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Mono filter options


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I'm considering going mono soon but I am overwhelmed by the options (and prices) of filters.

Can someone give me the heads up on what they think is garbage and what produces very good results for a reasonable price?

Astrodon and Chroma seem to be some of best from what I have read so far. Unfortunately, a set of them are out of my budget price range if buying from new.

Please PM me if you feel uncomfortable criticizing any specific brands.

Edited by Pitch Black Skies
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Baader LRGB appear to be OK, but their "ultra narrow band" filters had reports of some worrying halos. I also (Back in 2014) had severe halos with their [OIII] filter that sent me down the Astrodon black hole.

Astronomik could be worth a look. I have a set of their LRGB and NB in 36mm unmounted in my SX wheel, but haven't had much opportunity to use them much.

And the new player in the game,  Antlia who have 3nm NB filters in addition to the LRGB set.

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My SHO standard speed Baader filters don't really have an issue, if you're imaging a bright star for any extended length of time then you will get bloat/extended glow but that's a given.

To save some money on a set of LRGB I bought Skies the Limit (they're made via Optolong), no issues other than they're a little bit thicker (7.5mm from bottom of thread to top of cell) so couldn't use them with my original filter drawer, they fit the ZWO one but you have to screw them in a little more than the Baader.

All mine are 2 inch for future proofing so price was a factor.

Edited by Elp
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All my filters are Astronomik L3, RGB and SHO (6nm). I don't really have a bad thing to say about them, they work and they work well. The only slight things that stop them from being perfect:

1. Oiii is difficult to get flats right for, due to a central bright spot which shows up. This may be my light source, or some other internal reflection from the optics, rather than the filter itself, but the issue does not show up on any of the other filters. 

2. I noticed a small halo with the blue filter on a very bright star. It was no issue to deal with it in processing and maybe I'm being a little unfair as it was Alnitak!

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I am in this boat right now and was going 31mm Chroma across the board but for well, reasons, I am almost certainly swapping to 36mm and most likely it will be Antlia LRGB to save a bit of money and Chroma SHO, yeah I know ouch. I could get a very nice scope for the price of the Chromas, tell me about it.....

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My 36mm chromas (LRGBSHO) are great but I have no context for whether they're worth the extra £££ or not! They gave me a very detailed optical density scan (broad 300-1100nm, all filters) and narrow (e.g. 645-665nm for the H of my SHO). I don't know if other's do that. I have heard that Chroma and Astrodon are the only brands that totally avoid halos around bright stars with all 3 major narrowband filters, but when I point towards a bright star using my hydrogen filter i can see odd reflections regardless of filter orientation, so they aren't impervious (maybe this is a result of using an f4 scope, since dichroics change their bandpass when you drift out of their designed working angle, f4 is their lower limit advertised and I suppose any reflections from the corrector will have more eccentric angles perhaps)

Unfortunately, even my LRGB set which was made from the same pane of glass in theory, are not perfectly parfocal. The shift is small but on my f4 scope it's noticable (wasn't so much on my f5, it was tolerable there). So I'd say an autofocuser is a must if you don't have one already.

If you do have an auto focuser however, then mixing brands won't hurt you. You could buy a cheaper LRGB brand (afaik they're most tolerant) and then put the big £££ towards Chromas or Astrodons when it comes to narrowband later on.

Just steer clear of optolong, I have not seen much good from them personally...

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Part of the answer is dead simple: go for the Baader LRGB. They are excellent. I've also processed data from the much more expensive Astrodon LRGB set and felt there was no big difference. The Baader LRGB are so reliable, and used by so many well known imagers, that I would look no further.

The Baader 7nm Ha filter is OK but is blown into the weeds by the Astrodon 3nm. (I have both.) So it should be, given the spectacular price of the Astrodon. I have also used the 5nm Astrodon and been less impressed. The gap to the Baader is smaller.  What you get with the 3nm is the tiniest of stars and the most striking  of local contrasts or structural details. However, modern processing using star removal and replacement gives a new degree of star control in post processing so you can fight back, as it were.

I've had bad OIII filters twice from Astronomik and once from Baader. The halo problem is well known. Because I only use OIII to enhance LRGB, rather than to make pure narrowband images, I can process out the halos but it would be much nicer not to have to. So I don't know what to recommend for OIII, though I hear that some more recent Baaders are OK.

 

We've had a fair numbers of doubts about the ZWO filters expressed on here. I've only read the posts and never tried them. Likewise, Chroma get a good press.

Olly

Edited by ollypenrice
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I run a set of 2" Chromas in the ODK (Bought before they became stupidly expensive) and did a trial to determine filter offsets for the autofocus, but when I found that the difference between RGB was less than the difference between runs of the same filter didn't bother going further.

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3 minutes ago, DaveS said:

I run a set of 2" Chromas in the ODK (Bought before they became stupidly expensive) and did a trial to determine filter offsets for the autofocus, but when I found that the difference between RGB was less than the difference between runs of the same filter didn't bother going further.

If your equipment in your signature is accurate to when you took the readings, that would be consistent with my findings between my f4 and f5 scope. If you have a slower scope the chromas are parfocal in practice... Just not when you get down to f4. Your f6.8 and f7 scopes would be very tolerant of focus position. That said, the difference between the focus position of the LRGB set and the narrowbands (and between each narrowband) was quite considerable, enough to move the middle line out of the bahtinov pattern from an LRGB to my OIII filter.

