Replacing the Rusted BF30 Filter

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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Sun May 20, 2018 3:31 am

mdwmark wrote:
Sun May 20, 2018 2:55 am
You got me worried here. When you start replacing part without knowing the design.
If you look at the blocker filter. It will be between .6nm-1nm HW. I'm petty sure its a standard coating. Well put it at 656.3nm +/-.3nm. Just the bandpass will turn back on at about 700nm on the red side and 480m on the blue side. If they designed it to be blocked to 1000nm. Then the KG3 or KG5 will block the long side just fine.But if it's not block that far in the red, then the ITF is what is required. The KG glass is still transmitting at 700nm. For the short side the RG630
can handle that. So if they have a ITF in the stack there probably a reason. If you can replace it for less then $300 then that is still a good deal. If made right they should last 5-8 years.
There was a comment about using a hard coated blocker. You still have the problem of the IR pass the 1500nm . There is still a lot of IR light making it way through. Once you get out to 2400nm the amount of IR making it pass the atmosphere is very low. You shouldn't have to worry about anything that far out. Besides the ITF and the KG are still working at 3000nm.
PS: I have been using hard coated blockers for two years on the TEC models . Also I do not use KG glass because of the problems that were stated earlier.
Mark W.

Hi Mark,

OK you are worried. I understand but I am not visual ¿ so what ?

I compared before and after. My camera is still alive. The filter did not crack.

If there is no risk there is no fun. If there would be no people risking something there would be no development and we would be still climbing trees and throwing stones at each other ( well, maybe that would be better then having G36 or AR-15 rifle or whatever)

Some time people like to make things more complicated then necessary ...

OK, Different strokes for different folks.

When I have time I perhaps will measure on of the rusted filters.

Rainer
Last edited by rsfoto on Sun May 20, 2018 2:46 pm, edited 1 time in total.
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Sun May 20, 2018 3:45 am

mdwmark wrote:
Sun May 20, 2018 2:55 am
You got me worried here. When you start replacing part without knowing the design.
If you look at the blocker filter. It will be between .6nm-1nm HW. I'm petty sure its a standard coating. Well put it at 656.3nm +/-.3nm. Just the bandpass will turn back on at about 700nm on the red side and 480m on the blue side. If they designed it to be blocked to 1000nm. Then the KG3 or KG5 will block the long side just fine.But if it's not block that far in the red, then the ITF is what is required. The KG glass is still transmitting at 700nm. For the short side the RG630
can handle that. So if they have a ITF in the stack there probably a reason. If you can replace it for less then $300 then that is still a good deal. If made right they should last 5-8 years.
There was a comment about using a hard coated blocker. You still have the problem of the IR pass the 1500nm . There is still a lot of IR light making it way through. Once you get out to 2400nm the amount of IR making it pass the atmosphere is very low. You shouldn't have to worry about anything that far out. Besides the ITF and the KG are still working at 3000nm.
PS: I have been using hard coated blockers for two years on the TEC models . Also I do not use KG glass because of the problems that were stated earlier.
Mark W.
Hi Mark,

Look at the images and that is what is inside the BF30 ... all of my 3 three BF30

It is not only one but 2 cells inside the 2" nosepiece
Coronado_1a.jpg
Coronado_1a.jpg (119.21 KiB) Viewed 1040 times
Coronado_0a.jpg
Coronado_0a.jpg (113.17 KiB) Viewed 1040 times
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Re: Replacing the Rusted BF30 Filter

Post by Merlin66 » Sun May 20, 2018 4:46 am

Mark,
I'd appreciate hearing your comments/ concerns with the IR >1500nm.
This region is well beyond the sensitivity of commercial CCD/ CMOS cameras and hence should have no impact.
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Sun May 20, 2018 7:17 pm

Hi,

Well I warmed up my Spectrograph and measured the Original first filter towards the Sun as well as the Astronomik Ha 12nm filter which I am using now and that looks like this.

Interesting are the parasite lines around 5000Å and 5200Å in the Original Coronado Filters as well as in the Astronomik but by far not so pronounced at 4860Å and 5150Å

CoronadoFilter.jpg
CoronadoFilter.jpg (193.36 KiB) Viewed 1024 times
Astronomik12nmHa.jpg
Astronomik12nmHa.jpg (194.02 KiB) Viewed 1024 times
comparison.jpg
comparison.jpg (185.04 KiB) Viewed 1024 times
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Re: Replacing the Rusted BF30 Filter

Post by christian viladrich » Sun May 20, 2018 7:42 pm

Hello Rainer,
Can you go beyond 780 nm with your spectrograph ? 1500 nm ?
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Re: Replacing the Rusted BF30 Filter

Post by christian viladrich » Sun May 20, 2018 7:44 pm

BTW, I have some friends who are using the Astronomik 12 nm or the Astrodon 6 nm Ha filters to replace their rusted ITF.
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Sun May 20, 2018 8:06 pm

christian viladrich wrote:
Sun May 20, 2018 7:42 pm
Hello Rainer,
Can you go beyond 780 nm with your spectrograph ? 1500 nm ?
Hi Christian,

No, my Spectrograph is a poor man's LISA from Shelyak :oops:

What would I need or how does that work ?

