Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 12/09/2021 - 20:43
https://www.baader-planetarium.com/en/blog/coming-soon-new-baader-sloan-sdss-ugriz-photometric-filters/
I wonder whether anyone has tried them already.
Cheers
HB
I am also waiting on any feedback from these. Two Chroma V filters I had have failed and are in need of replacement. The reports on the same new line of Baader imaging filters on the astrophotography forums have not been great, with reports of QC issues between filters. Baader's reply is that they are targeting and price point, and that Chroma or Astrodon quality is not to be expected essentially.
With Astrodon now out of the picture, I feel a bit lost as to what filter brands of J-C UBVRI are considered acceptable or 'approved' by the AAVSO. To my knowledge there is no list provided by the AAVSO, and I don't really understand why not. From perusing these forums, Astrodon was the closest to be universally (but unofficially) accepted.
Keith
You may wish to look at Custom Scientific BVRI filters. I do not know if any AAVSO members evaluated their filters. I purchased some Sloan versions and received them in a reasonable timeframe. They are a little more expensive than Astrodon filters. They are a US based company and I felt they were responsive to my questions.
http://www.customscientific.com/astronomy.html
-Paul
I started with Custom Scientific B & V filters but found that one of them (I can't remember which) became scabrous after <~10 years and I switched to Astrodon. I believe this was a common problem but I don't know if it still is. The CS filters (coloured glass) didn't have the throughput of the Astrodons (interference.)
My problem now is that I want to add a clear filter (one of my scopes has a custom built focuser that I have not yet managed to automate so I have to manually refocus in the observatory whenever I switch from B or V to CV) but haven't been able to get one. And Astrodons are 3mm thick which seems to be different from everybody else.
Is Astrodon really dead or is this recent unavailability just a Covid supply issue? If it is dead then it didn't take Optical Structures long to kill it.
Richard
Just received a reply from Farpoint/OSI support to my question "Will you ever be making the Astrodon Johnson/Cousin's filters again?".
Reply: "Yes, I just don't [sic] a good date for when they will be back in stock. We are targeting early next year.".
Sooo.... maybe?? Who knows at this point as responses to the same question from different people seem to vary.
Keith
Keith,
I would be interested to know the age of your Chroma V filters and how they failed. Were these the current flat top, straight side interference filters? Custom Scientific makes a similar line of BVRI interference filters. I haven't heard any negative reports on these CS filters.
CS will also make Bessel (colored glass UBRVI) filters on special order, but they don't recommend them for use in damp climates.
"Baader's reply is that they are targeting and price point, and that Chroma or Astrodon quality is not to be expected essentially."
Do you know the source of this statement? It doesn't sound like something a representative of a company would say.
Phil
Hi Phil. The original filters were purchased directly from Chroma in 2015, and were the not the newer flat top filters but the older more J-C like ones. I'm not sure exactly when the original B filter started to degrade, but it got bad enough that I contacted Chroma last summer (2020). To their credit, despite being long out of warranty, they replaced both B and V (V was fine) with new old (2015) stock they still had on hand. Customer service was excellent.
Unfortunately, now the replacement V has already failed and is unusable (B is still good). Note in the photo of the V failure, it was installed in my filter wheel last year clean, and never touched since. I did try to clean it (which you can see a bit in the photo), but the failure is obviously not going to be solved by a cleaning. The linear pattern is especially interesting.
Chroma's best guess to the failures was temperature/humidity, and that the newer sputter technology filters are not affected by this.
https://drive.google.com/file/d/1WqnF3WyHgd3Tjqzb9NzTJnwAkpIssdMc/view?usp=sharing
https://drive.google.com/file/d/1StCqAjcCb1XRnZgGHIR9PVuaORxebQ-3/view?usp=sharing
Back in 2015, Chroma was not very well known, and were the most affordable for UBVRI filters. Times have changed. But I won't be buying Chroma again for several reasons.
As to the Baader statement, that was from a post on Stargazers Lounge (I assumed the poster was a legit rep of Baader):
https://stargazerslounge.com/topic/377079-new-cmos-optimised-baader-ultra-narrowband-filters/?do=findComment&comment=4117210
I'm probably going to go with Optolong, unless FarPoint actually comes through with their spring 2022 estimate on new Astrodon stock.
Keith
Keith,
Thanks for your very informative and somewhat worrisome reply.
Chromas: Do you know if the 2015 versions of the failed filters were colored glass or interference filters? These look like colored glass. I have never before seen the linear pattern which your picture shows in the V filter.
For the new UBVRI Chroma interference filters, we are all still waiting for information.
Baaders: I must at least give the guy credit for being frank about the quality of their new filters. I had always thought of Baader filters as being of very good quality.
For pretty pictures, I can kinda sorta see the point. He is saying that these new filters are less expensive. Yes, they have some problems but if you spend extra time in processing the images you can pretty much clean them up. Let us hope that this policy does not apply to the new photometric filters. I will look at the new Baader BVRI filters with an open mind, but now I'm worried.
Optolongs: Arne's testing showed red leaks in the U and B filters, but gave good results for the V,R,I filters. The red leak in B would cause problems for observations of "red" stars (the B magnitudes would be too bright), but the B would probably be okay for observations non-red stars. For transformed V measurements of red stars you could observe them in V and I.
Also, if your Chroma B is still good, you might experiment with using the Chroma B with Optolong V,R,I.
Phil
I'm pretty sure they were coloured glass. I read about the Optolong red leak in B, so was considering as you suggested and trying the Chroma B with Optolong V and I. But they'll be far from parfocal as Chroma are 4.9mm thick, whereas I think Optolong are 2mm.
I'm all for trying the Baader as well but was hoping someone else beats me to it! What should be made of the very different Baader I curve vs. the Astrodon or Optolong that only extend to about 900nm?
Keith
"What should be made of the very different Baader I curve vs. the Astrodon or Optolong that only extend to about 900nm? "
Keith,
I think that atmospheric attenuation and decreased silicon sensor response beyond 900nm would probably keep this from being a problem, but this might be worth checking once the filters are available.
I refer to my old Schuler booklet, dated 1999, which came with my first photometric filters. The booklet showed spectral transmission plots for each each filter, then for each filter with atmospheric attenuation at 45 degrees altitude, and sensor response with each of the common CCD chip makers of the day (Kodak, SITe, TX Instruments).
The Schuler Bessell I filter by itself had a transmission of about 60% at 900nm, but with the atmospheric attenuation and CCD responses the transmission was about 3%.
I have ordered a set from Baader but they have not arrived yet. Will report back when I have them.
TG
Have now received these, and in use for a few weeks. No cosmetic issues. Images look fine. I tested relative flux transmission on a range of stars, and they behave about the same as the set of Astrodon Gen2 I had on loan. Photometry ok as well.
So overall pretty satisfied.
TG
I thought about buying the Baader but decided against it since the Astrodon filters seemed to be the most established.
I suggest you read the complete contents of this topic:
https://www.aavso.org/survey-who-needsreceived-johnsoncousin-or-sloan-photometric-filters