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Who besides AstroSystems makes secondary holders

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#1 tag1260

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Posted 10 January 2015 - 05:37 PM

Like the subject says. Who besides AstroSystems makes secondary holders. I don't want a glue on type of holder.
Thanks

#2 Starman1

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Posted 10 January 2015 - 08:43 PM

There used to be several:

Novak

Protostar

Meridian

1800Destiny

But pretty much what's left is Astrosystems or "DIY".



#3 Pinbout

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Posted 10 January 2015 - 10:48 PM

Like the subject says. Who besides AstroSystems makes secondary holders. I don't want a glue on type of holder.
Thanks

 

get some soft alum flashing you can make it yourself, you just need to be able to make a 1/2" ply disc the inside size of the shroud.

 

 

http://www.cloudynig...ary shrouds.pdf

 

 

:p



#4 Ian Robinson

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Posted 10 January 2015 - 10:57 PM

others who I'm pretty sure have spiders and secondary holders are

Beakon Hill (UK)  = http://beaconhilltelescopes.org.uk/ ,

Orion Optical (UK) =  http://www.orionoptics.co.uk/home.html , they'll tailor make them for you for a few extra UKP,

Parks Optical (USA) = http://www.parksopti...cope Components

and http://www.observatory.org/spiders.htm

and http://www.dobstuff....ntsecondary.htm

and http://www.newportgl...com/atubehw.htm

 

come immediately to mind.

 

A google search will likely find other manufacturers in the USA, EU, and UK who also make OTA hardware components. Also checking foreign astronomy mags will reveal more likely sources.


Edited by Ian Robinson, 10 January 2015 - 11:15 PM.


#5 Jon Isaacs

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Posted 11 January 2015 - 04:11 AM

others who I'm pretty sure have spiders and secondary holders are

Beakon Hill (UK)  = http://beaconhilltelescopes.org.uk/ ,

Orion Optical (UK) =  http://www.orionoptics.co.uk/home.html , they'll tailor make them for you for a few extra UKP,

Parks Optical (USA) = http://www.parksopti...cope Components

and http://www.observatory.org/spiders.htm

and http://www.dobstuff....ntsecondary.htm

and http://www.newportgl...com/atubehw.htm

 

come immediately to mind.

 

A google search will likely find other manufacturers in the USA, EU, and UK who also make OTA hardware components. Also checking foreign astronomy mags will reveal more likely sources.

 

others who I'm pretty sure have spiders and secondary holders are

Beakon Hill (UK)  = http://beaconhilltelescopes.org.uk/ ,

Orion Optical (UK) =  http://www.orionoptics.co.uk/home.html , they'll tailor make them for you for a few extra UKP,

Parks Optical (USA) = http://www.parksopti...cope Components

and http://www.observatory.org/spiders.htm

and http://www.dobstuff....ntsecondary.htm

and http://www.newportgl...com/atubehw.htm

 

come immediately to mind.

 

A google search will likely find other manufacturers in the USA, EU, and UK who also make OTA hardware components. Also checking foreign astronomy mags will reveal more likely sources.

 

Ian:

 

I believe with the demise of Scope City, Parks is out of business.  Don Pensack (Starman1) who said Astrosystems were the only suppliers had worked for ScopeCity, I think he should know.

 

Paul Van Slyke (Observatory.org) suffered a fire that demolished his machine shop, I don't think he has rebuilt it yet.

 

I don't think Dennis at Dobstuff makes his own secondary holders but he might..

 

That Newport page is almost 20 years old. not sure they're still making them..

 

In the US, I really think Don is right, you have Astrosystems.

 

Jon 



#6 Ian Robinson

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Posted 11 January 2015 - 04:55 AM

 

others who I'm pretty sure have spiders and secondary holders are

Beakon Hill (UK)  = http://beaconhilltelescopes.org.uk/ ,

Orion Optical (UK) =  http://www.orionoptics.co.uk/home.html , they'll tailor make them for you for a few extra UKP,

Parks Optical (USA) = http://www.parksopti...cope Components

and http://www.observatory.org/spiders.htm

and http://www.dobstuff....ntsecondary.htm

and http://www.newportgl...com/atubehw.htm

 

come immediately to mind.

