Is a UHC filter suitable for galaxies?

[StuartT]

For bright emission nebulae I've been getting nice results with a OSC and an Optolong L Extreme in my Bortle 6 sky.

But I am starting to try galaxies with no filter and my question is would I get better results with a UHC filter? Or would losing the blue, green, orange and yellow cut too much good stuff from the galaxy?

Maybe it's just better to stick to no filter and get more integration time and process out the gradients?

Thanks

Edited March 24, 2022 by StuartT

[Stuart1971]

5 minutes ago, StuartT said:

For bright emission nebulae I've been getting nice results with a OSC and an Optolong L Extreme in my Bortle 6 sky.

But I am starting to try galaxies with no filter and my question is would I get better results with a UHC filter? Or would losing the blue, green, orange and yellow cut too much good stuff from the galaxy?

Maybe it's just better to stick to no filter and get more integration time and process out the gradients?

Thanks

I use the Optolong L pro, seems to work well, I sold my Idas, as this worked better…👍🏼

[StuartT]

34 minutes ago, Stuart1971 said:

I use the Optolong L pro, seems to work well, I sold my Idas, as this worked better…👍🏼

Excellent! Thanks. I didn't know about the L Pro, but it looks just the job! I've now ordered one 🙂

[ONIKKINEN]

My mantra on galaxy imaging is that broadband filters have too many negatives to be of any decent use and i dont see how one would be useful, unless in awful conditions (Bortle 8 maybe).

Firstly, real colour results are off the table, because a large part of the spectrum is blocked. Expect everything to look blue with most broadband filters. With CLS filters you get green results as most of the reds are gone.

Second, blocking light pollution also blocks the galaxy itself. Starlight is mostly the same colour as sunlight, which is what artificial lighting tries to emulate, and light from galaxies is almost entirely starlight with a speck of emission here and there in actively starforming galaxies. So by blocking the part of the spectrum where light pollution is most intense, you also block the brightest* part of the galaxy.

* Depends on the galaxy partly. Very active spiral galaxies like M33 are noticeably bluer than most other galaxies, so the negatives are less apparent while still there.

[Stuart1971]

4 minutes ago, ONIKKINEN said:

My mantra on galaxy imaging is that broadband filters have too many negatives to be of any decent use and i dont see how one would be useful, unless in awful conditions (Bortle 8 maybe).

Firstly, real colour results are off the table, because a large part of the spectrum is blocked. Expect everything to look blue with most broadband filters. With CLS filters you get green results as most of the reds are gone.

Second, blocking light pollution also blocks the galaxy itself. Starlight is mostly the same colour as sunlight, which is what artificial lighting tries to emulate, and light from galaxies is almost entirely starlight with a speck of emission here and there in actively starforming galaxies. So by blocking the part of the spectrum where light pollution is most intense, you also block the brightest* part of the galaxy.

* Depends on the galaxy partly. Very active spiral galaxies like M33 are noticeably bluer than most other galaxies, so the negatives are less apparent while still there.

Hmmm, I used an L-extreme 7nm Ha, and OIII, last week, and got some good subs of M81 and M82, but each to there own…👍🏼

Any filter I have ever used shows the stars, so should show any galaxy, just with a lack of colour, but some BB subs with no filter will give the colour….

Edited March 24, 2022 by Stuart1971

[ONIKKINEN]

2 minutes ago, Stuart1971 said:

Hmmm, I used an L-extreme 7nm Ha, and OIII, last week, and got some good subs of M81 and M82, but each to there own…👍🏼

M82 has a significant starburst thing going on that is bright in Ha so its not a bad choice for that, or the many emission regions within M81. But to capture the galaxy itself, especially M81 since its face-on towards us would be faster without the filter. Starlight will still radiate in OIII and Ha even though they do not "emit" in it like nebulae so filter or not there will be a picture in the end.

[Clarkey]

39 minutes ago, ONIKKINEN said:

My mantra on galaxy imaging is that broadband filters have too many negatives to be of any decent use and i dont see how one would be useful, unless in awful conditions (Bortle 8 maybe)

I'm with Onikkinen on this. I try to avoid filters (except for narrowband) and collect as much data a possible then deal with the gradients in processing. Use more shorter subs and get a better S/N ratio. I image in Bortle 5/6 and don't use LP filters. If I lived in a city centre I might feel differently......

[powerlord]

yeh I'm Bortle 6 and have found LP filters don't help for galaxies. shoot ones that are high, avoid moon in the sky and take lots of subs.

and APP is great at light pollution removal.

Edited March 24, 2022 by powerlord

[jacko61]

I accidentally left my explore scientific UHC filter on instead of my UV/IR cut when I imaged NGC2903 in LEO the other night and I was very disappointed with the results.  For whatever reason, there seemed to be an overwhelming yellow/orange cast that no amount of fiddling in Startools would remove. On the other hand, Wednesday night's M51 using the UV/IR has turned out exactly as I'd hoped with minimal colour adjustments. 

Graeme

[StuartT]

22 hours ago, powerlord said:

and APP is great at light pollution removal.

could you elaborate on how this is done? I don't understand any of the settings in APP, so I only ever use it with all the defaults (i.e. I just load up my frames, hit 'integrate' and go to bed)