First timer, focusing (?) problem
Re: First timer, focusing (?) problem
Much thanks chongo,
I did, in fact, play with the histogram (for hours)...I'm going to try your suggestion of a longer exposure, etc.. So, you don't think my "halo" is a photographic artifact?
Joe
I did, in fact, play with the histogram (for hours)...I'm going to try your suggestion of a longer exposure, etc.. So, you don't think my "halo" is a photographic artifact?
Joe
Re: First timer, focusing (?) problem
Joe
M31 is a huge object. The following shows what can be expected to be 'seen' by various telescope/camera combinations. The diagram from the centre outwards:
The image was generated via the Astronomy Tools Field Of View Calculator https://astronomy.tools/calculators/field_of_view/
The SCT with the CCTV camera will only be able to capture the core of Andromeda. Adding a 0.5x reducer will not really improve things.
I would consider M27 & M15 more realistic targets for the SCT + CCTV + 0.5x reducer combination.
Using the Astronomy Tools FOV Calculator during observation session planning to identify suitable objects for various equipment combinations can save lots of wasted time and disappointment.
From my previous post in this thread
M31 is a huge object. The following shows what can be expected to be 'seen' by various telescope/camera combinations. The diagram from the centre outwards:
- an SCT 8" with focal length 2032 and CCTV camera with a 720x576 capture area
- refractor 81mm with focal length 625mm with CCTV camera
- refractor 66mm with focal length 400mm with the CCTV camera
- refractor 66mm with focal length 400mm and ~$1000 CMOS camera with a ~4500x3500 capture area
The image was generated via the Astronomy Tools Field Of View Calculator https://astronomy.tools/calculators/field_of_view/
The SCT with the CCTV camera will only be able to capture the core of Andromeda. Adding a 0.5x reducer will not really improve things.
I would consider M27 & M15 more realistic targets for the SCT + CCTV + 0.5x reducer combination.
Using the Astronomy Tools FOV Calculator during observation session planning to identify suitable objects for various equipment combinations can save lots of wasted time and disappointment.
From my previous post in this thread
Daveto achieve results will require hard work, discipline, attention to detail and patience
Re: First timer, focusing (?) problem
After years of trying to get to the point where I actually captured a deep sky image, I finally managed to capture Orion. I realize this image has a lot to be desired and I'm hoping to get some feedback as to how to proceed (i.e., better focus, etc., etc.). But, like your first child, this image means a lot to me. All suggestions will be greatly appreciated.
FYI: This was captured under an almost full moon
Thank you all
Joe
FYI: This was captured under an almost full moon
Thank you all
Joe
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Re: First timer, focusing (?) problem
Joe
My early M42 attempts looked like this, once I obtained a Bahtinov Mask things improved rapidly - best £20 I ever spent on this hobby.
Dave
To improve focus, buy a Bahtinov Mask and have a look at viewtopic.php?f=18&t=1151. Focus on a star near the object you want to image, put the mask over the end of the scope, zoom in to at least 100%, enable Display Histogram Stretch then adjust focus until you achieve the pattern in the link above. Note - I would suggest you don't use the Bahtinov focusing routine in SharpCap, as that will just introduce complexity you do not need at the moment.hoping to get some feedback as to how to proceed (i.e., better focus,
My early M42 attempts looked like this, once I obtained a Bahtinov Mask things improved rapidly - best £20 I ever spent on this hobby.
Dave
Re: First timer, focusing (?) problem
Thank you Dave,
Not clear on one thing. You say to zoom in 100% and to stretch the histogram then adjust the focus with the mask, but then you say do not focus in SharpCap. I only have a histogram in SharpCap…can you clarify.
Not clear on one thing. You say to zoom in 100% and to stretch the histogram then adjust the focus with the mask, but then you say do not focus in SharpCap. I only have a histogram in SharpCap…can you clarify.
Re: First timer, focusing (?) problem
Joe
In the attached image,
1) to set the Zoom to at least 100%
2) to turn on the Display Histogram Stretch
Clarification: In Sharpcap, under Tools > Focus Assistant you will find an entry for Bahtinov Mask. I am suggesting you don't use that as it will introduce complexity that I feel you do not need at this stage.