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Thanks all, really helpful advice there.

I watched a video by Cuiv about narrowband filters from a reputable brand and was a little spooked. The quality control seemed to be non existent.

I have a friend who is selling these and these. They are labelled CCD but I will be using a CMOS. Will this make any difference? She said she uses CMOS with them too.

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4 minutes ago, pipnina said:

If your equipment in your signature is accurate to when you took the readings, that would be consistent with my findings between my f4 and f5 scope. If you have a slower scope the chromas are parfocal in practice... Just not when you get down to f4. Your f6.8 and f7 scopes would be very tolerant of focus position. That said, the difference between the focus position of the LRGB set and the narrowbands (and between each narrowband) was quite considerable, enough to move the middle line out of the bahtinov pattern from an LRGB to my OIII filter.

In the case of the TS apo I did find a shift, especially towards the blue. I also had to measure offsets as I had 2mm thick Baader and 3mm thick Astrodon. I have found no significant shift with the ODK, and the NB that I have done (Not a lot admittedly) shoes [OIII] and H-alpha to be in the same focus.

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Generally any filter I use requires a slight focus adjustment. Red to blue is quite significant, green to blue is generally the same. SHO differences are quite minimal.

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36 minutes ago, Elp said:

Generally any filter I use requires a slight focus adjustment. Red to blue is quite significant, green to blue is generally the same. SHO differences are quite minimal.

Sure, but is this offset from the filters themselves or from the optics? I ended up concluding that the filter difference was negligible with good optics (Tak FSQ106 and TEC 140) meaning the Baader LRGB filters were parfocal.

Olly

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Considering the QA variability with filters I wouldn't count them out atm. But I suspect it's the scope even though it's very capable (WO Z61). I also don't use an auto focuser. Doesn't really bother me too much as long as the target is captured well.

Edited by Elp
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Okay, I'm almost there.

So I will be imaging from Bortle 8/9.

Is it even be possible to image LRGB from a heavily light polluted city with mono?

I'm trying to decide on whether to buy a set of LRGB with a filter wheel, or simply just buy a single Ha instead and add an Oiii and Sii later down the road.

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8 hours ago, Pitch Black Skies said:

Okay, I'm almost there.

So I will be imaging from Bortle 8/9.

Is it even be possible to image LRGB from a heavily light polluted city with mono?

I'm trying to decide on whether to buy a set of LRGB with a filter wheel, or simply just buy a single Ha instead and add an Oiii and Sii later down the road.

Not quite bortle 8/9. But I took this recently in twilight (no astro dark that night) and near the most light polluted part of my bortle 6 sky. One 10 minute sub of red green and blue, processed in pixinsight. No flats or anything.

Image07_ABE-rawtherpapee.thumb.jpg.7f1bf1956acbca6cf4fdfb81d85fb1f9.jpg

So 30 minutes of RGB total with my f4 200mm reflector, and there's already signs of integrated flux nebula on the right.

Light pollution makes things slower and a bit more awkward but it doesn't make it impossible. I could have taken 30 minute subs and still had room for more exposure (7000 ADU peak in the nebula, out of 65000)

My equipment still needs a lot of work to make me happy with it all, but the results it can put out in terms of speed are still surprising. Not regretting the mono switch so far.

(edit, I accidentally claimed to have a 200mm refractor... I am not actually made of money haha. Also I said the IFN was on the left, but it's on the right edge of the image. I am a bit tired)

Edited by pipnina
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The Baaders are the best option for the price point. My first OIII had terrible halos but the replacement didn't. Bit of a gamble on that. I have all Astronomiks now and they are great. No halos on the 6nm narrowbands. I do get the odd faint halo on the green or blue filters, depending on the star but I can't say for sure if that's the Astronomiks or the IDAS D2 LPS filter I use. Nothing near as bad as the Baader OIII I had.

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8 hours ago, Pitch Black Skies said:

Looks great 👍

I wonder if something similar would be possible from Bortle 8/9.

I had given up on the idea of LRGB but maybe there's still hope.

https://www.cloudynights.com/topic/662843-galaxy-imaging-from-bortle-89-skies/

Seems like people here can still get great results. No doubt it relies somewhat on local air turbulence from the city and sky transparency due to atmospheric pollution etc, but while light pollution makes images noisier, it doesn't make imaging impossible thankfully!

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10 hours ago, Pitch Black Skies said:

Looks great 👍

I wonder if something similar would be possible from Bortle 8/9.

I had given up on the idea of LRGB but maybe there's still hope.

It's all about the processing and removing LP gradients, with narrowband images are much cleaner and easier to process I find, each sub however needs to be exposed for longer in NB I tend to use 2-3 minutes typically, sometimes 5 minutes at f6.

Edited by Elp
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I have an offer for a set of Baader LRGB + SHO (all ~8nm range).

Given my Bortle scale (8/9), I'm wondering if it might be more sensible to just dump the whole budget on a Ha 3nm and build the collection very gradually.

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1 hour ago, Elp said:

It's all about the processing and removing LP gradients, with narrowband images are much cleaner and easier to process I find, each sub however needs to be exposed for longer in NB I tend to use 2-3 minutes typically, sometimes 5 minutes at f6.

Narrowband sure does reject a lot of light. I've done 10 min subs and my signal is barely above the noise floor of the camera (no light pollution in individual subs though!)

But because the optical contrast is so high, those 10 min subs are almost usable as pictures as-is, as long as you don't zoom in!

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