Adding new data to existing data

[Chefgage]

Had a search on here but could not see the answer.

I took a set of data earlier in the year and processed it. Very happy with the result. This was data taken with a modified DSLR and samyang lens, no filters.

I now want to add Ha data to it using my Ha filter. Question is do I need to match the exposure time for the Ha with that of the DSLR data. I just took 180s exposures with the dlsr (no filter). Could I go longer with the Ha?

The Ha will obviously be stacked separately and then blended in PI with the existing image.

[AstroNebulee]

I'm not an expert by any means but if I were in your situation, I would do them the same exposure length. 

[scotty38]

I'd actually go the other way and say there's no need to match exposure, in fact capturing just Ha most likely wants a longer exposure than catching all wavelengths.