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How much larger than my lens diameter should my solar filter be?


MKHACHFE

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Hello all,

Im looking into imaging the ISS transiting the sun in a few weeks and have decided to go with the cheapest option for now as its my first attempt.

I will be using my Canon 70-300mm lens with my ASI 120mm attached to my Star Adventurer 2i (not sure if i need the tracking or not, but thats not important in this thread)

Its a fairly old lens and the filter thread size is 58mm. I have read that the solar filter cap should be about 6mm larger than the diameter of the lens. Is that correct?

Would this 60mm one fit?

 

https://www.firstlightoptics.com/solar-filters/baader-asbf-solar-filters-for-binoculars-and-camera-lenses-50mm-aperture.html

I only want to image, not view. 

 

Thanks everyone

 

Marc

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Here is the data sheet for the Baader filters, it gives the outside tube/lens ID that each work will work for.

 

It doesn't have to be 6mm over the aperture size, if the filter covers the whole aperture then great, if it doesn't then as long as the unfiltered aperture is blocked off completely then that will work too, just you'll be working with a slightly reduced aperture.

baader_solar_fi.pdf

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13 hours ago, MKHACHFE said:

Hello all,

Im looking into imaging the ISS transiting the sun in a few weeks and have decided to go with the cheapest option for now as its my first attempt.

I will be using my Canon 70-300mm lens with my ASI 120mm attached to my Star Adventurer 2i (not sure if i need the tracking or not, but thats not important in this thread)

Its a fairly old lens and the filter thread size is 58mm. I have read that the solar filter cap should be about 6mm larger than the diameter of the lens. Is that correct?

Would this 60mm one fit?

 

https://www.firstlightoptics.com/solar-filters/baader-asbf-solar-filters-for-binoculars-and-camera-lenses-50mm-aperture.html

I only want to image, not view. 

 

Thanks everyone

 

Marc

If the filter thread size is 58 mm, then a 60 mm filter is unlikely to fit. It has to go over the body of the lens, which will be significantly larger than the filter thread dimension. Measure it with a ruler or calipers and then add at least 6mm for clearance. Make sure the filter is secured properly before pointing it at the Sun, even if imaging only. You don't want to destroy your sensor.

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14 minutes ago, Mandy D said:

If the filter thread size is 58 mm, then a 60 mm filter is unlikely to fit. It has to go over the body of the lens, which will be significantly larger than the filter thread dimension. Measure it with a ruler or calipers and then add at least 6mm for clearance. Make sure the filter is secured properly before pointing it at the Sun, even if imaging only. You don't want to destroy your sensor.

The shop in the link I posted has 58mm filters that just screw direct to the front of the lens just like any other photographic filter ... 😉

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2 minutes ago, Steve Ward said:

The shop in the link I posted has 58mm filters that just screw direct to the front of the lens just like any other photographic filter ... 😉

Ah, right! I know the ones. I use them on my camera lenses, too and have imaged the Sun with one.

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