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Commercially Available Filter Cells For LARGE ERF's

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Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Sun May 05, 2019 10:52 am

Hi All.

I want to start a thread, ultimately to go for reference in the library, for the benefit of all in the solar community who have / are purchasing large diameter ERFs, 8" and upwards. It is more difficult to get hold of these filter cells than it is for the smaller diameter ERFs.

I want to be quite clear what i'm looking for here, essentially I want to start a list where if someone bought a large ERF then they could contact a 'manufacturer' that they would be able to make a cell for it for a large (probably) SCT telescope. I'm looking for definites here, not 'maybe' they could manufacture.

I'm not interested in any Heath Robinson modifications here, none of the hypothetical you could 3D print it, no you could laser cut it etc, no can make it from an old plastic pipe etc, no visit a local machine shop. Just looking for links / contacts where we know for 100% sure if someone wanted to buy one they could contact and get it ordered / manufactured. I want to compile a list based on ERF size.

I'm going to be harsh here in moderating this thread as I want to keep it solely on 'commercially available' solutions, so, please keep to topic! Not wanting to sound a grump though, I will start a topic in our mods section on homebrew filter cell options.

So, over to you all, Where can we get these from? I think if I remember Marty got a cell made by Telescope Express in Germany for the 8" Aries ERF he has for his 8" C8? That could be our starter for one...
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Valery » Sun May 05, 2019 6:06 pm

TS has made also a 10" cell for Patrick's Hsieh 10" Meade SCT.

Eric Roel told me that his friend is a mechanist and can make cells up to 11". May be even larger.
Eric also mentioned that his friend is definitely interested if he will have the orders for cells.

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by bart1805 » Sun May 05, 2019 6:14 pm

TS sells them indeed. I ordered this one when I bought the 160mm Baader D-Erf. It is perfect.
https://www.teleskop-express.de/shop/pr ... 161mm.html

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by MalVeauX » Sun May 05, 2019 8:00 pm

Heya,

I recently did this, so I'll share everything I can.

D-ERF:

I have an 8" (214mm x 15mm) Aires Tri-Band D-ERF (passes 393nm, 430nm & 656nm). It clocks in at 4.5lbs (2kg) for just the glass.

214mm_ERF_Triband.jpg
214mm_ERF_Triband.jpg (75.37 KiB) Viewed 1684 times

Ordering a Commercial Filter Holding Cell:

To mount this D-ERF, I had several people refer me to Teleskop-Service (https://www.teleskop-express.de) out of Germany. There are many ways to get someone to make one for you, however, I wanted to go with a commercial group that absolutely knows what this is for and appreciate the need so that more care for the specifics of handling such a heavy piece of glass and fitting it perfectly to specification is as important them as it is to me.

This is the link I used to the product from Teleskop-Service that I used to generate my order (item FF180):

https://www.teleskop-express.de/shop/pr ... 161mm.html

To put in the order, you need to supply some measurements of both your filter that it will house, and also the telescope it will be mounted to. They will make it to whatever specification you supply. I wanted a little wiggle room on mine. I wanted it to hold the D-ERF with a little wiggle room for the filter for exansion, but also fit over most potential 200mm telescope options (such as C8 SCT designs and 8" reflector designs and potentially even 8" refractor designs). So, supply the size of your filter in diameter and thickness. Supply the room around the size of your filter that you want to maintain for wiggle room within the holding cell. Tell them the clear aperture you want to maintain through the filter cell. Supply the outer diameter of the telescope that the cell will be fit over, or supply them the size you want it exactly. They will opt to make it slightly bigger if you are not precise on your measurements to be safe. After you supply the measurements & instructions, you will receive an email to confirm everything before the specifications are sent to the fabricator of the cell. Note: the cell comes with felt padding lining the surfaces that will touch both the filter and contact the telescope.

Here's example how I ordered mine in terms of the instructions I gave them:
The filter is 214mm diameter x 15mm thick. I want 0.5mm room around the filter in all directions in addition to any felt padding that is provided for expansion room on the filter in the holding cell. I want to maintain a 200mm clear unobstructed aperture. The cell will be fit to a C8 Edge telescope with an outer diameter of 235mm, therefore I want the cell to fit to 240mm to have room for screw heads.
Cost & Shipping:

The cost was 206 Euros, plus shipping to the USA (Florida) from Germany. I did not pay VAT or taxes, so I cannot speak to that. All in all it was about $250 USD give or take a few dollars for the entire cost of the cell & shipping combined. I had to sign for it to receive it from USPS. I did not have to pay any duties or import fees or taxes.

From the date of my order to shipping to receiving the cell, took approximately 2 weeks.

The Filter Holding Cell:

The filter holding cell showed up great. It is in one piece. However, to use it, you have to disassemble it. The filter holding chamber has to first be unmounted from the telescope mounting portion of the filter. This is done with an allen wrench. The holding cell then separates. The cell is just like a big filter holding cell in the sense that inside the chamber is felt padding and a threaded ring threads down onto the filter when you place it into the chamber to hold it in place, again with felt touching all surfaces. It has two holes to allow easy turning of the threaded ring. This is just like a typical filter holding cell, but much bigger and padded. This cell then attaches via bolts to the filter house that contacts the telescope, which can be any size. Mine had lips with big bolts that are felt covered on all surfaces that touch the scope, three bolts, which tighten down against the scope's outer diameter.

