upgraded spider vanes

[Daniel-K]

looking to upgrade my spider vanes to something a bit more solid any ideas were to get them from for my 8inch quattro

[Bizibilder]

What material were you planning on using?

[Moonshane]

I'd think you could make your own carbon fibre tube for less than a good quality spider? this would make the whole thing a lot more rigid.

[Steve Ward]

looking to upgrade my spider vanes to something a bit more solid any ideas were to get them from for my 8inch quattro

Why ?

[Daniel-K]

Why ?

just seem quite flimsy. and the secondary barley holds its collimation

I'd think you could make your own carbon fibre tube for less than a good quality spider? this would make the whole thing a lot more rigid.

theres a guy in germany i have emailed a few time that produces carbon tubes so thats something im looking into.

[Zakalwe]

just seem quite flimsy. and the secondary barley holds its collimation

They work on tension don't they? Are the vanes under tension? If they are then they shouldn't move, unless the OTA wall is deforming under the tension?

[crazyjedi]

So long as the tension is right they should be ok. I thought the idea of upgraded spiders was usually to swap to a set of thinner vanes? I've seen an advert somewhere for curved- extra thin vanes. The diffraction spikes are supposedly reduced

[John]

My new-to-me Orion Optics 30cm F/5.3 newt has the curved secondary vanes fitted to it. I've not used the scope yet but I'm assuming (from what I've read) that diffraction will still be there but not in the form of the traditional spikes. We will see when I get 1st light with the scope.

[crazyjedi]

My new-to-me Orion Optics 30cm F/5.3 newt has the curved secondary vanes fitted to it. I've not used the scope yet but I'm assuming (from what I've read) that diffraction will still be there but not in the form of the traditional spikes. We will see when I get 1st light with the scope.

Wow! Imagine if the diffraction "spikes" were of the same curved shape as the vanes?? That would look spectacular and of a somewhat spiral shape I would imagine judging by the pictures of the curved vanes that I have seen.

I actually rather like the spikes, being something of a romantic at heart.

[cantab]

just seem quite flimsy. and the secondary barley holds its collimation

I'd look at the secondary holder itself before the vanes in such a case - though I suspect replacements might come together.

On curved vanes: They produce more diffraction overall, but spread it out evenly so you don't get spikes.

[crazyjedi]

I'd look at the secondary holder itself before the vanes in such a case - though I suspect replacements might come together.

On curved vanes: They produce more diffraction overall, but spread it out evenly so you don't get spikes.

Boo!! I want swirly spiral spikes!!

[Daniel-K]

i would like the ones that come with the ODK or RC style rock solid they is

[russ.will]

On curved vanes: They produce more diffraction overall, but spread it out evenly so you don't get spikes.

That was the way I understood it - With no straight edge to diffract off, the diffraction is spread over all directions equally.

The one question I've never seen asked is; Are clean (traditional) diffraction spikes, with maximum contrast between them, worse than no diffraction spikes, but with a lower overall contrast? I think we should be told! After all, the assumption is that removing the spikes is the ultimate goal, but in reality, that light scatter hasn't been reduced - It's just been spread out.

I think the answer lies somewhere between whether you're an imager and/or, whether you're a viewer and if so, are you planetary or DSO.

Russell

[John]

...The one question I've never seen asked is; Are clean (traditional) diffraction spikes, with maximum contrast between them, worse than no diffraction spikes, but with a lower overall contrast? I think we should be told! After all, the assumption is that removing the spikes is the ultimate goal, but in reality, that light scatter hasn't been reduced - It's just been spread out....

Thats the question in my mind too. All my newts up to now have had the usual 4 thin vanes. I bought the 30cm F/5.3 newt used and it came with the curved vanes which do look just a little thicker than the standard straight ones. The secondary obstruction is 21% and the primary (according to the Zygo report) is a good one and Hiluxed so I'm hoping for decent performance.

As a refractor fan I'm not addicted to diffraction spikes so I won't miss them if they are absent

I had a russian 6" mak-newtonian for a while with no secondary supports (or course !) and a 19% secondary obstruction. That really did produce star images that looked like the classic refractor airey disks and excellent planetary sharpness and contrast. The ED120 was just a tad better and cooled a lot quicker which is why thats still in my fleet and the MN has moved on to another lucky SGL owner.

[crazyjedi]

I think for visual use better contrast is always a winner so straight vanes would be better. For A/P though could you not improve the contrast using clever image editing software? In which case the curved vanes showing no spikes may be more desirable.

[Zakalwe]

No diffraction spikes also makes it easier to combine data that's been collected over different nights.