Once you have done 1) & 2) then just use the focuser on the telescope to achieve the pattern. You will need to carry out all the steps with the camera attached to the scope. Choose a medium brightness star rather than a very bright one.
It takes practise and may take a few minutes to achieve good focus. Without good focus the whole imaging session is just a waste of time.
It might be worth posting back a screenshot showing your focus with the mask.
Dave
In the attached image,
1) to set the Zoom to at least 100%
2) to turn on the Display Histogram Stretch
Clarification: In Sharpcap, under Tools > Focus Assistant you will find an entry for Bahtinov Mask. I am suggesting you don't use that as it will introduce complexity that I feel you do not need at this stage.
Once you have done 1) & 2) then just use the focuser on the telescope to achieve the pattern. You will need to carry out all the steps with the camera attached to the scope. Choose a medium brightness star rather than a very bright one.
It takes practise and may take a few minutes to achieve good focus. Without good focus the whole imaging session is just a waste of time.
It might be worth posting back a screenshot showing your focus with the mask.
Dave
Re: First timer, focusing (?) problem
Dave
Forgot to ask this. You say turn on the display histogram to apply stretch. Why do this? Do I need to manipulate the histogram? Looking at the histogram in your last post, the curve is on the left side...not sure what the histogram is showing. I guess what I'm saying is what should I be doing with the histogram and why. Thank you in advance.
Joe
Forgot to ask this. You say turn on the display histogram to apply stretch. Why do this? Do I need to manipulate the histogram? Looking at the histogram in your last post, the curve is on the left side...not sure what the histogram is showing. I guess what I'm saying is what should I be doing with the histogram and why. Thank you in advance.
Joe
Re: First timer, focusing (?) problem
Dave,
One more question. Since I'm interested in post-processing of deepsky images, is there an advantage to using capture vs lifestack? I guess I'm not clear what the difference is other than Livestack showing a live stacked image. If you have a minute, I'd love to hear what you have to say.
Thanks in advance,
Joe
One more question. Since I'm interested in post-processing of deepsky images, is there an advantage to using capture vs lifestack? I guess I'm not clear what the difference is other than Livestack showing a live stacked image. If you have a minute, I'd love to hear what you have to say.
Thanks in advance,
Joe
Re: First timer, focusing (?) problem
Joe
The Display Histogram Stretch is useful for seeing if faint targets are centred - a better option than increasing the exposure to 60s or 120s and waiting around. See the 2 images below, which are a capture in progress of M13 using 30s exposures. In the first one the Display Histogram is reset (yellow line is straight) and there is only 1 star visible. We don't even know if we are on target. In the second one the Display Histogram Stretch is enabled (yellow line is curved). The cluster is clearly visible. This action only affects the display, the data being captured remains unchanged. The alternative to using the stretch would be to increase to exposure to 60s, 90s or even 120s and wait around. This was because the camera in use was an Atik 314E CCD which only has 1 control - exposure.
Hope this clarifies things. Sometimes you just have to try things to progress.
Dave
No - just click the button with the lightening symbol. This will brighten any objects in the display.Do I need to manipulate the histogram
Brightening the objects in display makes the diffraction pattern (the X plus the line) easier to see. It also makes the 3 parallel lines visible - if these are not visible, then good focus has not been achieved. The alternate way to brighten is to increase the exposure (and/or gain). The exposure I was using was 1s (1000ms) if you look at the capture screen. To achieve the same effect as the Display Histogram Stretch might mean the exposure has to be increased to 15s. Trying to adjust focus and then wait 15s to see the result is going to mean getting good focus might take many minutes.apply stretch. Why do this
The Display Histogram Stretch is useful for seeing if faint targets are centred - a better option than increasing the exposure to 60s or 120s and waiting around. See the 2 images below, which are a capture in progress of M13 using 30s exposures. In the first one the Display Histogram is reset (yellow line is straight) and there is only 1 star visible. We don't even know if we are on target. In the second one the Display Histogram Stretch is enabled (yellow line is curved). The cluster is clearly visible. This action only affects the display, the data being captured remains unchanged. The alternative to using the stretch would be to increase to exposure to 60s, 90s or even 120s and wait around. This was because the camera in use was an Atik 314E CCD which only has 1 control - exposure.
Hope this clarifies things. Sometimes you just have to try things to progress.
Dave