 

A google search will likely find other manufacturers in the USA, EU, and UK who also make OTA hardware components. Also checking foreign astronomy mags will reveal more likely sources.

 

others who I'm pretty sure have spiders and secondary holders are

Beakon Hill (UK)  = http://beaconhilltelescopes.org.uk/ ,

Orion Optical (UK) =  http://www.orionoptics.co.uk/home.html , they'll tailor make them for you for a few extra UKP,

Parks Optical (USA) = http://www.parksopti...cope Components

and http://www.observatory.org/spiders.htm

and http://www.dobstuff....ntsecondary.htm

and http://www.newportgl...com/atubehw.htm

 

come immediately to mind.

 

A google search will likely find other manufacturers in the USA, EU, and UK who also make OTA hardware components. Also checking foreign astronomy mags will reveal more likely sources.

 

Ian:

 

I believe with the demise of Scope City, Parks is out of business.  Don Pensack (Starman1) who said Astrosystems were the only suppliers had worked for ScopeCity, I think he should know.

 

Paul Van Slyke (Observatory.org) suffered a fire that demolished his machine shop, I don't think he has rebuilt it yet.

 

I don't think Dennis at Dobstuff makes his own secondary holders but he might..

 

That Newport page is almost 20 years old. not sure they're still making them..

 

In the US, I really think Don is right, you have Astrosystems.

 

Jon 

 

Been a several years since I've personally needed tube hardware for a project or contacted any of the US sups, so based on my lack of activity and distance and simply not being in the know - I'll stand corrected.

 

Sounds like there have been some accidents and a big shake up in the USA astro-supplier trade :( ..... 


Edited by Ian Robinson, 11 January 2015 - 04:59 AM.


#7 Jon Isaacs

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Posted 11 January 2015 - 05:25 AM

 

 

Been a several years since I've personally needed tube hardware for a project or contacted any of the US sups, so based on my lack of activity and distance and simply not being in the know - I'll stand corrected.

Sounds like there have been some accidents and a big shake up in the USA astro-supplier trade. :(

 

Ian:  I am not sure really if there has been anyone else in the last 10 years that was a major contributor.

 

Technically Protostar is still a supplier of spiders and secondary holders but as much as I like Bryan Greer, I see too many problems with delivery and communication.  Plus I had a scope with a Protostar secondary mount, it had a nylon center bolt and it sheared off.  Fortunately when it fell, nothing was damaged.. 

 

Jon Isaacs



#8 tag1260

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Posted 11 January 2015 - 03:00 PM

 

Like the subject says. Who besides AstroSystems makes secondary holders. I don't want a glue on type of holder.
Thanks

 

get some soft alum flashing you can make it yourself, you just need to be able to make a 1/2" ply disc the inside size of the shroud.

 

 

http://www.cloudynig...ary shrouds.pdf

 

 

:p

 

 

 

Excellent!!!   I can do that!!!  Do you trust the three tabs or do you use a touch of glue?  Gonna get started on Tuesday.  Now, where did I put that roll of flashing?



#9 Pinbout

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Posted 11 January 2015 - 03:39 PM

 

 

Like the subject says. Who besides AstroSystems makes secondary holders. I don't want a glue on type of holder.
Thanks

 

get some soft alum flashing you can make it yourself, you just need to be able to make a 1/2" ply disc the inside size of the shroud.

 

 

http://www.cloudynig...ary shrouds.pdf

 

 

:p

 

 

 

Excellent!!!   I can do that!!!  Do you trust the three tabs or do you use a touch of glue?  Gonna get started on Tuesday.  Now, where did I put that roll of flashing?

 

 

no glue. how heavy is your secondary. get a harder metal. McMaster sells steel. I got some .022 that was coated for making my spider vanes.

 

here's the 2.7 cut out of paper just to prove a point.

 

gallery_106859_3508_89897.jpg

 

maple dowels can be threaded for the hub.

 

20141130_200018.jpg

 

but I glue them anyway. maybe I'll switch someday.

 

20141221_211312.jpg

 

this is how I make my holes in sheet steel, a no.7 whitney punch.

 

whitney no7b.jpg


Edited by Pinbout, 11 January 2015 - 04:54 PM.


