Summary of Aluminized Newton Imagery (2022 August)
-
- Almost There...
- Posts: 521
- Joined: Sun Mar 22, 2015 7:48 pm
- Has thanked: 714 times
- Been thanked: 496 times
Summary of Aluminized Newton Imagery (2022 August)
Solar imagery is dangerous. The fluxes involved are high, the concentration of local energy strong, the material is subject to stress and can deteriorate, any kind of circumstance can occur such as uncontrolled reflections, interception of the direct or reflected flux or any other phenomenon unexpected.
If you do not understand and master the phenomena involved, you should not do this kind of manipulation.
I decline nay responsibility in the event of an incident or accident.
It should also be noted that I do not practice any visual observation with non-commercial material.
I had in the past tried to image with an aluminized Newton, to gain flux in order to observe in CaK and Ha with large diameter optics, while wishing to maintain a reasonable exposure time.
The first tests proved inconclusive, instrumental turbulence being dominant.
Aluminum coating has a reflectance of ~90 or ~95% depending on the quality of the treatment. The part not transmitted is transformed into heat.
I had tried to ventilate the mirrors, in order to eliminate the heat where it forms, on the surface of the mirrors.
Additional turbulence in addition to vibration problems has accumulated to the instrumental turbulence.
The solution used here consists in using interferential optics in the system.
The energy density produced at the surface of the primary mirror is quite low. It will prove to be non-obtrusive, in the context of this approach at least.
The tests were made with 2 primary mirrors:
- An older generation 320mm mirror. Its quality of aluminum coating is not known; it is supposed to be standard
- A 300mm mirror recently re-aluminated by Orion Optics UK, with a 'Hilux' type coating
With a diameter of around 300..320mm, due to the incident energy density at the Zenith, an energy of around 70W is sent back to the secondary.
At the secondary level, a dielectric elliptical mirror is implemented.
This mirror reflects the visible wavelengths (~400 to 700nm) with a transmission of around 98 to 99%.
The balance passes through the secondary mirror.
It should be noted that the support of the secondary mirror heats up noticeably; the secondary mirror itself heats up slightly.
The flux reflected by the dielectric secondary is returned to the focuser.
At this level, an interference filter is placed.
A blue filter for imaging in Kline and Calcium K; a red filter to image in Hydrogen Alpha.
The optics used are slow, at F/D 6, the goal being high resolution imaging.
5x barlow lenses or 5x telecentric lenses are used here.
The flow of energy leaving the system after filtration is such that it can burn the skin (and the retina). The power through depends on the filtration.
In the proposed schemes, with magnification factors of x5, the resulting flux density is low.
It is, however, more than more than direct vision can bear.
A narrow band filtration system is then set up. In the cases implemented here:
- KLine filter, to image in KLine
- KLine filter + 'standard' Calcium K filter for CaK imaging
- Tight Ha filter (ex. 12nm) + Ha standard.
The tests were made with a ZWO ASI174 camera.
The exposure times (gain) are of the order of:
- KLine: 200 to 300 µs (0)
- CaK: 2.0ms (180)
- Ha: 1.7ms (180)
Some images of the assembly and the tests.
The 320mm aluminized mirror
The 300mm aluminized mirror
The dielectric secondary and an interference filter in front of the focuser
Some residual energy passes through the pre-filter; the heat flow is felt.
After implementing 5x amplification, the residual heat is bearable. Here in blue.
In red.
Here is a summary of the images
At T320 in KLine
At T300
In KLine
In CaK
In Ha
Alex
August 2022
If you do not understand and master the phenomena involved, you should not do this kind of manipulation.
I decline nay responsibility in the event of an incident or accident.
It should also be noted that I do not practice any visual observation with non-commercial material.
I had in the past tried to image with an aluminized Newton, to gain flux in order to observe in CaK and Ha with large diameter optics, while wishing to maintain a reasonable exposure time.
The first tests proved inconclusive, instrumental turbulence being dominant.
Aluminum coating has a reflectance of ~90 or ~95% depending on the quality of the treatment. The part not transmitted is transformed into heat.
I had tried to ventilate the mirrors, in order to eliminate the heat where it forms, on the surface of the mirrors.
Additional turbulence in addition to vibration problems has accumulated to the instrumental turbulence.
The solution used here consists in using interferential optics in the system.
The energy density produced at the surface of the primary mirror is quite low. It will prove to be non-obtrusive, in the context of this approach at least.
The tests were made with 2 primary mirrors:
- An older generation 320mm mirror. Its quality of aluminum coating is not known; it is supposed to be standard
- A 300mm mirror recently re-aluminated by Orion Optics UK, with a 'Hilux' type coating
With a diameter of around 300..320mm, due to the incident energy density at the Zenith, an energy of around 70W is sent back to the secondary.
