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Re: WILL IT BURN? - ..Filter Killer..

Posted: Mon May 28, 2018 9:37 pm
by mdwmark
Yep, I know. Over the years repairing filters, I have come across many that where damage using to fast of scopes. Like your burning ants analogy. 100mm F/15 with no ERF will melt a .54" spot in the delrin of the front plate and take out the blocker over time.
The point of the front mounted ERF was to keep the heat out of the scope and also lessen the thermal load on the filter.
The yellow ERF does very little , the old surplus red glass drops some of the heat. I tested how much, with my 3" F/30 scope. The temperature at focus was around 54C. The RG610 dropped in down to the high 40's. and the RG630 mid 40's.
The Baader D-ERF ( the day I checked) just read the air temperature. These where all at F/30. I didn't check them at F/8 or faster.
The internal ERF, like the Baader 35nm would be the next best approach with dealing with the heat. This filter is hard coated so it can handle the heat. Just keep it up in the beam so the energy density is spread out.

The front blocker of a Quark is rated at a maximum temperature of 70C(according to Andover's catalog).

I think you made your point.
Mark W.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Mon May 28, 2018 11:45 pm
by mdwmark
I was thinking, The front of the telecentric is not at prime focus. So it will be hot but not as bad as prime focus. If your using an F/5 then I don't think it would make much difference.
I'm not sure the distance for the Quark but I would guest about 45mm in front of prime focus would be a good place to try. See what type of temperatures you would be talking about at that point. That is a more realistic test.
Mark W.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Tue May 29, 2018 3:37 am
by mdwmark
BUT , when you move in and out to focus, you will run into that problem of high heat.

Mark W.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Tue May 29, 2018 9:49 pm
by bart1805
I am sorry, but don't fully understand what you are trying to prove. You say for example that "Beloptik KG3 IR/UV cut filter is effectively useless on its own for solar imaging". Ok, but is that news? Where does Beloptik say that this filter can be used "on its own for solar imaging". As far as I understand Beloptik says that these filters should be used in conjunction with an Erf in front of the telescope. So if you want to test if what a manufacturer says is right you should test it the way it is advised to be used.
Even a Baader D-Erf in front of a 150 mm F8 achromat lets through quite a lot of heat. If you combine it with a Baader 35nm filter this is solved.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Tue May 29, 2018 11:17 pm
by bart1805
Baader UV/IR blocking filters open at 1100 nm. ... filter.pdf
Did you prove that they open up before 1100 nm?

Re: WILL IT BURN? - ..Filter Killer..

Posted: Wed May 30, 2018 3:27 am
by Spectral Joe
I've had this discussion before, it rarely sinks in but I'll try again.

Rather than just burn stuff why not just think for a minute about what radiation actually reaches the Earth from the Sun. How many people here have ever seen a solar radiation plot and thought about what it means? The great assumption is that "heat" is only the result of infrared radiation, and that filtering out the IR will eliminate the heat. Wrong. Most of the energy that reaches the Earth's surface from the Sun is visible light, which peaks in intensity at around 500nm. Even if all of the IR is eliminated heat will be generated when the remaining visible light is absorbed. Here's an exercise to try: get a spreadsheet program, any one will do. Search for a solar radiation file (just search "solar spectrum", the ASTM G173 Direct file is a good one), integrate the whole spectrum and then integrate what's left after you multiply various filter transmissions by the spectral curve. Then you can feel like an actual scientist, doing quantitative work. You will be surprised at how much energy is left when the extreme ends of the spectrum are cut out.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Wed May 30, 2018 7:06 am
by bart1805
TheSkyBurner wrote:
Wed May 30, 2018 12:20 am
Look at 1200nm... So this just confirms everything, they already know their system passes a ton of heat.
Yep, that is my point. What you "discovered" you can find easily on their website. Combined with what spectraljoe wrote the question for me is did you really believe that a UV/IR blocking filter, stacked or not, could prevent you from burning something?
And where exactly do manufacturers like Beloptik or Baader say that their filters are capable of preventing just that?

Re: WILL IT BURN? - ..Filter Killer..

Posted: Wed May 30, 2018 3:00 pm
by bart1805
If a filter fully blocks UV and IR does this filter reduce the thermal load? The answer is yes.
So, is there less thermal load than when you do not use this filter? The answer is yes.
Is there no thermal load at all when you use a filter that fully blocks UV and IR? The answer is no.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Wed May 30, 2018 7:26 pm
by christian viladrich
+1 with Bart :-)

See some temperature measurements there : ... atures.htm

I think two additional points have to be taken in consideration :
- the amount of energy per square millimiter also depends on the distance to focus ;
- the temperature of a material depends on the amount of energy absorbed. If the material reflects or transmit light, there is no increase of temperature.

An example : I have been using a FFC for solar observation with my TOA 150 for many years (no ERF). The FFC is still in perfect conditions since it is basically transparent (and ahead of the focus).

This being said, I 've never seen that Beloptik has ever said their ITF filter was to be used without an ERF ;-)

Basically, when you observe in Ha, you need an ERF (front position or internal position) to cut a large part of the incoming energy.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Thu May 31, 2018 6:44 pm
by christian viladrich
I understand fully the stance of Baader Planetarium. I would do the same if I was selling FFCs ;-) They have to deal with safety issues, and a variety of possible misuses of their products.
It would be impossible to draw an exhaustive list of what is safe or not safe (for the eye or for the products).
BTW, there is no reverse reflection.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Thu May 31, 2018 9:01 pm
by mdwmark
OK, I though the original concern was Daystar's statement that Quark didn't need an ERF. If they want to change blockers. That there concern. The filter is still safe to the eye even when a front blocker fails. I have been making Ha filters for 30+ years and have never hear of anyone having problems with there vision when used correctly . The only problems I have hear of where from people who knew better and were trying something. None of them had permanent eye damage. The most common was that they could not focus there eye for a while. This was always from the IR not being block well form about 700nm to 1000nm and using them visually .
All the filters you used except the D-ERF are for camera's or visual. The blocking is designed for them. So even if it is blocked to 900nm it would be block in the IR for what they were designed for. I have an 6" C-ERF that I have on my C-6. At f/10 there is heat there, but not enough to hurt the telecentric. Nothing like your burning images.

