Astronomik UHC-E filter users?

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daveco2
daveco2 Contributing Member • Posts: 931
Astronomik UHC-E filter users?

Questions for anyone who has used this filter clipped into a camera body:

Is there enough visible light getting through for framing and focus on stars, the Milky Way or terrestrial landscapes?

I'm thinking of clipping the filter into my Sony a7RIII to go as light as possible with only a tripod for travel. Anyone with this experience, any comments?

Thanks

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sharkmelley
sharkmelley Senior Member • Posts: 2,563
Re: Astronomik UHC-E filter users?

The Astronomic UHC-E cuts out more than half the visible light so it will make focusing a bit more difficult.

What kind of lens will you be using? If you are using an E-mount lens then the rear element of the lens is much closer to the sensor than for traditional lenses. So the filter will cause colour shifts towards the edge of the image because of the transmission band shifts caused by the angle of incidence of the light rays going to the edge of the sensor.

Here's a daylight shot taken with a different camera but it illustrates the kind of effect that happens:

Astronomik CLS colour shift with wide angle

Mark

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nighthiker Regular Member • Posts: 350
Re: Astronomik UHC-E filter users?

sharkmelley wrote:

The Astronomic UHC-E cuts out more than half the visible light so it will make focusing a bit more difficult.

What kind of lens will you be using? If you are using an E-mount lens then the rear element of the lens is much closer to the sensor than for traditional lenses. So the filter will cause colour shifts towards the edge of the image because of the transmission band shifts caused by the angle of incidence of the light rays going to the edge of the sensor.

Here's a daylight shot taken with a different camera but it illustrates the kind of effect that happens:

Astronomik CLS colour shift with wide angle

Mark

Yes, but you are using a WA zoom. This effect will disappear with longer focal length. Any example with >100mm?

I have the CLS clip-in filter from Astronomik and find it non-usable for nightscapes due to the strong color shift of the terrestrial foreground. I find it easier to do the LP removal later in post-processing like this: https://clarkvision.com/articles/astrophotography.image.processing2/

sharkmelley
sharkmelley Senior Member • Posts: 2,563
Re: Astronomik UHC-E filter users?

nighthiker wrote:

sharkmelley wrote:

The Astronomic UHC-E cuts out more than half the visible light so it will make focusing a bit more difficult.

What kind of lens will you be using? If you are using an E-mount lens then the rear element of the lens is much closer to the sensor than for traditional lenses. So the filter will cause colour shifts towards the edge of the image because of the transmission band shifts caused by the angle of incidence of the light rays going to the edge of the sensor.

Here's a daylight shot taken with a different camera but it illustrates the kind of effect that happens:

Astronomik CLS colour shift with wide angle

Mark

Yes, but you are using a WA zoom. This effect will disappear with longer focal length. Any example with >100mm?

I have the CLS clip-in filter from Astronomik and find it non-usable for nightscapes due to the strong color shift of the terrestrial foreground. I find it easier to do the LP removal later in post-processing like this: https://clarkvision.com/articles/astrophotography.image.processing2/

The filter coatings are interference coatings. They are very sensitive to the angle at which the light strikes the filter, the angle of incidence.

With longer focal length, if you place the filter in front of the lens then colour shifts will not be a problem. However if the filter sits between the lens and the sensor then it is necessary to consider both the distance of the rear lens element from the sensor and the f-ratio being used, since both affect the angle of incidence of the light, especially to the edges of the sensor.

The filter manufacturer IDAS illustrates the issues here:

http://icas.to/space/optical-filter/heuib-ii-e.htm

Mark

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daveco2
OP daveco2 Contributing Member • Posts: 931
Re: Astronomik UHC-E filter users?

Gentlemen,

Thanks for the tips, information and the clarkvision link. Very interesting.

My interest is in wide angle Milky Way and foregrounds on trekking and climbing trips. I have a refractor and cassegrain at home, but taking anything remotely like that on a trip is out of the question.

I was hoping to make use of a clip-in filter both at home and on travel, but have given up on that idea because of the color shift you show.  Thanks for pointing that out - saved me a lot of disappointment.  I'll just take what I can get and rely on post processing.

Dave

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