13 replies to this topic

[pgfossier]

Does anyone have experience or knowledge they can share about the Baader Triband-SCT - Multi-Purpose-Telescope, for Sun and Deep Sky?

I have not run into any post from users of that system.

 

https://www.baader-p...d-deep-sky.html

 

thanks

[C0rs4ir_]

Sure.. check my gallery "Solar WL-imaging". What do you want to know?

Edited by C0rs4ir_, 06 June 2023 - 02:07 PM.

[pgfossier]

Which aperture do you have ?

How long have you had it ?

Did you consider other models before deciding on this type of scope ?

What tilted your decision in favor of this model ?

Do you use a Solar Spectrum etalon ?

If yes, which model ?

Do you use this scope for deep sky or planetary also ?

 

I hope that's not too many questions.

 

Nice photo gallery.

What camera do you use ?

What do you use for image processing and finishing ?

 

thanks

[MalVeauX]

Hi,

 

What's your daytime seeing conditions through the year that you will be available to use it?

 

Start with that. It's the gate keeper. If you don't have commonly sub-arc-second seeing, I wouldn't suggest anything bigger than 150mm for casual attempts. But if you're serious about this then you should start with measuring your seeing via SSM or data from a white light setup in the max aperture you want to explore before comitting to an h-alpha or near UV capable setup. I do not recommend SCT for near UV. The better instrument for all wavelengths is a newtonian or a classical cassegrain. SCT corrector plates have bad SA in near UV, so without correction, they're poor for this. It's fine for green to red wavelengths and into some IR though. Overall, the better "do all" scope is the newtonian and classical cassegrain for a big solar scope though.

 

I used a C8 Edge and added my own 214mm tri-band D-ERF (Aries).

 

 

 

 

I've also done a 200mm F6 newtonian with the same 214mm D-ERF.

 

 

High Res Solar + Planetary at the same time:

 

https://apod.nasa.go...d/ap191113.html

 

Overall, this is not something I would suggest casually to anyone. This is only if you're dedicated to exploring high res solar imaging and it's 100% dependent on your actual seeing conditions. So unless you commonly have sub-arc-second seeing, this simply will produce whatever the seeing is (if seeing is 1.5 arc-seconds, in red, that's equivalent to a 100mm aperture, just as an example). As long as you can get relatively frequent spikes of sub-arc-second seeing, you can lucky image and go into high res. I routinely get down to around 0.8 arc-seconds as spikes. My sampling is 2 times per second for these measurements. I image at around 170 FPS so 1 second of good seeing is 85 frames captured, which is plenty to produce a clean image. High res imaging is very much lucky imaging, but you have to start with measuring seeing or just play around and "get lucky." I don't like wasting a session so I measure seeing to know what's possible first.

 

Example of how many times I spiked sub-arc-second in a sub-hour session (this is typical of my sessions, early morning, Florida):

 

 

Despite all this, I actually prefer to use a 150mm refractor for a plethora of reasons. Mirrors are superior for this (newtonian and classical cassegrain), but mirrors have their own issues (collimation has to be nearly perfect, temperature acclimation or delay delta is paramount just like it is at night, heat barrier on the primary, etc). I also prefer 150mm because most chromosphere features are just so huge that I prefer to capture most of it in one FOV shot instead of relying on mosaics with variable seeing. Also, 393nm is heavily dependent on seeing conditions and more effected by seeing, and is higher angular resolution, so trying to use a big aperture for near UV requires very good seeing conditions. I try to image around my seeing limits and I'm pretty much successful every session (less than 1 hour of effort, usually 15~45 minutes max for all three wavelengths when I image). My seeing doesn't support 200mm in all wavelengths every session through the year, so I mostly use my 150mm which is supported sub-arc-second all year round and I can tri-band image with it without fuss (no collimation, no acclimation time, etc).

