[HP 56948]

Is the focus on the K1 live screen always "true" (absolutely in focus)

Explanation: Took 2 pictures the other night of Venus through one of my telescopes...on an Ioptron Eq45 equatorial mount.
Scope was 7.1 inch 2750 mm.
I focused the image on the live view. took the 2 shots. Took the memory card inside to computer. Both shots looked slightly out of focus. Is it the K1 or something else? (I can find the something else )

[Steve.Ledger]

Did you use 'focus peaking'?

[stevebrot]

It is the image from the sensor and is the gold standard for focus accuracy. Magnification to 1:1 seals it. Atmospheric fluctuation after focus was attained? Camera/lens motion?


Steve

[seventhdr]

Did you zoom in to the maximum amount to see critical focus?

What was the atmosphere like when you took the shots? There is a LOT of distance between your camera and Venus!

How windy was it? How stable was your platform?

Regards

Chris

[pschlute]

Did you use electronic shutter ? That will eliminate first curtain shutter vibration. What shutter speed were you using?

[Adam]

Live view shows you the actual focus, yes. But for astrophotography, not only is the focus tolerance super low, but additional factors such as optical quality, tripod stability/tracking accuracy, and shutter speed can play a big role in the final outcome.

[TedH42]

Is the focus on the K1 live screen always "true" (absolutely in focus)

Explanation: Took 2 pictures the other night of Venus through one of my telescopes...on an Ioptron Eq45 equatorial mount.
Scope was 7.1 inch 2750 mm.
I focused the image on the live view. took the 2 shots. Took the memory card inside to computer. Both shots looked slightly out of focus. Is it the K1 or something else? (I can find the something else )

Live View focusing for astrophotography is NOT adequate, even using 10X magnification. And especially with the high magnification of your 2750 mm scope. You should be using a Bahtinov mask for manual focusing, or software-assisted motorized focusing at that magnification. The latter will require significant research and equipment. The Bahtinov mask is quite simple in use, but requires precise manual tweaking using your focuser, which should be able to lock without moving the focus point. Use of the Bahtinov mask can be easily researched on the web. Try the CloudyNights site for a large astro community that is very helpful.

Oh, the Bahtinov mask must be used only on stars (point light sources), not planets or other extended objects. But as they are all at infinity, a nearby, bright star will do. You may have to repoint your scope to get a star bright enough to be effective. Then move back to your subject.

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Last edited by TedH42; 01-30-2017 at 11:09 AM.

[stevebrot]

Live View focusing for astrophotography is NOT adequate, even using 10X magnification. And especially with the high magnification of your 2750 mm scope. You should be using a Bahtinov mask for manual focusing, or software-assisted motorized focusing at that magnification. The latter will require significant research and equipment. The Bahtinov mask is quite simple in use, but requires precise manual tweaking using your focuser, which should be able to lock without moving the focus point. Use of the Bahtinov mask can be easily researched on the web. Try the CloudyNights site for a large astro community that is very helpful.

Oh, the Bahtinov mask must be used only on stars (point light sources), not planets or other extended objects. But as they are all at infinity, a nearby, bright star will do. You may have to repoint your scope to get a star bright enough to be effective. Then move back to your subject.

Thanks for this very useful suggestion, though the fact remains that live view focus at 1:1 (direct pixel mapping to the rear LCD) is a true representation of the state of focus for capture. Assuming adequate focus lock, secure support, accurate/precise tracking, and stable atmosphere, live view should be WYSIWYG. For sure, more accurate focus (so-called sub-pixel focus) may be attained with a Bahtinov mask when coupled with appropriate focus mechanism, but such cannot overcome focus drift, atmospheric instability or vibration.

FWIW, focus failure on Venus (~ 0.5 degrees of arc) using live view is somewhat unexpected, even without a mask.


