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Doing away with 130pds mirror clips?


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Hi all I’ve seen people making masks to cover the mirror clips of Newtonians to eliminate the shadow they cast on brighter stars, but I’ve also seen people totally do away with them and silicone the mirror onto the mirror cell, I was thinking of doing the same to my 130pds using the silicone method to secure the mirror doing away with the clip. Has anybody done this to their 130pds and how secure is the mirror when the silicone is cured? Does this affect the mirror in any way? 

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Perfectly reasonable approach if the clips bother you.  Use 3 blobs of silicone equally spaced.  Remember to place something like 3 coins or washers in between them also equally spaced, this will ensure level settling and provide spaces to allow cutting through the silicone when/if the mirror needs recoating.  Remove the spacers when the silicone has set.      🙂  

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Thank you for your reply, any special silicone I need to use? High modulus, low modulus? I was thinking of aquarium silicone as it’s designed for glass? 

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2 hours ago, Craig a said:

Hi all I’ve seen people making masks to cover the mirror clips of Newtonians to eliminate the shadow they cast on brighter stars, but I’ve also seen people totally do away with them and silicone the mirror onto the mirror cell, I was thinking of doing the same to my 130pds using the silicone method to secure the mirror doing away with the clip. Has anybody done this to their 130pds and how secure is the mirror when the silicone is cured? Does this affect the mirror in any way? 

You don't mask the edge of the mirror to prevent shadows from the mirror clips. You mask the edge of the mirror to remove the scatter/diffraction spikes from the mirror edge. If you have shadows corresponding to the mirror clips, those shadows are the only places where you don't have a problem and you need to mask the rest of the edge. 

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That’s what I mean the scatter/diffraction from the mirror clips causing the pattern on brighter stars, I’m not a fan of it and looking for a way of getting rid without making a mask to cover the whole perimeter of the primary covering the clips 

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2 hours ago, Craig a said:

That’s what I mean the scatter/diffraction from the mirror clips causing the pattern on brighter stars, I’m not a fan of it and looking for a way of getting rid without making a mask to cover the whole perimeter of the primary covering the clips 

That is my point. The mirror clips are not causing the issue, they are preventing the issue at three points. If you take them off the problem becomes worse. 

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Posted (edited)
1 hour ago, Ricochet said:

That is my point. The mirror clips are not causing the issue, they are preventing the issue at three points. If you take them off the problem becomes worse. 

We’re not on the same wavelength here I don’t think I’m not on about the bright diffraction from the mirrors edge but the dark ghost pattern off the clips is what I want rid of 

Edited by Craig a
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1 hour ago, Craig a said:

We’re not on the same wavelength here I don’t think 

What he's saying is if you remove the clips, you will have more of the scatter as the clips block part of it giving you the three scatter/diffraction spikes. If you want to totally be rid of scatter, I think you would have to flock or paint the side of the mirror as well.

I have the same scope and went for the 3D printed baffle sitting on the mirror clips. It's not perfect but it is much better than it was. I'm going to flock the mirrors edge next to see what difference it makes.

 

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3 hours ago, Craig a said:

We’re not on the same wavelength here I don’t think I’m not on about the bright diffraction from the mirrors edge but the dark ghost pattern off the clips is what I want rid of 

Ok, perhaps a picture will help. Look at the image below.

  • The left hand star shows what your stars currently look like, with both mirror edge diffraction spikes and clip shadows.
  • The middle star shows what your stars will look like if you get rid of the clips.
  • The right hand star shows what your stars will look like if you mask the mirror edge.

It's not the shadows that are the problem, it is all the excess spikes.

Star_Diffraction_patterns.png.df1356b8d3375648189f9e95013f8911.png

 

I'm a solely visual, but even then masking the mirror edge is the single best upgrade that I have made. It's also the cheapest, as my mask is just made from black card.

Edited by Ricochet
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8 minutes ago, Ricochet said:

Ok, perhaps a picture will help. Look at the image below.

  • The left hand star shows what your stars currently look like, with both mirror edge diffraction spikes and clip shadows.
  • The middle star shows what your stars will look like if you get rid of the clips.
  • The right hand star shows what your stars will look like if you mask the mirror edge.

It's not the shadows that are the problem, it is all the excess spikes.

Star_Diffraction_patterns.png.df1356b8d3375648189f9e95013f8911.png

 

I'm a solely visual, but even then masking the mirror edge is the single best upgrade that I have made. It's also the cheapest, as my mask is just made from black card.

Yes that helps loads thanks, I will have ago at making a mask too, is it critical to get the masks inner edge perfect? 

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2 minutes ago, Craig a said:

Yes that helps loads thanks, I will have ago at making a mask too, is it critical to get the masks inner edge perfect? 

