KG3 IR Absorption vs IR Blocking filters? Same?

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by MalVeauX » Sat Jun 02, 2018 2:22 pm

Welp, I'm proper undecided on what to do.

Any suggestions on how to proceed from this point? I want to use my 393nm stack and the 395nm cut filter, but I have to find a way to manage the heat. The KG3 popped with the 120mm aperture. Any definitive suggestion on what to put in front of the KG3 to lower the heat from the 120mm aperture?

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Sat Jun 02, 2018 9:42 pm

I cant say for certain because i dont know what that 395 filter is, but it definitely belongs infront of the kg3 since it has a metalluc coating. , it is basically metal and will take the brute heat. That being said it must also be in a negative focal distance because this is the only way to avoid the heat. No filter will get ride of it so there must always be a load bearing filter before the transmissions. So at least 50mm in front of the skybendr.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by MalVeauX » Sat Jun 02, 2018 9:52 pm

All I know is that the filter I have is a 380~395 filter that blocks everything but that little patch. And then the two 393nm filters. I'm wondering if I can put a blue filter, like the blue CCD filter (2") on an extension tube and insert that into the focuser well into the light cone. Behind it, the 380~395 filter. Then after that either a KG3 or some other IR blocking filter. Then a 393nm in the skybender. Then a 393nm on the camera nose.

I'm happy to try it out, but I need to get the blue filter or an ERF of some kind first, as I do not want to bust the 380~395nm filter as I cannot replace it.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by Merlin66 » Sat Jun 02, 2018 11:19 pm

Marty,
What you're proposing is exactly what I intend doing with my Omega CaK stack. A Baader CCD -B filter well in front of the stack.....
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by MalVeauX » Sun Jun 03, 2018 3:22 am

I just need to know it works, I can't keep popping KG3's! :) hah.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Sun Jun 03, 2018 11:38 pm

marty here is what the baader planetarium B-ccd filter looks like; I mounted mine today in the 2", it is yellow/gold on both sides and transmits a dark blue. I returned the 1.25"
skybender filter cell 2a.jpg
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skybender filter cell 3.jpg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Sun Jun 03, 2018 11:54 pm

Here is what my new filter train is labeled as, The b-ccd filter is tilted; the b&w ir/uv cut filter is not tilted; the bandpass filter is also tilted. B-ccd = ERF ONE Bandpass filter = ERF TWO. I am probably just going to remove the B&W. The beloptik KG3 has no front filter thread.

I am taking a major gamble, and I have the solar focus directly on the second erf filter. If lunt does not have any problems doing that with their calcium filter, then I dont have a problem doing it on a bandpass filter.. Everyone on here says that metal reflective surfaces can take the heat so we will see what happens!
Dual 2inch skybender baader planetarium b-ccd and 393.4 erf labled.jpg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by Merlin66 » Mon Jun 04, 2018 12:08 am

"" I have the solar focus directly on the second erf filter..."
Why?
Surely if your imaging, this final filter would be at some distance in front of the camera?? In my case about 30mm.
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 1:50 am

Merlin66 wrote:
Mon Jun 04, 2018 12:08 am
"" I have the solar focus directly on the second erf filter..."
Why?
Surely if your imaging, this final filter would be at some distance in front of the camera?? In my case about 30mm.
Nope, i am having the focal length extended using a reverse refraction method utilizing two pst cak objectives. Basically it will be placed so that both solar focuses align and create a negative beam that adds a controlable amount of magnification. the third cak objective will refocus it all. Will be somewhere around 2000mm total without a Barlow

reverse refractor solar calcium telescope with aluminum extruder pieces and two 90 degree mirrors to retroreflect the negative beam to the second alignment ring where the third objective will be placed with a focuser.
3D746096-B3C1-4139-88AF-9A6529633E92.jpeg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:13 am

updated assemble but not final.

full size image link. download/file.php?id=32034
100mm PST CaK stage-4 extruder dual skybender.jpg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by Merlin66 » Mon Jun 04, 2018 6:34 am

Hmmm Interesting arrangement!!
Have a filter element at a focus point is usually bad news in that every bit of dust etc. will be in focus.....
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 7:37 am

i am open/ready for suggestions, I only put it there because its 1.25" was a limiting factor in the 62mm - 58mm - 48mm back end.

I could move it back or forward 50mm by removing one of the 58mm reduction spacer's! I considered placing the filter itself on a helical focuser to make moving them a bit easier.

Also I can make an imaging flat to sort out the bunnies.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by MalVeauX » Mon Jun 04, 2018 2:33 pm

Interesting,

I'm looking forward to your report, thank you for taking the time (and expense!) to share this info with everyone.

