18 replies to this topic

[bluesilver]

Hi,  I am in the process of trying to find a good filter to use with the ZWO asi2600mc

Scope is Skywatcher Esprit with a focal ratio of f7 and if i use a reducer/flattener it become f5.6

 

The is just so many different filters out there and i am just plain lost in what i should be looking at or not at.

Dual band, tri bands and i think quad band filters.

Then there is narrow band and broad band,  as you can see i am at a complete lost here.

 

I am thinking possibly broad band due to it being colour camera?

 

I was looking at imaging NGC6334,  it is an emission nebula, but also like to image nearby NGC 6357 which is a diffuse nebula

There is many more,  just these are placed very good for me right now this month.

 

I think for galaxies, i am better of with no filter with this camera?

I am in around Bortle 2-3 area

 

Any advice on this broad question would be appreciated.

 

 

[matt_astro_tx]

Because your camera already has an IR cut window on it, for galaxies you are best off not using any filters.  I'll leave the narrow band/dual band discussion for others.

[DeepSky Di]

The key for me with OSC duoband is capturing and separating Ha and Oiii. I don’t see the point of mixing Hb with the Oiii, as it is then impossible to separate. Askar color magic now has a pair of duobands - one Ha Oiii and the other Sii and Oiii.

Why do this instead of mono? Depends on your environment. I image through a gap between trees and don’t get a long time on each target. I started with OSC so that I could get something usable each night. I currently use the Optolong L-extreme.

[dan_hm]

Modern star removal software makes star color a non-issue.  Get a dual band Ha+OIII filter and shoot star data separately without the dual band filter if you want better star colors.  Although the 2600's sensor window cuts UV/IR, you may want to get a separate UV/IR cut filter with the same thickness as the dual band filter.  Otherwise, stars at the corners and edges might distort with the change in backfocus.

[smiller]

 

I think for galaxies, i am better of with no filter with this camera?

I am in around Bortle 2-3 area

 

You just answered it, you are in Bortle 2-3, you can do very well without any filter for most anything to start with.

 

I expect there are those that use narrowband filters even in Bortle 2-3 because despite how dark that is, there is still sky background that can be further dampened to optimize even further, but that is beyond my pay grade as I’m in Bortle 6/7 and don’t have a long exposure rig.   But if you are just starting, probably start without a filter at Bortle 2-3 because filters cost money, add some complexity, they mess with star colors, and they do attenuate/reduce some useful signal.

 

This is my recommendation for you in Bortle 2-3.

 

1) Galaxies:  Never every every use a filter

2) Star clusters: Never every ever use a filter

3) Relfection nebula or mixed narrowband/reflection:  Never ever use a filter

4) Planetary nebula:  Never use a filter

5) Dark nebula: Never ever use a filter

6) Diffuser emission nebula:  Don’t use a filter for now, when you advance, narrowband filters could be considered if you learn from others that they are wise in Bortle 2-3 and worth the money, complexity, and tradeoffs.

Edited by smiller, 13 June 2023 - 09:06 AM.

[bobzeq25]

Hi,  I am in the process of trying to find a good filter to use with the ZWO asi2600mc

Scope is Skywatcher Esprit with a focal ratio of f7 and if i use a reducer/flattener it become f5.6

 

The is just so many different filters out there and i am just plain lost in what i should be looking at or not at.

Dual band, tri bands and i think quad band filters.

Then there is narrow band and broad band,  as you can see i am at a complete lost here.

 

I am thinking possibly broad band due to it being colour camera?

 

I was looking at imaging NGC6334,  it is an emission nebula, but also like to image nearby NGC 6357 which is a diffuse nebula

There is many more,  just these are placed very good for me right now this month.

 

I think for galaxies, i am better of with no filter with this camera?

I am in around Bortle 2-3 area

 

Any advice on this broad question would be appreciated.

This is really simple.  Really.

 

On emission nebulae ONLY (includes planetary nebulae) use a modern duoband filter (or tri or quad but they're expensive).  They work really well, in all skies.  Because emission nebulae emit light mostly in 1-3 narrow bands, ideal for sorting out with a filter.  Many like the LEnhance.

 

Singleband filters are for mono cameras, the duoband is specifically designed for color cameras.

 

On all other targets (which emit over the entire spectrum), ANY filter is dubious.  It will cost you a lot of signal and you have none to spare.  For those you reduce the effects of light pollution (and Bortle 2-3 does have some) with gradient reduction in processing.  Not perfect, but doesn't cost you signal.  Astro Pixel Processor has an excellent gradient reduction tool, and most astro specific processing programs also do gradient reduction.  I, and most all experienced imagers, use GR on everything we do.  APP makes it easy.

Edited by bobzeq25, 13 June 2023 - 09:17 AM.

