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Advice needed - considering the jump to a dedicated astronomy camera


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43 minutes ago, Adam1234 said:

When you say move the gear, I assume you just mean like removing the camera or anything else in the image train as opposed to say moving the mount?

I plan on keeping the camera attached to the scope so it's always in the same orientation. Filters I'll change using the filter wheel, so if I take flats for each filter they'll be ok for while right? Unless I change camera orientation or something in which case, take new flats. 

Yup this will work fine! Also as long as your collimation stays intact. This is the main reason I switched to fracs :) 

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44 minutes ago, Adam1234 said:

When you say move the gear, I assume you just mean like removing the camera or anything else in the image train as opposed to say moving the mount?

I plan on keeping the camera attached to the scope so it's always in the same orientation. Filters I'll change using the filter wheel, so if I take flats for each filter they'll be ok for while right? Unless I change camera orientation or something in which case, take new flats. 

Pretty much, I suppose dust bunnies can move, if carrying about the scope, but I dont do this so I'm not sure how big an issue that is.

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1 hour ago, Obi Wan Ken00bi said:

Focus is a fine art and every wavelength has its own focal point

Not in a reflector. Difference in focal point is a result of dispersion, ie difference in refractive index for different wavelengths. But refractive index isn't relevant for mirrors, because the light never goes through glass. If you have a corrector, there may be minimal chromatic abberation. Most ca is generated in the objective of a refractor.

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1 hour ago, Obi Wan Ken00bi said:

Focus is a fine art and every wavelength has its own focal point

Not in a reflector. Difference in focal point is a result of dispersion, ie difference in refractive index for different wavelengths. But refractive index isn't relevant for mirrors, because the light never goes through glass. If you have a corrector, there may be minimal chromatic abberation. Most ca is generated in the objective of a refractor.

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2 hours ago, Obi Wan Ken00bi said:

Yup this will work fine! Also as long as your collimation stays intact. This is the main reason I switched to fracs :) 

Good job I have a frac then 😀

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5 hours ago, tooth_dr said:

Both my reflectors have glass correctors, will that shift the focus?

Depends on the corrector glass and how fast the optics are. Faster optics have a steeper light cone, and are more susceptible to aberration, afaIk. So far, I haven't found my reflectors at f/5 sensitive to chromatic aberration. The 150pds has a Baader coma corrector, and the 190 mak-newt has a corrector cell.

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11 hours ago, wimvb said:

Not in a reflector. Difference in focal point is a result of dispersion, ie difference in refractive index for different wavelengths. But refractive index isn't relevant for mirrors, because the light never goes through glass. If you have a corrector, there may be minimal chromatic abberation. Most ca is generated in the objective of a refractor.

Cool! Thanks for the explanation 😬

The light does go through glass before they hit the cmos.... the filters themselves. Doesn’t this have an effect?

The reason I mention this is because an experienced astrophotographer I'm following on youtube uses filter offsets (very tiny ones mind you!), despite having a reflector....

Edited by Obi Wan Ken00bi
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8 hours ago, wimvb said:

Depends on the corrector glass and how fast the optics are. Faster optics have a steeper light cone, and are more susceptible to aberration, afaIk. So far, I haven't found my reflectors at f/5 sensitive to chromatic aberration. The 150pds has a Baader coma corrector, and the 190 mak-newt has a corrector cell.

Thanks Wim.  I will maybe check that out sometime 👍🏻

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10 hours ago, Obi Wan Ken00bi said:

The light does go through glass before they hit the cmos.... the filters themselves. Doesn’t this have an effect?

Filters are plane with parallell surfaces, which won't result in much aberration. But the light travels at an angle, so the effect isn't completely absent. Otoh, if it was much of an effect, we wouldn't be able too look out a window without seeing a rainbow. For fast scopes, it is more of a problem, of course. And it depends on how accurate you want to be.

I don't know if ca is affected by atmospheric conditions, in the sense that it may be more visible when seeing is excellent than when seeing is poor. Colour aberration itself does not depend on atmospheric conditions, of course.

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