#10 Alterf

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Posted 13 January 2015 - 10:59 PM

1800 destiny still makes and sells them.

 

Val



#11 Oberon

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Posted 14 January 2015 - 03:55 AM

So he does. Thanks for the tip, I haven't come across those before.

I'm curious as to why each vane describes 180 degrees; ideally the total curve of all vanes should *add up* to 180 degrees, requiring only a 60 degree curve for a 3 vane spider, and a mere 45 degree curve for a 4 vane spider. By making each vane curve 180 degrees the vanes are longer, floppier and heavier than they need to be for a given thickness, and don't minimise refraction.



#12 Oberon

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Posted 14 January 2015 - 04:27 AM

btw while I'm criticising other people's spider vanes I may as well point out that when straight vanes are joined to form a pair of V's either side of the secondary support to look something like this >O< the result is MUCH stiffer than the common arrangement of centered vanes, the secondary support is rock solid and does not twist when adjusted or flex when tilted.

Like this...

gallery_217007_4746_112572.jpg

Note: I've also offset the vanes to fit behind the mirror and so reduce height of secondary support.



#13 Jon Isaacs

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Posted 14 January 2015 - 06:50 AM

btw while I'm criticising other people's spider vanes I may as well point out that when straight vanes are joined to form a pair of V's either side of the secondary support to look something like this >O< the result is MUCH stiffer than the common arrangement of centered vanes, the secondary support is rock solid and does not twist when adjusted or flex when tilted.

Like this...



Note: I've also offset the vanes to fit behind the mirror and so reduce height of secondary support.

 

I am not sure why this is stiffer than a conventional straight pull design with the same diameter large hub.  

:shrug:

 

Jon



#14 Pinbout

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Posted 14 January 2015 - 07:38 AM

 

btw while I'm criticising other people's spider vanes I may as well point out that when straight vanes are joined to form a pair of V's either side of the secondary support to look something like this >O< the result is MUCH stiffer than the common arrangement of centered vanes, the secondary support is rock solid and does not twist when adjusted or flex when tilted.

Like this...



Note: I've also offset the vanes to fit behind the mirror and so reduce height of secondary support.

 

I am not sure why this is stiffer than a conventional straight pull design with the same diameter large hub.  

:shrug:

 

Jon

 

 

 

as many times I've seen that arrangement, that's the 1st time I've heard that.

 

I know lockwood likes JPAstrocraft and JP does use that similar arrangement, but keeps it centered.

 

people in the states usually are skeptical of the vanes cause they aren't symmetrical


Edited by Pinbout, 14 January 2015 - 07:39 AM.


#15 Oberon

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Posted 14 January 2015 - 08:16 AM

 

btw while I'm criticising other people's spider vanes I may as well point out that when straight vanes are joined to form a pair of V's either side of the secondary support to look something like this >O< the result is MUCH stiffer than the common arrangement of centered vanes, the secondary support is rock solid and does not twist when adjusted or flex when tilted.

 

I am not sure why this is stiffer than a conventional straight pull design with the same diameter large hub.  

:shrug:

 

Jon

 

Let me assure you the difference is at least an order of magnitude. Its chalk and cheese. If you grab any common style secondary using thin vanes in tension you can easily twist it back and forth by several degrees. Just twisting the collimation screws is enough to unsettle some of them. Not so with offset vanes; they are rock solid.

Why?

The conventional straight pull (its not conventional actually, most professional telescopes use offset vanes) cannot resist initial twisting of the secondary irrespective of the hub size because a rotational movement at the secondary begins at right angles to the tension; the vanes are not resisting right angled movements, and cannot until rotation is sufficient to increase the tension enough to resist the force applied.

In contrast the >O< style is a pair of triangles in tension against each other; because the vanes are also locked in tension at right angles to each other they resist rotational forces as well.

Sorry if that's not a brilliant explanation...where's a mechanical engineer when you need one?


Edited by Oberon, 14 January 2015 - 10:00 AM.


#16 Oberon

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Posted 14 January 2015 - 08:38 AM

For other explanations...

http://members.shaw....ski/SPIDERS.HTM

http://www.stathis-f...mechaniceng.htm

 

and some discussion on this thread here...

http://www.cloudynig...er#entry6293490


Edited by Oberon, 14 January 2015 - 10:00 AM.