[dan_hm]

6) Diffuser emission nebula:  Don’t use a filter for now, when you advance, narrowband filters could be considered if you learn from others that they are wise in Bortle 2-3 and worth the money, complexity, and tradeoffs.

In my experience they are definitely wise in dark skies.  I thought just a UV/IR cut filter would be sufficient for emission nebulae in dark skies until I actually tried it at a dark site and the results were very disappointing. 
 

[David Boulanger]

The L Extreme does very well with emission nebula.  And actually, I have taken short 120 second subs with it when I have many passing clouds, really long exposures are not always necessary.  I know someone with the L - Ultimate and he loves it.

[bluesilver]

Appreciate all the replies and advice.

The only light pollution i mainly get is from the moon.

I do have a 2" OPTOLONG L-PRO FILTER that i picked up some time ago,  I am not sure if it is suitable for my setup or not really.

Would i get any noticeable effects from using it or would it actually be worse off using it?

 

In general,  it is sounding like i may be better off imaging without any filters at all.

[Fegato]

I image in Bortle 3 skies, and others have said, the beauty of dark skies is that you just don't need to use a filter. Moonlight is the only "enemy"! (and these days I usually don't bother when the moon is large). 

 

I mostly use a similar, but full frame, OSC with my RASA 11 - the ASI2400MC Pro. I have a couple of dual narrowband filters - the Optolong L-eNhance which works well on my 8 Edge HD, and an IDAS NBZ, which is better for my the RASA. Both are good filters.  But I normally shoot broadband (i.e. no filter), and use a clear glass filter to maintain my backfocus distance. This is essential for me using the RASA at F/2.2, and may not be such an issue for you, but it's recommended. I have one clear glass filter each from the two manufacturers above, so that they have the same glass thickness.

 

I enjoy shooting all sorts of objects in broadband, including most of the favourite narrowband emission nebula targets (see my Astrobin). I'm only really tempted to use narrowband on the faintest of targets, often using it to enhance a broadband shot. Really faint OIII will often just not be visible at all (e.g. see my Sh2-129 with Barnard 150 shot - no squid is visible at all). But to be honest, the really faint ones like this are probably easier to pull out with mono and very narrow filters, and with broadband you can pull out all sorts of intermediate hues of dust and so on.

 

With this approach, you're using "natural" colours. If you want to produce bright false colour palettes emulating the mono / narrowband shots, you can do this using the dual narrowband filters, at least up to a point, but I'm just not so interested in doing this.

 

re: Moonlight - the filter will help, but mostly only with the Ha. I find that moonlight washes out the OIII signal (L-eNhance has a fairly wide 20nm band for OIII and Hb making this worse, but I still don't get much better results with the NBZ and its 10nm band).

 

re: L-Pro - this is a broadband filter. it attempts to remove some of the light pollution in broad bands. I can't see any circumstances where this is really going to give you any advantage at all in dark skies.

[matt_astro_tx]

In general,  it is sounding like i may be better off imaging without any filters at all.

[smiller]

I image in Bortle 3 skies, and others have said, the beauty of dark skies is that you just don't need to use a filter. Moonlight is the only "enemy"! (and these days I usually don't bother when the moon is large). 

 

I should have prefaced my comments on basically “never using a filter and only possibly on emission nebula” based on when there is basically no bright moon.  With a bright moon out, certainly a dual narrowband filter helps for emission nebula because, depending on how bright the moon is and how far from your target, the moon is similar to being in a light polluted sky.   So a filter can extend the number of good imaging nights to those that have a bright moon, as long as you have emission nebula you want to shoot at that time.

[Gopens]

Appreciate all the replies and advice.

The only light pollution i mainly get is from the moon.

I do have a 2" OPTOLONG L-PRO FILTER that i picked up some time ago,  I am not sure if it is suitable for my setup or not really.

Would i get any noticeable effects from using it or would it actually be worse off using it?

 

In general,  it is sounding like i may be better off imaging without any filters at all.

I use the L pro on my 2600 Mc with the Redcat 51 in Bortel 5. I think it does a great job for enhancing galaxies and stars as it does not have a heavy hand. I do however bump up the gain to maybe 140..145 to compensate for the filter.

Edited by Gopens, 14 June 2023 - 05:30 PM.

[mjanzou]

You just answered it, you are in Bortle 2-3, you can do very well without any filter for most anything to start with.

 

I expect there are those that use narrowband filters even in Bortle 2-3 because despite how dark that is, there is still sky background that can be further dampened to optimize even further, but that is beyond my pay grade as I’m in Bortle 6/7 and don’t have a long exposure rig.   But if you are just starting, probably start without a filter at Bortle 2-3 because filters cost money, add some complexity, they mess with star colors, and they do attenuate/reduce some useful signal.

 

This is my recommendation for you in Bortle 2-3.