Steve

[stevebrot]

Both shots looked slightly out of focus. Is it the K1 or something else? (I can find the something else )

In my original response I forgot to ask the usual question, "Did you remember to turn the SR function off". Leaving SR "on" can result in motion artifact when working with a firmly fixed camera. My bad


Steve

[TedH42]

Thanks for this very useful suggestion, though the fact remains that live view focus at 1:1 (direct pixel mapping to the rear LCD) is a true representation of the state of focus for capture. Assuming adequate focus lock, secure support, accurate/precise tracking, and stable atmosphere, live view should be WYSIWYG. For sure, more accurate focus (so-called sub-pixel focus) may be attained with a Bahtinov mask when coupled with appropriate focus mechanism, but such cannot overcome focus drift, atmospheric instability or vibration.

FWIW, focus failure on Venus (~ 0.5 degrees of arc) using live view is somewhat unexpected, even without a mask.


Steve

In my experience, the Bahtinov mask beats live view 1:1 for high-magnification imaging. I find the live view to be a good starting point. Steady atmosphere is still needed, focus drift must be accounted for (redo focus, but the automated way is better (I don't have it )), vibration is inadequate equipment ,etc.

At the end of January, Venus only gets up to 30.4 arc-seconds in diameter (Sky & Telescope). This is rather high magnification territory. The moon is ~ 0.5 degrees in diameter.

I suspect that the OP was imaging Venus at night, as Venus is about 3 hours behind the sun in January. If so, a problem of the extreme contrast between the sun-illuminated very bright clouds of Venus and the black sky surrounding is "irradiation", a bleeding of the brightness into the dark. Always a problem for our eyes, it is also present in optical systems, and the sharp line between light and dark is not adequately represented in the final image. Many viewers and imagers of Venus prefer the daytime for their operations, as the much brighter daytime sky reduces the extreme contrast and provides for much better, sharper viewing and imaging. The contrast between the planet and the blackness is much greater for Venus than any astronomical object (leaving out the Sun). Could be a problem here.

[stevebrot]

At the end of January, Venus only gets up to 30.4 arc-seconds in diameter (Sky & Telescope). This is rather high magnification territory. The moon is ~ 0.5 degrees in diameter.

Thanks for the correction.

I suspect that the OP was imaging Venus at night, as Venus is about 3 hours behind the sun in January. If so, a problem of the extreme contrast between the sun-illuminated very bright clouds of Venus and the black sky surrounding is "irradiation", a bleeding of the brightness into the dark. Always a problem for our eyes, it is also present in optical systems, and the sharp line between light and dark is not adequately represented in the final image. Many viewers and imagers of Venus prefer the daytime for their operations, as the much brighter daytime sky reduces the extreme contrast and provides for much better, sharper viewing and imaging. The contrast between the planet and the blackness is much greater for Venus than any astronomical object (leaving out the Sun). Could be a problem here.

I wondered about that as well.


Steve

[TedH42]

Explanation: Took 2 pictures the other night of Venus through one of my telescopes...on an Ioptron Eq45 equatorial mount.
Scope was 7.1 inch 2750 mm.

Just more ideas here. Your scope seems to be a Mak-Cass, judging by the specs. They are notoriously slow in cooling down. And as Venus was only ~3 hours behind the sunset, was there enough time for the scope to cool down to stability before your shots? And after sunset, the atmosphere takes its own sweet time cooling down to some semblance of stability. You might have been squeezed between slow cool-down and image deterioration as Venus descended into more and more atmosphere with bad seeing and/or poor transparency.

Oh, have you had this problem with other DSLRs?

[HP 56948]

Did you use 'focus peaking'?

I use manual. Should I use focus peaking? Thanks!

---------- Post added 01-31-17 at 03:39 PM ----------

Did you zoom in to the maximum amount to see critical focus?

What was the atmosphere like when you took the shots? There is a LOT of distance between your camera and Venus!

How windy was it? How stable was your platform?

Regards

Chris

Mount is rock-solid. Embedded in concrete. Thanks!

