SolarSpectrum?

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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SolarSpectrum?

Post by Montana »

Hello,

I was wondering if anyone could tell me the difference between the various SolarSpectrums as I do not understand?

I also cannot find the model Jozef (Oreoluna) has on Astrograph, is this no longer made?

I am going through a mid life crisis at the moment. When I first started solar imaging my first loves were detailed Hydrogen alpha full discs and high resolution white light. Back in 2009 I dreamed and bought a TEC140. I then had a choice of a Solarscope for full disc imaging or a Solarspectrum for high res. I chose a Solarscope and I have never regretted it.

I imagined one day I would get to do high res Hydrogen alpha and bought a Quark + 135mm D-ERF for the TEC140. It was happiness for 3 months and [hot place] on earth for 18 months.

I then bought a C11 and had heaven in white light and I am still very happy. However, for CaK and Hydrogen alpha it is absolute rubbish and have never even seen remotely anything in all the times I have tried. When you lose happiness and solar imaging becomes frustrating and you have no will to process your images, then something is very wrong.

I don't understand how my PST mod works and have been told it cannot work on the TEC140. However it was useful in being able to replace my blocking filter on my original PST.

I would now like to move towards my original dream and see high res Hydrogen alpha on my TEC140. I know this is possible as Luca used to use a SolarSpectrum on his TEC180. The question is which to go for, I know it needs to be 0.3A but which model? I don't want to waste more money. Also do I invest in a 160mm D-ERF as I am limited to 125mm with the 135mm due to the filter cell and I am losing the 140mm?

The TEC140 is like a dream, when I use it my eyes light up and the live views on the screen light my soul. The C11 just does not do this for me (unless I view in WL), I can never see anything at all no matter what I try, it is not even close. Maybe one day if I move to a mountain top it will give me joy, but I will stick to WL for now. Solar viewing should not make you sad but make you happy. The C11 makes me sad. The TEC140 makes me jump for joy.

I hope you can help.
Alexandra


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Re: SolarSpectrum?

Post by Carbon60 »

Hi Alexandra,

Don't get disheartened, I'm positive the Tec140 can be made to work. It just needs some optics at the rear to turn the f7 cone into a substantially parallel beam (i.e. a plano-concave lens) to feed the PST etalon (with front module lens removed as it wont be needed). A UV/IR filter in front of this lens could also be used as an energy rejection filter at least to start with. I've done this with my 150 mod previously. Of course, it's better to use a front mounted ERF to minimise thermal energy entering the OTA. You could save yourself the cost of a solar spectrum and buy an ERF instead :)

This approach has been very successful in my 150 (albeit using Lunt 35 etalons, but the principle is the same). Imaging with a suitable barlow keeps the image target within the sweet spot.

I'm sure others will offer alternative solutions.

I can totally understand your frustration with the C11.

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Re: SolarSpectrum?

Post by marktownley »

Hiya Alexandra.

My C8 makes me sad too. Not the fact it's a HaT, just the fact it's an SCT. The TEC is the pinnacle of optical design, and the cost / build quality - everything, is reflected in that. I might not have a TEC, but over time I have selected the scopes (refractors) that I have now based on their performance in the far blue and the red end of the spectrum, i've ended up retrofitting these scopes often with focusers that cost more than the scope itself.

SCT's are big, cheap light buckets. They are great for globular clusters / galaxies, but there are endless threads on '5" frac vs 8" SCT' etc when you start looking around, the smaller fracs win everytime on solar system objects, the SCTs win everytime on deep sky.

If you look at Strehl graphs for SCTs the value plummets away once you are in the blue or red end of the spectrum, with them being optimised in the green. Lower strehl just gives lower contrast in simple terms.

Then there is spherical aberration. SCTs have abysmal SA in the blue, not too bad in the red. Simple achro refractors are great for SA generally all the way from blue to red, cheap / mid range triplet apos generally have poor SA in the blue. Top end triplets (TEC/APM) have no issue with SA - you get what you pay for. Poor SA gives less sharp images / contrast.

I wonder how much of an issue collimation is with SCTs, or more to the point how well they hold collimation. I think if you have one mounted in an abs and collimate regularly not at all. If like me you haul an SCT out a handful of times a year when the seeing is worth bothering, I wonder how much collimation remains. There is also the effect of image shift when focusing an SCT, I wonder how much this impacts collimation. Viewing visually the Orion nebula with a nice low power eyepiece very little I suspect, imaging hi-res at >f30 in 'extreme' wavelengths I suspect more so. I'm sure others will know or have experience.

