Anyone using a CNC secondary spider on their Newt

[Northernlight]

Hi All,

Just wondering if anyone out there had upgraded their secondary spider to use one of these CNC secondary cells ?  just looking for some feedback to see how much of a difference they make - primarily interested from a collimation perspective, but also interested to see how much it impacts your diffraction spikes.

Cheers,

Rich.

Edited January 9, 2021 by Northernlight
update

[markse68]

Where did you find that Rich? It looks like it's designed for very thin walled light weight OTAs which can't take tensioned thin vanes- a bit like the one on the scope I just bought which came off a Vixen R200SS- except that has really thick vanes that produce really pronounced spikes from what I've read.

I don't know if the depth of the vanes has any impact on spikes but thickness does- those don't look too thick at all though- looks a nice solution though the outer ring looks pretty chunky.

I'd be interested in where you can get these as I might look to upgrade mine at some point

Mark

[Northernlight]

Hi Mark, here is the link to the 10" one, but they also do a 8" version, but they are bloody expensive

https://www.telescopi-artesky.it/en/artesky/tuning/5087-retrofit-secondario-artesky-per-newton-250-skywatcher-8055517137109.html

[Northernlight]

Going to have a look online to see if i can see any imaging examples.  I can only assume they help with holding collimation and dont have too much of a detrimental impact on the diffraction spikes as all the high end scopes are using them.

[johninderby]

Orion Optics UK did some tests a few years ago using vanes from 1mm to 5mm thick and no one could tell the difference  through the scope. 

[Northernlight]

Hi John, was that for visual or Imaging ?  It's good news if there is very little impact on diffraction spikes as i only want one of these CNC cells to stiffen up the front of the scope as i think the oversized secondary of the Quattto Series flexes the standard spider vanes as it moves across the sky.

[johninderby]

Can’t find the article but as I recall they took images using the different vanes and asked people to guess which vanes were used.

[Captain Scarlet]

I think the strength of the diff spikes depend on the lengths of straight edges, thickness doesn’t really come into it. The thickness will increase obstructed area of course and thereby reduce contrast, but the spikes will be unaffected.

a single vane obviously has 2 edges and will throw out 2 spikes from a star in two directions perpendicular to the edges

M

Edited January 9, 2021 by Captain Magenta

[Northernlight]

I guess for imaging - contrast is less important than visual - for me it'a about holding collimation across the sky better

[DaveS]

I don't know about newts, but my ODK12 has a CNC spider and throws fairly sharp spikes, Still getting to grip with it though. Permacloud, grrr .

[JamesF]

4 hours ago, Captain Magenta said:

I think the strength of the diff spikes depend on the lengths of straight edges, thickness doesn’t really come into it. The thickness will increase obstructed area of course and thereby reduce contrast, but the spikes will be unaffected.

This is also my understanding.

James

[markse68]

22 hours ago, johninderby said:

Can’t find the article but as I recall they took images using the different vanes and asked people to guess which vanes were used.

Would be really interesting to see that if you do manage to find it John 

22 hours ago, Captain Magenta said:

I think the strength of the diff spikes depend on the lengths of straight edges, thickness doesn’t really come into it. The thickness will increase obstructed area of course and thereby reduce contrast, but the spikes will be unaffected.

a single vane obviously has 2 edges and will throw out 2 spikes from a star in two directions perpendicular to the edges

M

according to theory the width should have an effect- thicker vanes are supposed to make shorter stubbier brighter spikes 

“the wider vanes, the more energy spread out, the higher its peak intensity, but the shorter spike length.”

“Thicker vanes may appear to be producing less intrusive, shorter spikes, but they drain more energy from the Airy disc, causing greater negative effect on the contrast level.“

https://www.telescope-optics.net/spider.htm

so would be really interesting to see the article John mentioned- theory vs reality 

Mark

[Captain Scarlet]

Interesting. Got me thinking. Suiter also says thicker vanes produce stubbier brighter spikes. I guess as a vane gets infinitesimally thin the diffractions produced by each other side of the edges will interfere each other out. As the lengths get further apart they interfere less until there’s negligible interference and the effect is then simply one of obstructed and reduced aperture and extra edge-lengths.

Edited January 10, 2021 by Captain Magenta
Infinitesimally thin not think

[Northernlight]

apparently they are not available until end of Fed, so a bit of wait to get my hands on one. I'll do proper review once i get one.