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How do I install the primary mirror in the mirror cell (Starsplitter 10" dob))

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#1 dasganu

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Posted 27 January 2022 - 09:51 AM

Greetings,

 

I have a Starsplitter 10" Dobsonian with 2 truss poles. I disassembled the primary mirror from the cell for shipping and now I can't install it back in to the cell.

 

There are 3 retaining clips, three short black screws with washers and 3 white nylon screws (without a head). I tried different permutations and combinations, but I don't know how to use the screws/clips to install the mirror.

 

I've attached a picture of the screws that the scope came with.

 

Any help will be appreciated.

 

Thanks,

Ganesh.

 

IMG_20220127_192509.jpg



#2 dasganu

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Posted 27 January 2022 - 12:20 PM

If someone could put me in touch with Jim Brunkella, founder of Starsplitter Telescopes, I would be grateful.

 

Perhaps he could throw some light on it or point me to a user manual.

 

Thanks,

Ganesh.



#3 cuzimthedad

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Posted 27 January 2022 - 12:38 PM

Moving to Reflectors

 

And welcome to CN!


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#4 dasganu

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Posted 27 January 2022 - 12:49 PM

Thank you!



#5 Pinbout

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Posted 27 January 2022 - 02:02 PM

where's the pic of the cell



#6 Waynosworld

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Posted 27 January 2022 - 03:40 PM

Here is a photo of my 14.5" Starsplitter mirror cell post.

 

DSC00176.JPG


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#7 Jon Isaacs

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Posted 27 January 2022 - 08:04 PM

If someone could put me in touch with Jim Brunkella, founder of Starsplitter Telescopes, I would be grateful.

 

Perhaps he could throw some light on it or point me to a user manual.

 

Thanks,

Ganesh.

 

If Wayne's image is not sufficient, Jim Brunkella's Cloudy Nights handle is jrb 

 

Jon



#8 dasganu

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Posted 27 January 2022 - 11:48 PM

Firstly thank you all, Wayne, Pinbout and Jon for taking the time to respond.

 

Wayne, thanks for the photo of your 14.5 inch scope. It must be phenomenal!

 

I'm attaching a picture of the mirror cell on my 10 inch Starsplitter.

 

What I don't understand is the function of the white nylon screws. Does the mirror rest on top of them, or do they hold the mirror in place, like a wedge?

 

Also should there be a gap between the mirror and the retaining clips, or should it be a snug fit?

 

I have sent a note to Jim.

 

Thanks,

Ganesh.

 

IMG_20220128_095857.jpg



#9 Waynosworld

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Posted 28 January 2022 - 01:00 AM

The white nylon screws sort of hold the primary mirror in the center.

 

DSC00177.JPG


Edited by Waynosworld, 28 January 2022 - 01:02 AM.

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#10 Waynosworld

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Posted 28 January 2022 - 01:06 AM

I forgot, there should be a gap between the clips and the primary mirror, my clips will not go down far enough for them to hit the mirror as the lower part of the clip hits the white nylon screw, you can sort of see it in the photo.

 

The former owner wrapped electrical tape around the top of the clip to make the gap between the clip and the mirror closer as it would have quite a gap otherwise.


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#11 Waynosworld

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Posted 28 January 2022 - 01:17 AM

Your mirror cell looks like it is missing a mirror pad at 7 o'clock in your photo in this post.

 

If Jon reads this is that normal to have 9 support points on a single solid piece of metal?

 

Firstly thank you all, Wayne, Pinbout and Jon for taking the time to respond.

 

Wayne, thanks for the photo of your 14.5 inch scope. It must be phenomenal!

 

I'm attaching a picture of the mirror cell on my 10 inch Starsplitter.

 

What I don't understand is the function of the white nylon screws. Does the mirror rest on top of them, or do they hold the mirror in place, like a wedge?

 

Also should there be a gap between the mirror and the retaining clips, or should it be a snug fit?

 

I have sent a note to Jim.

 

Thanks,

Ganesh.

 

attachicon.gifIMG_20220128_095857.jpg


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#12 dasganu

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Posted 28 January 2022 - 01:37 AM

The white nylon screws sort of hold the primary mirror in the center.

 

attachicon.gifDSC00177.JPG

Thank you for the picture! That seems to clear up a few things. I do notice that the mirror appears raised above the base, like there is a gap between the mirror and the base. How did you achieve this? Shouldn't it rest on the pads in the cell?



#13 dasganu

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Posted 28 January 2022 - 01:47 AM

I forgot, there should be a gap between the clips and the primary mirror, my clips will not go down far enough for them to hit the mirror as the lower part of the clip hits the white nylon screw, you can sort of see it in the photo.

 

The former owner wrapped electrical tape around the top of the clip to make the gap between the clip and the mirror closer as it would have quite a gap otherwise.

My problem exactly! I was wondering why the retaining clip wouldn't slide all the way down. The electrical tape idea sounds interesting. I could have sworn everything was perfect before I disassembled the mirror. There is a web-site - stellafane.org that talks about the necessity of a gap between the clip and the mirror. Apparently the clips are meant to not allow the mirror to tip over if the scope is turned upside down (who would do that anyway?)



#14 Waynosworld

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Posted 28 January 2022 - 01:52 AM

My last post I asked Jon about what your cell looks like to me, I cannot recall seeing a mirror cell like yours.