The filter holding cell weighs 2.5lbs (1.1kg) on its own without a filter in it.

Total weight of my D-ERF & holding cell is 6.9lbs (3.13kg).

D-ERF_01.jpg
D-ERF_01.jpg (94.3 KiB) Viewed 1684 times
D-ERF_02.jpg
D-ERF_02.jpg (103.85 KiB) Viewed 1684 times
D-ERF_03.jpg
D-ERF_03.jpg (80.08 KiB) Viewed 1684 times

I store my filter & holding cell with my Quark and PST etalon in an Apache hard case for taking it inside/outside for use. I keep it in the house where humidity and temperature is controlled.

X10S1144-copy.jpg
X10S1144-copy.jpg (171.2 KiB) Viewed 1684 times

Installed on my C8 Edge:

X10S1134-copy.jpg
X10S1134-copy.jpg (57.31 KiB) Viewed 1684 times
X10S1132-copy.jpg
X10S1132-copy.jpg (44.46 KiB) Viewed 1684 times

I'm happy to answer any questions about any of it.
I'm very pleased with the work and the price was quite fair for the quality of the holding cell.
I would do it again without hesitation with TeleskopService.

Very best,

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by LTHB » Sun May 05, 2019 8:51 pm

+1 for a Teleskop-Express filter cell for the 8" Aries-ERF. I got one for my Mewlon 210 (just like Marty's cell, but with a few milimeters more clear aperture) : https://www.teleskop-express.de/shop/pr ... 161mm.html

Frank

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Tue May 07, 2019 7:43 pm

Thanks guys, useful information there. So, seems like Telescope Express happily make them up to 8", question is do they do an 11"?
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Montana » Wed May 08, 2019 7:08 am

No

Alexandra

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by yltansg » Wed May 08, 2019 7:35 am

marktownley wrote:
Tue May 07, 2019 7:43 pm
Thanks guys, useful information there. So, seems like Telescope Express happily make them up to 8", question is do they do an 11"?
Same answer as Alexandra's. Teleskop Express' manufacturer is not able to make a holder for a C11. This is their reply:

[Hello Mr. Tan,

we have asked the manufacturer for the filter cell.

Unfortunately, you cannot make the cell for such a large filter. The lathe cannot handle such a large diameter.

Freundliche Grüße | Kind regards]

Alfred

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Wed May 08, 2019 9:05 am

OK, making some good progress in this thread (unless you are looking for a filter cell 11" +)... Size of tooling is always going to be the issue...
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by gabrieli » Wed May 08, 2019 10:46 am

Hi, Mark

Thanks for beginning this very useful thread and inspiring my first post of this season. I've been looking for a more robust cell for my 265mm Aries ERF. I wrote to TS for information and listed the following requirements:

All these measurements are precise

Telescope: Celestron C9.25(not Edge): 275 mm front cell diameter
Filter dimensions: 265mm diameter x 15 mm thickness
Clear aperture desired : 254 mm
1 mm between filter edge and inside of cell all around

Their rep indicated that I could order one by using the order form for their FF180 ERF range which is described as "from D = 161mm". He also stated the shipping cost to Canada with UPS. The other 2 filter cell options are described as FF135(up to 135 mm) and FF160(from 135mm to 160mm). So, I assumed "from D = 161mm" meant above 161mm.

I noticed that the order( ordered May 7) is described as “being processed” at the time of this writing. I had to go as far as the payment (but before confirming the order) before I could write my specific order requirements on the order form comments section.
The receipt shows a price of 238.88 Euros (including shipping to Canada but not VAT) and lists my specific requirements. I found it peculiar that each of the cell ranges (FF135, FF160, and FF180) lists a fixed price on the website regardless of the cell diameter.

So, I felt a tiny bit of uncertainty about this item, mainly due to the cost being low and I would advise anyone considering a purchase beyond an 8 inch scope to write TS first with complete requirements and ask for confirmation.

This morning(May 8), I received another, more reassuring email indicating that my cell specs were sent in for manufacturing and that the cell would be delivered in about 4 - 5 weeks with no mention of a different price. So, it seems that TS can deliver cells for a C9.25 but not one that will fit an 11" scope. Again, if anyone orders a cell larger than for 8" scopes, ask TS for confirmation first.

I will update this info when the cell arrives or before that if there is any significant news.

Lou

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Valery » Wed May 08, 2019 12:26 pm

Alfred Tan wrote me this morning that he was able to place an order for his 11" ARIES DERF.

I see I need to star the manufacturing of the cells for filters larger than 10".


