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Old 06-10-2011, 04:33 PM
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Which Filters

All you experts let me know which are the best filter set to get. I need 50 x 50 mm LRGB and HA and O3 with a bit of S.

FLI can supply filters. Who makes them?

Should I go for 5nm even at f3?

Bert
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Old 06-10-2011, 07:28 PM
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I have used Astronomik, Baader and a few sets of Astrodons. Who makes FLI research? Its proprietary knowledge of FLI. I suspect Custom Scientific do but I can't confirm or be certain of that.

The latest Astrodon Gen 11 are very very good, parfocal, equal exposure times or close to it. Baaders weren't absolute latest and had some reflections in green. They weren't parfocal ( a bit off) and they were definitely not equal exposure times. Astronomiks were good but they are thin (1mm) so you need a filter wheel that can handle them (FLI's latest per their site says they can handle any thickness filter, my CFW4/5 cannot). They have a later version out that Mike uses and his images speak for themselves.

FLI research are good and I thought everyone was happy with them but one guy recently posted reflections with his.

As far as Ha etc nm. I use 5nm and find them good. I have used them at F3.64 with an FSQ106ED and they work fine. 3nm I believe bring out more detail but require a lot more exposure time otherwise they could be noisy. I am interested at some point in a 3nm Ha as my setup with the CDK17 may require it and has lots of light coming in. 5nm sometimes isn't narrow enough when the moon is up and I get gradients.

So the filters I know work with Proline 16803:

Astrodon Gen 11
Astronomik latest and that's all I know. Baader's latest may be OK and FLI Research may be OK but best to post on FLI Yahoo Group for opinions as these filters are expensive as you know.

I personally like my Astrodon Gen 11. The Baaders weren't bad and are good with red response.

As you probably know filter selection with 16803 cameras is critical as they will show bad reflections easily and there are a million posts about this topic as a result.

Edge blackening with a black paint pen is recommended. Perhaps Astrodon are doing that now. They weren't when I bought mine.
There is a cheap Testors black paint pen available from amazon.com that is recommended by others for this purpose. I used a black texta and it works but is not 100% opaque.

Baaders and Astrodons are made differently. Astrodons are cut from a sheet, Baaders are cut beforehand then coated. Some say that makes a difference with Baader's being the better method. But as I say, my experience has been Astrodons are very very good.

Greg.

Last edited by gregbradley; 07-10-2011 at 09:07 PM.
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Old 07-10-2011, 08:30 AM
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Thanks for that Greg. It looks like the Astrodons Gen II will be better. I have read the info on their site and it all looks good.

Bert
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Old 07-10-2011, 06:58 PM
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Bert, I have astronomiks but I hear very good things about Astrodon gen II. If I was going to take a punt I would go with the Astrodons over any other filters.
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Old 07-10-2011, 07:22 PM
Hagar (Doug)
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Bert, Filters have been quite a bug for me to bear over the years. I have tried quite a few starting with CS, then Astrodons, astronomics and finally Baaders. Fair enough none were the new models being sold at the moment but have settled myself on Baader. They have been light years ahead of the others with regard to reflections and should I buy a newer bigger camera requiring larger filters I expect I would stick with Baader.
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Old 07-10-2011, 07:32 PM
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+1 to Baader. I have had no reflection issues with my 2" LRGB and hydrogen alpha set with my STL-11000M at f/5 or f/8 on the FSQ-106N.

H
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Old 07-10-2011, 08:34 PM
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+1 Astrodon Series II.

I currently have the 50x50mm square LRGB set with 5nm Ha and 3nm OIII and SII filters. The latter 3nm filters aren't cheap but really dig out the signal over the background ADU, ideal for getting weak SII photons. I don't do much narrowband work as dark skies tend to provide for traditional RGB imaging.

What I also like about the Astrodon's (also present in the CS filter set) is that there is no wavelength cross-talk between the red and green bandpasses, thus the red filtered data can make a great luminance for emission nebula as opposed to clear filtered data (RRGB compostion). Alan Holmes of SBIG did a write up a long time ago on the topic;
Quote:
In the new filter set, the red and green passbands have been slightly reduced. The
attenuation of red H-alpha nebulosity that occurred in the old filter set has been corrected.
...
There is a “hole” in the new filter set between 570 and 610 nM. While this may
offend the purist, there are no significant astronomical emission lines in this hole. Stars
have very wide spectral distributions, as illustrated in Figure Two, so no loss of
information results from this hole – you do not miss “yellow” stars (which are yellowwhite).

