Building a Large Flat Panel for a 24" Telescope - Forums

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Frequent contributor

Dec 28, 2023

Over time I've seen a number of posts from folks who believe that running a remote observatory means that you don't get to fiddle with equipment. I run two telescope remotely and I fiddle with stuff all the time. This is the story of one such project. I originally intended to post it as an image on my AB page, but it's too big for that. I wrote this up as a PPT presentation in order to gather all the images and to organize it with the idea that I'd take it all apart to present it, but that's too much trouble so so bear with me while I tell the story using a bunch of slides.

One operational detail that I didn't mention is that in remote community ROR observatories where there are a lot of scopes running in one building, it is forbidden to turn on a flat panel when the roof is open and the sky is clear. For anyone with a flat panel, flats are only taken during the day time (if possible) or when the weather is bad and the roof is closed. That makes it very important to seal the imaging system as tight as possible to keep internal dust to an absolute minimum. This new scope will not have a rotator so as long as dust doesn't get in, flats can last for a very long time (like a year).

This was a really fun little project and hopefully it's useful for anyone considering a larger scope. It's sure something that I wish I had thought of when I configured my 20" scope! I hope that you at least enjoy the story...

John

Eddie Pons

Dec 28, 2023

A great presentation! Thanks for sharing.

John Hayes

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Dec 28, 2023

Thanks Eddie!

John

Paul Frank Romero

Dec 28, 2023

Hi,

I noticed your pier is 16” high. Would it feasible to cut the pier height (if this were an option) and forego the need to lift the panel up?

Clear Skies,

Paul

John Hayes

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Dec 28, 2023 · Edited: Dec 28, 2023

Paul Frank Romero:
Hi,

I noticed your pier is 16” high. Would it feasible to cut the pier height (if this were an option) and forego the need to lift the panel up?

Clear Skies,

Paul

Paul,
First a high pier is better and I consider a 16" pier to be really low! Regardless, that's the height of the pier that the observatory supplies so it's not a variable. But that's all irrelevant. Go back to slide #7 and you'll see that if you lower the pier by 16" and you lower the flat panel by 16", you are still blocking the same amount of sky with the telescope pointing up by 10 degrees. The scope would still have to point to an altitude of 50 degrees to look over the panel--and the panel would still block the sky for surrounding telescopes. Perhaps I should have mentioned that all of the surrounding telescopes are quite large (>20") and sit equally high. I'll have to look for a photo of my 20" with its flat panel mounted so the scope points at it horizontally, which is how the guys in the observatory originally mounted it. They told me that the guy with the scope next to mine was really nice about it but he still mentioned that it blocked a chunk of his sky. So the next time I went down there, I had them re-weld the frame to lower the panel to get it totally out of the way. To take flats, I just have to point down at the panel, which works well with the 20". Unfortunately, the new 24" can't point down; hence the need for the lift stand.

John

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Brian Valente

Dec 28, 2023

Looks great John, nice job. Are you going to add your patented dark panel next to it?

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Dave Erickson

Dec 28, 2023

Great project, and narrative, very well done John!

I like your use of the the 4066 bilateral switch, low power and no mechanical movements, or contact bounce, like with a relay. The 4066 are great...

I did something similar a while back as well as part of the CDK17 control system. Fully remote 24"x30" EL Flat, integrated into my control software.
pages 55-60 of:
https://cdn.astrobin.com/ckeditor-files/14617/2023/7731b0ae-eeca-46ff-aa72-8a804642acf7.pdf

Regards,
Dave

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John Hayes

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Dec 28, 2023

Hahaha! No Brian, not this time. This new scope has primary mirror covers, which should make taking darks much easier.

On a related note, I've recently designed a new variant of my wide field ONAG that will mount a Moravian C5A-100M (with a IMX461 sensor) mated to a EFW-5XL filter wheel. It is designated as the ONAG-UWF and it's designed for the CDK17 but it should fit other large scopes with enough back working distance. Since the C5A-100M has a shutter, that's the end of any need for a dark panel! I'm working with Gaston on some other ideas as well so eventually, I may switch to that camera/FW/ONAG combination.

John

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John Hayes

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Dec 28, 2023

Dave Erickson:
Great project, and narrative, very well done John!

I like your use of the the 4066 bilateral switch, low power and no mechanical movements, or contact bounce, like with a relay. The 4066 are great...

I did something similar a while back as well as part of the CDK17 control system. Fully remote 24"x30" EL Flat, integrated into my control software.
pages 55-60 of:
https://cdn.astrobin.com/ckeditor-files/14617/2023/7731b0ae-eeca-46ff-aa72-8a804642acf7.pdf

Regards,
Dave

Hi Dave,
Your report is absolutely fantastic!! Wow...you are the king of remote observatories. Heck, my efforts are completely amateur compared to what you've built! I especially like your idea of having the flat panel retract into its own "case" when not in use. Even if I had thought of that approach, I probably wouldn't have used it simply due to the size and weight, which are problematic for shipping to Chile.

Thanks for your comments and for sharing your report. There are a lot of gems in there that I'm going to have to explore.

