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Narrowband Filter Exposure length

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#1 Huangdi

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Posted 14 January 2020 - 12:07 PM

I finally got enough money saved up to buy some narrowband filters. Now here's my predicament: How narrow?

I'm shooting in Bortle 4 skies and will soon have access to Bortle 2 skies. I use a ha-modded D3300 which I intend to attempt to mono-mod in the near future.

My scope is an Orion Ed80 which will be shooting at F6, mounted on an iExos100.

Now for the fun part, I've decided that astrodons or chromas are too expensive, optolong seem to produce worse results so I believe Baader will be the right choice. They offer 3.5nm and 7nm filters.

My mount isn't the best but it can easily do 10-15 min subs at that FL. Would this be enough for a 3.5nm filter in my skies and with my optics?

I would have loved to borrow a filter and see for myself but sadly Noone does NB-AP in my region.

Thanks for your help in advance!

Edited by Huangdi, 14 January 2020 - 12:08 PM.


#2 Madratter

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Posted 14 January 2020 - 12:13 PM

Buy the narrowest filters you can afford. You get much better contrast with narrower filters. The actual emissions you want are very narrow indeed, and the narrower, the less other light gets in to kill your signal to noise.

 

I know you're not interested in Astrodon's but this page explains what I am saying.

 

https://astrodon.com...owband-filters/

 

There are exceptions if you have very fast optics, but you don't.



#3 Huangdi

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Posted 14 January 2020 - 12:27 PM

Buy the narrowest filters you can afford. You get much better contrast with narrower filters. The actual emissions you want are very narrow indeed, and the narrower, the less other light gets in to kill your signal to noise.

I know you're not interested in Astrodon's but this page explains what I am saying.

https://astrodon.com...owband-filters/

There are exceptions if you have very fast optics, but you don't.


I do understand that the narrowest is the best. But even the website states exposure times of 30-45 minutes and I many images with very narrow filters that I've seen use exposures in that range as well. I can't expose for that long. Will this filter cause my images to be underexposed at let's say 10 minutes?

#4 terry59

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Posted 14 January 2020 - 12:41 PM

If you are considering Baader 7.5nm Ha take a look at Chroma 8nm

 

https://www.cloudyni...-8nm-ha-filter/



#5 bobzeq25

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Posted 14 January 2020 - 12:56 PM

I finally got enough money saved up to buy some narrowband filters. Now here's my predicament: How narrow?

I'm shooting in Bortle 4 skies and will soon have access to Bortle 2 skies. I use a ha-modded D3300 which I intend to attempt to mono-mod in the near future.

My scope is an Orion Ed80 which will be shooting at F6, mounted on an iExos100.

Now for the fun part, I've decided that astrodons or chromas are too expensive, optolong seem to produce worse results so I believe Baader will be the right choice. They offer 3.5nm and 7nm filters.

My mount isn't the best but it can easily do 10-15 min subs at that FL. Would this be enough for a 3.5nm filter in my skies and with my optics?

I would have loved to borrow a filter and see for myself but sadly Noone does NB-AP in my region.

Thanks for your help in advance!

 

 

I do understand that the narrowest is the best. But even the website states exposure times of 30-45 minutes and I many images with very narrow filters that I've seen use exposures in that range as well. I can't expose for that long. Will this filter cause my images to be underexposed at let's say 10 minutes?

3.5 will be better, no matter what the exposures.  Just shoot more subs.  Total imaging time is the most important thing.

 

Some underexposure simply means read noise will intrude a bit more.  Not a deal breaker.

 

This is one reason why people like better mounts, of course.  The reason you see long exposures with the 3.5nm is that people serious enough to spend the extra for the 3.5s are usually serious enough to have the better mounts.  I think you'll find those go along with the long exposures.  It's not the filters themselves.


Edited by bobzeq25, 14 January 2020 - 12:58 PM.


#6 Huangdi

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Posted 14 January 2020 - 01:03 PM

3.5 will be better, no matter what the exposures. Just shoot more subs. Total imaging time is the most important thing.

Some underexposure simply means read noise will intrude a bit more. Not a deal breaker.

This is one reason why people like better mounts, of course. The reason you see long exposures with the 3.5nm is that people serious enough to spend the extra for the 3.5s are usually serious enough to have the better mounts. I think you'll find those go along with the long exposures. It's not the filters themselves.


Alright that decides it then! 3.5nm it is

Yeah if it was up to me I'd buy a cem60... Sadly it's up to my bank account :D
  • bobzeq25 likes this


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