In my experience, I don't think so. Maybe carefully examining a photo you might be able to spot something but close enough is probably fine. If you want something really accurate I think I've seen commercial masks for Skywatcher scopes somewhere, Telescope Express perhaps.

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So is it just the very edge of the mirror coating that is the offending area? Just wondering if somthing can be done to it without using a mask and shrinking the diameter of the mirror slightly? 

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@Craig a You can 3D print a mask and it takes a couple of minutes to fit with a little bit of Velcro. If you're unhappy with the results, etc, it is none destructive and 100% reversible. 👍

Here's mine and I got the 3D Mask Design file from HERE.

20210504_143315.thumb.jpg.da6aa1d88c8fd2529ebb04457fe8d610.jpg

20210504_144759.thumb.jpg.8c3c9766875cbf4064aab5fb35063add.jpg

20210504_144844.thumb.jpg.7591624bb88758ebae79165e6908cb21.jpg

20210504_145422.thumb.jpg.bdf0db26f9e3054884b8fcf3944cef70.jpg

Another thing that made a big different to my 130PDS images was a change of Coma Corrector. I was using the Baader MPCC and the focuser was pretty much cranked all the way in leaving the focuser tube blocking a lot of light. I changed over to a TS-Optics Superflat GPU CC and the difference is huge. The main reason being the TS-Optics CC pushes the focuser out by around 20mm.

This is where my focuser sits now. No protrusion into the OTA at all.

20210401_075554.thumb.jpg.d95a39dfecd1ac4f551b840d3b636a4d.jpg

 

 

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On 05/10/2021 at 18:03, Ricochet said:

In my experience, I don't think so. Maybe carefully examining a photo you might be able to spot something but close enough is probably fine. If you want something really accurate I think I've seen commercial masks for Skywatcher scopes somewhere, Telescope Express perhaps.

As I don’t have access to a 3D printer I looked at ts service and you were correct I ordered one from there for my 130pds should be here in a few days 

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2 hours ago, Craig a said:

As I don’t have access to a 3D printer I looked at ts service and you were correct I ordered one from there for my 130pds should be here in a few days 

Excellent. Let us know how you get on with it. 

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On 08/10/2021 at 15:41, Craig a said:

As I don’t have access to a 3D printer I looked at ts service and you were correct I ordered one from there for my 130pds should be here in a few days 

I don't think you'll regret it. It is one of the better mods I've done to my 130PDS so far.

Stars in my images have gone from looking like this......

Pleiades300.jpg.60fbab6eb8a05399aeafcdfa15512bb4.jpg

To this......

Pleiades-RGB1.thumb.jpg.15c8c7d7da842b790de16542b9b219e6.jpg

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  • 2 weeks later...

I doing some work on my tube which is not the 130PDS, but if i understood correctly the mirror clips are not to blame with stellar halos? So in this case the blue bit, the edge of the mirror is the cause and not the mirror clips (in red)?

I bought some black 2.0 paint for some other work but i was wondering if i could just paint the edge black while i have the mirror out and that would do the job of an aperture mask? Just thought id sanity check this as a reasonable thing to do before i unnecessarily start painting mirrors.

Inked20211023_190440_LI.thumb.jpg.2677be7a68bbf711135ae6ea57e6cee4.jpg

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2 hours ago, ONIKKINEN said:

I doing some work on my tube which is not the 130PDS, but if i understood correctly the mirror clips are not to blame with stellar halos? So in this case the blue bit, the edge of the mirror is the cause and not the mirror clips (in red)?

I bought some black 2.0 paint for some other work but i was wondering if i could just paint the edge black while i have the mirror out and that would do the job of an aperture mask? Just thought id sanity check this as a reasonable thing to do before i unnecessarily start painting mirrors.

Inked20211023_190440_LI.thumb.jpg.2677be7a68bbf711135ae6ea57e6cee4.jpg

You are understanding correctly. However, I don't think it is as simple as painting the edge as I tried that first and still ended up with a mask. I'm not sure where exactly the bloat comes from, but suspect it might actually be where the coating right at the edge isn't quite as smooth or the vertex at the edge of the coating rather than the uncoated chamfered section. 

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Intrested by this for my 150 PDS

I can definitely see the diffraction spikes in my images.

The baffle listed on Teleskop express is 170 OD 141 ID for the 6 inch while the one for the 130 P does not list a size.

I can easily draw up & 3D print a baffle but was intrigued to what inside diameter restriction would be needed. If the clips are not the problem does the baffle need to have an inside diameter small enough to completely obscure the clips, or does it only need to obscure the mirror edge effectively leaving more of the mirror to capture those precious photons?

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