 

I retro fitted my 214mm tri-band D-ERF to my 150mm F8 achromatic doublet:

 

 

Example of what 120~150mm does for tri-band if seeing is sub-arc-second (0.7~0.9 for my session for these):

 

 

 

 

And 150mm double-stacked, so no double limb, and proms are the same on the surface as off the limb, under excellent seeing:

 

 

The equipment is not as important as the atmospheric seeing. Perfect equipment just won't do this in 4 arc-second seeing. Seeing is everything. Always start with seeing if you care about solar resolution.

 

Very best,

Edited by MalVeauX, 06 June 2023 - 07:56 PM.

[davidpitre]

I have one. A 9.25”.
While it can be used at night, I certainly wouldn’t want it as my primary scope. The filter is a part of the corrector and can make some annoying optical effects at night. (Stars can have odd colors,…) It will not have the light gathering ability of a normal SCT of the same size.
As far as solar, you wouldn’t want it as your sole scope. Even the smallest (8”) requires excellent seeing. So unless you have measured your solar seeing and know it to be consistently very good, the scope would be frustrating. Marty mentions that you need moments of < arc” seeing, but I would go further and say you need consistent longer periods of this to find good focus. In my experience consistent 1-3” seeing does not provide the opportunity to find best focus for a second of .7-.8 “
Images.
If indeed, you do have some very good seeing, the scope can produce some very good images. I use an additional Herschel wedge for white light. If you intend to do Ha you will additionally need either a mica etalon or some kind of custom home brew. I use a SS RG18 which works well with it.
As far as other models of solar telescopes, it’s really apples to oranges. . Because of its aperture, it’s difficult to compare it to anything else commercially available.
I also use a 150 mm f/10. I would not recommend a Triband unless you have used a 6 inch for solar successfully, and know that you’re seeing can support substantially larger aperture.

Edited by davidpitre, 06 June 2023 - 07:47 PM.

[C0rs4ir_]

Which aperture do you have ?

How long have you had it ?

Did you consider other models before deciding on this type of scope ?

What tilted your decision in favor of this model ?

Do you use a Solar Spectrum etalon ?

If yes, which model ?

Do you use this scope for deep sky or planetary also ?

 

I hope that's not too many questions.

 

Nice photo gallery.

What camera do you use ?

What do you use for image processing and finishing ?

 

thanks

-I have the 9.25" one.

-Since about 1 year now (2 seasons).

-Yes i considered a separate full aperture D-ERF for my existing C9.25.

-I favoured it because at that time it was the only option to go for a bigger aperture for solar imaging. Apart of this it has a excellent filter curve which also includes 2 other bands, so its more flexible. I dont regret getting this solution despite you cant take it off like a separate D-ERF filter. The mechanical and optical quality of the scope sample is excellent for a celestron sct.

 

-No i use a Quark Chromosphere etalon. But with this scope you can basically use any rear mounted etalon solution.

-No i dont use it for deepsky or planetary.. i only use it for Solar imaging which is my main focus. For other things i use a normal C11. I once used it on the moon and it works, as already pointed out it works best for narrow band deepsky imaging (didnt try myself).

 

Thanks, i mostly use the Player One version of the imx432mm chip (Apollo Max).

Image processing is done with Autostakkert 3, then Imppg or Registax, then Photoshop.

 

Additional: Before this scope i used a 150mm f/8 achromat and realised that the daytime seeing at my location does support more then that.

If i had typical seeing like shown on the graph in the post above i would definitely go for an aperture around 250mm and with lucky imaging i would realize very nice high res images.

The best validation of your conditions remains image results, measurement devices of any sort might give you a good hint though.

Edited by C0rs4ir_, 07 June 2023 - 03:47 AM.

[ch-viladrich]

And additional point about seeing condition : it is not just about how good the seeing is at your place. It is mainly what amount of dedication you put into it. In order words, how long your observing session are.