 

Thank you for the picture! That seems to clear up a few things. I do notice that the mirror appears raised above the base, like there is a gap between the mirror and the base. How did you achieve this? Shouldn't it rest on the pads in the cell?

My mirror rests on 6 triangles with three support pads each that float, here is a photo of my mirror cell for my 16", it has whiffle tree supports that the mirror rests against when the scope is pointed anywhere but straight up.

 

post-345792-0-67572200-1610441995.jpg


Edited by Waynosworld, 28 January 2022 - 01:55 AM.

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#15 dasganu

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Posted 28 January 2022 - 01:52 AM

Your mirror cell looks like it is missing a mirror pad at 7 o'clock in your photo in this post.

 

If Jon reads this is that normal to have 9 support points on a single solid piece of metal?

I see what you mean, but there are only 3 bolts at the bottom for collimation. Would the missing pad make a difference?



#16 Waynosworld

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Posted 28 January 2022 - 02:02 AM

I see what you mean, but there are only 3 bolts at the bottom for collimation. Would the missing pad make a difference?

On your cell I do not know, a mirror should be supported evenly, yours appears to be missing a pad so that area is not supported now, if your mirror is thick it might not make a difference, but I would make a pad or buy one and put it on that plate if it were mine, but I sometimes cannot see what I need to in a photo, maybe it has 9 pads, I only see 8 pads and if all the pads are not exactly the same height it will cause an issue, it does not look like it ever had a pad there so maybe it was left out on purpose, Jon knows more about Starsplitters than I do, I only have the one.


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#17 dasganu

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Posted 28 January 2022 - 02:04 AM

My last post I asked Jon about what your cell looks like to me, I cannot recall seeing a mirror cell like yours.

 

My mirror rests on 6 triangles with three support pads each that float, here is a photo of my mirror cell for my 16", it has whiffle tree supports that the mirror rests against when the scope is pointed anywhere but straight up.

 

attachicon.gifpost-345792-0-67572200-1610441995.jpg

Your mirror cell looks substantially different from mine. Maybe your 14.5" mirror also floats on triangles - hence it appears raised. I will try installing the mirror again with the new information you provided me. Thanks!



#18 Waynosworld

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Posted 28 January 2022 - 02:08 AM

Most if not all dobs have 3 bolts for collimation connected to a triangle like mine or some other shaped piece of metal, yours does not have pads that float and that is confusing to me, but you have a smaller mirror and maybe it does not need a complicated mirror cell like mine have.

My 16'" has 18 pads, my 14.5" Starsplitter has 9 points like yours but the cell floats like my 16" cell.

 

Edit  

 

My 16" has a sandwich mirror, it is not a solid piece of glass, so I made that cell with a lot of supports.


Edited by Waynosworld, 28 January 2022 - 02:33 AM.


#19 dasganu

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Posted 28 January 2022 - 02:20 AM

On your cell I do not know, a mirror should be supported evenly, yours appears to be missing a pad so that area is not supported now, if your mirror is thick it might not make a difference, but I would make a pad or buy one and put it on that plate if it were mine, but I sometimes cannot see what I need to in a photo, maybe it has 9 pads, I only see 8 pads and if all the pads are not exactly the same height it will cause an issue, it does not look like it ever had a pad there so maybe it was left out on purpose, Jon knows more about Starsplitters than I do, I only have the one.

It's possible the pad was lost during shipping. I'll see what I can do. Yes, my mirror is fairly thick, so hopefully the missing pad won't make a difference, but I will look for a pad. I take it some adhesive would help secure the pad in place?


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#20 Starman1

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Posted 28 January 2022 - 02:24 AM

Discovery telescopes had a similar triangular metal piece for a mirror cell except the mirrors were glued instead of resting on pads.
As for the white thumbscrews, they should just touch the mirror with the force of a feather. No noticeable pressure. The clips should be slightly above the mirror and not touching. And the missing pad should be replaced.
If the screws and clips are tight, it will distort the mirror and cause astigmatism. Ditto for the missing pad.

Edited by Starman1, 28 January 2022 - 02:25 AM.

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#21 dasganu

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Posted 28 January 2022 - 02:33 AM

Discovery telescopes had a similar triangular metal piece for a mirror cell except the mirrors were glued instead of resting on pads.
As for the white thumbscrews, they should just touch the mirror with the force of a feather. No noticeable pressure. The clips should be slightly above the mirror and not touching. And the missing pad should be replaced.
If the screws and clips are tight, it will distort the mirror and cause astigmatism. Ditto for the missing pad.

Thanks for the detailed and clear explanation. I now understand the function of the white screws and clips. I will see what I can do about the missing pad.



#22 Waynosworld

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Posted 28 January 2022 - 02:34 AM

My white nylon screws are all bottomed out in the cell post, I believe I can remove the mirror without touching them, but it is a lot easier to just loosen them when taking it out so I can get it back in without breaking one of them.


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#23 dasganu

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Posted 28 January 2022 - 02:50 AM

So the white screws should apply minimum pressure to the mirror and the clips should be a bit raised.



#24 Waynosworld

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Posted 28 January 2022 - 02:51 AM

So the white screws should apply minimum pressure to the mirror and the clips should be a bit raised.

Yes



#25 dasganu

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Posted 28 January 2022 - 02:55 AM

Ok, great! Thank you for taking the time to answer my questions and happy seeing!




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