stars! On one or two it can be a nice effect, across the whole image and they distract from the content of the image.

[ollypenrice]

interesting topic, what is cheating and what is acceptable processing?

I have seen pics of star clusters where the colours of the stars within have obviously been altered, however the result looked superb, could you take a star cluster for instance into photoshop and add nebulosity to it and say it's not cheating, what is the end result we are looking for with astrophotography, a stunning image or accuracy to the original?

Neil.

Are you sure the star colours were altered? Maybe the imager just got them right, with plenty of accurate star colour. May people burn out star colour and so lose it.

Artificial spikes are often used to disguise bad stars. I fix mine by a different kind of cheat when they're bad!!

Olly

[neil groves]

Are you sure the star colours were altered? Maybe the imager just got them right, with plenty of accurate star colour. May people burn out star colour and so lose it.

Artificial spikes are often used to disguise bad stars. I fix mine by a different kind of cheat when they're bad!!

Olly

The main stars in the pleaides a beautiful yellow glow, yes Olly, definitely altered lol

Neil.