May I ask why is over 1500nm so important ?

Rainer
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Re: Replacing the Rusted BF30 Filter

Post by christian viladrich » Mon May 21, 2018 8:02 am

Hi Rainer,
At sea level, 89% of incoming solar energy is at wavelengths < 1500 nm.
By comparison, 80% of solar energy is at wavelengths < 1100 nm, and 46% < 700 nm.
So, the knowledge of the transmission up to 1100 nm (or better 1500 nm) is good information.
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Re: Replacing the Rusted BF30 Filter

Post by Merlin66 » Mon May 21, 2018 8:42 am

Christian,
Agreed. But that’s the total energy....our visual systems function <700nm and the commercial CCD looses all sensitivity beyond 1100nm, beyond that we experience “heat”.
I have not seen any evidence that IR beyond 1200nm has any negative impact on solar observing.
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Re: Replacing the Rusted BF30 Filter

Post by christian viladrich » Mon May 21, 2018 8:55 am

My point was to give a general information on the amount of energy beyond 1100 nm. Indeed, most of multicoated filters block IR up to 1100 nm while there is still some amount of energy beyond this limit.

I agree there is no problem for imaging on small size telescopes.
In larger size telescopes (> 150 mm), the amount of energy beyond 1100 nm is not negligeable. It is difficult to assess the impact of this on actual solar observing.
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Re: Replacing the Rusted BF30 Filter

Post by Merlin66 » Mon May 21, 2018 9:07 am

Christian,
We really need to find an objective method of assessing the issues of NIR radiation Re solar observing/ imaging.
IMO there are no safety or performance concerns.
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Tue May 22, 2018 1:03 pm

Hi,

I just got an e-mail from Oliver Smie from Beloptik.

He wrote me that using for example the Astronomik Ha filter for photography is OK but not for visual as the filter blocks only up to 1150nm and for visual is it not recommendable to use it due to the Optical Density of this filter.

He also wrote that with Optical Density 3 it should block up to 1500nm and with Optical Density 4 it should block up to 1000nm.

Now I have to ask how is the Optical Density defined ? Glass thickness, refractive index, etc. ?

What amazes me most is how is Coronado (Meade) not able to make a good filter ? The BF30 has a price of US $ 1,600.00 ... and at the moment at one US Big shop with waiting list ...

Rainer
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Tue May 22, 2018 9:10 pm

Hi TheSkyBurner,

We are talking about BF30 filters and not PST = Personal Solar Telescope ...

... but thanks anyway as now I am understanding all this a bit more then before.

So the optical train of a Solar telescope using a BF30 is in my case as following

1 one SM60 with ERF then another SM60 with no ERF, 4 optical lenses from a Petzval telescope (Takahashi FSQ 85ED), then first element of BF30 (be it the original or as in my case a 12nm H-alpha filter DSO purpose) then the second original filter from Coronado BF30 (Blocking Filter 30mm Ø)

Rainer
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Re: Replacing the Rusted BF30 Filter

Post by GeorgeIonas » Wed May 23, 2018 2:56 am

My BF30 has been used on double stacked SM90 Etalons (having the ERFs on both Etalons) and has lasted for only 6 years. The "rust" in the ITF filter now covers about half of the filters diameter.

So my option were; buy another BF30 at US$1600 which is expensive or send it back to Meade and wait months for it to be repaired which will deteriorate again or get a UV/IRcutKG3 as a ITF replacement filter from Beloptik within a couple weeks for 137.50 Eur shipped to me here in New Zealand.

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Re: Replacing the Rusted BF30 Filter

Post by Bob Yoesle » Wed May 23, 2018 1:27 pm

Thank you very much Mark for your input and expertise ;-)
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Wed May 23, 2018 5:34 pm

TheSkyBurner wrote:
Wed May 23, 2018 12:13 am
How long have you had your bf30, and are you the original owner?

Getting rust on a bf30 from such a small etalon/ objective with its ERF still in place is quite worry some!