There is only two common ways to block farther then 1500nm to the FIR( +2000nm). That is either using an ITF or an IR glass like an KG glass. Also when it come to blocking, OD4 ((average from UV to FIR) has been the standard for 50 years.
When you see a filter that says blocked to OD6. That OD6 is only measured closed to the band pass wavelength. It is not blocked to that OD6 from the UV to the IR.

Mark W.

Re: WILL IT BURN? - ..Filter Killer..

Posted: Sat Jun 02, 2018 1:08 pm
by Valery

1. The filters you tested were not designed for use in telescopes pointed at the summer sun, without full size ERF filter and near focus. These filters were not intended for such a critical use.

2. Some peoples trying to save money and start to use these filters as secondary or even main ERFs - depends of a telescope type and size.

3. Large full size DERF are not advertised as filters which blocks all the unwanted heat except, say, H-a in 10nm bandwidth. They advertised as DERF which significantly decrease the unwanted heat. If to make a large full size DERF which blocks all and keep your desired temp +37C, no one will buy a filter like that. Even now when these filters are barely profitable peoples complain that they are too expensive.
So, a simple way of two stage heat decreasing is the cheapest and very effective way to go.

While you burning small night time Baader filters and bla-bla-blaing about them and other non-solar filters here and there, trying to get a credibility among solar imaging enthusiasts, my 295mm filter continue to prove that you are wrong and what you are saying here, as Frederic correctly noted, just not credible.
And, note for your further bla-bla-bla that I can easily keep my palm at the focus of C11 equipped with my first generation DERF, and I can image with this DERF and ultranarrow Ca and H-a filters, as well as in continnum near these lines.

In prove of my credibility in this particular field, I can show and sell my filters and I can show the CaK, H-a and continuum photos, taken in hot summer weather with this large telescope. Nothing burned, nothing even heated to the level which produce turbulence inside a tube.

So, better stop bla-bla-blaing here and make your promised filter 1A CaK, DERF for CaK and corrected for CaK scopes. As soon as you finish them and test with proved results, we continue to speak about facts.

In the attachment here are two photos with diffraction limit resolution at CaK and H-a May 31 with 28C at the morning.


Re: WILL IT BURN? - ..Filter Killer..

Posted: Tue Jun 05, 2018 6:58 am
by Valery
TheSkyBurner wrote:
Mon Jun 04, 2018 11:49 pm
okay here is the baader planetarium B-ccd filter, BURNING inside of a solid magnesium telescope. This is a reflection from the gold
coating. Better luck next time gadget.

Valery: I have nothing to prove. This is a situation of reality, and I am doing all this for the sake of experimentation. Out of my own pocket; By myself. I am sacrificing valuable equipment that most people would cry if it even got a single speck of pollen on it..

I am also Using what is regularly talked about in these forums by quite lots of users; I have no need for attitude's, nor sarcasm and bitterness. You either help people complete a project or you dont.

I do have a need for showing that some of this stuff, like you say is wrong. I have no experience with your filters. I have no idea who makes your filters. Where do you source them from, feel free to tell everybody. I will gladly buy one and do the same burn tests with it.

Can we see a picture of your LAB and vacuum chamber? Otherwise no offense intended, maybe you are just reselling a product that some other company is sourcing for you?

baader planetarium B-ccd filter interna tube reflection burning.GIF

Most of the manufacturers do use the service from specialized companies or outsoursing of components. Coating companies are example of such specialized companies. The very first examples of such outsourcing are Baader, Astrodon, Lumicom etc etc. Even Lunt and DayStar use the filters/coating outsoursing. We are not any kind of exception. We do use the coating service from peopels who can do this much better and much faster than we can do. And this is not a secret at all.


Re: WILL IT BURN? - ..Filter Killer..

Posted: Tue Jun 05, 2018 7:52 pm
by christian viladrich
I am afraid your statement is not true:

"They are all advertised as "reducing the thermal load on your filters" , and it just isnt true especially if we take into the curve-ball point that spectral joe threw out."

I have posted here and there the amount of energy transmitted by various filter combinations. I am a bit in a hurry, so I won't post it extensively again, but here some results for sea level and Sun at 42% elevation:

- Daystar yellow ERF transmits 71 % on the incoming energy, and absorbs the remaining 29% => no comment ;-)
- the old Daystar red ERF, transmits 60% of the incoming energy, a bit better but still a long way ...
- Astronomik L (ie UV cut) transmits 51 % of the incoming energy => draw your own conclusions ;-)
- Astronomik blue transmits 25% of the incoming energy,
- Baader ERF transmits 17% of the incoming energy
- Beloptik ERF transmits 10% of the incoming energy
The calculation is based on the integration of the solar spectrum and on the transmission curve of the filters. The concept of blockage is completely useless for this.

The problem with the "burn test" is that it shows the combination of the energy transmitted by the filter and the energy absorbed by the material. There is no direct relation with the temperature the Ha filter (or other) will reach, since the amount of energy absorbed by the Ha filter depends on the filter type.
BTW, my Daystar operates at 40°C and my SolarSpectrum at 55°C, so acheiving low temperature at the focus is not necessarly the target ;-)