SolarChat!

Baader announced the prices of their Triband SCT's yesterday.
3.275 euro's for the 8 inch version.
Clear skies, Bart.

https://www.baader-planetarium.com/en/t ... p-sky.html

Skyburner,
What cheaper full aperture multi-wavelength filters have you come across?
These filters are very effective.

Skyburner, I suggest you ask Schott a quote for one 220 mm ERF lambda/4 P-V.
Once you have the answer, you might have a different appreciation ;-)

Hi Group,
I've seen Schott's ERF. But not a 220mm one, it might have been 160mm. They take an thin RG630 and laminate it to a coated bandpass. The one at the show was about 4mm thick. I asked how it would keep the 1/4 wave they clam, if it was in the heat. The problem I have with this idea is that I have seen laminated part fail with heat. Also over the years I have come across a lot RG630 that would not hold up optically in large sizes. This is why Baader's ERF's are no longer on RG630 but BK7.
I don't know how it could cost less in a small batch of one. Just the coating run could cost $5000 with out the glass.
Mark W.

I am just wondering whether we are talking of the same things ?

ERF are large band filters (50 to 150 nm FWHM) centered on Ha and (usually) installed in front of the aperture of the telescope. The optical quality should be OK (better than L/4 P-V).
They become very expensive when aperture increases.There are two reasons for that :
- optical flats windows (typically BK7)are very expensive,
- the process of coating is very expensive.

Mark gave a 5000 USD for a coating run.

This assumes that the coating process is already tuned to what is expected . Usually, it takes several coating tests to succesfully tune the coating process to what is expected. Depending on how many units of ERF you want, you have to pay for the coating test runs or not.

Futhermore, the size of the vacuum chamber is limited. It maybe be that it can accomodate 6 x 200 mm ERF, but only one 300 mm ERF. So the cost of the coating run increases drastically when the size of the ERF increases.

Presently, the largest ERF are made by Aries (about 14") and Baader (280 mm). This being said, it would be nice to have another provider there (further to Aries, Baader, Beloptik and AiryLab).

Skyburner, I am a bit confused. I know the price of a 160 mm Baader Erf because I payed for one: 995 euro without a cell. But the filter you describe is 48mm, with a price of 800 dollar. And it is 3.250 euro for a 8 inch Celestron Edge HD telescope with a Triband-ERF-coated Schmidt corrector plate. That includes the scope. What am I missing that makes Schott cheaper? Thanks! Bart.

christian viladrich wrote: ↑Tue May 08, 2018 1:36 pm

Presently, the largest ERF are made by Aries (about 14") and Baader (280 mm). This being said, it would be nice to have another provider there (further to Aries, Baader, Beloptik and AiryLab).

I can only confirm, that custom made large DERF filters with necessary precision are expensive. We are somewhat less expensive because of labor, electricity etc cost here (Ukraine) are not as high as in the EC countries or in the USA.

Speaking as both an Airylab and Baader Solar reseller, I can assure you that Frederics (Airylab) product is nothing to do with Baaders and its a lot harder to do all this than is being suggested. Low PV maybe but not L4+. It is also easy to see the difference visually between an L4 Glass ERF and an L10 D-ERF. L4 is also L4 what? Glass, Transmission? The filter could be L10 on both sides but if the sides are not parallel, transmission might only be L2.

I know Airylab have experienced lots of pain getting reliable coating and ERF's manufactured. I'm sure Valery has too. You get what you pay for.

Yes, pretty painful as you mentioned Rupert

I did get exchange with Schott Yverdon factory at a time as I know people there. They would make the 200 or 235mm flat windows L/8 at a quite decent price (that is already 4 digits in €, and that was before the swiss Franc increase). But they won't do the coating for such a large size with the quality metric I was asking for (ie less than 10% inhomogeneity, plus a >80% transmission in the Ha band).

Making those ERF get very difficult on a large size because of the inhomogeneity issue. If you have too much difference in term of transmission that causes the same issue as an optical default. Actually making a FFT of the intensity map give an idea of the induced PSF.

BTW, Baader are stad SCT, not edge HD, and have nothing to do with Airylab beside taking over the idea.
And I don't have to remind that making CaK with a SCT is just not possible due to spherochromatism.

Honestly, SkyBurner, what you say is just not credible.

fjabet wrote: ↑Fri May 11, 2018 12:26 pm BTW, Baader are stad SCT, not edge HD

Thanks for clearing that up, my mistake. Thought I had read somewhere they used the Edge.

An easy mistake as the scope is not black.

I've completly missed the fact that the Tri-band is not an Edge-HD :



BTW, my 210 mm AiryLab ERF is L/10 P-V :-)

And your C8 also
I didn't notice that Baader ray tracing is very wrong. At the entry those are the chief and marginals rays, at the exit its a mixed of chiefs rays or standard rays. Actually we could even believe that the system use an afocal rather than a telecentric, and that the last lens that is supposed to be a reducer is converging the beam. I think that the guy who did the drawing was not really into optics...

But its pretty. It has colour and arrows and stuff.....

Do you think when they did the three colour TRI part of the logo it was the same person? Purple for Calcium. Yep. Red for Ha. Yep. Yellow for Continuum, err. Ah but of course, the Sun's yellow

Old thread. But is this still the case that the Baader Triband SCT/D-ERF is not the Edge but a standard Celestron SCT?
Any recent comparison knowledge about the Baader vs Airylabs D-ERF?

Hello David,
I tried a triband 8" in June 2018 (or was it in June 2019 ?). It was a standard Celestron (=not an EdgeHD version).

I do have the "cheap" Baader 8" version. It is a great high definition visual system. Very high contrast and a trillion details. I am very surprised how many days I can use the system out in the real world (seeing). The SS 0.3A filter is a perfect match. I know the Airlab uses the Edge and an ERF with a different profile. But back in 2019 I needed to cut corners... Buying the SS filter and upgrading of my ATM filter etc...

Interesting System..
Would it work with a standard Quark too? Im trying to think this way: triband c9.25 (non edge) + standard reducer/corrector + Quark -> f/27 and then the daystar reducer..
what do you think about that?

DavidP wrote: ↑Mon Jun 21, 2021 4:40 am Old thread. But is this still the case that the Baader Triband SCT/D-ERF is not the Edge but a standard Celestron SCT?
Any recent comparison knowledge about the Baader vs Airylabs D-ERF?

Does it really make a difference if you are at f/30+?
Maybe im wrong, but the only application i see where the edge version is better is if you want to image at f/10 with larger camera-chips.

Dennis wrote: ↑Sat May 28, 2022 6:53 pm

DavidP wrote: ↑Mon Jun 21, 2021 4:40 am Old thread. But is this still the case that the Baader Triband SCT/D-ERF is not the Edge but a standard Celestron SCT?
Any recent comparison knowledge about the Baader vs Airylabs D-ERF?

Does it really make a difference if you are at f/30+?
Maybe im wrong, but the only application i see where the edge version is better is if you want to image at f/10 with larger camera-chips.

The coma free field is the optical difference, which won't matter with image scales in solar on these from F10 to F30+.

The other physical difference is the edge has mirror locks. That would be important to position the mirror and collimate it and lock it (no mirror shift) and then use a secondary focuser in the imaging train (crayford or helical).

Very best,