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DIY Solar Wedge ND3.0 alternatives for Imaging only

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Martin_S
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DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Tue May 21, 2019 9:40 pm

Hi, I'm building a Herschel wedge for white Light solar Imaging. I am sourcing a ND3.0 ND filter at a reasonable cost . Most of my parts I buy from Asia,as the postage and exchange rates from the UK or USA to Australia can be expensive. There was a nice set of ND filters from Svbony . but they have been discontinued. I have a UV /IR cut and a variable polarising filter and a #58 green filter and Moon filter in my collection.

Any suggestions for filters for imaging only would be most welcome.

Thank you

Martin
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by MalVeauX » Tue May 21, 2019 9:54 pm

Heya,

Is this strictly for refractors?

What aperture range do you want to have on it?

You really do not have to make a Herschel wedge for imaging only. Wedges kill transmission, which is ideal for visual use, but for imaging, you don't have to do that. You just have to have transmission low enough to not saturate the sensor, and thermal load handled to not melt everything, so you can make an imaging only platform a lot better. Again, no need to make a wedge.

Very best,

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Tue May 21, 2019 10:05 pm

Marty , I'm using refactors up to 100mm , I just need a grab and go solution for travelling with my small refactors. I have tried film but thought I might do better with a wedge.

Martin

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by MalVeauX » Wed May 22, 2019 1:18 am

Heya,

All good, you mentioned this is for imaging only right? A UV/IR block filter and a KG3 with any sort of colored dielectrically coated imaging filter would effectively mitigate any serious heat issues and allow upwards of a 150mm refractor's aperture without any problems with the camera sensor... again, if this is for imaging only. For visual that's not safe. So if this is strictly for portable imaging, you could make a high transmission system. Then again, a Lunt wedge isn't that much more expensive. The cheapest thing is of course solar film and apertures this small its still a portable solution to carry a film filter in a cell around likely.

A single 2" Baader Red CCD-IR block filter would handle all thermal load in refractor apertures up to 150mm no problem.

https://agenaastro.com/baader-2in-r-ccd ... 8475r.html

A colored (red) filter behind that would further cut down transmission and left over thermal load. A Baader 610nm long pass filter comes to mind. You can mount both right into a diagonal and you have your own high transmission wedge. Wedges have low transmission, this would be way, way, way higher transmission. If that matters. Again, I assume it does if this is strictly for imaging.

Very best,

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Wed May 22, 2019 1:35 am

strictly Imaging...... my eyes are shot from working as a welder for over 45 years

Thanks Marty

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Mon Sep 23, 2019 3:48 am

Hi everyone , Here's a follow up from my original post. I managed to get a ND 3.0 filter off Ken (Merlin66),so today I gave my wedge it's first light.
The wedge is a made from a Meade diagonal prism reverse mounted in two plastic star diagonal holders. The prism is held in place by pieces of foam rubber. no attempt was made to suppress stray light or align the prism this was just an exercise to see if it would work. I am happy with my initial results so now I will be making a wedge mounted in an aluminium case so I can collimate the prism, control stray light and diffuse the heat from the back of the wedge. Here are a few pictures from today's session, My Image train is as follows ED100 - Wedge - IR cut filter - ND 3.0 filter- Wratten #58
green filter - 2 x barlow - ASI120 mm camera.

The solar pictures are raw unprocessed stacks to show the difference in resolution I obtained using a wedge compared to solar film.


Martin
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by marktownley » Mon Sep 23, 2019 5:51 am

Nice looking rig!
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Mon Sep 23, 2019 6:16 am

Thanks Mark

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by allhoest » Wed Sep 25, 2019 4:36 pm

Hi, a few words to press what has been mentioned by others in this post.

For ccd use only.

Ccd interference filters let IR passing above 1100nm, depending on the maker.
Take care for these polarizing filters; they led IR passing through.
I would use nd3 with care; baader is offering their ND3 for use along their wedge, but having tempted various experiences with filters, mass tinted filters get "blown" by the remaining heat very easily. I would really take care.

CS
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Wed Sep 25, 2019 9:55 pm

Thanks for your comments and your concerns Alex.I have followed the design principles of commercial wedges. Yesterday I was able to catch up with Merlin66 (Ken) he came to my house and we spent an afternoon going over the finer points of solar imaging and spectroscopy. We had two Scopes set up Ha and WL . The solar wedge after 4 hours in the hot sun, was as cool as a cucumber (as we say over here). My next addition to my wedge will be a diffuser for the exit port as Ken told me how he once burnt his tie. In all it was a great afternoon . If any members ever get the opportunity to meet Ken don't pass it by, he has a wealth of solar knowledge to share and he'll sign his books for you.

Martin
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Fri Oct 11, 2019 6:44 am

Here's an update on my DIY wedge.I made a new one out of Aluminium..

The casing was made from two pieces of Aluminium angle bolted together and machined on my lathe and mill. The prism has collimating screws inside the casing.
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The difference in Image quality is quite amazing here is a comparison from an Image I took last week using the same setup but with different wedges.

Both Images stacked and sharpened in AS3 using the same settings, no further post processing.

SW ED100 ds pro Wedge IR cut filter, ND3.0 filter, #58 green filter ASI120mm camera.
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Merlin66 » Fri Oct 11, 2019 6:53 am

Martin,
Well done mate! Looking good.
You may be interested in that ND1.8 filter......
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Martin_S » Fri Oct 11, 2019 7:11 am

Ken, will it improve my imaging? I get 12fps on USB2 with these settings ROI=1280x960 ,Exposure=3.9ms_ZWO ASI120MM-S_Gain=2(off)_Gamma=52_1.ser with USB3 I drop too many frames with my crappy computer and what's your opinion on the Baader solar continuum filter with this setup?.

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Merlin66 » Fri Oct 11, 2019 8:41 am

Martin,
I still have the ND1.8 and the Continuum filter from my early Herschel Wedge trials.
I use the USB3 cameras to gain even faster frame rates....and SSD drives.
Well worth considering.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by marktownley » Sat Oct 12, 2019 5:14 am

That's a well made and nice looking wedge Martin.

With your boiling seeing Ken which did you find best? The wedge or the film?
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Re: DIY Solar Wedge ND3.0 alternatives for Imaging only

Post by Merlin66 » Sat Oct 12, 2019 5:35 am

Having used the Baader film on scopes up to 100mm I always though it was pretty good.....
Now using the Baader wedge I feel the difference is noticeable. Obviously needs those moments of steady seeing which are far between.
Good processing techniques (which I don't have!) can make the difference.
Ken
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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