If you had the thing less than 3 years I would say there is something seriously up with the danger zone coming out of the back of the SM60. Only way you can control by adding a secondary IR UV cut filter over the face of the etalon, or before the blocking filter....

etalon is transmitting a range of IR/UV intensity strong enough to cause environmental damage.. That is a slightly upsetting considering the cost of a bf30,. (obviously its first element was intended to be sacrificial)
Hi,

Yes I am the original owner and since around 2007 I have exchanged the three BF30 I have already one and a half time. They even rust when not in use and I have them in a more or less dry climate ...
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Re: Replacing the Rusted BF30 Filter

Post by christian viladrich » Wed May 23, 2018 7:01 pm

Unfortunately, it is not usual to have rusted BF30. This is really a pity considering the cost of these filters. This leaves us to experimenting and find more cost effective solutions (at least for imaging) ;-)
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Re: Replacing the Rusted BF30 Filter

Post by GeorgeIonas » Wed May 23, 2018 9:50 pm

Hi Christian,

I agree with you, we need to find a cost effective solution but at present even if the Beloptik UV/IRcutKG3 filter lasts for 6 years as did my BF30 it is still at present the cheapest option.

George
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Thu May 24, 2018 3:45 pm

christian viladrich wrote:
Wed May 23, 2018 7:01 pm
Unfortunately, it is not usual to have rusted BF30. This is really a pity considering the cost of these filters. This leaves us to experimenting and find more cost effective solutions (at least for imaging) ;-)
Hi Christian,

¿ what do we need as filters ?

Do you have specifications ... ?

I think there is more of a mistery behind it in order to cash a good amount of money ¿ or am I wrong ?
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Thu May 24, 2018 7:09 pm

Hi,

As far as I know Valery a member of this forum makes such filters ¿ right ?

What is his opinion about this ?
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Thu May 24, 2018 9:07 pm

TheSkyBurner wrote:
Thu May 24, 2018 7:55 pm
nobody makes blocking filter replacements because the specifications vary so widely between all the filters and brands. from 5mm to 34mm all the specifications are completely different because they are designed to operate at different focal lengths. The filters are probably hand selected based on spectral response from a large batch production and the rejects are just tossed/returned as unusable B stock.

bf5 designed for full disc at 500mm bf30 designed for full disc at 2000mm

ITF replacements is all you will find, and it seems like this is a gamble for visual use.
Interesting and I guess that is for visual use because if that would be valid I would have strong vignetting with my equipment using a BF5

My telescope is 450mm focal length and my camera has a diagonal size of 8.2mm and using a BF 5 that would look like this ...
BF5.JPG
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Re: Replacing the Rusted BF30 Filter

Post by Merlin66 » Thu May 24, 2018 10:52 pm

The size of the the solar disk image at a focal length of 450mm is 4.22mm.
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Re: Replacing the Rusted BF30 Filter

Post by rsfoto » Thu May 24, 2018 10:57 pm

TheSkyBurner wrote:
Thu May 24, 2018 10:32 pm
I think the solar image is much smaller than 5mm coming out of a 450mm scope so this is why you have no vignetting. The full image transmits right though the port hole.
I do not use a 5mm BF but I am using a BF30. Below the reasons why I use a BF30 as well as I do not like diagonals as they make life hard in regard to focusing distances.

Look at the image below which was taken with 450mm focal length through the BF30. It has a diameter of 4.18mm on the chip I am using. My chip is 1616 x 1216 pixels and the image is a ROI of 1200 x 1200 pixels.
2018-05-20_13-02-34_pp-1f_500.jpg
2018-05-20_13-02-34_pp-1f_500.jpg (917.98 KiB) Viewed 525 times
Now as I do mosaics with the same setup but just with a 2x extender and so I have 900mm focal length then I would have vignetting in my images because when making the center image of the SUN this fills up the 1216 x 1216 ROI ...

Look here how I do assemble my mosaics
2017-02-10_14-19-10_pp-1f_944_500_mosaico.jpg
2017-02-10_14-19-10_pp-1f_944_500_mosaico.jpg (1.16 MiB) Viewed 525 times
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Re: Replacing the Rusted BF30 Filter

Post by ronatu » Sun Sep 23, 2018 2:53 pm

So there's no replacement for bf? Even substitute?

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Re: Replacing the Rusted BF30 Filter

Post by Merlin66 » Sun Sep 23, 2018 10:26 pm

Ronatu,
It's very rare that the final sorting/blocking filter fails...usually the ITF goes first.
Do you have a "failed" BF?? If so can you upload an image of it.
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