Antlia triband RGB Ultra - thoughts?

[ONIKKINEN]

New(?) filter from Antlia caught my eye when doing some window shopping for kit that i definitely dont need, but maybe could find a use for. Does this have a use or is it dead on arrival?

This one: https://www.firstlightoptics.com/antlia-filters/antlia-triband-rgb-ultra-filter.html

Bandpass:

Here is why i think it could be useful: Wide bandpass so presumably exposure times are still more or less normal and not narrowband length, something that i need to keep in mind with a newtonian under typically at least somewhat windy skies with a hiccup every now and then guaranteed in guiding. With an OSC camera like the one i shoot with i could easily just extract the greens for OIII and the reds for Ha-SII. I dont expect SII to contribute much here, but still its there. Blue would be extracted more or less as normal blue would and this i would just throw in with the rest of my blue data so its not "lost" like maybe with typical dual pass filters its not contributing nearly as much, and since blue in the IMX571 is quite weak its a welcome addition to get more blue data. I would not use this filter entirely, but perhaps try to get 10h of UV/IR and ? hours of this filter (remains to be seen how much would be needed to get some meaningful emission data). The existence of the blue pass here also means its a lot easier to work into a normal real colour image, unlike just OIII and Ha which is guaranteed to not be presentable as real colour, at least thats what the gimmick of this filter seems to be.

I would initially use it to shoot OIII and Ha on M33 and M31, maybe M101 later in the season (this list is already 2 full imaging years long..). Dont really plan on shooting emission nebulae so im not all that stressed about the very wide bandpasses that would for sure be less than ideal for some dim supernova remnant hunting.

The filter seems like a bit of a gimmick, but an attractive gimmick at that. Maybe a good old L-enhance/Extreme/Ultimate would be better still.

Any thoughts?

[vlaiv]

9 minutes ago, ONIKKINEN said:

Does this have a use or is it dead on arrival?

I would think of it as UHC that preserves star colors (to some extent).

[drjolo]

This filtering path is getting towards some LP filters, like IDAS D2:

[ONIKKINEN]

50 minutes ago, drjolo said:

This filtering path is getting towards some LP filters, like IDAS D2:

Between that and an L-enhance, looks like:

High pressure sodium lamp suppression is of little use these days since more and more of them get replaced by broad spectrum LEDs (might even be 50/50 now here). Maybe better to think of the Antlia one as a wider pass narrowband + blue filter instead of a light pollution one.

[uhb1966]

Hi Onikinnen,

did you go ahead on the filter?

[ONIKKINEN]

1 hour ago, uhb1966 said:

Hi Onikinnen,

did you go ahead on the filter?

I did, and have used it a number of times since. I think its a nice compromise filter for someone who wants to dip their toe into narrowband imaging but isn't just mainly interested in emission nebulae (and preferably no major light pollution - not the ideal filter for that).

Some example images with the filter below:

Couple of hours if i recall, from B8 and moonlight:

This one was a test image on how much it picks up Ha (for 8h total), not sure i ever posted it anywhere since its not really a finished image:

38 minutes from Bortle 3-4:

2h40min, bortle 5-ish maybe:

3 hours if i recall, from bortle 6-ish conditions or thereabouts:

As some closing thoughts RGB processing is not too difficult with the filter with only minor adjustments needed to get an image that has passable/neutral looking star colours, which is the strong point of the filter.

For OAG guiding purposes i had issues with a 120MM that would not guide all that well trough the filter with my f/5 newtonian (filter before coma corrector in this case). Upgraded to a 220MM and never lost a guide star again, so this filter is not too difficult to use from that point of view either. Price seems very cheap too. Overall a recommended purchase for someone who knows what they want.

[uhb1966]

Wow i wish i could make pictures like your test pics...

Edited October 2, 2023 by uhb1966
typo

[ONIKKINEN]

8 minutes ago, uhb1966 said:

Wow i wish i could make pictures like your test pics...

Maybe calling an 8 hour image taken from bortle 3-4 is not all that fair...

Did end up using the data in a 35h total image in the end so not just a test in the end, but this stack and image was processed as a test is what i meant with that.