Moving from broadband to narrowband...

[TiffsAndAstro]

...and stuff I haven't thought of

will I need to up my exposure time from my now default 60 seconds, as I'll be getting less light, but a higher proportion of the good stuff? 90% reduction in light means I might need 10 minutes subs. Total exposure time won't be too much different except maybe minus 20 minutes of rgb subs for stars.

I'll need flats for each filter, but not darks and bias?

processing, I can carry on as I have been or I can split Ha and Oiii and process them separately and then composite them. Can also do a fake sho pallette.

are there any obvious stuff I might not have considered when moving to narrowband with my osc?

[carastro]

I believe there is a second dual band filter you can buy which includes Sii so you can do real SHO.  
 

Can’t advise on sub length as l use mono and CCD so others will have to advise on that.  Pretty sure you will still need darks and Bias.  
 

l always process narrow band filters separately before combining as Ha has the strongest signal and the others need a bigger stretch.  

[TiffsAndAstro]

6 minutes ago, carastro said:

I believe there is a second dual band filter you can buy which includes Sii so you can do real SHO.  
 

Can’t advise on sub length as l use mono and CCD so others will have to advise on that.  Pretty sure you will still need darks and Bias.  
 

l always process narrow band filters separately before combining as Ha has the strongest signal and the others need a bigger stretch.  

Sadly siril only has a split Ha/Oiii script. I'll look see if anyone wrote one I could use or maybe edit the values to work on different frequencies.

Lots of options on pallettes.

I meant do I need filter specific darks and biases? Do you use different dark and bias  library sets for each filter?

Thanks for the help

Edited Monday at 19:09 by TiffsAndAstro

[smashing]

49 minutes ago, TiffsAndAstro said:

...and stuff I haven't thought of

will I need to up my exposure time from my now default 60 seconds, as I'll be getting less light, but a higher proportion of the good stuff? 90% reduction in light means I might need 10 minutes subs. Total exposure time won't be too much different except maybe minus 20 minutes of rgb subs for stars.

I'll need flats for each filter, but not darks and bias?

processing, I can carry on as I have been or I can split Ha and Oiii and process them separately and then composite them. Can also do a fake sho pallette.

are there any obvious stuff I might not have considered when moving to narrowband with my osc?

I think you will need to up your exposure time but its not as much as you think. Using a 2500MC pro i've not had to go beyond 5 min subs using an L-extreme filter (see my other post recently to see what I mean) and I have messed around with 3 mins ones and its been ok

You wont need specific darks or biases for filters, flats you will.

Edited Monday at 19:39 by smashing

[TiffsAndAstro]

9 minutes ago, smashing said:

I think you will need to up your exposure time but its not as much as you think. Using a 2500MC pro i've not had to go beyond 5 min subs using an L-extreme filter (see my other post recently to see what I mean) and I have messed around with 3 mins ones and its been ok

You wont need specific darks or biases for filters, flats you will.

Ty will have a read. Planning on sticking with 60sec but if my guiding changes go well will go higher.

Depending on what I read in your recent post

[Elp]

Duration depends on target, local LP and what you're trying to achieve.

I usually stick to 60-120 but recently have been going up depending on what I'm trying to capture.

[TiffsAndAstro]

1 minute ago, Elp said:

Duration depends on target, local LP and what you're trying to achieve.

I usually stick to 60-120 but recently have been going up depending on what I'm trying to capture.

Guess maybe I'll try a range see how they come out.

[TiffsAndAstro]

Should I 3ppa and phd2 calibrate with my UV/ir cut then swap in the dual narrowband filter? Then a focus check and go ?

[WolfieGlos]

You will definitely need longer exposures in narrowband over broadband.

Just look at the histogram and the min values. For my skies, if in an area less affected by light pollution and with Moon, I tend to go for either 120 or 180s on broadband.

With narrowband, I have just recently been imaging at 360s with the 585mc on gain 252 with the Askar C1 Ha/OIII filter and to be honest, it's probably not quite enough as it's barely off of the left-hand side. But with my DSLR with the l'enhance on ISO-400, 300s was perfectly OK on the histogram. This might be down to a tighter bandpass between the filters, but I work on the basis that as long as you are not clipping the darks on the left-hand side, it'll be OK. Try experimenting and working within the limits of your mount and like Elp says, it will depend on your skies and LP.

4 minutes ago, TiffsAndAstro said:

Should I 3ppa and phd2 calibrate with my UV/ir cut then swap in the dual narrowband filter? Then a focus check and go ?

Wouldn't hurt I suppose, but you could always crank up the gain for 3ppa using the dual narrowband if you're worried. I plate solve with 7s exposures with the dualband with no issues, so see no reason why 3ppa wouldn't work?

[TiffsAndAstro]

24 minutes ago, WolfieGlos said:

You will definitely need longer exposures in narrowband over broadband.

Just look at the histogram and the min values. For my skies, if in an area less affected by light pollution and with Moon, I tend to go for either 120 or 180s on broadband.

