Dedicated ERFs versus Filters

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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Dedicated ERFs versus Filters

Post by Starry Jack »

Folks,
I am totally excited about the PST Mod project. It looks completely doable and I can even rebuild the PST if it fails!

I am looking for an ERF and OPT has a couple of options for filters while Lunt and Baader have dedicated ERFs. Would you recommend the filter route or the ERF route? Keeping in mind: Protecting Eyes; Protecting Mallincam; Protecting Dollars

1. OPT: $134: Baader Planetarium IR-Pass 670nm Filter + the Baader UV-IR Cut I already own
a. These go in front of the PST components but after the Celestron 100mm objective
b. + 1.25” Baader UV IR Cut on the nosepiece of the Mallincam because I am paranoid
2. OPT: $60: Baader Planetarium IR-Pass 610nm Filter + the Baader UV-IR Cut I already own
a. These go in front of the PST components but after the Celestron 100mm objective
b. + 1.25” Baader UV IR Cut on the nosepiece of the Mallincam because I am paranoid
3. LUNT: $100: 40mm ERF (630nm passthrough) + the Baader UV-IR Cut I already own
a. These go in front of the PST components but after the Celestron 100mm objective
b. + 1.25” Baader UV IR Cut on the nosepiece of the Mallincam because I am paranoid
4. BAADER $600 ERF
Thanks,
Jack Swaton


http://www.optcorp.com/ba-fuvir-2-uv-ir ... 2inch.html : $132
Baader UV-IR Cut Filter - 2"
• The Baader UV-IR Cut Filter has an unmatched 98% Average Transmission! Freedom from ghost images (very low reflection multi-coating, Striae-free, and plane-parallel substrate).
• Extremely Sharp Cutoff at 690nm (leaves all the visible red, including the important 656nm H-alpha emission line).
• The Baader Planetarium UV-IR Cut Filter has a sharp cutoff below 400nm. Eliminates violet halos around bright stars (more effectively than simpler so-called Minus Violet photographic filters).
• True optical quality glass substrate and coatings. Why spend all your money on quality primary optics - only to place a lower grade filter optic in the path?
• Combine the Baader Planetarium UV-IR Cut Filter with any of the other Baader filters, to deliver the sharpest images possible.

Baader Planetarium has introduced the world's finest UV/IR cut filter. This filter is a must for all digital imaging with Digital Cameras, CCD Cameras, and modified WebCams. Also useful for protecting valuable H-Alpha filters from heat stress and damaging IR (Daystar, etc).

Due to their extremely high optical quality, these filters may be stacked and used far in front of the focal plane (necessary for imaging uses). Like the Baader Planetarium Contrast-Booster, the UV-IR-Cut filter uses the very latest coating technology, to deliver the finest filtration quality - and lifetime durability.
Baader Planetarium UV-IR Cut Filter Features...
True Optical Quality: Baader glass substrates are of true optical quality. Most other filters are merely made from raw flame-polished, "optically flat", or sometimes a top quality commercially polished filter glass (fine for camera filters), resulting in wavefront deformations that damage image sharpness and contrast when used with telescopes. Baader Planetarium filters are made from striae-free substrates, and actually fine optically polished flat to within 1/4 wave p-v over the entire surface, plane parallel to within 30 seconds of arc! This important and unique custom step adds cost - but the result is a filter that maintains the full wavefront quality of the telescope without double images or ghosting, even at high magnifications. Critical to maintaining this level of flatness are Baader's carefully balanced coating designs, which prevent coating surface stresses from warping the substrate. Such high flatness enables Baader filters to be used far in front of the focal plane, ahead of star diagonals and digital cameras. They are particularly well suited for attachment to the nosepiece of the Maxbright Binocular Viewer (other manufacturer's filters must be used in pairs, attached to the eyepieces).

Filter Durability: Filter durability has always been a hallmark of Baader Planetarium. The multi-layer dielectric coatings are plasma-assisted and Ionbeam-hardened using the latest technology (the coatings are harder than the glass substrate itself!). Baader filters withstand repeated real-world exposure to the elements and physical cleaning. Users need not leave their precious filters dull and dust encrusted to avoid cleaning - Baader filters may be used and cleaned without fear. We have heard sad stories from owners of other simpler soft-coated dielectric filters, who have seen their coatings degrade from normal exposure to moisture, or wiped away from routine cleaning. Some manufacturers even resort to sandwiching their delicate coatings in between two layers of glass (and risking blurred double images as well as eventual degradation from the edges inward). Baader Filters will truly last a lifetime.

