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ASI 533MC PRO looking for filter for nebulas

Astrophotography Beginner DSO
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#26 bobzeq25

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Posted 28 September 2023 - 02:32 PM



Ok, that sound logical. Better to choose dedicated filters for emission nebulas(like Dualband) and second one like LPro for broadband DS objects. Fortunately this one I've. I t looks that in my case for now I need to buy the only first one.

Filters work well on emission nebulae because the light from emission nebulae is concentrated into 1-3 very narrow bands, and is ideally suited for being sorted out from light pollution by a filter.

 

For other targets, the filter strategy has major flaws.

 

It reduces signal, and you have none to spare.

 

It distorts color.

 

Even the person above giving a lukewarm recommendation for that strategy doesn't use it.

 

The best strategy for reducing  the effects of light pollution for broadband targets is gradient reduction in processing.  Not perfect, but doesn't reduce signal or distort color.  Astro Pixel Processor has an excellent gradient reduction tool, as does other astro processing software.

 

Below is an image I shot of a broadband target from a light polluted backyard (B7).  No (not so) magic light pollution filter was used.  Gradient reduction?  Of course.  Click on the CN thumbnail for a good version, and details.

 

Gradient reduction also improves images of emission nebulae shot with a duoband.  I use it on all my images, and that's pretty much standard practice.

 

get.jpg?insecure


Edited by bobzeq25, 28 September 2023 - 02:40 PM.

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#27 KrisJot

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Posted 28 September 2023 - 04:43 PM

Filters work well on emission nebulae because the light from emission nebulae is concentrated into 1-3 very narrow bands, and is ideally suited for being sorted out from light pollution by a filter.

 

For other targets, the filter strategy has major flaws.

 

It reduces signal, and you have none to spare.

 

It distorts color.

 

Even the person above giving a lukewarm recommendation for that strategy doesn't use it.

 

The best strategy for reducing  the effects of light pollution for broadband targets is gradient reduction in processing.  Not perfect, but doesn't reduce signal or distort color.  Astro Pixel Processor has an excellent gradient reduction tool, as does other astro processing software.

 

Below is an image I shot of a broadband target from a light polluted backyard (B7).  No (not so) magic light pollution filter was used.  Gradient reduction?  Of course.  Click on the CN thumbnail for a good version, and details.

 

Gradient reduction also improves images of emission nebulae shot with a duoband.  I use it on all my images, and that's pretty much standard practice.

 

get.jpg?insecure

Nice photo. Thx for the clarification. It makes makes some things more clear.

 

P.S.

Is it a M31?


Edited by KrisJot, 28 September 2023 - 04:47 PM.


#28 bobzeq25

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Posted 28 September 2023 - 05:04 PM

Nice photo. Thx for the clarification. It makes makes some things more clear.

 

P.S.

Is it a M31?

Yes.



#29 KrisJot

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Posted 29 September 2023 - 03:42 AM

I'm seriourly thinking about Antlia ALP-T. In your opinion, will the 5nm filter be not too narrow for my TSA120 F/6 to properly illuminate weaker nebulas?

Edited by KrisJot, 29 September 2023 - 03:44 AM.


#30 Skysmacker

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Posted 29 September 2023 - 08:53 AM

I'm seriourly thinking about Antlia ALP-T. In your opinion, will the 5nm filter be not too narrow for my TSA120 F/6 to properly illuminate weaker nebulas?

Probably a good choice from what I’ve read about it.

 

If you are asking if 5nm band-pass will be too barrow, then no, it won’t be.

 

It will simply isolate the signal that you want. 5nm is great for a dual band pass filter. The photons from the specific Ha and Oiii emissions hit the camera sensor at the same rate regardless of band pass width. The narrower the band pass, the more “other stuff” (as in light pollution and sky glow) you block out which is what we want in this hobby. 
 

For “weaker nebulas” you simply collect more data to increase total imaging time.

 

5nm won’t be an issue at all. Just fyi, my narrowband filters (SHO) for my mono set up are 3nm band-pass for each. 2.5nm filters were just released not too long ago.


Edited by Skysmacker, 29 September 2023 - 09:14 AM.

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#31 KrisJot

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Posted 29 September 2023 - 04:51 PM

Probably a good choice from what I’ve read about it.

 

If you are asking if 5nm band-pass will be too barrow, then no, it won’t be.

 

It will simply isolate the signal that you want. 5nm is great for a dual band pass filter. The photons from the specific Ha and Oiii emissions hit the camera sensor at the same rate regardless of band pass width. The narrower the band pass, the more “other stuff” (as in light pollution and sky glow) you block out which is what we want in this hobby. 
 

For “weaker nebulas” you simply collect more data to increase total imaging time.

