filter opinions wanted - Forums

Topic starter

Apr 9, 2021

Hello everyone,
I have a full set of 36mm Antlia filters. The narrowband are 3.0nm for the Ha and 3.5nm for the Sii and Oiii. I also have a full set of 31mm Astronomic with the 6nm narrowband set. I'll be using either set on a Redcat 51 with the asi1600 camera. Which do you all think would be the best combination living in a Bortle 6-6.5 area?
Clear Skies

Olaf Fritsche

Apr 10, 2021

It depends on your target and the radiation it emits. For your telescope and camera every set of your filters should be great.

Bogdan Borz

Apr 10, 2021

Go for the Antlia filters. Narrower means better SNR. Larger (36 vs 31mm) means less chance of vignetting. The only discussion is the 3nm Ha vs 6nm Ha. The 3nm will not capture the N2 emission line. Since you want to use it with the Redcat, it won't matter, because it is usually found in planetary nebulae. You will be fine with the large field emission nebulae you target with the Redcat.

CS,

Bogdan

Brian Meyerberg

Topic starter

Apr 10, 2021

That’s what I’ve been leaning towards and I haven’t noticed any vignetting at all the 3 nights I used them. The Astronomiks are great filters even though only 6nm, I feel their quality is better. Thank you.

HR_Maurer

IOTD Staff

Apr 11, 2021 · Edited: Apr 11, 2021

Hi,
without having considerable experiences, i'd add the following two cents to the discussion:
If the argument for the wider HII filter is the by-catch of NII, one has to consider that SII and OIII double lines. OIII being 500.69 and 495.89 nm.
SII being 671.7 and 673.0 nm.
So, at least the Sulphur lines are close togehter, and it would require a somewhat wider SII band to get them both. For OIII the width of the transmission band had to be quite large for catching both, thus allowing more continnuum to come through.

I think it always depends on the light pollution at your site, and also on your f-ratio (blue-shift). The Redcat has f/4.9, this shouldnt cause any problems with the narrower filters. With faster optics there will be transmission loss, for the narrower filters first.

CS
Hoschie

Brian Meyerberg

Topic starter

Apr 11, 2021

Thank you. I guess there can always be some trade off in which band pass width filters one uses. I’m currently processing images in LRGBHa for the Markarian galaxy chain and the Jellyfish nebula to test the Antlias out.

Brian Meyerberg

Topic starter

Apr 11, 2021

I just tested the Antlia filters with the Redcat 51 using the asi1600mm camera. I didn’t like the halos the Ha 3.0 filter produced. I will be shooting the same target same parameters with the 6.0nm Astronomik filters to compare. I don’t ever remember getting any halos with the Astronomik filters using my Meade 80mm triplet and the same camera.

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