With narrowband, I have just recently been imaging at 360s with the 585mc on gain 252 with the Askar C1 Ha/OIII filter and to be honest, it's probably not quite enough as it's barely off of the left-hand side. But with my DSLR with the l'enhance on ISO-400, 300s was perfectly OK on the histogram. This might be down to a tighter bandpass between the filters, but I work on the basis that as long as you are not clipping the darks on the left-hand side, it'll be OK. Try experimenting and working within the limits of your mount and like Elp says, it will depend on your skies and LP.

Wouldn't hurt I suppose, but you could always crank up the gain for 3ppa using the dual narrowband if you're worried. I plate solve with 7s exposures with the dualband with no issues, so see no reason why 3ppa wouldn't work?

7 sec exposures is fine for 3ppa so I'll go with the new filter and up it from my usual 3 sec if needed.

Only experience I have in this is the usual YouTubers. Some might be exaggerating how much more time I might need I think. Maybe

Edited Monday at 23:03 by TiffsAndAstro

[TiffsAndAstro]

Also Nina's histogram is not great, so I use the min median max stuff.  It's possible I might have to up my offset.

 

[Vroobel]

All my images made using 2600MC and L-eXtreme were based on 300s subs, but recently I moved to 180s. The LP leaking through 'wider' dual-band filters will affect your subs less this way.  Also, the shorter the subs the smaller the loss if you have to remove bad ones. 

It would be best if you do flat frames every time you are imaging and for every filter you use unless you have a 'sealed' filter wheel. But even with that, your optics may catch dust affecting the subs.

Just from my experience.

[TiffsAndAstro]

26 minutes ago, Vroobel said:

All my images made using 2600MC and L-eXtreme were based on 300s subs, but recently I moved to 180s. The LP leaking through 'wider' dual-band filters will affect your subs less this way.  Also, the shorter the subs the smaller the loss if you have to remove bad ones. 

It would be best if you do flat frames every time you are imaging and for every filter you use unless you have a 'sealed' filter wheel. But even with that, your optics may catch dust affecting the subs.

Just from my experience.

just a filter drawer. supposed to be 7nm bandpass will be interesting to see what i get. ill do some tests and see what happens at different sub lengths. depends if my guiding is improved as i hope

who knows when?, weather is still rubbish

Edited Monday at 23:46 by TiffsAndAstro

[900SL]

Steve Bellavias excellent spreadsheet for the 533MC Pro

https://www.cloudynights.com/topic/685994-gain-and-sub-exposure-calculation-spreadsheet-for-the-zwo-asi533/?p=11743376

Input your sky brightness at D6 (19.5 for my B5 location)

Input aperture, focal length, dark current if different. Select a matching bandpass filter (you can see the bandwidth and line in the appropriate boxes)

For my ALP-T I need 7 minute exposures, for my IDAS NBZ I need 4 minutes. Basically the wider the band pass the less the exposure

I usually cap any narrowband at 6 minutes though, and accept a reduction in swamp factor.

I also pay close attention to the ASI Air Histogram and the min/median ADU values there

 

Edited Tuesday at 06:39 by 900SL

[TiffsAndAstro]

2 hours ago, 900SL said:

Steve Bellavias excellent spreadsheet for the 533MC Pro

https://www.cloudynights.com/topic/685994-gain-and-sub-exposure-calculation-spreadsheet-for-the-zwo-asi533/?p=11743376

Input your sky brightness at D6 (19.5 for my B5 location)

Input aperture, focal length, dark current if different. Select a matching bandpass filter (you can see the bandwidth and line in the appropriate boxes)

For my ALP-T I need 7 minute exposures, for my IDAS NBZ I need 4 minutes. Basically the wider the band pass the less the exposure

I usually cap any narrowband at 6 minutes though, and accept a reduction in swamp factor.

I also pay close attention to the ASI Air Histogram and the min/median ADU values there

 

LP swamps read noise in under 10 sec...for broadband....hadn't even considered this would change for nb

Will have a look ty

[Clarkey]

Personally, I would not get too hung up over exposure times and theory. Yes, you will need longer for NB, but this will be dependent on your mount / guiding etc. In theory I should be running at around 10 secs for RGB exposures, but then I would need a super-computer to process the results. Similarly, if you are in a dark sky location you may need very long exposures for NB - potentially over an hour. Like most AP, it will need to be a balance between best possible options and what is possible in reality. As a rule, with a standard set up (refractor around f5) you can do 1-3 minutes for BB and 2-5mins for NB. Ultimately, just see what works best for you.