Stackability: Unlike other filters, Baader Planetarium filters are truly designed to be stacked and combined. This is possible due to the high optical quality and highly efficient anti-reflection multicoatings. The ability to combine filters opens up many exciting possibilities, permitting unique spectral characteristics unachievable with any single filter.
http://www.optcorp.com/ba-firp-2-ir-pas ... 2inch.html
Baader IR-Pass 670nm Filter - 2": $134
Baader Planetarium delivers the latest tool in the planetary imager's bag of tricks. The Baader IR-Pass filter blocks wavelengths below 670 nm. At these longer wavelengths, planetary images are less disturbed by wavefront distortions in the atmosphere (seeing). By combining a luminance image taken with the IR-Pass filter, along with RGB frames, overall image sharpness is significantly enhanced. Some of the world's best amateur planetary images have been taken with this technique.

The IR-Pass filter shares the same outstanding features as all the other Baader filters. High optical quality, Striae-free substrate, and high efficiency multicoatings result in the sharpest and highest contrast image possible.
Baader Planetarium IR-Pass 670nm Filter Features...
True Optical Quality: Baader glass substrates are of true optical quality. Most other filters are merely made from raw flame-polished, "optically flat", or sometimes a top quality commercially polished filter glass (fine for camera filters), resulting in wavefront deformations that damage image sharpness and contrast when used with telescopes. Baader Planetarium filters are made from striae-free substrates, and actually fine optically polished flat to within 1/4 wave p-v over the entire surface, plane parallel to within 30 seconds of arc! This important and unique custom step adds cost - but the result is a filter that maintains the full wavefront quality of the telescope without double images or ghosting, even at high magnifications. Critical to maintaining this level of flatness are Baader's carefully balanced coating designs, which prevent coating surface stresses from warping the substrate. Such high flatness enables Baader filters to be used far in front of the focal plane, ahead of star diagonals and digital cameras. They are particularly well suited for attachment to the nosepiece of the Maxbright Binocular Viewer (other manufacturer's filters must be used in pairs, attached to the eyepieces).

Filter Durability: Filter durability has always been a hallmark of Baader Planetarium. The multi-layer dielectric coatings are plasma-assisted and Ionbeam-hardened using the latest technology (the coatings are harder than the glass substrate itself!). Baader filters withstand repeated real-world exposure to the elements and physical cleaning. Users need not leave their precious filters dull and dust encrusted to avoid cleaning - Baader filters may be used and cleaned without fear. We have heard sad stories from owners of other simpler soft-coated dielectric filters, who have seen their coatings degrade from normal exposure to moisture, or wiped away from routine cleaning. Some manufacturers even resort to sandwiching their delicate coatings in between two layers of glass (and risking blurred double images as well as eventual degradation from the edges inward). Baader Filters will truly last a lifetime.

Stackability: Unlike other filters, Baader Planetarium filters are truly designed to be stacked and combined. This is possible due to the high optical quality and highly efficient anti-reflection multicoatings. The ability to combine filters opens up many exciting possibilities, permitting unique spectral characteristics unachievable with any single filter.

Special Filter Cell: Baader's special filter cell design offers unique features that enhance their reliability and usability. Though difficult to produce, the ultra-thin filter cell results in the maximum possible clear aperture, in order to minimize vignetting (1.25" Filter clear aperture is 27mm, 2" Filter aperture is 45mm). The special threading has been designed to fit a wide variety of eyepieces and accessories (there is significant variation between the 1.25" filter threading used by eyepiece and accessory manufacturers). The front 'crown' of the filter incorporates milled notches which make handling and threading the filter a more secure operation in the dark.

Low cost: Despite high quality and advanced technology, Baader Planetarium filters are affordable. By leveraging high volumes across all filters in the Baader family, these filters can be offered at very reasonable prices.

Baader Planetarium Product Number: FIRP-2



http://www.optcorp.com/baader-red-610nm ... 2inch.html
Baader Red 610nm Long-Pass Filter - 2" $60
Baader Planetarium astronomy filters by far supersede the mediocre quality of common "flame polished" color filters. A fine optical polish and 2 mm thick glass allows these filters to be inserted anywhere into the optical path without introducing astigmatism or other defects. For instance, they can be used in front of a binocular viewer without degrading the image in any way. Substrates are free of striae and plane-parallel polished to within 30 seconds of arc. This eliminates any double images or ghosting due to wedge errors in the glass.