#17 jtsenghas

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Posted 14 January 2015 - 10:42 AM

 

 



In contrast the >O< style is a pair of triangles in tension against each other; because the vanes are also locked in tension at right angles to each other they resist rotational forces as well.

Sorry if that's not a brilliant explanation...where's a mechanical engineer when you need one?

 

As a mechanical engineer, let me give that a shot. It is a simple matter of evaluating stress (force/area) and strain (fractional or percentage change of length), which are proportional to each other as long as elastic limits are not reached (and things deform permanently). 

 

In the case of the vanes attached radially, a tiny rotation of the secondary holder about its axis barely changes the length of any vane. Regardless of its initial tension, a tiny strain (relative change in length) only creates a tiny change in stress and total force. That small force is also applied to a tiny moment arm about the axis of the secondary so it doesn't have much torque either to restore the initial position. The vane is still pointed nearly at the center of the secondary for small rotations. 

 

In the case of the vanes attached as described with two "V" arrangements, that same tiny rotation would require a much greater force because it would create a greater change in length of each vane. Because their attach points are at an angle, that change of strain, stress, and force would be greater than in the radial arrangement.  In addition, that larger force is applied to a much bigger moment arm about the axis of the secondary holder so the resulting torque to restore the secondary holder to its original position is also greater.  The larger the secondary holders, and the further away these attach points are, the greater these angles and the greater the effect. Attaching two vanes about one point constrains that point from rotating about the other end of either vane--the two arcs of rotation meet at nearly right angles. Imagine potential centers of rotation drawn from the opposite end of each vane where it meets the tube.

 

Note that a very similar effect is seen with wire spiders whose attach points are spread at greater angles both about the axis of the secondary and along its length, such as the excellent offerings we've seen with crossed wires posted by Mark Cowan over the last few years. Same concept. Radial wires would have the same issues as these radial vanes.

 

 

The same goes for the tension cables in string telescopes. Attaching two members at angles under tensions constrains them against rotation about the other end of either line.

 

Does that help?


Edited by jtsenghas, 14 January 2015 - 11:25 AM.


#18 jtsenghas

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Posted 14 January 2015 - 10:57 AM

I see in the above discussion Pinbout showed how he makes holes in sheet steel with a punch.  I have another tip to offer if very hard thin spring steel that can't be easily drilled is used, and the person making the holes hasn't high speed grinding tools and appropriate bits: Use a large finish-nail set as a hollow punch. As long as the nail set has a contact area of a circle with a fairly sharp edge (and it can be spun with a drill against a sharpening stone if needed) Then a good hard strike with a hammer against a vane placed on a hard plate of steel can provide surprisingly easy holes.



#19 Starman1

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Posted 14 January 2015 - 11:17 AM

Stiff yes.

But if I look at the diffraction pattern, I see the same 4 spikes as with a radial-4-vane arrangement, but the spikes

are much broader, essentially being two thin spikes so close together as to be indistinguishable from one fat spike.

Which brings up a question: Is this stiffer arrangement of 4 thin vanes superior to an arrangement with 4 thick, but radial, vanes?

Perhaps, if the area of mirror coverage is less.

I guess it doesn't matter if they are both quite stiff.

 

However, looked at from the standpoint of collimational stability, the radial 4-vane arrangement is adequately stable if the vanes are very taut.

I suppose this offset arrangement would be too.  In contrast, curved vanes usually aren't.  Fortunately, they are usually used on smaller

scopes, with smaller (hence, lighter) secondary mirrors.  The )-( curved pattern appears to be more stable in dobs because of its symmetry

on either side of a vertical line, but wouldn't work much better than any other curved system in an EQ-mounted newtonian.

 

Interesting to see some good ideas being applied.



#20 jtsenghas

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Posted 14 January 2015 - 12:14 PM

As long as the v-arrangement has symmetry, so that only two angles are involved, why would there be two thin spikes close together adding up to a broader spike on a straight V-arrangement as compared to a radial one?  I would expect that, as with a radial arrangement, each vane would create two spikes perpendicular to the vane.  If the vanes don't reach at exact right angles, then the resulting diffraction pattern would have spikes that aren't exactly perpendicular, but I don't see why they wouldn't be coincident if only two angles were involved in a symmetrical design.  Can someone who has these vanes on a spider please tell me if I am mistaken?


