A big solar newton for ultra narrowband imaging, possible?
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A big solar newton for ultra narrowband imaging, possible?
The here subject cover the observing with aluminized mirror, thus having high flux suitable for Ha / Cak imaging.
Warning: Solar observation is dangerous, we know it.
There are solutions for reducing the danger: front filter, Herschell prism, de-aluminized mirror, etc. But solar observation still remains dangerous.
The here subject copes with the use of the full aperture of a telescope, partly without pre-filtering. We are clearly in a zone, where we should know what we are doing and where the dangers are. Dangers are direct (ie direct viewing), indirect (ie reflection), affecting equipment (ie reflection aside, heat-up / burning parts), etc.
If you don't know what you are doing, if you are not mastering your working process, strictly refrain for any solar scope action.
I can not take any responsibility for any action you would do in solar observation, especially with modification.
Certainly never put an eye in a moded scope
Considering again the dangers, expected and unexpected, I'll take over word by word the comments posted along my previous post:
"anyone doing this should take all necessary precautions."
"I cannot stress enough the dangers "
"Use with caution and respect!"
--------------------------
In the here trial, a 300mm aperture scope, with coating, is used.
The amount of solar power collected by the mirror is estimated to 90w. As much as a quite powerful light bulb.
The scope is of newton type, thus a big part of the heat is concentrated on a circle of about 50mm in diameter at the location of the secondary mirror, then further concentrated to the focus and forth.
We all know that there big front ERF filters are difficult to make and also very expensive. A 300mm front ERF doesn't cost a few thousand of Eur, but several thousand of Eur.
So the idea of a smaller ERF set into the system.
Here the ERF would be as big as the secondary, thus about 50mm in diameter, located in front of the secondary.
I started with various trials, measuring temperatures, etc.
You can figure what will come into these fingers...
... A blue interference filter suffering the full flux
The filter resists.
I tried also to partly target the filter, so to have one side "cold" and the other side "hot".
The filter still resists.
The wished color (blue here) passes through the filter.
The remaining flux is reflected back.
This is one of the indirect danger of the application. In this picture the flux is reflected back toward the body of the telescope, leading to a local heating. I experienced also a returning flux against the carbon truss; they started then to generate smoke.
The test filter was a 1.25" model.
Then I went for the final version, a 50mm filter.
The setup is quite artisanal. We are in the test phase.
I tried with a blue "ERF" and a red "ERF" aiming for CaK and Ha
In my area, a small city suburb, surrounded by streets and houses, I could get some granulation.
Looks "interesting" at this stage. Here in blue.
So, I went out of the city for further trials.
I could get better granulation pictures, in the red domain. In the blue, the pictures were awful.
The next step was a trial in Ha.
Here also, I could get some results, but not easily. Only when the seeing was stable. And only with a focal reducer.
Very full of hope, I went to the St Veran Observatory site, expecting for further progress.
The first results were promising. Christian detected filigrees on my first image in KLine.
But the picture quality was poor.
Finally, getting further progress was difficult.
We checked the temperature in the system with an IR camera.
Certainly, we don't know the emissivity of the filter surface, nor from the surrounding material, but it looks that hot parts to have are about 10°C higher than the surrounding.
Image courtesy Frederic Jabet.
Even the focusser side is getting warmer, sign of energy passing through the filter and heating the setup the system behind
Image courtesy Frederic Jabet.
In Halpha, the results were not better.
Now, I remember that I could get the former Halpha "reasonable" results only when clouds were passing. The clouds were leading to temporary cool down of the equipment.
An other fellow made a similar test in St Veran, with a different optic and he also had trouble getting high resolution imaging.
After one additional trial, I came to the conclusion of instrumental turbulence due to the local heat of some telescope parts, despite the system was fully open (made out of a truss system).
So, I went for removing the primary mirror coating.
Here, the first pics in bad seeing and bad wind conditions, in KLine with no coating on the primary.
I had later a chance to observe with the de-coated mirror in better seeing conditions. Here under 450nm
The conclusion is clear.
Bye Bye cheap ultra narrow band imaging.
CS
Alex
2019-Aug-31
Warning: Solar observation is dangerous, we know it.
There are solutions for reducing the danger: front filter, Herschell prism, de-aluminized mirror, etc. But solar observation still remains dangerous.