The filter cell features the largest clear aperture of any telescope filter on the market for complete freedom from vignetting at any focal length. The front "crown" incorporates milled notches, which makes handling and threading the filter an easy operation in the dark. All surfaces are treated with a 7-layer Multi-Coating, featuring a mere 0.25% residual reflection. It is the most elaborate coating ever applied onto amateur color filters, resulting in a filter free of any false reflections under any incident angle of light. Light is the hottest commodity for all planetary observation. Especially during high magnification work, whether you have enough light or not is the deciding factor for the recognition of the subtlest planetary surface detail, much more important than a horde of different filters of mediocre execution. Less is more: 7-layer MC-coatings not only provide a brighter image, they prevent the softening effect of scattered light! Scattered light kills exactly those subtle features in planetary detail that you are longing to see. Painstaking attention to coatings and perfect optical figuring are simple reasons why the image contrast through these premium filters is so rock-solid.
Baader Planetarium Red 610nm Long-Pass Filter Features....
• Freedom from ghost images, even when stacked.
• Striae-free substrates are polished parallel to within 30 seconds of arc to avoid wedge errors.
• Finest 7-layer hard multi-coatings on both faces feature 0.25% residual reflections (Baader filters are unique, no other colored filter incorporates anti-reflection multi-coatings).
• Extremely high transmission results in maximum contrast and isolation of planetary details, even with smaller telescopes.
• Efficiencies of the three longpass filters (Red, Orange, and Yellow) peaks at 98%, and efficiencies of the three bandpass filters (Green, Blue, Dark Blue) achieve 70%.
• Carefully designed spectral characteristics. Filters may be stacked without image degradation or ghosting, in order to provide even narrower passbands. Or, combine with any of the other Baader filters for interesting possibilities.
• No reduction in sharpness, even at high magnifications or when using the filter far ahead of the focal plane (ie, digital imaging, or in front of a diagonal or binoviewer).
• With the 2" size, only one filter is needed for binoviewing. Only Baader colored filters have the optical quality necessary for use this far ahead of the focal plane.


http://telescopes.net/store/ls90erf-90m ... ilter.html
LUNT SOLAR SYSTEMS Energy Rejection Filter - 100mm

Energy Rejection Filters (ERF's) reduce the heat load on your filter assembly by absorbing or reflecting ultra-violet and/or infra-red light and transmitting light in the desired visual spectrum, passing the light through in the desired visual spectrum.
High quality diffraction limited IR Cut Energy-Rejection-Filter with 100mm aperture for h-alpha solar filters.
All LUNT ERF filters are unmounted - filters only.
• Material: RG630
• Diameter: 105mm
• Aperture: 100mm
• Thickness: 3.5mm
• Side 1: Dielectric IR Blocking Coating
• Side 2: Broadband AR coating
• Wavefront: <1/4 wave T


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Re: Dedicated ERFs versus Filters

Post by Merlin66 »

Jack,
Option #1 won't work....Ha is at 656.3nm - below the pass band of the filter.
Option #2 - could work OK
Option #3 - probably the cheapest solution....
Option #4 - probably the best quality solution.


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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Thank you, Ken
Much appreciated.

Best,
Jack


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Re: Dedicated ERFs versus Filters

Post by swisswalter »

Hi Jack

bearing in mind protection (eyes and equipment) I would always go with option #4


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Re: Dedicated ERFs versus Filters

Post by marktownley »

Ken is spot on with his answers, but i would go with option 4 myself.


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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Thank you, gents.

To press in a bit more...it seems to me there are four bits of information I am juggling with and I am looking for ways to mitigate. My theory is that if I know the demons I'm fighting, I'll have the most efficient tool. These would be: Total Energy; UV/IR; Wavefront.

1) All things being equal, is the damage to a camera or the eyes more from total energy (described by "nm") or from UV and IR? In other words, if I filter out for UV and IR via either coatings on the ERF or additional IR UV cut filters does it matter for safety if I go with a 610nm filter, 630nm traditional filter or traditional ERF (which is 630nm?).

2) Does an ERF provide additional protection other than energy and UV/IR that I could not compensate for from a traditional filter perspective?

3) Since I am using a Celestron 102gt rather a high-end Televue, do I really care about 1/4 wave versus 1/10 wave? I called Lunt and theirs is, "at least 1/4 wave". I called Celestron and they said even a lowly 102GT was likely 1/8th but thought a 1/4 wave filter was sufficient.

Am I making sense or beating a dead horse?

Best,
Jack


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Re: Dedicated ERFs versus Filters

Post by swisswalter »

Hi Jack

UV and IR are harming the eyes. IR brings the thermal load to the equipment. So you will reduce both UV and IR as much as possible. Look up Bob's thread


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Dedicated ERFs versus Filters

Post by marktownley »

Jack, you need to do more reading around to see what others are doing, and see the reasons they are doing it. As a rule of of thumb a sub aperture filter should not be less than 50% the diameter of the objective, and this should be mounted in such a way mid tube so that it's full aperture in energy rejection is utilised.


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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

You are absolutely correct to advise me to keep researching and I’m having a ton of fun doing so. The solution I leaning towards is using the Baader traditional filters. I'll see if I can upload these files with specifications in this post.