At the secondary level, a dielectric elliptical mirror is implemented.
This mirror reflects the visible wavelengths (~400 to 700nm) with a transmission of around 98 to 99%.
The balance passes through the secondary mirror.
It should be noted that the support of the secondary mirror heats up noticeably; the secondary mirror itself heats up slightly.
The flux reflected by the dielectric secondary is returned to the focuser.
At this level, an interference filter is placed.
A blue filter for imaging in Kline and Calcium K; a red filter to image in Hydrogen Alpha.
The optics used are slow, at F/D 6, the goal being high resolution imaging.
5x barlow lenses or 5x telecentric lenses are used here.
The flow of energy leaving the system after filtration is such that it can burn the skin (and the retina). The power through depends on the filtration.
In the proposed schemes, with magnification factors of x5, the resulting flux density is low.
It is, however, more than more than direct vision can bear.
A narrow band filtration system is then set up. In the cases implemented here:
- KLine filter, to image in KLine
- KLine filter + 'standard' Calcium K filter for CaK imaging
- Tight Ha filter (ex. 12nm) + Ha standard.
The tests were made with a ZWO ASI174 camera.
The exposure times (gain) are of the order of:
- KLine: 200 to 300 µs (0)
- CaK: 2.0ms (180)
- Ha: 1.7ms (180)
Some images of the assembly and the tests.
The 320mm aluminized mirror
The 300mm aluminized mirror
The dielectric secondary and an interference filter in front of the focuser
Some residual energy passes through the pre-filter; the heat flow is felt.
After implementing 5x amplification, the residual heat is bearable. Here in blue.
In red.
Here is a summary of the images
At T320 in KLine
At T300
In KLine
In CaK
In Ha
Alex
August 2022
-
- Way More Fun to Share It!!
- Posts: 2139
- Joined: Sun Jul 24, 2022 5:20 am
- Has thanked: 4206 times
- Been thanked: 3805 times
Re: Summary of Aluminized Newton Imagery (2022 August)
Excelent work and fantastic pictures. I love Newton for Sun.
I do not look at the sky with the eyes of an astronomer, but of a person looking for the beauty of nature.
- marktownley
- Librarian
- Posts: 42269
- Joined: Tue Oct 18, 2011 5:27 pm
- Location: Brierley Hills, UK
- Has thanked: 20424 times
- Been thanked: 10242 times
- Contact:
Re: Summary of Aluminized Newton Imagery (2022 August)
Excellent write up Alex, thanks for shafring.
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!
-
- Almost There...
- Posts: 1054
- Joined: Mon Jun 04, 2012 8:13 pm
- Location: London, England
- Has thanked: 42 times
- Been thanked: 1487 times
Re: Summary of Aluminized Newton Imagery (2022 August)
The results are impressive and speak for themselves. My own modest experience with solar Newtonians is there was more than enough light when the primary was non-aluminized. I even experimented with both the primary and secondary having been stripped, but this did cut down the light too much.
I have also found that dielectric narrowband filters cut out a surprising amount of photons even from the ones you want to get through. I'm skeptical now of the graphs that show close to 100% transmission at the wavelength of interest (I measured this with my spectroheliograph).
Another thing that I learned: you don't need the secondary mirror to be as large as typically suggested by the normal telescope making programs. Generally, for an inside tube diameter somewhat larger than the outside diameter of the mirror, a secondary is suggested to give maximum coverage of the sky without much vignetting. As you can see in the reflection off your secondary, solar imaging requires only a narrow field of view. So the secondary can be significantly reduced to minimize the effect of the obstruction. In my case, I chose a secondary that matched the size of the secondary mirror holder (as I didn't what to change that) and it looks to me that that might be a good choice for you also.
I have also found that dielectric narrowband filters cut out a surprising amount of photons even from the ones you want to get through. I'm skeptical now of the graphs that show close to 100% transmission at the wavelength of interest (I measured this with my spectroheliograph).
Another thing that I learned: you don't need the secondary mirror to be as large as typically suggested by the normal telescope making programs. Generally, for an inside tube diameter somewhat larger than the outside diameter of the mirror, a secondary is suggested to give maximum coverage of the sky without much vignetting. As you can see in the reflection off your secondary, solar imaging requires only a narrow field of view. So the secondary can be significantly reduced to minimize the effect of the obstruction. In my case, I chose a secondary that matched the size of the secondary mirror holder (as I didn't what to change that) and it looks to me that that might be a good choice for you also.
-
- Im an EXPERT!