The here subject copes with the use of the full aperture of a telescope, partly without pre-filtering. We are clearly in a zone, where we should know what we are doing and where the dangers are. Dangers are direct (ie direct viewing), indirect (ie reflection), affecting equipment (ie reflection aside, heat-up / burning parts), etc.
If you don't know what you are doing, if you are not mastering your working process, strictly refrain for any solar scope action.
I can not take any responsibility for any action you would do in solar observation, especially with modification.
Certainly never put an eye in a moded scope
Considering again the dangers, expected and unexpected, I'll take over word by word the comments posted along my previous post:
"anyone doing this should take all necessary precautions."
"I cannot stress enough the dangers "
"Use with caution and respect!"
--------------------------
In the here trial, a 300mm aperture scope, with coating, is used.
The amount of solar power collected by the mirror is estimated to 90w. As much as a quite powerful light bulb.
The scope is of newton type, thus a big part of the heat is concentrated on a circle of about 50mm in diameter at the location of the secondary mirror, then further concentrated to the focus and forth.
We all know that there big front ERF filters are difficult to make and also very expensive. A 300mm front ERF doesn't cost a few thousand of Eur, but several thousand of Eur.
So the idea of a smaller ERF set into the system.
Here the ERF would be as big as the secondary, thus about 50mm in diameter, located in front of the secondary.
I started with various trials, measuring temperatures, etc.
You can figure what will come into these fingers...
... A blue interference filter suffering the full flux
The filter resists.
I tried also to partly target the filter, so to have one side "cold" and the other side "hot".
The filter still resists.
The wished color (blue here) passes through the filter.
The remaining flux is reflected back.
This is one of the indirect danger of the application. In this picture the flux is reflected back toward the body of the telescope, leading to a local heating. I experienced also a returning flux against the carbon truss; they started then to generate smoke.
The test filter was a 1.25" model.
Then I went for the final version, a 50mm filter.
The setup is quite artisanal. We are in the test phase.
I tried with a blue "ERF" and a red "ERF" aiming for CaK and Ha
In my area, a small city suburb, surrounded by streets and houses, I could get some granulation.
Looks "interesting" at this stage. Here in blue.
So, I went out of the city for further trials.
I could get better granulation pictures, in the red domain. In the blue, the pictures were awful.
The next step was a trial in Ha.
Here also, I could get some results, but not easily. Only when the seeing was stable. And only with a focal reducer.
Very full of hope, I went to the St Veran Observatory site, expecting for further progress.
The first results were promising. Christian detected filigrees on my first image in KLine.
But the picture quality was poor.
Finally, getting further progress was difficult.
We checked the temperature in the system with an IR camera.
Certainly, we don't know the emissivity of the filter surface, nor from the surrounding material, but it looks that hot parts to have are about 10°C higher than the surrounding.
Image courtesy Frederic Jabet.
Even the focusser side is getting warmer, sign of energy passing through the filter and heating the setup the system behind
Image courtesy Frederic Jabet.
In Halpha, the results were not better.
Now, I remember that I could get the former Halpha "reasonable" results only when clouds were passing. The clouds were leading to temporary cool down of the equipment.
An other fellow made a similar test in St Veran, with a different optic and he also had trouble getting high resolution imaging.
After one additional trial, I came to the conclusion of instrumental turbulence due to the local heat of some telescope parts, despite the system was fully open (made out of a truss system).
So, I went for removing the primary mirror coating.
Here, the first pics in bad seeing and bad wind conditions, in KLine with no coating on the primary.
I had later a chance to observe with the de-coated mirror in better seeing conditions. Here under 450nm
The conclusion is clear.
Bye Bye cheap ultra narrow band imaging.
CS
Alex
2019-Aug-31
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Re: A big solar newton for ultra narrowband imaging, possible?
Very interesting Alex, thanks for posting. What kind of filter were you using as a blue Erf? I am experimenting with a 150mm aluminised Newton (f/8) and a Baader Blue 2 inch CCD. No succes yet...
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Re: A big solar newton for ultra narrowband imaging, possible?
Very well documented post there Alex, which gives us all a lot to think about. Especially the thermals from equipment heating.
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
Re: A big solar newton for ultra narrowband imaging, possible?
Thanks Alex, very informative, in particular the IR images!
I've been experimenting with a Mewlon 210 with a front ERF for some weeks now. When I am taking a sequence of a dozen or so CaK videos, after processing the best image almost always proves to come from the first or second video. I suspect that the explanation for this is tube seeing that quickly builds up after the start of the session when some inner parts of the telescope are absorbing light (despite the front ERF) and getting warmer.
I'll have access to a thermal camera in a couple of weeks and then look into that. Removing the mirror coating is, however, not an option with the Mewlon...
Regards,
Frank
Edit (09/11/19): As I have been asked (by PM) I'd like to add a clarifying remark: I did not and do not want to state or to suggest that I am in any way dissatisfied with my DERF (or that I am looking at it as being the cause of the problem described above or anything like that), on the contrary: So far the DERF has made some very nice images possible (some of which I posted in other threads) – I just would like to get more of them, and this will be my aim for the next solar season!
I've been experimenting with a Mewlon 210 with a front ERF for some weeks now. When I am taking a sequence of a dozen or so CaK videos, after processing the best image almost always proves to come from the first or second video. I suspect that the explanation for this is tube seeing that quickly builds up after the start of the session when some inner parts of the telescope are absorbing light (despite the front ERF) and getting warmer.
I'll have access to a thermal camera in a couple of weeks and then look into that. Removing the mirror coating is, however, not an option with the Mewlon...
Regards,
Frank
Edit (09/11/19): As I have been asked (by PM) I'd like to add a clarifying remark: I did not and do not want to state or to suggest that I am in any way dissatisfied with my DERF (or that I am looking at it as being the cause of the problem described above or anything like that), on the contrary: So far the DERF has made some very nice images possible (some of which I posted in other threads) – I just would like to get more of them, and this will be my aim for the next solar season!
Last edited by LTHB on Wed Sep 11, 2019 4:58 pm, edited 1 time in total.
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Re: A big solar newton for ultra narrowband imaging, possible?
Bart,
The Astronomik B, that I have, are passing from 385nm.
The Baader that I have form an LRGB set is almost passing at about 400nm, so it has a poor transmission at 390..395nm.
I would suggest that you get in touch with the supplier and ask for "selected" filters.
Astronomik should be responsive on the subject. I didn't check with Baader.
Frank, I understand that you are not willing to play with your Newlon. But anyway, we see that there room for bigger size, so a bigger newton?
CS
Alex
The Astronomik B, that I have, are passing from 385nm.
The Baader that I have form an LRGB set is almost passing at about 400nm, so it has a poor transmission at 390..395nm.
I would suggest that you get in touch with the supplier and ask for "selected" filters.
Astronomik should be responsive on the subject. I didn't check with Baader.
Frank, I understand that you are not willing to play with your Newlon. But anyway, we see that there room for bigger size, so a bigger newton?
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
This is very interesting Alex.
The idea of keeping a fully coated mirror in a newtonian reflector and simply finding a way to install an ERF in front of the secondary mirror and it handling the thermal load is very interesting. That keeps transmission really high for high resolution imaging with dim filters, like etalons. It is interesting for HA. Really interesting of course for short wavelength, like 430nm or similar, in white light.
After dealuminizing the primary mirror, is the transmission high enough to still image with dim filters like HA etalons? Or CalciumK with an appropriate 2.4A filter? Or does it become a white light only filter?
Very best,
The idea of keeping a fully coated mirror in a newtonian reflector and simply finding a way to install an ERF in front of the secondary mirror and it handling the thermal load is very interesting. That keeps transmission really high for high resolution imaging with dim filters, like etalons. It is interesting for HA. Really interesting of course for short wavelength, like 430nm or similar, in white light.
After dealuminizing the primary mirror, is the transmission high enough to still image with dim filters like HA etalons? Or CalciumK with an appropriate 2.4A filter? Or does it become a white light only filter?
Very best,
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Re: A big solar newton for ultra narrowband imaging, possible?
Unfortunately, these tests proved that this idea was a dead end.
For Ca K imaging with my TOA150, the 50 mm internal ERF is 33% of the diameter of the objective. I have no internal turbulence.
With the 300 m Newtonian of Alex, the ratio is 16%. Now, we can say this is too low...
Maybe, another factor is that with the TOA, the distance between the internal ERF and the focus is about 250 mm, while in Alex setup the 50 mm ERF is next to the diagonal mirror.
As said by Alex, other tests were made with a 200 mm F4-12 Cassegrain with the same bad results due to strong internal turbulence...
So, we are left with full aperture ERF ...
Frank : interesting feeback. Still a little bit unexpected. I have no internal turbulence with my 200 mm ERF and C8 (in Ha).
Marty : there is not enough light for Ha or Ca K imaging with a not coated mirror. This is only for white light imaging (say 1 to 2 nm FWHM).
As a side note, these FLIR cameras are very interesting to check was is going on inside the optical tube in terms of thermal balance.
For Ca K imaging with my TOA150, the 50 mm internal ERF is 33% of the diameter of the objective. I have no internal turbulence.
With the 300 m Newtonian of Alex, the ratio is 16%. Now, we can say this is too low...
Maybe, another factor is that with the TOA, the distance between the internal ERF and the focus is about 250 mm, while in Alex setup the 50 mm ERF is next to the diagonal mirror.
As said by Alex, other tests were made with a 200 mm F4-12 Cassegrain with the same bad results due to strong internal turbulence...
So, we are left with full aperture ERF ...
Frank : interesting feeback. Still a little bit unexpected. I have no internal turbulence with my 200 mm ERF and C8 (in Ha).
Marty : there is not enough light for Ha or Ca K imaging with a not coated mirror. This is only for white light imaging (say 1 to 2 nm FWHM).
As a side note, these FLIR cameras are very interesting to check was is going on inside the optical tube in terms of thermal balance.
Christian Viladrich
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Re: A big solar newton for ultra narrowband imaging, possible?
Interesting stuff.....
I assume the ambient temperatures were around 18 deg? that would represent a temperature increase of around 10 deg for the "ERF"
That doesn't sound too bad to me....
The ambient temperatures down here in Oz in Summer can be up to 40 deg in the shade!
I assume the ambient temperatures were around 18 deg? that would represent a temperature increase of around 10 deg for the "ERF"
That doesn't sound too bad to me....
The ambient temperatures down here in Oz in Summer can be up to 40 deg in the shade!
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Re: A big solar newton for ultra narrowband imaging, possible?
We were on top of a mountain, 2930 m altitude. Ambient temperature was from 2°C to about 15°C.
So an increase of 10°C is huge. Basically, a delta of more than 2°C between ambient air and an optical part is detrimental to the seeing.
So an increase of 10°C is huge. Basically, a delta of more than 2°C between ambient air and an optical part is detrimental to the seeing.
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Re: A big solar newton for ultra narrowband imaging, possible?
Christian,
I understand....
But I would think many internal ERF applications might give significant heat loads on filters in the optical train.
The point is the actual temperature of the element may not be as critical as assumed.
I understand....
But I would think many internal ERF applications might give significant heat loads on filters in the optical train.
The point is the actual temperature of the element may not be as critical as assumed.
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Re: A big solar newton for ultra narrowband imaging, possible?
I was off a few days, sorry for not being responsive.
After stripping the coating, I checked the mirror temperature vs surrounding.
The mirror T°, taken from the side
The bottom cell supporting ring (Wood paint in white)
The center cage (Wood paint in white)
The IR measurements are taken with a small portable camera. Courtesy Frederic Jabet.
We don't know the measured surface emissivty; the camera is giving numbers you have to trust or not.
The difference in T° is about 3°C.
CS
Alex
After stripping the coating, I checked the mirror temperature vs surrounding.
The mirror T°, taken from the side
The bottom cell supporting ring (Wood paint in white)
The center cage (Wood paint in white)
The IR measurements are taken with a small portable camera. Courtesy Frederic Jabet.
We don't know the measured surface emissivty; the camera is giving numbers you have to trust or not.
The difference in T° is about 3°C.
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
Christian,
Could you use the IR camera to measure the temperature of a blocking filter diagonal against an ambient temperature.
Ideally on different aperture scopes.
Ken
Could you use the IR camera to measure the temperature of a blocking filter diagonal against an ambient temperature.
Ideally on different aperture scopes.
Ken
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Re: A big solar newton for ultra narrowband imaging, possible?
Can you compare that effect with using a very small secondary mirror in a Solar Newton? A lot of vignetting, but maybe interesting when you just want to use it for highres imaging. CS! Bart.
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Re: A big solar newton for ultra narrowband imaging, possible?
@Bart: A small secondary only to some (minor) extent could replace the 1.6mm DOT pinhole - the pinhole is only 1.6mm. A small secondary would be something like 20mm minor axis. Moreover, the DOT pinhole is mounted in a quite complex structure made of copper, with water cooling channels, silvering and pressurized air.
Moreover, a small secondary limits - among others - some of the rays of the primaries' near edge rays. I.e. those, which make the high angular resolution possible.