---------- Post added 01-31-17 at 03:42 PM ----------

Just more ideas here. Your scope seems to be a Mak-Cass, judging by the specs. They are notoriously slow in cooling down. And as Venus was only ~3 hours behind the sunset, was there enough time for the scope to cool down to stability before your shots? And after sunset, the atmosphere takes its own sweet time cooling down to some semblance of stability. You might have been squeezed between slow cool-down and image deterioration as Venus descended into more and more atmosphere with bad seeing and/or poor transparency.

Oh, have you had this problem with other DSLRs?

Scope and mount is outside all the time. (homebuilt 10 foot observatory. Thanks!

---------- Post added 01-31-17 at 03:47 PM ----------

In my experience, the Bahtinov mask beats live view 1:1 for high-magnification imaging. I find the live view to be a good starting point. Steady atmosphere is still needed, focus drift must be accounted for (redo focus, but the automated way is better (I don't have it )), vibration is inadequate equipment ,etc.

At the end of January, Venus only gets up to 30.4 arc-seconds in diameter (Sky & Telescope). This is rather high magnification territory. The moon is ~ 0.5 degrees in diameter.

I suspect that the OP was imaging Venus at night, as Venus is about 3 hours behind the sun in January. If so, a problem of the extreme contrast between the sun-illuminated very bright clouds of Venus and the black sky surrounding is "irradiation", a bleeding of the brightness into the dark. Always a problem for our eyes, it is also present in optical systems, and the sharp line between light and dark is not adequately represented in the final image. Many viewers and imagers of Venus prefer the daytime for their operations, as the much brighter daytime sky reduces the extreme contrast and provides for much better, sharper viewing and imaging. The contrast between the planet and the blackness is much greater for Venus than any astronomical object (leaving out the Sun). Could be a problem here.

You're absolutely correct. I was doing several things wrong. Ugh..Tarzan learn fast.

---------- Post added 01-31-17 at 03:51 PM ----------

In my original response I forgot to ask the usual question, "Did you remember to turn the SR function off". Leaving SR "on" can result in motion artifact when working with a firmly fixed camera. My bad


Steve

Steve, I was doing just about every thing wrong. Are you sure the Function SR doesn't stand for "Somewhat Retarded"

[WPRESTO]

I'll add my support to several observations already made. Long lens astrophotography is extremely demanding for 1) focus accuracy; 2) motion by the object during exposure; 3) camera motion; and 4) atmospheric distortion caused by high altitude winds that is not apparent to your eye. You are using over 2700mm - - what would be required to get a perfectly sharp image in full daylight, no blur induced by camera motion? General procedure for astrophotos of objects not as bright as the Moon that I learned in the film era: put something black an inch or so in front of the lens; open the shutter with a cable release, let go of the cable release, wait several seconds, pull away the obstruction and count the seconds of your exposure; put the obstruction back in front of the lens; pick up the cable release and close the shutter. Your mount is anchored in concrete. Sometime look through your scope visually at some stars or Venus and give the scope the tiniest tap with your finger,

[HP 56948]

I'll add my support to several observations already made. Long lens astrophotography is extremely demanding for 1) focus accuracy; 2) motion by the object during exposure; 3) camera motion; and 4) atmospheric distortion caused by high altitude winds that is not apparent to your eye. You are using over 2700mm - - what would be required to get a perfectly sharp image in full daylight, no blur induced by camera motion? General procedure for astrophotos of objects not as bright as the Moon that I learned in the film era: put something black an inch or so in front of the lens; open the shutter with a cable release, let go of the cable release, wait several seconds, pull away the obstruction and count the seconds of your exposure; put the obstruction back in front of the lens; pick up the cable release and close the shutter. Your mount is anchored in concrete. Sometime look through your scope visually at some stars or Venus and give the scope the tiniest tap with your finger,

I finally got it right. I was doing several things wrong but after the dismal results I was determined to learn what I was doing wrong.
Thank you so much for your wisdom!