 

For example, my observing sessions are about 3-hour long. If I cut it down to 20 min, I would never got good images. As said by Marty, this is about lucky imaging ;-)

 

In any case, a Hat 8" is certainly not a good "first" solar telescope. It is way preferable to play with a 150 mm refractor before.

[Coconuts]

Marty (et al):  For places with excellent daytime seeing, would an RC be better than a classical Cass or uncorrected DK?  A corrected DK is another option, but I'm not sure if the near focus lenses would add any SA, or absorb at 393 nm.

 

All the best,

 

Kevin

[MalVeauX]

Marty (et al):  For places with excellent daytime seeing, would an RC be better than a classical Cass or uncorrected DK?  A corrected DK is another option, but I'm not sure if the near focus lenses would add any SA, or absorb at 393 nm.

 

All the best,

 

Kevin

Hi,

 

They will both work ok, they do not use corrector plates that induce SA in near UV. Any pure mirror system will work well. The real issue is simply thermal regulation. If a lens is introduced, it has to be ensured it doesn't induce SA at an important wavelength. So if you're at all concerned for any performance in near UV or long IR, do not use lenses and instead use pure mirror system, such as newtonian or classical cass or the RC or other design with no lenses. The issue with all of them is thermal regulation. I wouldn't use an RC personally (way too fussy to collimate for solar in daytime for my tastes, and the huge central obstruction is a heat sink you would have to cover maybe. I would use something with a small central obstruction. The other issue is back focus distances on these instruments depending on your filter system. A newtonian can be problematic for this if its commercial and not designed for imaging with filter systems that need lots of back focus. A classical cassegrain will be the easier of the bunch to deal with the imaging train. A newtonian is the most flexible, if you can move the primary mirror as needed for back focus purposes. I use a 200mm F6 and 150mm F6 for this purpose, lots of tube space for moving the mirror to get more back focus when needed. If you're using a telecentric system, you usually can be fine with back focus without changing anything. It's collimator lenses that are fussy with placement and would be problematic. Ultimately a refractor lens in a tube with no obstruction is the easiest to thermally regulate and has no issues with collimation and you can use sub-aperture D-ERF to save cost big time (up to around 120mm; I suggest full aperture D-ERF at 150mm and up). Really large ones can be thermally regulated with smaller (but still large) internal D-ERF such as a 200mm lens with a 100~120mm D-ERF behind the primary objective (custom job, truss refractor OTA usually for this). A refractor tube is super easy to deal with back focus because you can shorten the OTA if needed and no obstructions.

 

The 8~10" classical cass that were recently released by GSO are a good platform for all wavelengths for high res attempts and easy to manage. They're a little pricey.

 

Newtonians are cheap, plentiful, and great for all wavelength imaging (especially if F5~F6 or longer). The only thing to deal with is back focus (if needed) depending on the filter system.

 

Very best,

[spatzek]

Its a high fidelity system. I do own the 8” and use it in my observatory at my summerhouse. We have just sold the house. The seeing can support the Triband with my Quantum 0.6Å and SS 0.3Å filters. It really shines with the SS filter. I do own Airylab’s Solar Scintillation Monitor. But back home I have somewhat more turbulence and worse seeing. Thats why I had bought a 155mm TS apo and a 160mm Baader ERF. It will be my new night scope too. 
Even that the Triband is a lot of fun, I know my “new” place will not be the perfect match and its on my sales list. 

[C0rs4ir_]

Its a high fidelity system. I do own the 8” and use it in my observatory at my summerhouse. We have just sold the house. The seeing can support the Triband with my Quantum 0.6Å and SS 0.3Å filters. It really shines with the SS filter. I do own Airylab’s Solar Scintillation Monitor. But back home I have somewhat more turbulence and worse seeing. Thats why I had bought a 155mm TS apo and a 160mm Baader ERF. It will be my new night scope too. 
Even that the Triband is a lot of fun, I know my “new” place will not be the perfect match and its on my sales list. 

Thats a sad story, tough choices with the location for the hobby.