So, a small secondary may not be the way to get thermal power managed.
Best wishes,
Laura
Moreover, a small secondary limits - among others - some of the rays of the primaries' near edge rays. I.e. those, which make the high angular resolution possible.
So, a small secondary may not be the way to get thermal power managed.
Best wishes,
Laura
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Re: A big solar newton for ultra narrowband imaging, possible?
The DOT is a Gregorian telescope, not a Netwonian. This is a huge difference and explains why a cooled diaphragm can be installed at the primary focus. Remember that in a Gregorian telescope the focus of the primary mirror is in front of the secondary mirror, not behind. This makes thing much easier.
Still a Gregorian is very cumbersome, and a liquid cooling system is a bit complex to handle. Not a solution for an amateur portable telescope.
Langleif2 : can you be more specific about the coated 12-inch mirror ? What company did the coating ?
Still a Gregorian is very cumbersome, and a liquid cooling system is a bit complex to handle. Not a solution for an amateur portable telescope.
Langleif2 : can you be more specific about the coated 12-inch mirror ? What company did the coating ?
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Re: A big solar newton for ultra narrowband imaging, possible?
Thanks Laura and Langleif!
I understand the difference between the DOT and a Newton with a small secondary is huge. This winter I am going to grind my first mirror, 8 inch f/8. Will try different secondary sizes to see what the results are going to be.
I understand the difference between the DOT and a Newton with a small secondary is huge. This winter I am going to grind my first mirror, 8 inch f/8. Will try different secondary sizes to see what the results are going to be.
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Re: A big solar newton for ultra narrowband imaging, possible?
Good luck with grinding your own mirror, Bart. Have done this loooong time ago. Fascinating experience to be able to obtain such high accuracy with so little technical means. With your own mirror for a solar Newton, observing will be even more satisfying!
CS, Laura
CS, Laura
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Re: A big solar newton for ultra narrowband imaging, possible?
Hello lanleif2, thanks for this clarification.
I am afraid you were a bit mislead. I know rather well AiryLab and MCM. Alex do so since he is the one you got his 250 mm coated by MCM. So far, this is the larger Newtonian telescope with such a coating on the mirror. This telescope and MCM coating is presented in our book "Astronomie Solaire" (unfortunately in French language). You can also do a search in Solar Chat archive.
There are only three other mirrors coated (ERF) by MCM (all in 200 mm). None of them are operational.
MCM is not able to coat (ERF) mirrors larger than 250 mm (except mirrors with a central hole like primary of Cassegrain). This is why there is a 280 mm Hat telescope with an ERF coated Schmidt plate.
BTW, MCM has nothing to do with Missiles ;-)
In a nutshell, after having tested (with Alex and Fred) a number of options since the last 4-5 years, we are unfortunately left with the use of a large ERF for large Ha solar Newtonian.
I am afraid you were a bit mislead. I know rather well AiryLab and MCM. Alex do so since he is the one you got his 250 mm coated by MCM. So far, this is the larger Newtonian telescope with such a coating on the mirror. This telescope and MCM coating is presented in our book "Astronomie Solaire" (unfortunately in French language). You can also do a search in Solar Chat archive.
There are only three other mirrors coated (ERF) by MCM (all in 200 mm). None of them are operational.
MCM is not able to coat (ERF) mirrors larger than 250 mm (except mirrors with a central hole like primary of Cassegrain). This is why there is a 280 mm Hat telescope with an ERF coated Schmidt plate.
BTW, MCM has nothing to do with Missiles ;-)
In a nutshell, after having tested (with Alex and Fred) a number of options since the last 4-5 years, we are unfortunately left with the use of a large ERF for large Ha solar Newtonian.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
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Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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Re: A big solar newton for ultra narrowband imaging, possible?
Or a newton with a central hole and treat it like a SC corrector plate, ie by MCM.In a nutshell, after having tested (with Alex and Fred) a number of options since the last 4-5 years, we are unfortunately left with the use of a large ERF for large Ha solar Newtonian.
But like in every treatment, there is a risk.
Second issue: there is no more central part reflecting the laser for collimation.
You need then a very sturdy setup suitable to keep the collimation stable (star collimation).
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
Maybe that can be solved when using something like this:
https://www.teleskop-express.de/shop/pr ... copes.html
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Re: A big solar newton for ultra narrowband imaging, possible?
I use the Concentrer to prepare the collimation, for centering the secondary.
