Askar ColourMagic Duo with fast focal ratio scope - Forums

Topic starter

Feb 13, 2024

Hello all,
I've been seeing some amazing images taken with the Askar Color Magic Duo Super-Narrowband H-a/O-III & S-II/O-III (D1 + D2) Imaging Filter Set and OSC's. I'm considering purchasing a set. Some filter manufacturers have filters optimized for fast focal ratio scopes (usually f/3.6 and faster) to take account of the centerline shift at fast focal ratios. I'm using a SharpStar 150/2.8 HNT. Does anyone know if these filters will perform well at f/2.8?
Thanks so much,
Arnie

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Georg N. Nyman

Feb 13, 2024

Arnie:
Hello all,
I've been seeing some amazing images taken with the Askar Color Magic Duo Super-Narrowband H-a/O-III & S-II/O-III (D1 + D2) Imaging Filter Set and OSC's. I'm considering purchasing a set. Some filter manufacturers have filters optimized for fast focal ratio scopes (usually f/3.6 and faster) to take account of the centerline shift at fast focal ratios. I'm using a SharpStar 150/2.8 HNT. Does anyone know if these filters will perform well at f/2.8?
Thanks so much,
Arnie

I am following you....same OTA and same question....!

andrea tasselli

Frequent contributor

Feb 13, 2024

Arnie:
Hello all,
I've been seeing some amazing images taken with the Askar Color Magic Duo Super-Narrowband H-a/O-III & S-II/O-III (D1 + D2) Imaging Filter Set and OSC's. I'm considering purchasing a set. Some filter manufacturers have filters optimized for fast focal ratio scopes (usually f/3.6 and faster) to take account of the centerline shift at fast focal ratios. I'm using a SharpStar 150/2.8 HNT. Does anyone know if these filters will perform well at f/2.8?
Thanks so much,
Arnie

If it is the 6nm (which is wrongly quote as the typical passband) Duos you are referring I'm not too pleased with their efficiency, especially in the OIII band. I'd consider it a pass. No halos that I can see at f/4 and at f/2.8 but the test at f/2.8 wasn't very extensive to rule out halos with different star spectra.

Tom Boyd

Feb 14, 2024

For what it's worth, love these filters. I don't, however, use them at F2.8.

I recall, however, in another forum post another user was using them at this focal length and reported no problems.

To Andrea's comment on quoted band width, this is correct. Testing that I've seen, and the way Agena advertises these, suggests the bandwidth is actually 8 to 9 nm…

Gaillard Jérôme

Feb 14, 2024

Unfortunately for you I use them until f/3,8 with my FSQ106ED and it’s focal reducer.
I haven’t noticed any problems with such a focal ratio.

Arnie

Topic starter

Feb 14, 2024

Thanks everybody for the input! I will continue my research and report about what I find. Since these are going to be installed in a remote observatory about 1700 miles away, returning them if they don't perform well at f/2.8 is not an attractive option.

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Daniel Carter

IOTD Staff

Feb 15, 2024

Arnie:
Thanks everybody for the input! I will continue my research and report about what I find. Since these are going to be installed in a remote observatory about 1700 miles away, returning them if they don't perform well at f/2.8 is not an attractive option.

I'm looking forward to seeing how those work out Arnie. I was thinking of using fhose filters for my 135mm Rokinon and ASI2600MC. I'll be stopping down to roughly f/3.0 to f/3.5.

Arnie

Topic starter

Feb 15, 2024

Daniel Carter:
Arnie:
Thanks everybody for the input! I will continue my research and report about what I find. Since these are going to be installed in a remote observatory about 1700 miles away, returning them if they don't perform well at f/2.8 is not an attractive option.

I'm looking forward to seeing how those work out Arnie. I was thinking of using fhose filters for my 135mm Rokinon and ASI2600MC. I'll be stopping down to roughly f/3.0 to f/3.5.

I'll let you know!

Manuel Peitsch

Feb 16, 2024

For what it's worth, I have a good experience with these filters (HaOiii and SiiOiii) on a Takahashi E180 with f/2.8 (FL=500mm). A couple of examples:

HaOiii filter on the Heart nebula.

A) HaOiii filter on the Heart nebula. Raw integration 50x120s exposures (60):

OK Halos that can be rather easily dealt with in post-processing:

B) SiiOiii filter on the Heart nebula. Raw integration 50x120s exposures (60):

Again, halos that are bearable

CS
Manuel

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Arnie

Topic starter

Feb 16, 2024

Manuel Peitsch:
For what it's worth, I have a good experience with these filters (HaOiii and SiiOiii) on a Takahashi E180 with f/2.8 (FL=500mm). A couple of examples:

Thanks, Manuel! Nice images! I'm so glad to see how good they look at f/2.8. I'm going to order a set.

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Jake Lancaster

15 days ago

I'd like to add that I use these filters on my SharpStar 13028HNT and results have been fantastic. I don't feel like I'm losing much signal due to band shift either. They do an excellent job cutting through light pollution too! So much so that I didn't notice much difference shooting in Bortle 7 or Bortle 1!

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Arnie

Topic starter

13 days ago

I completely forgot I even started this thread! Since I promised to report back, here ya' go. This is my first image using the Askar ColorMagic D1 (Ha plus Oiii) and D2 (Oiii and Sii) dual-band filters with my f/2.8 SharpStar and a QHY268C color camera. Even though these are not marketed as "high-speed" filters, they seem to work well even on this scope! Of course, it will be even better once I've collected more data. This is SNR G132.7+01.3, just west of the Fish Head Nebula (NGC 896) which is itself just west of the Heart Nebula (IC 1805). I have not uploaded the full resolution image to my gallery yet, so hopefully it's OK posting this thumbnail image here.

Arnie

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