- Posts: 429
- Joined: Sun Mar 08, 2020 9:25 pm
- Location: Austin Texas
- Has thanked: 146 times
- Been thanked: 277 times
Re: Summary of Aluminized Newton Imagery (2022 August)
That is some great experiment. Your WL images are fantastic. What type of Ha set-up did you use. Are you concerned with too much energy at the etalon?
- MichaelTeoh
- Im an EXPERT!
- Posts: 302
- Joined: Tue Nov 16, 2021 9:22 am
- Has thanked: 254 times
- Been thanked: 547 times
Re: Summary of Aluminized Newton Imagery (2022 August)
Does an interference filter works like an ERF? How much does it cost?
Michael Teoh, Penang, Malaysia
APM-TMB 228/2050, Lunt LS152
https://www.flickr.com/photos/michael_teoh
APM-TMB 228/2050, Lunt LS152
https://www.flickr.com/photos/michael_teoh
- MapleRidge
- Way More Fun to Share It!!
- Posts: 10199
- Joined: Fri Jan 13, 2012 11:58 pm
- Location: Cambray, ON Canada
- Has thanked: 64 times
- Been thanked: 4340 times
- Contact:
Re: Summary of Aluminized Newton Imagery (2022 August)
Very interesting setup Alex and the images really show the potential for this setup!
Tanks for sharing,
Brian
Tanks for sharing,
Brian
Brian Colville
Maple Ridge Observatory
Cambray, ON Canada
Photos: https://www.flickr.com/photos/185395281@N08/albums
10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
Deep Sky Work - ASI294MM Pro+EFW 7x36/Canon 60D (Ha mod), ONAG
Planetary Work - SBIG CFW10, ASI462MM
2.2m Diameter Dome
iOptron CEM70G Mount carrying:
Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
ASI1600MM, ASI432MM, ASI294MM Pro, ASI174MM, ASI462MM
Maple Ridge Observatory
Cambray, ON Canada
Photos: https://www.flickr.com/photos/185395281@N08/albums
10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
Deep Sky Work - ASI294MM Pro+EFW 7x36/Canon 60D (Ha mod), ONAG
Planetary Work - SBIG CFW10, ASI462MM
2.2m Diameter Dome
iOptron CEM70G Mount carrying:
Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
ASI1600MM, ASI432MM, ASI294MM Pro, ASI174MM, ASI462MM
- OlegLviv
- Almost There...
- Posts: 629
- Joined: Mon Sep 13, 2021 4:24 am
- Location: Ukraine/Lviv
- Has thanked: 881 times
- Been thanked: 907 times
Re: Summary of Aluminized Newton Imagery (2022 August)
Ohhhh Impressive!!!!
https://www.facebook.com/oleg.lavigne/
https://www.astrobin.com/users/RamonLviv/
https://www.astroclub.kiev.ua/forum/ind ... ic=46758.0
Telescope: TS 152/900/Bresser 102/1350
Baader D-ERF 160MM
2xBaader 1.25 GPC
2xLunt 50mm
Lunt Cak B1200
Coronado BF15
Camera: Apollo Max 432M/ Apollo Mini 429M/Player One Mars II 462M/QHY 290MM
Mounh: 2xSky Watcher AZEQ6
Telecentric Lense: Televue Powermate 2/2.5x/4X/5X
https://www.astrobin.com/users/RamonLviv/
https://www.astroclub.kiev.ua/forum/ind ... ic=46758.0
Telescope: TS 152/900/Bresser 102/1350
Baader D-ERF 160MM
2xBaader 1.25 GPC
2xLunt 50mm
Lunt Cak B1200
Coronado BF15
Camera: Apollo Max 432M/ Apollo Mini 429M/Player One Mars II 462M/QHY 290MM
Mounh: 2xSky Watcher AZEQ6
Telecentric Lense: Televue Powermate 2/2.5x/4X/5X
-
- Almost There...
- Posts: 521
- Joined: Sun Mar 22, 2015 7:48 pm
- Has thanked: 714 times
- Been thanked: 496 times
Re: Summary of Aluminized Newton Imagery (2022 August)
" I even experimented with both the primary and secondary having been stripped"thesmiths wrote: ↑Tue Aug 16, 2022 4:36 pm The results are impressive and speak for themselves. My own modest experience with solar Newtonians is there was more than enough light when the primary was non-aluminized. I even experimented with both the primary and secondary having been stripped, but this did cut down the light too much.
I have also found that dielectric narrowband filters cut out a surprising amount of photons even from the ones you want to get through. I'm skeptical now of the graphs that show close to 100% transmission at the wavelength of interest (I measured this with my spectroheliograph).