But for finishing the collimation, the Concentrer requires the central spot and dark conditions:
http://www.spheretec.de/pdf/Collimating ... epiece.pdf
When there is not central spot, then star test is the natural option to go.
As alternative, maybe the goldfocus solution may help; I didn't evaluate it however.
http://www.goldastro.com/
CS
Alex
But for finishing the collimation, the Concentrer requires the central spot and dark conditions:
http://www.spheretec.de/pdf/Collimating ... epiece.pdf
When there is not central spot, then star test is the natural option to go.
As alternative, maybe the goldfocus solution may help; I didn't evaluate it however.
http://www.goldastro.com/
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
Hello langleif2,
This is a textbook example of loss of information in a communication process : A tells a story to B, which B repeats it to C, etc. After a short while the story becomes quite another story :-)
So here the actual story :
Every year, we have a solar gathering at Serbannes (France). New stuff are presented, either homemade or commercial. 80 - 100 people attend this gathering, and we are happy to welcome some German solar nuts too.
For example, I remember having look through a vintage Zeiss Meniscas 180 mm equipped with a Lunt 50 mm etalon. It was quite good. This year, we were honored to have Oliver (Beloptik) with some other German friends.
In 2016 and 2017, Fred Jabet (AiryLab) presented his 11" Hat with an ERF coated Schmidt plate. It was indeed through this instrument that "Fensterrollo" looked though, not a 300 mm.
Here is one of the images I took with this telescope. The solar activity was much more exciting than now :
http://astrosurf.com/viladrich/astro/so ... 3A-F27.jpg
The 250 mm Newtonian telescope equiped with an ERF mirror you are refering too was the one of Alexandre.
The ERF coating of Alexandre's mirror and of the Schmidt plate of the Hat was done by MCM, and no missile stuff ;-)
Here is the website of the ROS. I think there is a link somewhere to the presentations:
https://www.soleilactivites.fr/
Best regards
This is a textbook example of loss of information in a communication process : A tells a story to B, which B repeats it to C, etc. After a short while the story becomes quite another story :-)
So here the actual story :
Every year, we have a solar gathering at Serbannes (France). New stuff are presented, either homemade or commercial. 80 - 100 people attend this gathering, and we are happy to welcome some German solar nuts too.
For example, I remember having look through a vintage Zeiss Meniscas 180 mm equipped with a Lunt 50 mm etalon. It was quite good. This year, we were honored to have Oliver (Beloptik) with some other German friends.
In 2016 and 2017, Fred Jabet (AiryLab) presented his 11" Hat with an ERF coated Schmidt plate. It was indeed through this instrument that "Fensterrollo" looked though, not a 300 mm.
Here is one of the images I took with this telescope. The solar activity was much more exciting than now :
http://astrosurf.com/viladrich/astro/so ... 3A-F27.jpg
The 250 mm Newtonian telescope equiped with an ERF mirror you are refering too was the one of Alexandre.
The ERF coating of Alexandre's mirror and of the Schmidt plate of the Hat was done by MCM, and no missile stuff ;-)
Here is the website of the ROS. I think there is a link somewhere to the presentations:
https://www.soleilactivites.fr/
Best regards
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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Re: A big solar newton for ultra narrowband imaging, possible?
I also have the TS concenter. It is indeed quite good to align the secondary mirror of the 300 mm solar Newtonian.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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Re: A big solar newton for ultra narrowband imaging, possible?
Hi Alex, after I de-aluminized my 150mm mirror, I marked the central spot. With the center spot I could use the concenter to collimate both the primary and secondary.allhoest wrote: ↑Wed Sep 11, 2019 6:11 pm I use the Concentrer to prepare the collimation, for centering the secondary.
But for finishing the collimation, the Concentrer requires the central spot and dark conditions:
http://www.spheretec.de/pdf/Collimating ... epiece.pdf
When there is not central spot, then star test is the natural option to go.
As alternative, maybe the goldfocus solution may help; I didn't evaluate it however.
http://www.goldastro.com/
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
Hi Bart.
I use to collimate during the day at the location where I travel to.
Can you collimate with the concentrer under daylight?
CS
Alex
I use to collimate during the day at the location where I travel to.
Can you collimate with the concentrer under daylight?
CS
Alex
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Re: A big solar newton for ultra narrowband imaging, possible?
Hi Alex,
Yes, that is no problem. Could the difference be that my telescope is a closed tube?
CS, Bart.