Double stack Ca K / October 6 / comparing telecentric mount or not
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Double stack Ca K / October 6 / comparing telecentric mount or not
Hi,
Here are some old images taken in a test session comparing telecentric and not telecentric mounts for a double stack Ca K configuration.
It started with a FD image suffering from seeing effect due to the low elevation of the Sun :
http://astrosurf.com/viladrich/astro/so ... SI1600.jpg
The same with prominences (and a lot of glare ...) :
http://astrosurf.com/viladrich/astro/so ... 00-ddp.jpg
But my main objective was to compare my usual setup using Baader FFC as a Barlow lens, and the Airylab f/27 telecentric I use for Ha observation with my Celestron 8 EdgeHD. A double stack combination (Alluxa 0.37 nm + Alluxa 1 A Ca K filters) was used.
Measurements with the SHG Sol'Ex show there was indeed a small advantage to the telecentric combination :
- the bandpass of the combination at 10% peak transmission is 3.3 A in a telecentric beam,
- while it is in the range of 4.5 A with the FFC.
This is because the 0.37 nm filter needs to be tilted to be on Ca K.
In real life, the difference is very small.
With the FFC :
http://astrosurf.com/viladrich/astro/so ... AR3116.jpg
With the telecentric :
http://astrosurf.com/viladrich/astro/so ... entric.jpg
Christian
Here are some old images taken in a test session comparing telecentric and not telecentric mounts for a double stack Ca K configuration.
It started with a FD image suffering from seeing effect due to the low elevation of the Sun :
http://astrosurf.com/viladrich/astro/so ... SI1600.jpg
The same with prominences (and a lot of glare ...) :
http://astrosurf.com/viladrich/astro/so ... 00-ddp.jpg
But my main objective was to compare my usual setup using Baader FFC as a Barlow lens, and the Airylab f/27 telecentric I use for Ha observation with my Celestron 8 EdgeHD. A double stack combination (Alluxa 0.37 nm + Alluxa 1 A Ca K filters) was used.
Measurements with the SHG Sol'Ex show there was indeed a small advantage to the telecentric combination :
- the bandpass of the combination at 10% peak transmission is 3.3 A in a telecentric beam,
- while it is in the range of 4.5 A with the FFC.
This is because the 0.37 nm filter needs to be tilted to be on Ca K.
In real life, the difference is very small.
With the FFC :
http://astrosurf.com/viladrich/astro/so ... AR3116.jpg
With the telecentric :
http://astrosurf.com/viladrich/astro/so ... entric.jpg
Christian
Christian Viladrich
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Great work.
I do not look at the sky with the eyes of an astronomer, but of a person looking for the beauty of nature.
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Hi Christian: beautiful images. Interesting comparison: hard for me to see any differences unless I see the images side by side, but good to know. The 2.7x Airylab telecentric is very good quality.
Franco
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Excellent comparison Christian. It is close, but like Franco says good to know the Airylab telecentric is good, which mirrors my findings with CaK.
Also interesting about the measured bandpass of the filter in the FFC / Airlylab optical trains.
Also interesting about the measured bandpass of the filter in the FFC / Airlylab optical trains.
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Hi Christian,
thx for the comparison, to me the closeup image with the FFC is clearly crisper then the other one for whatever reasons.
thx for the comparison, to me the closeup image with the FFC is clearly crisper then the other one for whatever reasons.
Triband C9.25
H-a: Quark Chromosphere with BF mod
WL: Antlia 500nm/ 3nm, 393 nm/ 3nm
Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo)
Player One Apollo Max + Mars MII
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
H-a: Quark Chromosphere with BF mod
WL: Antlia 500nm/ 3nm, 393 nm/ 3nm
Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo)
Player One Apollo Max + Mars MII
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Gorgeous images and plenty for me to learn from,
Thanks
Nic
Thanks
Nic
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Thank you, Christian. Great images and nice comparison. If only I could get anywhere near this quality
Stu.
Stu.
H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
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More images at http://www.flickr.com/photos/solarcarbon60/
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
All of these are absolutely terrific but I do think I prefer the FFC image, no idea why but I just do
Alexandra
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Thanks to all !
Franco and Mark, indeed it was following your various comments and discussions that I finally decided to test the Airlab telecentric in Ca K :-)
Denis, yes the version with the FFC is a bit crisper. This may be why you prefer it Alexandra.
At this stage, there are three possible (and not exclusive ...) explanations :
- seeing was better when the image with the FFC was done,
- in Ca K, the optical quality of the FFC is a bit better than the optical quality of the telecentric,
- this is the "normal" results of a narrower bandpass. Indeed, in CaK when we narrow the bandpass, we sample a higher layer of the chromosphere. And because the magnetic lines are "divergent", the details become fuzzier and larger when observed with a smaller bandpass.
And now the Sun is too low for any more testing....
Christian
Franco and Mark, indeed it was following your various comments and discussions that I finally decided to test the Airlab telecentric in Ca K :-)
Denis, yes the version with the FFC is a bit crisper. This may be why you prefer it Alexandra.
At this stage, there are three possible (and not exclusive ...) explanations :
- seeing was better when the image with the FFC was done,
- in Ca K, the optical quality of the FFC is a bit better than the optical quality of the telecentric,
- this is the "normal" results of a narrower bandpass. Indeed, in CaK when we narrow the bandpass, we sample a higher layer of the chromosphere. And because the magnetic lines are "divergent", the details become fuzzier and larger when observed with a smaller bandpass.
And now the Sun is too low for any more testing....
Christian
Christian Viladrich
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http://planetary-astronomy.com/
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http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
That's a wonderful Calcium image Christian.
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Interesting the exposure / gain were the same for both images. Did you adjust spacing with the FFC to get the same image scale?
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Thanks Maurits :-)
Mark, yes and no. By chance, in just happens that I have the same image scale with both setup.
Mark, yes and no. By chance, in just happens that I have the same image scale with both setup.
Christian Viladrich
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Thanks Christian.christian viladrich wrote: ↑Wed Nov 23, 2022 8:58 pm Measurements with the SHG Sol'Ex show there was indeed a small advantage to the telecentric combination :
- the bandpass of the combination at 10% peak transmission is 3.3 A in a telecentric beam,
- while it is in the range of 4.5 A with the FFC.
This is because the 0.37 nm filter needs to be tilted to be on Ca K.
Any idea, even mathematically, how the filters would perform in a collimated beam?
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
Basically, there could be a "sweet spot", but some calculation is need to evaluate it.marktownley wrote: ↑Sat Nov 26, 2022 6:39 am
Thanks Christian.
Any idea, even mathematically, how the filters would perform in a collimated beam?
I am developping a little piece of software to answer this kind of question. Still, the project is a bit on hold since I am busy on other stuff.
Christian Viladrich
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Re: Double stack Ca K / October 6 / comparing telecentric mount or not
I look forward to it Christian!
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