Then there is seeing. Seeing in CaK is 1.4x more sensitive than WL (540nm), 1.6x more sensitive than Ha. Think i've said plenty on seeing in the past :lol:

When we image in solar it is hi-res - f30-f50(?), at these long focal ratios all these things start stacking up. How many times do you see full disk images of the moon taken with a SCT and DSLR and it looks absolutely great? All the time as the image is hugely undersampled... Same with full disk solar images and a DSLR, they look great but the same can be achieved with proper image sampling with a much smaller refractor.

So I guess what i'm trying to say is i've thought exactly the same thing as you. I said in one of Stuarts posts i'm seriously thinking about sacking off the HaT, not because it is a bad scope (every respect for Airylab and the HaTs), but because it is not the right scope for me.

I've been seriously impressed with my £300 127/1200 Bresser achro Fi got me for xmas, in both Ha and CaK (not tried WL yet but sure will be fine). On the times when i've felt the seeing was supportive of more aperture than this scope gives in Ha and i've got the HaT out the results have been dire (sound familiar?). After several years experiencing this my conclusions are all of the above.

I think my next step will be a 6" frac for Ha and WL (not sure which). I think where I live and observe the vast majority of the time, 120mm CaK 150mm Ha is my ceiling with seeing without just capturing Tb of data that is just discarded. The HaT can just sit there while I frown at it and mull it's fate over...

There's no reason why you can't do a PST mod with the TEC, just put a barlow ahead of the etalon nose cone so it 'sees' an effective longer focal ratio. The other way is to replace the collimating lens in the etalon unit with one designed for f7 rather than f10.

Using the TEC for >100mm CaK is possible, the altair tri-band has a free aperture of 130mm https://www.altairastro.com/altair-140m ... 6354-p.asp if you can get the DERF without the cell it would be easy to make one on the laser cutter which would give you a free aperture of 138mm, so you're not loosing much.

Regards a SS, I would go for either a 19mm or 25mm version (larger only needed if you want to do visual without vignetting), minimum I would be looking at is the solar observer series 1.5, If I had the cash to splash I would go with the 03a 32mm research grade (£10k).

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Re: SolarSpectrum?

Post by marktownley »

I think the other thing I missed, is that you (and I include myself here too) are a critical imager, standards are high and you're not prepared to accept anything but the best results from kit... That's a compliment btw... ;)


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Re: SolarSpectrum?

Post by GreatAttractor »

I got interested in SolarSpectrum filters myself for a potential future (...as in: distant) upgrade, and I found among other things this thread on CN where Mark Wagner from SS himself answers some questions.

In summary, for temperature control they use a thermoelectric heater/cooler (TEC) (except the cheapest series - "Sundance"?), superior to resistive heating-only in e.g. a Quark. And it seems much care is taken in production when assessing image uniformity, so getting a non-uniform lemon is probably not an issue.

Out of curiosity, I asked Teleskop-Express this week what's the wait time for the Solar Observer 1.5 0.3Å, and they said 30-40 days.


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Re: SolarSpectrum?

Post by christian viladrich »

Hello Alexandra,
I would concur to the previous answers. Maybe you can try again with the PST Mod ?


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Re: SolarSpectrum?

Post by Montana »

Thanks guys for all the wisdom and support. I feel I want to just enjoy solar viewing and not fighting and wasting time in the rare chances of sunshine.

With the C11 I don't see how I can collimate it any better. I have spent many hours and it is always the same. I even tried a Tribahtinov mask and this really helped.
ImageTribahtinov mask by Alexandra Hart, on Flickr

If the Holy Grail of collimation is more than this then I just can't do it.
White light is fine, CaK and Halpha is not. I have never seen anything even close to Alfred's worst images.

The last time I asked about the PST mod I was told it wasn't possible as I would need to stop down to 100mm to use, why bother when I have the Solarscope. Also the sweet spot is not in the centre and I am not clever enough to correct it. So any image is worse than my old Quark with half the photo off band and half on band. It is pretty useless.