 

1) Galaxies:  Never every every use a filter

2) Star clusters: Never every ever use a filter

3) Relfection nebula or mixed narrowband/reflection:  Never ever use a filter

4) Planetary nebula:  Never use a filter

5) Dark nebula: Never ever use a filter

6) Diffuser emission nebula:  Don’t use a filter for now, when you advance, narrowband filters could be considered if you learn from others that they are wise in Bortle 2-3 and worth the money, complexity, and tradeoffs.

Since your in a 6/7 area, do you follow the same recommendations and use a narrow/duo band filter on emission nebula by default or just with higher moon glow conditions as mentioned. Im in a 4/5ish. Thx.

Should mention that my 533mc has no uv/ir cut window and instead use a zwo 2” uv/ir in my drawer by default.

Edited by mjanzou, 14 June 2023 - 07:35 PM.

[smiller]

Since your in a 6/7 area, do you follow the same recommendations and use a narrow/duo band filter on emission nebula by default or just with higher moon glow conditions as mentioned. Im in a 4/5ish. Thx.

Should mention that my 533mc has no uv/ir cut window and instead use a zwo 2” uv/ir in my drawer by default.

For my Bortle 6/7 I always use a narrowband filter on emission nebula except some of the brighter planetary nebula as they are often bright enough and sometimes have secondary emissions that add a lot of color that I don't want to lose out on.   It makes a big difference for the dimmer nebula and the productivity increase when using a good dual narrowband filter is just enormous.

 

I don't know how dark a sky has to be before you typically don't need one, that's going to be very situation, target, and personal imaging goal dependent.  I had the chance to visit a Bortle 1/2 site and used no filter on some mixed emission/reflection nebula and my capture productivity was excellent with good star color without any filter.  I would be reticent to use a filter in that case because I enjoyed the subtle secondary colors and the nice stars so much.   That's why I said for Bortle 2/3 you can try without one and you'll do pretty darn good, but you can learn from others that have more dark sky experience the advantages and tradeoffs if you use one... it'll be very situation dependent but the benefits will clearly be lower.

 

For galaxies, star clusters reflection nebula, comets, galaxy clusters I never use a filter.  

 

On some mixed emission/reflection nebula, I'll mix a broadband with a dual narrowband capture, such as the Horsehead/Flame nebula which also has some smaller reflection nebula mixed in.

Edited by smiller, 14 June 2023 - 07:48 PM.

[bobzeq25]

Since your in a 6/7 area, do you follow the same recommendations and use a narrow/duo band filter on emission nebula by default or just with higher moon glow conditions as mentioned. Im in a 4/5ish. Thx.

Bortle 7 here.  The "filters on emission nebulae, ONLY" thing is pretty straightforward.  The light from emission nebulae is inherently narrowband, so a narrowband filter works well.  The light from other targets covers the whole spectrum, so filters don't work very well.  Gradient reduction only instead.

 

Imaging dim stuff under moonlight is so low quality, I won't waste the time and effort.  That's a good time for star clusters.

 

Samples, all Bortle 7.  Click on each for a better version than the small CN thumbnail, and acquisition details.  Emission nebulae with a duoband.  Galaxy with no filter.  Star cluster in moonlight.  The last used a mono camera with broadband LRGB filters, which works better in light pollution/moonlight.

 

Gradient reduction, always.

 

 

 

 

Edited by bobzeq25, 14 June 2023 - 11:40 PM.

[junktrunk]

My best work so far was under B9 skies with full moon and an L-Ultimate. I can't figure out why CN isn't letting me insert the image of it but it's the North America nebula at my astrobin below.

Edited by junktrunk, 15 June 2023 - 10:44 AM.

[Spaceman 56]

Bortle 2/3 is pretty dark. 

 

I suggest you shoot without filters, and see what the results are like.

 

Spaceman

[TigerSaw]

I’m New at this and learning.

I have taken several shots over the past few months. Learning how to do polar alignment, picking targets and doing stacking using Pixinsight.  Doing my first stacking and processing in pixinsight on the Horsehead Nebule it came out great had a lot of noise from light pollution, I’m in a Bortle 5 environment.  You can see my equipment below.  I’ve decided to go with a Optolong L-Ultimate and the Optolong L-Quad Quadband extreme. All the information says these will work great in a Bortle 5 with a OSC.  I just got a ZWO filter wheel to go with my system looking forward to using these filters.

 

 

William Optics Redcat 51

ZWO AM5 Mount

ZW0 120mm Guide Scope Camera

Asiair Plus

ZWO EAF

ZWO Asi2600MC Pro

ZWO Filter Wheel

 

 Here's the Image first processed Image I ever did...

 

https://www.astrobin.com/pt4w9i/

Edited by TigerSaw, 28 December 2023 - 08:54 PM.