[crazyjedi]

I think for visual use better contrast is always a winner so straight vanes would be better. For A/P though could you not improve the contrast using clever image editing software? In which case the curved vanes showing no spikes may be more desirable.

Hmm good point there.

That is probably why Apo's are so loved amongst the A/P people

[Mr Fiery Jack]

My Europa doesn't have a spider at all, it uses a thick box bar of what appears to be steel to hold the secondary. Strangely this scope does not produce any defraction spikes at all, I didn't think that was possible.

[cathalferris]

The Europa's secondary support edges are quite rough, rough enough that the diffraction is not purely in one direction. If you took a long exposure pic of a bright star, the diffraction halo would be a similar shape to a bow-tie with about 10 to 20 degrees between the extremities of the fan. How do I know? I had the same support before swapping for a 3-vane curved spider. I'm mainly visual with that scope, so the halo of diffraction from the curved vanes disappears into the background. Note that it's very hard to get exactly 180 or 360 degrees of curvature visible to the incoming light path, so the diffraction pattern will almost certainly have inhomogeneities present, creating the same difficulty with multi-night data gathering. The only real way to get multiple nights' data together is to either have the scope permanently set up and polar aligned such that the orientation of the spider never changes compared to the sky.

[crazyjedi]

The Europa's secondary support edges are quite rough, rough enough that the diffraction is not purely in one direction. If you took a long exposure pic of a bright star, the diffraction halo would be a similar shape to a bow-tie with about 10 to 20 degrees between the extremities of the fan. How do I know? I had the same support before swapping for a 3-vane curved spider. I'm mainly visual with that scope, so the halo of diffraction from the curved vanes disappears into the background. Note that it's very hard to get exactly 180 or 360 degrees of curvature visible to the incoming light path, so the diffraction pattern will almost certainly have inhomogeneities present, creating the same difficulty with multi-night data gathering. The only real way to get multiple nights' data together is to either have the scope permanently set up and polar aligned such that the orientation of the spider never changes compared to the sky.

Sounds like you would need a permanent observatory to keep that set up so accurately. Would a frac need to be permanently in place to do multi-night imaging?

[Zakalwe]

Would a frac need to be permanently in place to do multi-night imaging?

Nope. This image was taken with an 80mm using data from two separate nights. I had to set up and tear down each night.

[crazyjedi]

Excellent! I'm aiming to get a frac for A/P.

I just posted a question asking what the difference is between SW Pro ED series and SW Equinox series. You appear to have the Equinox and the ED . How do you find the two scopes how do they perform? What's the difference?

[Zakalwe]

Excellent! I'm aiming to get a frac for A/P.

I just posted a question asking what the difference is between SW Pro ED series and SW Equinox series. You appear to have the Equinox and the ED . How do you find the two scopes how do they perform? What's the difference?

The Equinox is faster at f6.25. Plus it has a better Crayford and is built like a tank. Plus the Skywatcher field flattener to match it only costs £70. If I was to make a complaint, then it would be at the focuser. Its a very decent Crayford, but it can be improved upon. I swapped it out for a Moonlite which makes it a lovely imaging scope.

I think that there are better ED80 out the now than the Skywatcher ED 80....have a look at Teleskop Express. The ED80 has brilliant optics though...you only have to look at some of the results that people are getting from them.

[cathalferris]

A refractor would not be affected by diffraction patterns changing with orientation, and the main issue would be camera rotation if the setup is taken down between the exposure sets. (This assumes that all flats and darks etc are taken at each session for each session).

If you try to add multiple images taken on multiple nights with a Newt, there's a risk that the diffraction spikes won't line up properly. I did a bit more research on the diffraction from the curved spiders, and it's probably not an issue for multiple night exposure additions as long as there's an even 180 degrees of curvature in the light path and no flat bits, as this situation will give an even diffraction pattern that will easily be added from multiple nights. I may have been overstating the effects of the unevenness of a slightly imperfect curved spider, as percentage wise the diffraction pattern is a *lot* less apparent than the spikes from a standard spider.

[crazyjedi]

The Equinox is faster at f6.25. Plus it has a better Crayford and is built like a tank. Plus the Skywatcher field flattener to match it only costs £70. If I was to make a complaint, then it would be at the focuser. Its a very decent Crayford, but it can be improved upon. I swapped it out for a Moonlite which makes it a lovely imaging scope.

I think that there are better ED80 out the now than the Skywatcher ED 80....have a look at Teleskop Express. The ED80 has brilliant optics though...you only have to look at some of the results that people are getting from them.

Thank you for the tip