Yes, those systems are challenging what is doable for amateur astronomers. Definite not a first solar scope.

And no, not getting good results in only 15-45 minutes imaging session in 3 wavelengths. 2-3 hours is also what i do usually.

No quick success, buts thats where the fun lies in.

[ch-viladrich]

Marty (et al):  For places with excellent daytime seeing, would an RC be better than a classical Cass or uncorrected DK?  A corrected DK is another option, but I'm not sure if the near focus lenses would add any SA, or absorb at 393 nm.

 

All the best,

 

Kevin

The first and foremost question is : what are the objectives (white light imaging, Ha, Ca K, all) and what aperture ?

 

Once the objectives are set, we can answer what is the best telescope/filter combination.

 

RC is certainly a very bad idea : the central obstruction is huge (about 40%) and it is very sensitive to back focus (in other words spherical aberration builds up rapidely if the distance between both primary and secondary mirors is not the nominal one).

See for example :

http://astrosurf.com...analysis-RC.htm

 

Still, I am contemplating using a 20" solar telescope for white solar imaging this summer. But there are some challenges to overcome ;-)

[pgfossier]

Catching up on all the posts...

 

MalVeauX:

Thank you for pushing the point on my "seeing conditions" - they're not very good where I live: San Francisco (Glen Park).

I can drive 50mns to Marin and get above the fog at 2,500ft where the conditions are much better.

Great pictures.  I am the person who was asking about Daystar Quark vs Lunt.  I am pretty much set on getting a Lunt 80mm with a double stack filter.

 

davidpitre:

Thanks for your comments on the Triband.  As stated above, I need to drive 30mi to get good seeing conditions.

Being somewhat familiar with Baader, I was curious whether their approach had merit.

 

C0rs4ir:

Thanks for the clarifications and details.  I have pretty much given up on Registax - it is becoming staleware at this point

and have opted for AstroSurface which offers a good array of features.

 

ch-viladrich:

My imaging sessions will last as long as needed to get as much data as I can.

I am using SharCap's Seeing Monitor which lets me filter out frames below a given threshold.

 

Thank you everyone for all the information.

I am grateful to have CN as a resource.

 

-p

[MalVeauX]

Catching up on all the posts...

 

MalVeauX:

Thank you for pushing the point on my "seeing conditions" - they're not very good where I live: San Francisco (Glen Park).

I can drive 50mns to Marin and get above the fog at 2,500ft where the conditions are much better.

Great pictures.  I am the person who was asking about Daystar Quark vs Lunt.  I am pretty much set on getting a Lunt 80mm with a double stack filter.

Hi,

The Lunt 80 is a lifetime class instrument that will work every day and give pleasing views; 2 arc-seconds is all you need to get nearly the most out of it. 80mm is a lot of aperture for solar. It's hard comparing nighttime concepts with solar concepts with respect to aperture and seeing. Especially wanting aperture without having a profound understanding of one's local seeing. Lots of people chase aperture, because they can, only to find out they have 2 arc-second seeing or worse.

 

Nothing wrong with going for a big aperture still. I would say go for it if you want, maybe start with photosphere imaging in high res with a 200mm or similar. It costs hardly nothing to use some ND3.8~N5.0 solar film on any 200mm instrument (or whatever size you want). It will let you get an idea of what's possible in your local seeing. If you did want to go forward on a large instrument for chromosphere, then the only producer of large high quality dielectrically coated ERF right now is probably Altair Astro (and they are good, optically flat to 1/8th wave, etc).

 

Having done all of this already myself, one thing I can reflect on is that max aperture is less desirable to me these days compared to simply having good seeing and higher quality more uniform etalons and filters in general and to have highest contrast on CWL of the filter system for isolation (double stack, etc). That's just my thoughts on it now though.

 

I could easily let go of all my stuff and die happy with a Lunt 80 double stack as a do-all instrument for solar.

 

Very best,