 

5nm won’t be an issue at all. Just fyi, my narrowband filters (SHO) for my mono set up are 3nm band-pass for each. 2.5nm filters were just released not too long ago.

May I ask You what is Your telescope, camera and what exposure time are You using?



#32 Skysmacker

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Posted 29 September 2023 - 08:54 PM

May I ask You what is Your telescope, camera and what exposure time are You using?

Sure, my 533 mono setup is on my Evo80 and my 2600MC is on my FRA300. 
 

Click on the Astrobin link in my signature and you can see more of this info and the exposure times used for each project I posted.


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#33 KrisJot

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Posted 01 October 2023 - 06:56 PM

Short update.

Antlia ALP-T OIII+Ha ordered. After receiving it I'm planning to send it for individual transmittance checking.


Edited by KrisJot, 01 October 2023 - 06:57 PM.

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#34 Skyshooter

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Posted 01 October 2023 - 08:27 PM

Antlia ALP-T. Buy once, cry once, never look back...



#35 GiffS

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Posted 02 October 2023 - 01:15 PM

+1, The NBZ would be my preference to the LExtreme in the $300-ish cost category.

 

However, if your leaning towards the LEnhance, you should consider the zwo DUO filter which has the same bandpass specs at $150 (2-inch).

 

I do know my DUO works great and have not experienced any star halo issues.

I also have the ZWO Duo and have been happy with the results. Down the line I might spring for something narrower but for now the ZWO works pretty well and at a significant savings.


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#36 Borodog

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Posted 02 October 2023 - 04:04 PM

In my opinion if you are in Bortle ~4.5 there is not much benefit from the L-Extreme vs. the ZWO Duo Band:

 

https://www.cloudyni...eme-comparison/

 

Definitely some, but not a tremendous amount, especially if budget matters to you.

 

post-346195-0-06747100-1659891086.jpg



#37 dcharlton

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Posted 02 October 2023 - 06:30 PM

For someone just starting out on a budget, the ZWO Duoband is not a bad option. For even lower cost, the 1.25” version works well with the 533MC. It is susceptible to haloes (as are some other more expensive options.) That said, options such as the NBZ and L-Extreme are superior products for experienced imagers.

 

Here is an example, however, of my ASI533MC Pro and ZWO 1.25” Duoband on the Wizard.

Nice pic of the Wizard!  I've used the L-Extreme and only got red coloring, how did you get the blue tint?

 

DC



#38 AhBok

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Posted 02 October 2023 - 07:15 PM

I’ll send a message showing how I did this rather than hijacking this thread.

#39 bobzeq25

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Posted 02 October 2023 - 07:31 PM

May I ask You what is Your telescope, camera and what exposure time are You using?

Note two things, order of importance.

 

In DSO AP (very unlike terrestrial photography) subexposure time, provided you don't get it really wrong, is much less important than total imaging time.  What counts is how many total photons you capture, how the total is divided into subs is substantially less important.

 

"Optimizing" subexposure is a site and equipment dependent thing.  What others use for subexposure is most often irrelevant to you.

 

Watch this video, see the subexposure table about 51 minutes in.  Look at the _extreme_ variability of optimum subexposure, from a few seconds to several minutes.  The table headers are optical speed (F number) and light pollution level, two key things.  The footnotes discuss read noise, mono versus one shot color, and filters.

 

The good news is that it doesn't matter that much what subexposure you use if you're at all close.  30-60 seconds is a good place to start, broadband.  2-5 minutes, narrowband.

 

The important thing is to shoot more subs.  One hour of total imaging time is minimal, 2 is better, 4 is good.


Edited by bobzeq25, 02 October 2023 - 07:32 PM.

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#40 arbit

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Posted 02 October 2023 - 07:59 PM

One slight tweak to Bob's post on sub time.

If you are guiding then yes.

If unguided, your mount tracking needs to be able to handle the 2-5 min subs (or more, depending on sky brightness and bandpass) that narrow band filters typically need.

Sent from my SM-S908E using Tapatalk

#41 KrisJot

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Posted 02 October 2023 - 08:05 PM

Hi bobzeq25, thx for exposing this. I've found tutorial how to calculate minimum & maximum exposure time based on the factors highlighted by You. I did some math, It looks ~280s should be fine. For darker place (~3.5 Bortle) I receive 320-350s. Better sky means longer exposure time, why? Because of less LP?

P.S.
All calculations done for narrowband filter.

Edited by KrisJot, 02 October 2023 - 08:07 PM.


#42 fmendes

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Posted 02 October 2023 - 08:08 PM

From my research when I was buying the ZWO duoband, the tri-band ones don't offer an increased performance proportional to the price they command (like the triad). At that price, I'd rather go mono. With a triband, Hb and Oiii are mixed in so I am not sure how the extra band will be useful in editing.