The problem is I am not technical and I have no clue, I sit and stare at it and that is all I can do. Also, I have great concerns that when I used my Solarscope blocking filters with the PST mod last year, suddenly I had a problem with them and they were damaged. I am not that keen in using them with the PST mod again as I am not sure what caused the damage. I need off the shelf stuff which just works because I feel not safe doing stuff I don't understand. I am sorry I am not as clever as you folks :(

Alexandra


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Re: SolarSpectrum?

Post by marktownley »

Collimation looks fine to me.

In that case I would suggest a solar spectrum and the TEC with TZ4, Altair Tri Band so you can do CaK.

Just use the C11 for WL.


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Re: SolarSpectrum?

Post by george9 »

I agree whatever Solar Spectrum you can afford. The smaller ones are all research grade in evenness; for the larger ones you have to make a choice. If you are only doing high-res imaging, then yes you can get by with a smaller one. I picked the 32mm to maximize the view through my 30mm binoviewer.

TZ4 works well with my AP155mm f/7. It is good up to a 36mm aperture or whatever T2 is.

I use the 160mm Baader DERF, but I agree tri-band would be nice.

My C11 with Aries tri-band can work as well as my AP155, but I have not encountered a day yet where it is better. Considering that the C11+Aries cost half as much as my AP155+DERF, that's not a bad deal. But I am still optimizing the C11.

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Re: SolarSpectrum?

Post by MapleRidge »

Hi Alexandra...

The ability to use the SCT is a challenge for me as well (C9.25 Edge) for solar work. I will have to give it a better test in the coming months after having a go a collimating it (I got the tri-bhatinov mask as well to see if I can't do better). Seeing is my limiting factor on the large scope and just don't bother with it when the 6 inch scope works better at the moment. I'd like to be able to put the Daystar Quark on it when there is good seeing with detailed AR's to image. Maybe I'll get there one day :lol:

I think you were advised the stop the TEC down to get it to f10 to match the PST optical preferences. As Mark mentioned you could add a barlow ahead of it or change the collimation lens to match the f7 your OTA produces. I would expect the PST mod route would give you excellent results once the effective focal ratio is modified. Likely invest in a blocking filter as well if you don't want to use the SolarScope unit. As you say, stopping the 140 down really doesn't gain you anything.

In my mind, if you were to get the full aperture ERF and the SolarSpectrum filter it would be free of the sweet spot issues with any mods...so a big thumbs up for the unrestricted FOV. It isn't going to be a full disk setup anyway, so the FOV on the chip becomes less an issue. Just a matter of how much you with to invest in the filters.

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Re: SolarSpectrum?

Post by Valery »

Alexandra,

Your PST mod may not work well due to improper BF filtration. When I tried to use Lunt B1200 with PST etalon it does not work. Contrast is quite low. As soon as I placed in the imaging rig a BF10 (Coronado) or PST's native BF5, the contrast becomes high - as it was in the PST scope. May be the Solar Scope blocker does not work with a PST etalon (alone) like this was with Lunt B1200.


Another common error. Most UK solar observers do use a following sequence of sun imaging: a) install a small 50-80mm telescope and do all the necessary works. Then if they see than the seeing looks OK they trying to start imaging with a larger telescope.
This way is totally WRONG. If one want to obtain excellent results with larger telescope he need to start and end his observing sessions with this single larger telescope hunting for a few best seconds of seeing. Better to do this with a SSM. And only the case when one can use a smaller telescope is when the good time for best seeing moments for larger telescope is over. Smaller aperture will work OK even at a worser seeing. DO NOT WASTE THE BEST TIME OF THE DAY WITH A SMALL TELESCOPE IF YOU CAN USE LARGER TELESCOPE AND YOUR AGENDA IS TO OBTAIN HIGHH RESOLUTION IMAGES WITH LARGER TELESCOPE. You always can make a next in a loooooong row full disk image with a 50-80mm telescope. High res solar imaging with a larger telescope is another level of patience and attention to all, even smallest details of an imaging rig and hunting for the very rare good seeing moments. Always remember this.
My two main observing locations are nothing special. Absolutely. But I paid for my hundreds of high res images in full. And it took a fair amount of time too.


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Last edited by Valery on Tue May 04, 2021 2:28 pm, edited 1 time in total.


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Re: SolarSpectrum?