John

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Patrick

Jan 3, 2024

Thanks very much for going to the trouble of sharing this. Based on what you’ve done I’m about to order the panel and power supply from Light Tape but before I do I’d like to know how well the illumination works.
Can you please give me a rough idea of the actual flat frame exposure times with narrowband?
This would also be for use in a remote observatory.
FYI, the power supply Light Tape offer is dimmable via a 0-10vdc signal. But that’s easy to deal with.

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John Hayes

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Jan 3, 2024 · Edited: Jan 3, 2024

Patrick:
Thanks very much for going to the trouble of sharing this. Based on what you’ve done I’m about to order the panel and power supply from Light Tape but before I do I’d like to know how well the illumination works.
Can you please give me a rough idea of the actual flat frame exposure times with narrowband?
This would also be for use in a remote observatory.
FYI, the power supply Light Tape offer is dimmable via a 0-10vdc signal. But that’s easy to deal with.

That's a great question Patric and I should have addressed that issue more carefully up front. I haven't yet tested the Media White phosphor on my scope with NB filters. I have the Glacier White phosphor in the panel for my 20" and the S2 filter is the worst. With my QHY600M-Ph camera, exposures are 600s with the S2 filter and the supply turned to max brightness. I'm expecting that to go down by roughly half with the Media White phosphor. O3 on the 20" is maybe 30 seconds, but Ha is still around 300s, which again is where the Media White should help. LGB exposures on the 20" require reducing the brightness of the panel to achieve ~ 4-10s exposures. Broadband red is around 10s with the panel at full brightness.

I used to have a LED panel on my 14" and that is really the way to go; however, achieving reasonably uniform illumination over larger sizes (like 30" x 30") with LEDs becomes more challenging. It's a solvable problem and large LED ceiling panels are now common and cheap so it's something that I'd like to look into.

If you are building an EL panel and you want to know how to control the brightness remotely, PM me. I have a simple solution that I can share.

John

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Jeffery Richards

Jan 3, 2024

Great project John! Did I miss it or did you not mention where you got the panel. I haven't been able to find larger panels.

Clear skies,
Jeff

John Hayes

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Jan 4, 2024 · Edited: Jan 4, 2024

Jeff,
The EL panel came from Light Tape and I built the flat panel using that as a light source. Slides 3, 4, and 5 describe the construction. What did I leave out?

John

Jeffery Richards

Jan 4, 2024

Sorry John, just didn't see a 30" panel on Light Tape's website.

John Hayes

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Frequent contributor

Jan 4, 2024

No worries Jeff. There is one important thing that I forgot to mention in the slides. Light Tape specifies their panels by the size of the illuminated region; not by the actual physical outside dimensions. Had I known that beforehand, I might have ordered a larger frame and diffusers. Instead, I had to trim the sides of the EL panel and reseal it to fit into my 30"x30" frame. If you build your own check on all the dimensions first. Light Tape can even trim the panel for you if you ask them and that's what I'd do the second time around.

John

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Jeffery Richards

Jan 4, 2024

So in looking over their faq, it seems like a simple call to discuss the size of panel and power supply. If you don't mind me asking, where did you get the diffuser panel (since you mentioned a particular type of panel)? I appreciate the write up and assistance.

Jeff

John Hayes

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Jan 4, 2024

I cannot remember where I ordered the diffusers. I'm out of town so I can't easily check my shop to find any clues until I get home next week. Normally I get an emailed receipt for the order but I can't find one. So right now, I can't tell you where I ordered those diffusers. I do remember that at 30" x 30" they were not particularly cheap. When you call Light Tape, ask for Zach Nelson. He was super helpful. Avoid mentioning that you are making something for astronomy. I'm not sure but they may have a supplier agreement not to sell their products for astronomical applications. I seem to recall that someone told me that many years ago back when I was making my first light panel. At that time, I wound up getting an EL panel from Technolight.

John

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Patrick

Jan 4, 2024

I did get a quote from them for the Media White panel plus a dimmable smart driver. They have been quite responsive. They are the only source I’ve seen that has a panel with a remotely controllable brightness (via 0-10vdc input).

Jeffery Richards

Jan 4, 2024

Great, thanks John!

Jeff

Carlo Caligiuri

Jan 4, 2024 · Edited: Jan 4, 2024

Hi John!
I love your methodic approach!
I just wanna share my experience maybe could be helpful.

I have had problems with color balance of my flat frames, since I use my modded DSLR the green channel was (off course) shifted too much and this generates an unwanted color gradient due the difference channel sensitivity.

So I decided to use a low cost RGB led strips with an IR remote that control color, saturation and brightness. I removed the remote control and connect the channels control MOSFET included in factory PCB to an esp32 microcontroller board.Then i have uploaded the dedicated Tasmota firmware for controlling everything via wifi directly from browser Just connecting the esp32 to my home wifi.
now I can easily control my RGB flat panel with setting stored once time without loosing it in power cycle of controller.

I hope this could help anyone that have problems like mine.

Carlo

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John Hayes

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Frequent contributor

Jan 4, 2024

Carlo,
Thanks for that! Your solution sounds very clever.

Back when I used to shoot with a DLSR, I made a flat panel using an EL panel from Technolight and I never experienced any problems with color balance between the channels. The biggest problem with that set up was that I didn't have a brightness control and with short exposures, I got banding. So, I had to use a stretched T-shirt to cut down the amount of light to use longer exposures.

John

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