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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Wed May 08, 2019 7:03 pm

OK, so definitely TS can manufacture upto and including C9.25 scopes, and now it seems they CAN do C11 too? Let's wait to hear from Alfred that all is confirmed and the cell is on the way to him...
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by eroel » Thu May 09, 2019 3:19 am

Mark:
I just finished my homemade cell for the Aries 265mm ERF, I will use it on my 10" f/20 Maksutov and on the 12" f/10 Meade SCT.
It is made of 1/8" aluminum plate and 1/8" aluminum crossbeams.
Just need to put some cork on the 3 blocks that will hold the ERF in place, and 3 or more evenly spaced resting cushions around the aluminum ring where the ERF will rest.
The setup shown fits the 12" SCT, for the Maksutov I just change the 3 holding legs, so to fit the smaller diameter tube.
Best regards,
Eric.
ERF-celda.jpg[/attachment [attachment=1]Cell-1.jpg
Cell-3.jpg
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Montana » Sat May 11, 2019 1:30 pm

Mark, it is unknown if TS can do an 11 inch, Alfred is having his made privately.

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Sun May 12, 2019 3:32 pm

So, no nearer for the 11" cell. Maybe Alfreds source can make more than one?
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Montana » Mon May 13, 2019 6:53 am

No Mark, that is not the point, he is private person not a business so shouldn't be relied upon to produce everyone's filter cell for fun. We need somewhere to buy large filter cells properly and reliably.

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Mon May 13, 2019 10:28 am

Doesn't look like we're any closer then to being able to get the 11" and upwards cells being manufactured... :(
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by Valery » Mon May 13, 2019 6:09 pm

marktownley wrote:
Mon May 13, 2019 10:28 am
Doesn't look like we're any closer then to being able to get the 11" and upwards cells being manufactured... :(
If there will be more or less stable flow of orders, I'd gladly make aluminium (cast under pressure) cells with bayonet
system like it were done for my C11 and C14. However these are more expensive to make than in Germany.
Custom casting under pressure is not a cheap process.

There is also a clever design of a cell by Jean Pierre Brahic. I hope he will please us with his excellent sun images
anywhere soon. 12" aperture in his hands is a monster cannon for the shooting of the sun.


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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Mon May 13, 2019 6:43 pm

Well if you do manufacture the cells to go with your ERFs I reckon you're onto a winning combination Valery.
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Wed May 15, 2019 7:06 pm

OK, I reckon we've come to a conclusion at this point of time with this thread. I'm locking it and putting in the solar reference library. If people have developments / contributions of sources that can commercially manufacture 11"+ ERFs them PM me and i'll unlock and return to this discussion forum.

In the mean time i'm starting a thread in the mods forum for the fine people of this forum to come up with creative and achievable solutions to the problem :)
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Sat Jun 08, 2019 9:00 am

Are you any further forward with this Alexandra?
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by yltansg » Sun Jun 09, 2019 12:29 pm

Montana wrote:
Mon May 13, 2019 6:53 am
No Mark, that is not the point, he is private person not a business so shouldn't be relied upon to produce everyone's filter cell for fun. We need somewhere to buy large filter cells properly and reliably.

Alexandra
Hi guys,

Sorry that I missed the the postings after 8 May 19. By the time I saw it, the thread was locked. I am glad Mark brought it back here.

Alexandra is right. The cell holder for my C11 was a special favour and it is not right to ask for another favour from this kind person. I need to make another cell holder for my ARIES C14 D-ERF and have placed an order for it with Jose, Eric's friend. Thanks Eric for the introduction. Jose lives in Mexico. Recently, with Jose's permission, I introduced another astronomer who has an ARIES C11 D-ERF to him. Jose has advised that there is a lead time of at least 6 weeks. I have not seen Jose's work and feel more comfortable to recommend him to this forum after I have received my C14 D-ERF holder in mid July.

Mark - Is it ok for me to put Jose's contact email in this forum?

Alfred

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by marktownley » Sun Jun 09, 2019 12:31 pm

I'm happy if Jose is happy :)
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Re: Commercially Available Filter Cells For LARGE ERF's

Post by yltansg » Sun Jun 09, 2019 12:32 pm

Thanks Mark.

Jose's e-mail address is: jose_villicana@prodigy.net.mx I have listed it here for those who want to get in touch with him.

I will update the forum once I receive my cell holder.

Cheers.

Alfred

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Re: Commercially Available Filter Cells For LARGE ERF's

Post by gabrieli » Thu Jun 13, 2019 10:27 pm

The filter cell from TS for my Aries 265 mm ERF finally arrived. This adapts the ERF to my C9.25.
It differs slightly from the cell (by MalVeauX)) depicted in a previous post (started by Mark Townley).

http://solarchatforum.com/viewtopic.php?f=4&t=26042

My version has the retaining ring right on the sun side of the cell so that it is not necessary to separate the telescope adapter from the filter holder to place the filter in the cell. The retaining ring is huge (about 265 mm in outer diameter but with a fine exterior thread).

I measured the filter housing diameter with a ruler and it seemed to be 265mm (same as the filter). I was, at first, afraid that the filter would not fit. It did fit with a small gap all around between the filter and cell to allow for thermal expansion. The gap seemed smaller than the 1mm I asked for but that was hard to measure precisely
because the retaining ring threads get in the way of doing a precise measurement.

All I need now is some decent seeing and I’m all set to go.

Lou
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