Post by Highbury Mark »

Wish you the best with this new project Alexandra. A TEC 140 and Solar Spectrum filter sounds like solar heaven, even if it requires a learning curve. I’m just starting out with imaging, using your advice and guidance to find my way around the software, which is incredibly helpful. Maybe the only piece of insight I could pass on would be that in my experience, some SCTs never give truly satisfactory views, even if they’re collimated perfectly. So maybe your C11 fell into that category?


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Re: SolarSpectrum?

Post by marktownley »

george9 wrote: Fri Apr 30, 2021 12:37 pm My C11 with Aries tri-band can work as well as my AP155, but I have not encountered a day yet where it is better. Considering that the C11+Aries cost half as much as my AP155+DERF, that's not a bad deal. But I am still optimizing the C11.
Interesting observation... ;)


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Re: SolarSpectrum?

Post by Montana »

Thanks guys, I'm still in two minds whether to spend yet more money or not ;) I'll have to see what Rupert says.

In answer to a few questions, my PST mod isn't lacking contrast but it is off centre, so when imaging only half the field of view is on band. It is like a very bad Quark and I don't have the knowledge to re-centre the sweet spot. I do have a 2" Hydrogen alpha filter in front of the PST mod as a blocking filter.

I do image first thing in the morning, I have the C11 cooling overnight in the greenhouse, I have a heat reflective jacket on it. I also start the imaging with the C11 first, then work the TEC140 afterwards. Luca Valantini taught me 10 years ago to start with High res first, start with CaK, then WL, then Halpha, then move to low res. I have always followed this track.

Highbury Mark, that is interesting to hear about the C11, I'm not sure of the quality of my optics, I am sure it isn't half as good as Alfred's. Thing is, you can blame the seeing for years and actually find the optics are bad and you will never have good seeing. I blamed seeing for my bad CaK imaging for 6 years, got suspicious, tested it against Stuart's CaK module and found mine had bad optics. Got it replaced and had brilliant seeing every time there after. Unless I had a telescope optical lab it is not easy to test a set up under ideal conditions to test it. I need to move to Hawaii :)

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Re: SolarSpectrum?

Post by marktownley »

Rupert always has sage advice :cool:

I always start off at the largest aperture in CaK then drop down through the wavelengths / aperture as the seeing allows.

The other way to jiggle this is you already have the Aries DERF (and these were my boat thoughts yesterday afternoon) - we just make a cell that fits the 140 and the c11. It's just measurements and fittings... Would make the TEC so nose heavy it's like a neutron star at the objective end, but with a long offset dovetail and strategic counterweights to balance it would save you a grand on the Altair DERF.

I can make you the collar to fit the Aries DERF (in it's cell) on the TEC, easy peasey. Just a SS from Rupert to knit it all together...


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Re: SolarSpectrum?

Post by Montana »

I'm not sure that would work Mark, the Aries ERF is enormous 11" and has a massive hole in the middle. You would have to off set the ARIES ERF to cover the small 5" of the TEC away from the hole, it would look mighty funny and weight distribution would be phenomenal on end and to the side :lol:
Good idea though :)

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Re: SolarSpectrum?

Post by Montana »

Mind you, I could pay the hubby to stand there and hold it for a hour and half while I imaged :lol: how many bottles of wine would that take :lol:

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Re: SolarSpectrum?

Post by marktownley »

Montana wrote: Mon May 03, 2021 4:50 pm and has a massive hole in the middle.
What's the hole?

Darren would have to have the wine after the holding process ;) before is asking for trouble :lol:


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Re: SolarSpectrum?

Post by Montana »

Here is a picture Mark to answer your question.

ImageCelestron C11 Halpha by Alexandra Hart, on Flickr

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Re: SolarSpectrum?

Post by marktownley »

Valery wrote: Sat May 01, 2021 6:04 am Tri band DERF
Valery, why is there a hole in the middle?


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Re: SolarSpectrum?

Post by Simon2940 »

People are probably going to disagree with me, but with a larger scopes, seeing is critical. On top of that, pixel size means everything.

For the C11, you really have to have that perfect seeing at 5/5 with transparency 4/5 to 5/5.

Your camera pixel size needs to be 7um or larger.

I cant always shoot with the Esprit 150mm, ive had 4/5 seeing days and it looks plain awful. I have only had 3-4 days in the past 2 years where it was a true 5/5 seeing and the details are worlds apart.