Particularly I am looking at:
1. Baader UV/IR Blocking Filter
2. Baader RB-610nm Red

I believe this combination will provide me with UV/IR and Total Energy Reduction. If I’m wrong, I’d love to hear!
Baader.pdf
(2.39 MiB) Downloaded 121 times
Attachments
Baader_colour_Filter.pdf
(221.75 KiB) Downloaded 84 times


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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

I did a very "cool" experiment. I took the focuser off of the 100mm scope and pointed the straight at the sun, which was unobstructed and at about 30 degrees above the horizon. And yes, the experiment was controlled.

I then took a meat themometer, you know, the kind with a digital readout in a box then a wire then a long metal prong you stick in the meat. The ambient temerature was 74 degrees F.

I then took my 1.25" Baader UV/IR Cut filter and held it by hand at about the -200mm (I'll measure exactly where later). I measured the air temp in front of the filter and it got up to about 116 F. I measured the air temp behind the filter and it was a much cooler 99 F. I measured the temp at the prime focus and it was 290 F.

I physically touched both filter and the objective and they were both nice and cool, even when in the direct path of the sun.

I then repeated the test multiple times and each time the temp behind the filter was 90-100 F while the temp infront of the filter was 110-116F. At no time was I able to cause pain on my hand or burn paper (in this case a yellow post-it note) anywhere in the light path from the -200 to the prime focus.

All this was only with the UV IR Cut and without the Baader RG 610 which I will pickup tomorrow morning.

FYI, I emailed Baader about whether or not their UV/IR Cut could handle the thermal load at -200mm in a 100mm F10 system and their response was they could absolutely NOT endorse such an (ab)use of the filter. Of course I could not blame them for that response.

At any rate, another friend of mine looked at the specs and suggested that the 98% throughput of the Ha line may in fact be too much for visual so a ND filter may be in order as well.

Having fun,
Jack


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Mallincam .5x focal reducer (large format)
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Re: Dedicated ERFs versus Filters

Post by swisswalter »

Hi Jack

how thick are the filters you are planing to use and which size do you go to buy?


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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Swiss Walter,
I attached 2 PDFs a few posts back. The complete specs are there all you could know and then some. :). I am going for the 1.25". If they heat up too much I will get the 2" versions.

starry jack


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Re: Dedicated ERFs versus Filters

Post by Valery »

Jak,

I can't decide for myself - do you playing with a risk or just trolling the thread.

If the first, I can tell you - stop playing, you don't have spare eyes.

Buy an appropriate size and quality filters and do not experiment yourself as you seems to be completely novice in this field.
If you can't afford these filters now, better start to save money and buy an appropriate filters later than try to save on potential high risk for your eyes!


Valery.


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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Valery,
Thank you for your reply. I'm definitely not trolling as I am indeed building a PST Stage 1 mod and have built scopes for decades. This latest endeavor is great fun. And I will certainly ultimately do what makes safety sense.

That said, money is not necessarily the issue. Lunt sells traditional ERFs for only $100 and I can indeed purchase one of those. The biggest downside I have seen with Lunt is that they are only 1/4 wave. I'm OK with that.

So now the telescope maker comes out in me...WHY are things done and HOW can they be done differently to suit different variables.

If my primary variables deal with reducing or eliminating various parts of the electromagnetic spectrum to reduce HEAT damage and NEURON damage and SENSOR damage (for imaging), then there are different ways to combat each of those.

I'm reading voluminous posts across forums and even contacting vendors because as you point out, we only get one shot at our eyes.

To that end, I am only using this for imaging. The rest is all a matter of addressing the properties of light with various technologies.

I like the Baader filter solution in part because of money, but also because the mechanics of the filters work for multiple uses for me.

Lastly, I've read numerous posts in other forums by even the most venerable veterans in this SOLAR CHAT forum that indicate my solution can work. I've also reached out to filter "experts" in several venues and am always double-checking. :)

So...I'm all for corrections but I'd rather aim at specific targets rather than just aim in the general direction. By ALL means, if you have specifics I'D LOVE to hear them. :-) :-) :-). Even if you have generalities I still love to hear them because it all goes into the puzzle of data from which we derive information.

Again, thanks for your concerns and safety first,

Jack


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Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
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Re: Dedicated ERFs versus Filters

Post by swisswalter »

Hi Jack

if you aren't as crazy as me, go and get at least 2" filters and as thick as possible. I fried a CaK filter, a UV/UR cut filter and a 805 nm filter in a simple 110 f/6 scope, My CCD has a molten plastic aperture stop ;)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Swiss Walter,
Now THAT's a great story LOL. so sorry for your loss but I love the lesson. Can you tell where your filters were in the path?

Best,
Jack


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
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Re: Dedicated ERFs versus Filters

Post by swisswalter »

Hi Jack

some where from -80 to -150 mm. I will not repeat the tests to find out exactly ;)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: Dedicated ERFs versus Filters

Post by Starry Jack »

Understood. Thanks!!


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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