[iantaylor2uk]

I tend to use 2-3 minutes subs when using my L-Enhance filter (as opposed to 30-60 secs for simple IR/UV filter). I would also look at increasing your gain value since you're less likely to saturate stars, and you get lower noise at higher gain 

[TiffsAndAstro]

25 minutes ago, Clarkey said:

Personally, I would not get too hung up over exposure times and theory. Yes, you will need longer for NB, but this will be dependent on your mount / guiding etc. In theory I should be running at around 10 secs for RGB exposures, but then I would need a super-computer to process the results. Similarly, if you are in a dark sky location you may need very long exposures for NB - potentially over an hour. Like most AP, it will need to be a balance between best possible options and what is possible in reality. As a rule, with a standard set up (refractor around f5) you can do 1-3 minutes for BB and 2-5mins for NB. Ultimately, just see what works best for you.

will do ty. no harm in me checking in advance. im gonna leave this morning's postal arrival in  my setup to start with, rather than swapping it in after 3paa.

will run some 1, 2, 3, 5 and 10 min tests see what they look like and guess at 120 sec to go with

[TiffsAndAstro]

14 minutes ago, iantaylor2uk said:

I tend to use 2-3 minutes subs when using my L-Enhance filter (as opposed to 30-60 secs for simple IR/UV filter). I would also look at increasing your gain value since you're less likely to saturate stars, and you get lower noise at higher gain 

i did consider upping gain, but for now im going to leave it at unity (100). might up my offset if im getting any zero pixels but need some clear sky see what happens.

[TiffsAndAstro]

3 hours ago, 900SL said:

Steve Bellavias excellent spreadsheet for the 533MC Pro

https://www.cloudynights.com/topic/685994-gain-and-sub-exposure-calculation-spreadsheet-for-the-zwo-asi533/?p=11743376

Input your sky brightness at D6 (19.5 for my B5 location)

Input aperture, focal length, dark current if different. Select a matching bandpass filter (you can see the bandwidth and line in the appropriate boxes)

For my ALP-T I need 7 minute exposures, for my IDAS NBZ I need 4 minutes. Basically the wider the band pass the less the exposure

I usually cap any narrowband at 6 minutes though, and accept a reduction in swamp factor.

I also pay close attention to the ASI Air Histogram and the min/median ADU values there

 

seems to give me 2.01minutes for 527.3nm 7nm bandpass. which seems a lot but, if i'd worked out about 12seconds with broadband, this is about 10x as much, and the filter maybe reduces total light by 90% ish, which means about 10x as much? so these figures seem ballpark at the very least?

i guess ill start with 120 seconds rather than 60 seconds then.  ty so much for that spreadsheet.

[TiffsAndAstro]

anyone know of, or the general name of a filter holder holder? what do i do with my uv/ir cut filter and holder when i pull it out and put the dnb filter holder in instead? some sort of external filter holder holster?

im sure there must be something for rasa owners who don't use filter wheels, surely? they won't just have a tupawear box with their filters and holders in? best i can do is the box my spare filter holder came in i guess?

[saac]

24 minutes ago, TiffsAndAstro said:

anyone know of, or the general name of a filter holder holder? what do i do with my uv/ir cut filter and holder when i pull it out and put the dnb filter holder in instead? some sort of external filter holder holster?

im sure there must be something for rasa owners who don't use filter wheels, surely? they won't just have a tupawear box with their filters and holders in? best i can do is the box my spare filter holder came in i guess?

There are lots of designs available for 3d printed filter cases. Also cases to hold for the filters when left in their filter drawers which is probably an easier method if you swap out filters regularly. 

https://www.thingiverse.com/thing:5537675

https://www.thingiverse.com/thing:6305446

https://www.printables.com/model/806383-parametric-solar-filter-box-openscad

https://www.printables.com/model/267124-starizona-filter-slider-storage-box-rasa-8

 

Jim 

Edited Tuesday at 10:40 by saac

[900SL]

I use two zwo 2" filter holders, they slot into the filter drawer and you can buy them separately

Make sure you check and get the right sizes

https://www.firstlightoptics.com/zwo-accessories/zwo-spare-extra-2-filter-holder-for-m42m54eosnikon-filter-drawers.html

When extracted I keep the spare one in a soft plastic wallet

Edited Tuesday at 10:38 by 900SL

[900SL]

43 minutes ago, TiffsAndAstro said:

seems to give me 2.01minutes for 527.3nm 7nm bandpass. which seems a lot but, if i'd worked out about 12seconds with broadband, this is about 10x as much, and the filter maybe reduces total light by 90% ish, which means about 10x as much? so these figures seem ballpark at the very least?

i guess ill start with 120 seconds rather than 60 seconds then.  ty so much for that spreadsheet.

It ;looks about right, I use 3 minutes. It's not a lot, you are cutting out a lot of light and remember that Oiii signal is usually weaker than Ha

[TiffsAndAstro]

40 minutes ago, saac said:

There are lots of designs available for 3d printed filter cases. Also cases to hold for the filters when left in their filter drawers which is probably an easier method if you swap out filters regularly. 

https://www.thingiverse.com/thing:5537675

https://www.thingiverse.com/thing:6305446

https://www.printables.com/model/806383-parametric-solar-filter-box-openscad

https://www.printables.com/model/267124-starizona-filter-slider-storage-box-rasa-8

 

Jim 

that is some cool links ty. i don't have a 3d printer, but could outsource that