Replacing the Rusted BF30 Filter

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TheSkyBurner
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Re: Replacing the Rusted BF30 Filter

Post by TheSkyBurner » 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.

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rsfoto
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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
BF5.JPG (192.4 KiB) Viewed 206 times
regards Rainer

Observatorio Real de 14 San Luis Potosi Mexico

TheSkyBurner
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Re: Replacing the Rusted BF30 Filter

Post by TheSkyBurner » 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. (4.05mm)

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Merlin66
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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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rsfoto
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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 198 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 198 times
regards Rainer

Observatorio Real de 14 San Luis Potosi Mexico

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