Question about back filters (Daystar, Solar spectrum)
- Geremia Forino
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Question about back filters (Daystar, Solar spectrum)
maybe it will be a stupid question, but, since the filter concept are similar, why Daystar employs so short focal points while Solar Spectrum has a long focal train ?
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- Bob Yoesle
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Re: Question about back filters (Daystar, Solar spectrum)
The Baader telecentric lenses are true telecentric designs which will have optimum performance with an objective with a 800 ml FL. They will perform well with other FL objectives if they are not too short a FL.
The DayStar filters do not have custom telecentric units designed for them, and are usually meant to be used with "telecentric barlows." These are not as well optimized and will suffer more from band-pass broadening and sweet spots, but do have the "shorter focal points." See Christian Valadrich's excellent analysis here: http://www.astrosurf.com/viladrich/astr ... lar/FP.htm
You could of course use a DayStar filter with a Baader telecentric lens.
The DayStar filters do not have custom telecentric units designed for them, and are usually meant to be used with "telecentric barlows." These are not as well optimized and will suffer more from band-pass broadening and sweet spots, but do have the "shorter focal points." See Christian Valadrich's excellent analysis here: http://www.astrosurf.com/viladrich/astr ... lar/FP.htm
You could of course use a DayStar filter with a Baader telecentric lens.
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- Geremia Forino
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Re: Question about back filters (Daystar, Solar spectrum)
Bob thanks for your clarification.
my question born from wanting to achieve f / 30 on my Tec140 f/7 scope, I tried to push my powermate 4X (f/28), as in the diagram of Televue It shows that, at a distance of 100mm, you get a 4.4X (f/30.8).
Now I have another question, according to the diagram of Televue, 100mm should be measured to the etalon or the camera chip ?
my question born from wanting to achieve f / 30 on my Tec140 f/7 scope, I tried to push my powermate 4X (f/28), as in the diagram of Televue It shows that, at a distance of 100mm, you get a 4.4X (f/30.8).
Now I have another question, according to the diagram of Televue, 100mm should be measured to the etalon or the camera chip ?
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- Valery
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Re: Question about back filters (Daystar, Solar spectrum)
To the camera chip. The distance will include the height of the filter (with it's body). So, the filter will work in a F/31 cone.Geremia Forino wrote:Bob thanks for your clarification.
my question born from wanting to achieve f / 30 on my Tec140 f/7 scope, I tried to push my powermate 4X (f/28), as in the diagram of Televue It shows that, at a distance of 100mm, you get a 4.4X (f/30.8).
Now I have another question, according to the diagram of Televue, 100mm should be measured to the etalon or the camera chip ?
Valery
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- Geremia Forino
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Re: Question about back filters (Daystar, Solar spectrum)
Valery,
just to clarify, if the chip is at 100mm distance from barlow (4.4X (f/30.8), the etalon, being first, will be at f/29 considering graph Televue
just to clarify, if the chip is at 100mm distance from barlow (4.4X (f/30.8), the etalon, being first, will be at f/29 considering graph Televue
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Re: Question about back filters (Daystar, Solar spectrum)
No no no! It will work at F/31 !Geremia Forino wrote:Valery,
just to clarify, if the chip is at 100mm distance from barlow (4.4X (f/30.8), the etalon, being first, will be at f/29 considering graph Televue
Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
- Geremia Forino
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Re: Question about back filters (Daystar, Solar spectrum)
I'm glad to hear this, but we are talking about a f/7 scope.
I'm confused , if from 0 to 100mm the f/. increases exponentially, how can an optical, placed before the other having a major factor ?
we are talking about, Barlow > DaystarQuantum > Chip see image below, if I'm wrong, sorry, maybe I omit some details which I am not aware.
I'm confused , if from 0 to 100mm the f/. increases exponentially, how can an optical, placed before the other having a major factor ?
we are talking about, Barlow > DaystarQuantum > Chip see image below, if I'm wrong, sorry, maybe I omit some details which I am not aware.
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Re: Question about back filters (Daystar, Solar spectrum)
You nail it. Exactly.Geremia Forino wrote:
we are talking about, Barlow > DaystarQuantum > Chip
Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
- Geremia Forino
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