Edited by jtsenghas, 14 January 2015 - 12:51 PM.


#21 davidpitre

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Posted 14 January 2015 - 12:21 PM

 

Note: I've also offset the vanes to fit behind the mirror and so reduce height of secondary support.

gallery_217007_4746_112572.jpg

 

 

Stiff yes.

But if I look at the diffraction pattern, I see the same 4 spikes as with a radial-4-vane arrangement, but the spikes

are much broader, essentially being two thin spikes so close together as to be indistinguishable from one fat spike.

Which brings up a question: Is this stiffer arrangement of 4 thin vanes superior to an arrangement with 4 thick, but radial, vanes?

Perhaps, if the area of mirror coverage is less.

I guess it doesn't matter if they are both quite stiff.

 

However, looked at from the standpoint of collimational stability, the radial 4-vane arrangement is adequately stable if the vanes are very taut.

I suppose this offset arrangement would be too.  In contrast, curved vanes usually aren't.  Fortunately, they are usually used on smaller

scopes, with smaller (hence, lighter) secondary mirrors.  The )-( curved pattern appears to be more stable in dobs because of its symmetry

on either side of a vertical line, but wouldn't work much better than any other curved system in an EQ-mounted newtonian.

 

Interesting to see some good ideas being applied.

Great points in regards to diffraction spikes.

 

As to collimation stability. Much of the problem is often in the vane set-up. i.e. not enough tension, poor arrangement, or not wide enough. With large secondaries, though, say >3", the secondary often sits too far away from the vanes creating to much of a moment arm. I see many very large Newtonians where the heavy secondary is suspended an unnecessary from the vane hub.  

Oberon's arrangement addresses this as does some of Pinbot's ideas, as well as JP Astrocraft.



#22 Pierre Lemay

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Posted 14 January 2015 - 01:08 PM

 

 

Note: I've also offset the vanes to fit behind the mirror and so reduce height of secondary support.

gallery_217007_4746_112572.jpg

 

 

Stiff yes.

But if I look at the diffraction pattern, I see the same 4 spikes as with a radial-4-vane arrangement, but the spikes

are much broader, essentially being two thin spikes so close together as to be indistinguishable from one fat spike.

Which brings up a question: Is this stiffer arrangement of 4 thin vanes superior to an arrangement with 4 thick, but radial, vanes?

Perhaps, if the area of mirror coverage is less.

I guess it doesn't matter if they are both quite stiff.

 

However, looked at from the standpoint of collimational stability, the radial 4-vane arrangement is adequately stable if the vanes are very taut.

I suppose this offset arrangement would be too.  In contrast, curved vanes usually aren't.  Fortunately, they are usually used on smaller

scopes, with smaller (hence, lighter) secondary mirrors.  The )-( curved pattern appears to be more stable in dobs because of its symmetry

on either side of a vertical line, but wouldn't work much better than any other curved system in an EQ-mounted newtonian.

 

Interesting to see some good ideas being applied.

Great points in regards to diffraction spikes.

 

As to collimation stability. Much of the problem is often in the vane set-up. i.e. not enough tension, poor arrangement, or not wide enough. With large secondaries, though, say >3", the secondary often sits too far away from the vanes creating to much of a moment arm. I see many very large Newtonians where the heavy secondary is suspended an unnecessary from the vane hub.  

Oberon's arrangement addresses this as does some of Pinbot's ideas, as well as JP Astrocraft.

 

Very interesting thread. Looking at the photograph of Oberon's UTA reminds me of another factor that swells difraction spikes: emissivity of the vanes and their effect on the warmer surrounding air. Back in the '50's AndrĂ© Couder demonstrated that spider vanes should NEVER be painted black and wrote an article about it (I posted a translation I made of his article on CN about two years ago but I can't find it. I can re-post when I get to my home computer tonight, if anyone is interested). This is a common mistake made by North American ATM's but less so by experienced French ATM's.

