Hey guys,
Was trying to take a stack of C27 and I see tails on stars. I'm not sure how I got that any thoughts? It looks like I'm going through warp speed almost lol.
Star Tails
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Buckrogers
- Posts: 78
- Joined: Wed May 13, 2020 2:22 pm
Star Tails
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Re: Star Tails
Hi
It almost looks like there are drops of water somewhere
It looks like your camera really is out of position, both in distance and in tilt.
The tilt is causing the uneven distribution: on the right very much warped, on the left less.
And the "warping" looks like your camera is too close to your telescope.
Did you change anything between this session and your previous session?
Menno
It almost looks like there are drops of water somewhere
It looks like your camera really is out of position, both in distance and in tilt.
The tilt is causing the uneven distribution: on the right very much warped, on the left less.
And the "warping" looks like your camera is too close to your telescope.
Did you change anything between this session and your previous session?
Menno
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Buckrogers
- Posts: 78
- Joined: Wed May 13, 2020 2:22 pm
Re: Star Tails
Hi,
Nope not really, maybe it's humidity? I only get this though through live stacking, if I put it in live mode, it looks good.
Nope not really, maybe it's humidity? I only get this though through live stacking, if I put it in live mode, it looks good.
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admin
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Re: Star Tails
Hi,
check that alignment is turned on ('Align Frames') in live stacking. It's also worth noting that by default live stacking applies a bit of a stretch to the image as viewed, so that can sometimes be enough to brighten the image up and see effects like this that are hard to spot in the individual frames.
cheers,
Robin
check that alignment is turned on ('Align Frames') in live stacking. It's also worth noting that by default live stacking applies a bit of a stretch to the image as viewed, so that can sometimes be enough to brighten the image up and see effects like this that are hard to spot in the individual frames.
cheers,
Robin
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Buckrogers
- Posts: 78
- Joined: Wed May 13, 2020 2:22 pm
Re: Star Tails
Thanks for the info guys, will look into this.
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Buckrogers
- Posts: 78
- Joined: Wed May 13, 2020 2:22 pm
Re: Star Tails
I'm still seeing these star tails and I confirmed aligned is check off in live stack. However, I know it's not in sharpcap. I used Nina and see the samething, so it's something with the camera or would it be my focul reducer maybe?
Re: Star Tails
Test without the focal reducer and that should indicate if it is the camera or the reducer. One problem might be that without the reducer you might not have enough stars in the FOV.
Dave
Dave
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Chuckwagon
- Posts: 30
- Joined: Thu Oct 17, 2019 1:29 am
Re: Star Tails
What equipment are you using? Telescope, Camera, Focal Reducer, Coma Corrector, etc.?
If you notice, all of the "tails" point toward the center, which looks like the symptom demonstrated here https://stargazerslounge.com/topic/3288 ... -distance/ for too close spacing on a coma corrector.
Chuck
If you notice, all of the "tails" point toward the center, which looks like the symptom demonstrated here https://stargazerslounge.com/topic/3288 ... -distance/ for too close spacing on a coma corrector.
Chuck
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Buckrogers
- Posts: 78
- Joined: Wed May 13, 2020 2:22 pm
Re: Star Tails
Hey guys,
Thank you for your replies. I tried last night without the .5 reducers and I saw no weird shapes and yes FOV is reduced so this is gonna make taking livestacks difficult going forward without one.
Nexstar 4se
ASI224
.5 reducer
What is a coma corrector?
Thank you for your replies. I tried last night without the .5 reducers and I saw no weird shapes and yes FOV is reduced so this is gonna make taking livestacks difficult going forward without one.
Nexstar 4se
ASI224
.5 reducer
What is a coma corrector?
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Chuckwagon
- Posts: 30
- Joined: Thu Oct 17, 2019 1:29 am
Re: Star Tails
If you were using a Newt it would have the optical aberration known as Coma. It makes stars have little tails, similar to what you see. The Coma corrector helps tame that. But you are using a Maksutov-Cassegrain, so I would think what you are seeing is field curvature, making things out of focus. (The design also has some coma too, so that may be contributing as well.)
One problem with reducers is that they tend to make the most unappealing area of your scope's performance more noticeable, namely the edge of the field. For most scopes, the middle of the field tends to be the area where things work the best. But as you get to the edge of the field, issues like coma can be more apparent. Often we don't notice these issues because it's off of the edge of the sensor and we are only looking at the "good" part of the field. But when we add a reducer we see more of the field and the poorer performing areas can stand out. Some reducers are designed to deal with some of the optical issues that can be present. For example, you might have a reducer that also flattens the field, which are common with SCT scopes. But in your case I would suspect you are using a simple reducer, and are seeing the field curvature of the scope as a result.
Who makes the .5 reducer you are using? How much space was between the reducer and your camera sensor? The spacing is critical. For example, if the reducer is designed for an F10 SCT and was a .63 reducer you would typically need 105mm of spacing between it and the sensor. To little and you don't get enough reduction, too much space and you get too much reduction. Some reducers are more forgiving of spacing errors, and will work acceptably with slight variations in spacing. Some are quite picky. So knowing which reducer you are using and what spacing it was designed for will help. If you have far too much space, you will get more reduction than planned and the reducer may be making problems worse, so a bit of a double hit.
It would be best to know the optimal spacing designed for your reducer. But if you can't find that number, you may be able to get better performance by testing various spacings. Try 55mm, since that seems to be a common spacing spec for many devices. Then experiment with shorter or longer spacing.
Keep in mind that a basic reducer isn't going to improve performance, just squeeze it all into a smaller circle of light. So the best part of the image will probably always be the middle, and you may always see poorly shaped stars along the edges.
Chuck
One problem with reducers is that they tend to make the most unappealing area of your scope's performance more noticeable, namely the edge of the field. For most scopes, the middle of the field tends to be the area where things work the best. But as you get to the edge of the field, issues like coma can be more apparent. Often we don't notice these issues because it's off of the edge of the sensor and we are only looking at the "good" part of the field. But when we add a reducer we see more of the field and the poorer performing areas can stand out. Some reducers are designed to deal with some of the optical issues that can be present. For example, you might have a reducer that also flattens the field, which are common with SCT scopes. But in your case I would suspect you are using a simple reducer, and are seeing the field curvature of the scope as a result.
Who makes the .5 reducer you are using? How much space was between the reducer and your camera sensor? The spacing is critical. For example, if the reducer is designed for an F10 SCT and was a .63 reducer you would typically need 105mm of spacing between it and the sensor. To little and you don't get enough reduction, too much space and you get too much reduction. Some reducers are more forgiving of spacing errors, and will work acceptably with slight variations in spacing. Some are quite picky. So knowing which reducer you are using and what spacing it was designed for will help. If you have far too much space, you will get more reduction than planned and the reducer may be making problems worse, so a bit of a double hit.
It would be best to know the optimal spacing designed for your reducer. But if you can't find that number, you may be able to get better performance by testing various spacings. Try 55mm, since that seems to be a common spacing spec for many devices. Then experiment with shorter or longer spacing.
Keep in mind that a basic reducer isn't going to improve performance, just squeeze it all into a smaller circle of light. So the best part of the image will probably always be the middle, and you may always see poorly shaped stars along the edges.
Chuck