 

 

There's a whole topic about the Antlia Tri-Band. Thing is that its bands are not very narrow, and one of the bands is deep into the blue. The filter is good for emission nebuale, some reflection nebulae and galaxies. It is actually cheaper than Optolong l-ehnance.

 

To me, the drawback is that flat files may be tricky because the blue light may saturate the filter, causing a blue smudge on the final image. Can be solved by taking flats with median darker than 50% median.


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#43 bobzeq25

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Posted 02 October 2023 - 11:49 PM

Hi bobzeq25, thx for exposing this. I've found tutorial how to calculate minimum & maximum exposure time based on the factors highlighted by You. I did some math, It looks ~280s should be fine. For darker place (~3.5 Bortle) I receive 320-350s. Better sky means longer exposure time, why? Because of less LP?

P.S.
All calculations done for narrowband filter.

Because...

 

There are a number of ways of calculating "optimum" subexposure.  The basic idea (there are wrinkles, described below) is...

 

If you shoot too many too short subs, you get too much read noise, which accumulates per subexposure.

 

If you shoot too few too long subs stars tend to saturate, and saturated stars have RGB maxed out, so you get white.  No processing can restore the color, it's been obliterated.  Highlights may also be saturated (or "clipped"), which blurs them.

 

To get a good balance, one method is to work on the first problem.  Your subs also have light pollution, "sky noise".  If the sky noise is large enough, the read noise doesn't matter.  It's been "buried" in the sky noise.

 

So, less light pollution, you need to expose longer, to get enough sky noise to bury the read noise with.

 

The problem is, if you have little light pollution, you need such long exposures to get enough sky noise, that the second problem appears.  By the time you've buried the read noise, stars are white, and highlights clipped.  Not good.

 

I used to use that method.  Now, I just work on the second problem, too long subexposures, instead.

 

I shoot a test sub, measure the number of saturated pixels.  Zero is bad, you're not using the full dynamic range of the camera.  So then I increase subexposure.  Thousands are bad.  White stars, blurred highlights.  I decrease subexposure.  I shoot for a few hundred saturated pixels.

 

All these methods work.  Because it's only subexposure, and not all that important.

 

But I've been on CN for years.  Looking at images people post I often see white stars, and blurred highlights.  I believe it's because people make the mistake of thinking you need long subs to capture dim detail.  After all, if you want to shoot a terrestrial photo in dim light, you increase subexposure.

 

But that logic doesn't work for DSO AP, because we stack subs.

 

I've gone back and looked at whether or not I'm burying the read noise.  Usually yes, at least somewhat.

 

Here's an example which shows all these things.  An image I did of the Pleadies.  Note the bright stars are pretty white.  That's always going to happen, they're bright.  But note the dim dust (and it's really dim).  How long did I have to expose to get it?  8 seconds, I took 8 (not a misprint, eight) second subs, and I got it.

 

662 of them.  <smile>  Click on the mediocre CN thumbnail for a better version, and capture details.

 

Another factor was also at work.  I was using an F2 C8 RASA.  Which sucks down photons real fast.  So optimal subexposure is always going to be a lot shorter than, say, an F5.6 scope.  8 times shorter.

 

See why what others use for subexposure may be meaningless for you?

 

One day, all this will be clear to you.  Until then, just do the important thing.

 

Shoot more subs.  <smile>

 

get.jpg?insecure


Edited by bobzeq25, 02 October 2023 - 11:50 PM.

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#44 KrisJot

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Posted 04 October 2023 - 05:51 AM

@bobzeq25 what is the name of this object in the photo above?

#45 fmendes

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Posted 04 October 2023 - 09:45 AM

@bobzeq25 what is the name of this object in the photo above?

Pleiades, Messier 45.


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#46 FortySixand2exas

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Posted 09 October 2023 - 05:10 PM

Bob,

did you post a link to a video in post #39?

 

-Scotty



#47 hoppes no9

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Posted 09 October 2023 - 05:36 PM

Bob,
did you post a link to a video in post #39?

-Scotty


I’m guessing it’s this excellent lecture by Robin Glover.

https://youtu.be/3RH...Q92G37kEM_i7Ots
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#48 TerryD1

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Posted 09 October 2023 - 10:07 PM

I have gotten some nice results with the ZWO duo band and just picked up the Antlia Tri-band which I'm really liking.  No halos and good color.  I'm imaging the SH2-155 as I write this under B6 sky.  I'll post results when I do some processing on it.  One think I'm noticing right away in the subs is very little star saturation at 10 minute exposures. This nebula needs the time. 




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