 

Instead of being painted flat black, the metal vanes should be as shiny as possible and, instead, the surrounding inner walls of the UTA should be painted flat black. Exactly the reverse we see in the picture above.  Wire spider vanes of course don't have that problem because they exchange heat with the surrounding air very quickly. Wether they are shiny of black matters little.



#23 jtsenghas

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Posted 14 January 2015 - 01:47 PM

So he does. Thanks for the tip, I haven't come across those before.

I'm curious as to why each vane describes 180 degrees; ideally the total curve of all vanes should *add up* to 180 degrees, requiring only a 60 degree curve for a 3 vane spider, and a mere 45 degree curve for a 4 vane spider. By making each vane curve 180 degrees the vanes are longer, floppier and heavier than they need to be for a given thickness, and don't minimise refraction.

 

(This thread is starting to go off in many related off-topic directions, although I think it is making for a generally worthwhile discussion. I hope the original poster doesn't mind this mass hijacking effort and will indulge us. I hope the off-topic comments will include any answers any of you may have to my question posed in post 20 above.) 

 

A bit more on the topic of the original post regarding vendors of spiders to be purchased:

 

I have a 3- vane curved Destiny spider on my folding hexagonal scope, and each of the three vanes only curves 60 degrees in the light path. As received, each vane curved about 10 degrees more than that. I chose to go the route of using a Destiny spider for the first time with this particular scope because the spider is mounted within a wooden oak ring and tensioning and moving the spider is not easily an option with this arrangement.  This did require careful precision on the build, but I do get excellent collimation.  The fact that the collimation screws are spring-loaded gave me a little longitudinal adjustment on the secondary mirror also. I did add a stainless steel fender washer (seen in the attached photo because it is not yet painted black) behind the collimation screws to keep them from indenting the wooden mirror holder. When the scope is folded up, these oak rings are stacked in the packaging with a 3" PVC pipe around the secondary, by the way.  When I mounted the spider within that hexagonal oak ring I had to straighten the vanes very slightly to match my dimensions and I tweaked them just a few degrees further to match a 60 degree arc as measured from the outside of the secondary radius to the outside of the primary radius.  I agree, 180 degrees total is sufficient and more only results in increased amounts of the vane in the light path and more collimation issues.  Here is a photo during construction.  I know the tube should be black, and it still needs final finishing with black paint, but I've been using it with removable flocking so far. I will be painting the back and edges of the secondary flat black also at that time. I was tempted to shorten the length of the holder for the very reasons discussed above for collimation and certainly would have if I had a larger mirror than the 2.6" one it holds.  I chose not to for clearance and structural reasons on the scope tube. I wanted that oak ring a little closer to the end of the tube so that the hinges and latch that surround it would be a bit further from the focuser.

curved 3 vane spider.jpg


Edited by jtsenghas, 14 January 2015 - 02:04 PM.


#24 GShaffer

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Posted 14 January 2015 - 01:51 PM

Very interesting thread. Looking at the photograph of Oberon's UTA reminds me of another factor that swells difraction spikes: emissivity of the vanes and their effect on the warmer surrounding air. Back in the '50's AndrĂ© Couder demonstrated that spider vanes should NEVER be painted black and wrote an article about it (I posted a translation I made of his article on CN about two years ago but I can't find it. I can re-post when I get to my home computer tonight, if anyone is interested). This is a common mistake made by North American ATM's but less so by experienced French ATM's.
 
Instead of being painted flat black, the metal vanes should be as shiny as possible and, instead, the surrounding inner walls of the UTA should be painted flat black. Exactly the reverse we see in the picture above.  Wire spider vanes of course don't have that problem because they exchange heat with the surrounding air very quickly. Wether they are shiny of black matters little.


Interesting indeed!! I kinda hope you are wrong though....not really into deconstructing and polishing mine :)

#25 jtsenghas

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Posted 14 January 2015 - 02:57 PM

It appears that the question of whether parallel spider vanes that are not in line would produce double diffraction spikes or similar diffraction spikes to a radial 4-vane spider was in fact discussed at length just two months ago in this forum here . It appears such a thing is called an offset spider and, regardless of how the vanes are offset, several people contend (as I suggested in post 20 above) that the diffraction spikes are virtually identical.


Edited by jtsenghas, 14 January 2015 - 03:03 PM.



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