Another thing that I learned: you don't need the secondary mirror to be as large as typically suggested by the normal telescope making programs. Generally, for an inside tube diameter somewhat larger than the outside diameter of the mirror, a secondary is suggested to give maximum coverage of the sky without much vignetting. As you can see in the reflection off your secondary, solar imaging requires only a narrow field of view. So the secondary can be significantly reduced to minimize the effect of the obstruction. In my case, I chose a secondary that matched the size of the secondary mirror holder (as I didn't what to change that) and it looks to me that that might be a good choice for you also.
And the collimation was also probably not easy.
"I'm skeptical now of the graphs that show close to 100% transmission"
I'm happy with my 2ms exposure in Ha, so I guess that the transmission is OK.
I have not spectro measurement of the elliptical mirror.
"you don't need the secondary mirror to be as large as typically suggested by the normal telescope making programs"
I have poor skills in optics; I'm rather having fun in imaging. But I guess that the secondary must be big enough to "see" the whole primary and catch the aperture (the resolution) of the primary.
Alex.
-
- Almost There...
- Posts: 521
- Joined: Sun Mar 22, 2015 7:48 pm
- Has thanked: 714 times
- Been thanked: 496 times
Re: Summary of Aluminized Newton Imagery (2022 August)
As shown, I can put my hand just after the telecentric; I may feel a little heat.
Anyway, just to be sure, I put another interferential filter before the etalon, in order to protect it in a worse case situation.
Alex
-
- Almost There...
- Posts: 521
- Joined: Sun Mar 22, 2015 7:48 pm
- Has thanked: 714 times
- Been thanked: 496 times
Re: Summary of Aluminized Newton Imagery (2022 August)
The first interferential filter is the elliptical mirror.MichaelTeoh wrote: ↑Wed Aug 17, 2022 4:24 pm Does an interference filter works like an ERF? How much does it cost?
It has a transmission ~400..700nm, so it cut a significant part of the flux.
The second one is either a blue, passing ~100nm or a red. The red I used in my test was a Baader 35nm.
Note that these filters are tagged "not for solar use " :-(
The elliptical is from Thorlabs; it should cost about 200..300Eur.
The other one are deep sky filters from the market.
Alex.
- OlegLviv
- Almost There...
- Posts: 629
- Joined: Mon Sep 13, 2021 4:24 am
- Location: Ukraine/Lviv
- Has thanked: 881 times
- Been thanked: 907 times
Re: Summary of Aluminized Newton Imagery (2022 August)
I have a question!
What type Etalon you use??
Coronado? Lunt? or Quark Daystar? 0.7 A? 1A? 0.5 A?
What size etalon?
Second question!
Do you use only 5x Powermate or you can use 2.5 Powermate?
Thanks!
What type Etalon you use??
Coronado? Lunt? or Quark Daystar? 0.7 A? 1A? 0.5 A?
What size etalon?
Second question!
Do you use only 5x Powermate or you can use 2.5 Powermate?
Thanks!
https://www.facebook.com/oleg.lavigne/
https://www.astrobin.com/users/RamonLviv/
https://www.astroclub.kiev.ua/forum/ind ... ic=46758.0
Telescope: TS 152/900/Bresser 102/1350
Baader D-ERF 160MM
2xBaader 1.25 GPC
2xLunt 50mm
Lunt Cak B1200
Coronado BF15
Camera: Apollo Max 432M/ Apollo Mini 429M/Player One Mars II 462M/QHY 290MM
Mounh: 2xSky Watcher AZEQ6
Telecentric Lense: Televue Powermate 2/2.5x/4X/5X
https://www.astrobin.com/users/RamonLviv/
https://www.astroclub.kiev.ua/forum/ind ... ic=46758.0
Telescope: TS 152/900/Bresser 102/1350
Baader D-ERF 160MM
2xBaader 1.25 GPC
2xLunt 50mm
Lunt Cak B1200
Coronado BF15
Camera: Apollo Max 432M/ Apollo Mini 429M/Player One Mars II 462M/QHY 290MM
Mounh: 2xSky Watcher AZEQ6
Telecentric Lense: Televue Powermate 2/2.5x/4X/5X
-
- Almost There...
- Posts: 521
- Joined: Sun Mar 22, 2015 7:48 pm
- Has thanked: 714 times
- Been thanked: 496 times
Re: Summary of Aluminized Newton Imagery (2022 August)
For the CaK, I use a Lunt. It should be a B1800.
For Lunt + Powermate x5, I use an ASI174 with 5.86µm pixel size.
For Lunt + Powermate x2.5, I use an ASI290 with 2.9µm pixel size.
For the Ha, I use a Solarspectrum 0.3A. It has a useful diameter of ~30mm (ASO model).
A daystar should do the job.
For the Ha + telecentric x5, I use an ASI174.
CS
Alex