Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Narrowband filter decision (3nm)?

  • Please log in to reply
4 replies to this topic

#1 jeffcrilly2

jeffcrilly2

    Explorer 1

  • *****
  • topic starter
  • Posts: 93
  • Joined: 25 Jun 2011

Posted 22 June 2021 - 01:52 AM

I have Baader SHO LRGB 36mm filters (iirc these are 6nm) from a while back when I purchased an ST-8300m.

I am now using the these filters with a QHY-268M.

 

I've been considering getting narrower SHO filters , e.g. 3nm.  

(And, btw, I won't be using fast optical systems -- the fastest OTA I have is f5, tho I'm doing some experiments with a 12" at f4.)

 

It seems the word on the 'net is the Astrodon or Chroma filters are the ones to get, but they are pricey at about (?) $2.5k for the set (Chroma may be more $$).

(Also, availability seems to be problematic, as was the case years ago when I considered Astrodon instead of Baader.)

Now, I see Baader has these "CMOS" optimized filters, and the message is lots of work/testing was done to reduce/eliminate Halos.

 

Fwiw, I do have some bright star halo issues with the current filters... and thinking about it, I'm thinking the halos are specific to using a flattner (and possibly a reducer).
(I'll need to do some experiments, but I don't think I get Halos with some OTAs where I don't use a flattner or reducer.)

Also, regarding the Halos and "CMOS":  I had halos with the ST-8300m camera, so it's not CMOS specific.

Anyhow, the new Baader 3nm filters are "reasonably" priced (afaict) (not sure about availability tho), and I'm considering taking the plunge.

 

Anything else out there I'm missing that I should consider?

 

thx

-jeff

 

Ps here's an M17 HOO with Baader filters and QHY268M, 6x5min on Ha and OIII each, and it could use better processing.

 

M17-HOO.jpeg

 


  • limeyx likes this

#2 Woodbridge_Dave

Woodbridge_Dave

    Vostok 1

  • -----
  • Posts: 183
  • Joined: 23 Jun 2009

Posted 22 June 2021 - 05:29 AM

The HA should not be 3nm because that will cut out the N2 line.   A 5nm HA is a better choice.   As for 03 and S2, 3nm is a great choice.  Don’t forget the AntLia brand.  Very good filters.  



#3 terry59

terry59

    Voyager 1

  • *****
  • Posts: 10,462
  • Joined: 18 Jul 2011
  • Loc: Colorado, USA

Posted 22 June 2021 - 06:17 AM

I purchased the Baader 3.5nm Ha filter and planned to get the OII and SII but the OIII was never available and the little I could find was negative due to halos. The Ha also shows some haloing on bright stars (ie Propus). It was used on my f/4.8 SV70T. I've gone with Chroma and have zero haloing.

 

Chroma really increased the price of 3nm filters recently but 5nm and 8nm prices for 1.25" and 36mm stayed the same (last I looked...it's been several months now)

Attached Thumbnails

  • Capture.JPG

Edited by terry59, 22 June 2021 - 06:18 AM.


#4 SilverLitz

SilverLitz

    Surveyor 1

  • -----
  • Posts: 1,609
  • Joined: 17 Feb 2018
  • Loc: Louisville, KY

Posted 22 June 2021 - 12:21 PM

Chroma & Astrodon filters are 3mm thick, while the Baaders are 2mm thick, so there will be focusing issues if you use an OAG, e.g. the OAG will have to be focused differently for the 3mm filters than the 2mm thick filters.  Because of this, I would expect Antlia would be a better/cheaper alternative if you use an OAG.  If you use a guidescope, this will not be an issue.  Astronomik (6nm) will also have OAG issues as they are 1mm thick.

 

Also, Baader NB are not 6nm, but 7/8/8.5nm bandpass.



#5 jeffcrilly2

jeffcrilly2

    Explorer 1

  • *****
  • topic starter
  • Posts: 93
  • Joined: 25 Jun 2011

Posted 23 June 2021 - 01:58 AM

The HA should not be 3nm because that will cut out the N2 line.   A 5nm HA is a better choice.

 

 

Thx for that info... I did not realize this and just read an article on astrodonimaging.com regarding the loss of NII signal on some objects (PNe) when using 3nm filters.  
The Baader "ultra narrow" Ha is actually (according to Baader it seems) 3.5nm.   And according to Baader, the Ha 3.5nm filter will indeed block NII.

I believe there are two lines of "new" (so-called CMOS-optimized) Baader filters, with marketing names:

 

  - Ultra narrowband and

  - Narrowband

 

Ultra-narrowband looks to be 3.5nm for Ha and 4nm for SII and OIII.  (However the specs have not been published)

These have the "Reflex Blocker" which I assume is intended to remove/minimize the halos

URL:

https://www.baader-p...iii--s-ii).html

 

Narrowband looks to be 6.5nm for Ha, SII and OIII.

These also have the "Reflex Blocker".  The only difference seems to be the passband width.

URL:

https://www.baader-p...).html?___SID=U

Additionally, the above two filter passband widths are available for "f/2" optics; The f/3.5-f/10 version is fine for my use.   So there are 4 different product filter sets:  NB, UNB, F/2 NB, F/2 UNB.

 

NOTE:  Prior to July 2021 the Baader narrowband filter sets do not have the "reflex blocker", as far as I can tell.

These older filter sets show on the website with the note: "Only while stocks last" as they will be replaced by the CMOS-optimized filters.    I see no reason for purchasing the pre-July-2021 filter sets except for the huge cost savings.

 

The Baader website does claim "no halos, no reflections, no ghosting" on the new and "old" filters.  However I suspect this claim has caveats, and are dependent on the imaging path.   Also, I'm not sure if this applies to the "vintage" Baader filters I have -- I would not be surprised if the filters were improved over the years.  (The date on my ST-8300m pictures are 2010, so I would likely have purchased those filters in 2010.)

Anyhow, I'm interested in the "new" filter sets, with "Reflex Blocker"; it seems these won't be out until July 2021; (I didn't realize that.)

 

I guess the next thing is to find some objective tests or pre-release reviews of the "new" CMOS optimized filters.  Baader has some pictures with high-end cameras.   I suppose the thing to do is just spring for a set, load them up in the filter wheel and compare them more-or-less side-by-side with the "vintage" Baader filters.

 

¯\_(ツ)_/¯

-Jeff


Edited by jeffcrilly2, 23 June 2021 - 02:00 AM.

  • j.gardavsky likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics