Stacking filters

[CraigD1986]

Hi All.

I use 1.25" filters with the ASI533MC Pro, which just screw into an adapter ring right in front of the sensor. I have an Optolong L-enhance and an Astronomik L3. It has been suggested that I physically stack the two when imaging nebulae so that I get the benefits of tighter stars from the L3 as well as the benefits of the L-enhance when using my doublet refractor (Skywatcher 72ED). Is it common practice to stack filters like this?

TIA.

[ONIKKINEN]

Doesn't look like stacking the 2 would have any effect because the L3 has a much wider pass than the L-enhance.

 

You could stack the L-enhance + red or green filter to let trough only OIII or Ha instead of both. This would tighten the stars a fair bit, but of course youre only letting one of the bands through so it will be more time consuming to get an HaOIII image out.

 

[CraigD1986]

That’s what I thought. It did seem like an odd suggestion. Thanks for the confirmation

[vlaiv]

On 10/04/2023 at 14:18, CraigD1986 said:

Is it common practice to stack filters like this?

Depends on filters in question.

You need to look at curves of both filters and see where they overlap. If they overlap completely - you don't need to stack - use one that is more restrictive - in above case, L-eNhance is completely within band of L3 - so you don't need to use both. You can use both if you have L3 "permanently" mounted in front of flattener for example (many people use 2" version in front of flattener so that it's always applied and they don't need to think about it and can use their filter wheel for other filters).

If they partially overlap - then their combination will be intersection of their bands.