The other thing that affects SCTs is heat currents. If you have the fans, turn em of and let the air constantly stir inside.

No idea if anything I said is of any use :S



Montana wrote: Fri Apr 30, 2021 9:02 am Thanks guys for all the wisdom and support. I feel I want to just enjoy solar viewing and not fighting and wasting time in the rare chances of sunshine.

With the C11 I don't see how I can collimate it any better. I have spent many hours and it is always the same. I even tried a Tribahtinov mask and this really helped.
ImageTribahtinov mask by Alexandra Hart, on Flickr

If the Holy Grail of collimation is more than this then I just can't do it.
White light is fine, CaK and Halpha is not. I have never seen anything even close to Alfred's worst images.

The last time I asked about the PST mod I was told it wasn't possible as I would need to stop down to 100mm to use, why bother when I have the Solarscope. Also the sweet spot is not in the centre and I am not clever enough to correct it. So any image is worse than my old Quark with half the photo off band and half on band. It is pretty useless.

The problem is I am not technical and I have no clue, I sit and stare at it and that is all I can do. Also, I have great concerns that when I used my Solarscope blocking filters with the PST mod last year, suddenly I had a problem with them and they were damaged. I am not that keen in using them with the PST mod again as I am not sure what caused the damage. I need off the shelf stuff which just works because I feel not safe doing stuff I don't understand. I am sorry I am not as clever as you folks :(

Alexandra


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Re: SolarSpectrum?

Post by Valery »

Alexandra,

The optics in your telescope looks very good (when I look at the off focus images), significantly better than in my own C11. The collimation you can check by looking at the star image. It must be concentric. This all.

Excellent seeing like 5/5 is not necessary for lucky imaging technique. Lucky imaging has been developed exactly for image reconstruction after dividing it in time and on numerouse fragments, selecting best of them and finally reconstruct an image close to undistorted. Seeing 3/5 is OK for lucky imaging. One just need good focus, short enough exposures, maximally low noise camera and enough good frames in a stack.

BTW I always did a ROI when I imaged with my C11, PST etalon, BF10 Coronado + barlows (1,5x, 2x and 2,5x).
It is possible to make a two parts adapter-interface for moving the camera so, that a sweet spot will be centered on the camera sensor. Or just use a ROI off center.


Mark,

The "hole" in the center is necessary. It is now covered by a round chrome spot.


Valery


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marktownley
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Re: SolarSpectrum?

Post by marktownley »

Valery wrote: Tue May 04, 2021 4:00 pm The "hole" in the center is necessary.
Why? What is it's purpose? Is it necessary for manufacturing, if so, why?


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Re: SolarSpectrum?

Post by DeepSolar64 »

Seeing is certainly going to affect the C11 worse than the TEC 140. I certainly would develop the TEC 140 for CaK and Ha and use the C11 for white light. CaK is more picky to seeing I read and WL often has better contrast than Ha does helping things show up.

I cannot speak personally concerning CaK because I haven't yet that capability.

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Re: SolarSpectrum?

Post by DavidP »

I feel like it’s asking a lot of an 11” SCT to do high res solar imaging. I have used all sizes of SCTs, and found thermal management to be tricky. I installed fans on some, and that helped, but big temperature swings were difficult to overcome. I never used one for solar, but I would imagine that Montana generally has large temperature swings from cold early mornings to warm temps at noon. I know there have been some wonderful planetary imaging with 11” SCTs, and I’ve seen a few goodish solar images, but I’d be willing to bet they were generally done in places with more stable temperatures.
Do you collimation on a star? It really is the best method. Also. Simply moving many SCTs can make them lose collimation. If you don’t have it set up permanently, you can star collimate the night before.
It sounds like your optics are relatively good, but there is no way around the fact that SCTs can not produce the contrast of decent refractors.
We’re it me, I would either sell my 11” SCT for an 8”, which is more easy to manage thermally ( financially it shouldn’t cost you) and likely to be the frequent limit of your resolution capabilities while still being a significant step up from a 6” refractor, or I’d install fans in the 11”. Do you measure your seeing? It seems like it would be worthwhile to know you have enough opportunities to take advantage of excellent seeing if you want to pursue the 11”.
You are very good at imaging and processing. I know you will end up with a set-up that works for you.


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