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6 votes

Is it possible to observe strong gravitational lensing with amateur telescopes?

If you have a good camera, a steady hand, good conditions and a lot of patience, you might. The Sunburst Arc, at a magnitude of around 17, has been observed with a 132mm refractor by Ian Woodward at ...
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  • 301
6 votes
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Why not building a swarm of space-telescopes?

There are a mixture of factors here. Firstly the telescopes used to photograph the black hole were radio telescopes. Radio-waves are at a low enough frequency that we can process them directly as ...
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1 vote
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Where can I find data on SDSS filter profiles?

The Filter Profile Service of the Spanish Virtual Observatory has the filter profiles for Sloan along with many other filter systems, telescopes and spacecraft. The link above for Sloan will take you ...
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1 vote

Can the Celestron Powerseeker 127EQ observe the moon during day time?

There should be absolutely no problem at all seeing the bright, sun-illuminated part of the Moon during the day at 1000 mm / 20 mm = 50x through your telescope. The part that's not illuminated by the ...
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2 votes

Focus Problems when using Barlow 3x or 4mm lens

Truth be told, there are a few factors: The 4mm eyepiece that comes with the Powerseeker just isn't very good, unfortunately. Neither is the Barlow that comes with the Powerseeker. This is a serious ...
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  • 201
1 vote

Why are photos from telescope stretched at their edges?

The primary challenges of telescope design are keeping good focus1 across a locally flat2 focal plane, meeting aperture and field of view targets while using the fewest optical elements. Now most ...
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2 votes

Focus Problems when using Barlow 3x or 4mm lens

You will experience this issue if the barlow is not designed for the particular telescope you are using. the manufacturer mentioned the maximum effective magnification as 300x which is a bit ...
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7 votes
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Why are photos from telescope stretched at their edges?

It's a general property of optics. In what way an image is distorted depends on the exact optical setup and will need careful calibration. Usually the best imaging quality is found in the center of an ...
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11 votes
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Why aren't reflector telescopes built with an offset secondary mirror?

To supplement @CarlWitthoft's insightful answer I'll mention some links related to off-axis operation: answers to Why aren't secondary mirrors offset to get rid of diffraction spikes due to the ...
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14 votes

Why aren't reflector telescopes built with an offset secondary mirror?

If your secondary is off-axis, then your primary has to be off-axis as well. That is, the primary will have to be a parabolic section rather than a pure spherical section. Not only is that a ton more ...
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