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Baader OIII and SII Filters


edjrgibbs
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Not sure if this is in the right forum, apologies if not. I'm looking at buying Baader OIII and SII filters. I had two questions thought, are they parfocal and also do they cut out moonlight similar to the Ha filter?

Thanks in advance.

Ed

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Hi Ed.

I can only speak form my own experience with these filters.

Firstly yes they are Parfocal,or as near as you can get.

Secondly,i would say that whil,st the H-Alpha Filter does a reasonable job when the Moon is prescent,the O111 & the S11 do not.

In my view,especially around the time of Full Moon,these Filters wont cut it.

Hope this helps.

Mick.

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The extent to which filters are parfocal depends on the focal ratio of your system.  I've used 2" Baader narrowband filters down to f/5.3 and for practical purposes found them to be parfocal (a slight difference, in fact, but within critical focus).

I've used the 7nm Ha and 8nm SII under ~95% lit moon and got pretty good results but of course it depends how close to the moon your target is.  Personally I find that the SII works OK under the moon - both the Ha and SII emission lines are in the red part of the spectrum - but the trouble is that the SII signal is almost always very much weaker than the Ha. 

The OIII is a different matter; that's in the blue/green part of the spectrum so I find the moon interfers quite a bit...

Just my two pennies worth...

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Never rely on parfocality claims. Focus will make or break an image and so for me it is one of the most important things in imaging. Personally I have never found any par focal filters, from Baader RGB, NB and now Astrodon NB filters. To be fair even if they were par focal I would still refocus.

Regarding the claims of being able to use narrowband filters in moonlight, I disagree with that as well. Ha is probably the best to use, but even then, the noise is so bad that I've taken to sitting on the sofa during such times.

For me, the moon and DSO imaging just don't work...... Period.

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Never rely on parfocality claims. Focus will make or break an image and so for me it is one of the most important things in imaging. Personally I have never found any par focal filters, from Baader RGB, NB and now Astrodon NB filters. To be fair even if they were par focal I would still refocus.

Regarding the claims of being able to use narrowband filters in moonlight, I disagree with that as well. Ha is probably the best to use, but even then, the noise is so bad that I've taken to sitting on the sofa during such times.

For me, the moon and DSO imaging just don't work...... Period.

What your saying Sara is more or less correct,and for your standard of work,i can see why you don't go out.

But not everyone is chasing perfection,and I would never pass up a clear sky here in the UK,full Moon or not.

Mick.

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As Sara said never found a true par focal combo and would not expect there to be one.  Focus is key I don't even like to change filters between focusing and imaging (IE the old maxim trick of changing filter when you select something different from your shot type menu).  I would always refocus on filter swap and every n-images depending on the stability of your system. 

However I will suffer the moon if I have to here in the UK as Mick said, a clear sky is a clear sky.  Few and far between here, I would shoot selectively though IE Ha when moon is at brightest and others when you get the chance to on darker nights.  You will loose some HA data but this is tolerable when few darks skies are available.  Typically I am running about 2 images behind with Oiii and Sii as always seems to be clear when the moon is bright.

Paddy

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Never rely on parfocality claims. Focus will make or break an image and so for me it is one of the most important things in imaging. Personally I have never found any par focal filters, from Baader RGB, NB and now Astrodon NB filters. To be fair even if they were par focal I would still refocus.

Regarding the claims of being able to use narrowband filters in moonlight, I disagree with that as well. Ha is probably the best to use, but even then, the noise is so bad that I've taken to sitting on the sofa during such times.

For me, the moon and DSO imaging just don't work...... Period.

What Sara says is bang on........ when the moon is out do something other than DSO imaging  :laugh:!   It is a right pain though as we have loads of cloud and on the one clear night we find it is werewolf time  :eek: , oh whooof!

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I used to treat the Baaders as parfocal & was fairly happy. However, now with the f5 Esprits & using the filter offsets builder script with ACP, I was surprised how much difference there is between them. I'm still not convinced about using offsets with longer sub length for NB either though, with such changeable conditions in the UK. As opposed to refocus on filter change & temp compensation? I'm still working that one out.

I do try & shoot Ha with the less than full moon if it's clear.. See how it turns out... Just can't stand wasting a clear sky!

I came close to ordering a 3nm Ha last night though. Typically totally clear on a full moon. I was stopped by the shock of the significant price hike since I last looked ... £410 now for 1.25"!! oh my.. Might have to downsize on kit for a set of NB's[emoji24]

Sent from my iPhone using Tapatalk

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I came close to ordering a 3nm Ha last night though. Typically totally clear on a full moon. I was stopped by the shock of the significant price hike since I last looked ... £410 now for 1.25"!! oh my.. Might have to downsize on kit for a set of NB's[emoji24]

Sent from my iPhone using Tapatalk

Ouch!

Glad I ordered mine before the exchange rate dropped, £385 each was bad enough! 4 at £410 each would be a bit horrible.

They aren't parfocal in my Meg 90, though that may be a function of only being an ED doublet. A Bahtinov mask tells all!

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Not sure if this is in the right forum, apologies if not. I'm looking at buying Baader OIII and SII filters. I had two questions thought, are they parfocal and also do they cut out moonlight similar to the Ha filter?

Thanks in advance.

Ed

They are parfocal to each other but a lot depends on the scope. Ha will help with the Moon but it depends on the phase of the Moon, how high up the sky and how close to your target is. The 7 nm will be fine for up to 1/2 Moon and 45 degrees from target. At full or near full Moon pack up and watch the TV, nothing would work even the 3nm super expensive Astrodons.

A.G

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What your saying Sara is more or less correct,and for your standard of work,i can see why you don't go out.

But not everyone is chasing perfection,and I would never pass up a clear sky here in the UK,full Moon or not.

Mick.

Yeah I agree Mick - if I ruled out imaging under the moon I would have cut my imaging in half...

Now that said, the quality of the data is much worse, but you can get something out of it.  Here for example are a couple of 600s Ha subs of IC 410 (these are taken from the FIT files with equivalent visualization parameters in AstroArt):

This one taken under a 40% lit moon

post-11821-0-33247400-1423151305_thumb.j

This one under an 88% lit moon

post-11821-0-74527600-1423151308_thumb.j

Now of course the atmospheric conditions were different as these captures were 11 days apart, but you get the drift.  If I had Sara's weather and skies then maybe I'd sit the moon out too.

(By the way, both subs were used in the final version of the image which was published as Picture of the Month in Astronomy Now in June 2013.)

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Never rely on parfocality claims. Focus will make or break an image and so for me it is one of the most important things in imaging. Personally I have never found any par focal filters, from Baader RGB, NB and now Astrodon NB filters. To be fair even if they were par focal I would still refocus.

Regarding the claims of being able to use narrowband filters in moonlight, I disagree with that as well. Ha is probably the best to use, but even then, the noise is so bad that I've taken to sitting on the sofa during such times.

For me, the moon and DSO imaging just don't work...... Period.

I guess if I lived under spanish skies, I might not bother when the moons about either :~)

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Please see above............. I only get 400-500 clear nights a year!!! As if :D

 Well the common denominator is we all want more time than we can get - one constant amongst the variables.

Once again sitting under cloud when weather man says its clear - might be able to set up in dark again and see if I can break my nose once more walking into things :grin: !!

Paddy

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