I'm very curious about -> B-CCD filter (ERF 1) -> 380~395 filter (cut) -> 393 filter (Skybender) -> 393nm filter (Camera nose).

I'm curious whether a KG3 needs to be inserted somewhere in there.

I know I can't use a UV/IR cut filter, because when I put my Baader UV/IR cut filter inline with my original setup, I couldn't see anything as the UV filter cut off chopped the wavelength so I saw nothing with the 393nm filters. So I may need to put a KG3 or other 2nd ERF in there. Just not sure yet.

Just trying to manage the cost. Too much extra stuff and I might as well buy a Lunt module or Quark CaH if it gets too close to those costs.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 5:51 pm

Marty I have confirmed that the B&W Schneider-Kreuznach IR/UV cut filter does not affect 393 transmission what so ever s. This means the transmission peak is somewhere around 380nm 385nm probably very similar to the IDAS filter suggested by daystar. They are very cheap and you can get much larger ones.

however the beloptik kg3 clearly lowers the transmission of my filter meaning it has a cut-on close to 390nm. It is noticeably dimmer when a 390nm filter is held in front of a lamp. Ill try to take a photo to show this affect on transmission.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:02 pm

B&W Schneider-Kreuznach 010 UV absorption filter
B+W_010-8deg.png
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:09 pm

beloptik KG3 filter scan

Image

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:09 pm

B&W 486 filter scan
486.jpg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:13 pm

baader planetarium "double stacked" K-line filter scan, from 2013. This filter may have been changed since then, alot of the baader planetarium stuff have updated coatings.
Filter 2 Baader K-line.jpg
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Last edited by TheSkyBurner on Mon Jun 04, 2018 6:24 pm, edited 1 time in total.

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Mon Jun 04, 2018 6:21 pm

More filter scans, B&W 415 filter, B&W 403 filter and B&W 486
curves combined.jpg
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Also a scan of all three above filters stacked.



curves combined final transmissioon2.jpg
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1nm scan zoom
zoom1nm.jpg
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by marktownley » Mon Jun 04, 2018 7:05 pm

Thanks for the K-line plot, I was looking for this the other day.
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Tue Jun 05, 2018 12:03 am

for what it is worth, here is the baader planetarium B-ccd filter creating some kind of internal vaporization with a reflective focal point inside of my tube. This may be due to the gold coating. (the scope has zero plastic and the reflection is touching nothing but air)

I am going to move it closer to the objective to see if this stops it, but as of right now this filter is not something i would recommend.

This did not happen with the g-ccd filter, and that has a red coating.
focal reflection.jpg
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baader planetarium B-ccd filter interna tube reflection burning.GIF
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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Thu Jun 07, 2018 4:11 am

This may seem counterintuitive, but I went against everything being said here and actually moved the B-ccd 40mm closer to focus, and it is now sending a very tiny elliptical reflection across the threaded baffles on two of my spacer tubes.

It is now adjacent to all optics and line of sight. It is not causing smoke or vapors here and the heat is actually being dissipated across all the extension tubes (they are acting like a very large heat sink!). I am going to keep it at this location, and will have no need to install a polarizer to reduce the intensity anymore. (i am still going to see what i can do with one however)

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Thu Jun 07, 2018 4:38 pm

Marty: not sure about the quality of this filter but it is strictly dielectric reflective for infrared.
It is omega optical so its a gamble...

25mm
https://www.ebay.com/itm/Optical-Filter ... 2155902531

50mm
https://www.ebay.com/itm/Optical-Filter ... 1650196606

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Fri Jun 08, 2018 4:54 pm

I sent an email to omega about that infrared block coating to ask if it was made by him and he said yes. I also asked if he was willing to put the coating on any other filters and he said yes. So if you guys have any high quality optical flats, like the baader planetarium clear filter, https://www.baader-planetarium.com/en/b ... ction.html he will apply the coating to them.

I did not talk price because obviously this changes with amount of filters and size of filters.

Something to think about, My initial question was if he would apply it to my polarizer..

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Re: KG3 IR Absorption vs IR Blocking filters? Same?

Post by TheSkyBurner » Wed Jun 13, 2018 9:28 pm

So today i let the baader planetarium b-ccd filter track direct solar focus for more than 4 hours, started at 1130pm. Just took it off. 100mm at f5 no other rejction filters added and it did not crack or break. This means it is rather enduring of heavy stress. I cannot measure glass expansion or optical performance characteristics but i can confidently say this filter will not break when it is close to the solar focus. I will stress test with an 8 inch f5 next.

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