However, sodium vapor streetlights terribly pollute this region, ...
Ref:http://ftp.sbig.com/pdffiles/SBIGFilterSet.pdf
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Old 07-10-2011, 08:56 PM
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Quote:
Originally Posted by Octane View Post
+1 to Baader. I have had no reflection issues with my 2" LRGB and hydrogen alpha set with my STL-11000M at f/5 or f/8 on the FSQ-106N.

H
The 16803 chip is more demanding of antireflection coatings than STL11.
Although having said that I did get smallish green halos on bright stars with Astrodon Gen 1 with STL11 which could be annoying at times.

But with the 16803, reflections become more of an issue. I am not 100% clear on why this is as STL11 requires scopes to have a flattener usually as does the 16803. But it definitely started this need for an antireflection coating on the filters that is now usual with the top brands.

Greg.
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Old 07-10-2011, 10:34 PM
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I feel completely inadequate now.

Looks like I'll have to go out and buy a 35mm square chip to feel better.

H
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Old 08-10-2011, 02:31 AM
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I defy anyone to say with certainty which filter brand will work best for Berts new system. Without a thorough reflection and band pass analysis you simply can't, it is all plain and simple guess work based on anecdotal evidence. Astrodon Gen II, Baader, latest low reflection Astronomik, none of you know for certain which will provide the best results.

Bert, all these are good filters and all have been involved with systems producing halos or reflections of some sort with one system or another.

I have used the latest generation Astronomiks on a slow (F8) APO refractor with 2 element 4" flattener and I have also used them on a fast (F3.8) Newt with 4 element Wynn corrector and the results a very different.....and you have an exotic F3 mirrored system on its way...The Astronomiks are good to about F2.8 I believe but drop a line to Gerd Neumann: info@gerdneumann.net

Regardless, in my case, both systems have returned award winning images - so don't get too hung up about'em, as far as halos your guess is as good as anyone's Bert, the fast F3 is the issue here and the responses you get from the various manufacturers in this regard may be very interesting

Mike

Last edited by strongmanmike; 08-10-2011 at 03:01 AM.
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Old 08-10-2011, 09:01 AM
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After reading as much as is available on line and the advice offered here, thanks all, I have decided to go with the following.

I think I will get the ten position filter wheel that takes 50mm square filters. This gives me more filter options without constant swapping that I do not even know about yet.

Initially I will buy the Astrodon LRGB filter set as I like the idea of the Sodium street light pollution suppression with the limited red filter or the hole Jason mentioned.

The Astrodon fiters have far better specifications as far as filter thickness variation (More parfocal - thickness 3+/-0.025 mm) and so not affect focus. This of course assumes that the rest of the optical system is perfect as far as CA etc is concerned. But why add more variables?

They also have a nifty red 5nm continuum filter that can be used for subtracting stars from NB data. Has anyone tried this or seen it done.

Finally I have decided to go for broke literally and get the full set HA,OIII and SII with 3nm spectral width. I am more interested in 'real' nebula colours than artificial pallettes. This may change with time.

They also make a 3nm NII filter although how many objects have this emission line I can only guess at. This NII line is passed by a 5nm HA but not the 3nm HA.

See here
http://www.astrodon.com/products/filters/narrowband/

As Mike said we just do not know what will work but the Astrodon filters seem to have a better lot of specs all round at least on paper.

Any further advice is gratefully accepted.


Bert
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Old 08-10-2011, 06:31 PM
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Quote:
Originally Posted by Octane View Post
I feel completely inadequate now.

Looks like I'll have to go out and buy a 35mm square chip to feel better.

H
Not meant to make you feel bad. But it caught lot of people out when the 16803's first were being used. What worked or wasn't too bad with their STL11's was very bad with their 16803s.

Greg.
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Old 08-10-2011, 06:33 PM
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Mike's point is valid - noone is posting images with the Veloce RH200 yet. It may have its own pecularities. I know bandpass rating varies with F ratio. There is an article about that on Astrodon site I believe.

Its also true there are probably similar numbers of fans for Baader, Astrodon and Astronomik as long as they have the antireflection coatings. But it is also true my Baaders are not parfocal as claimed, they are not equal exposure as claimed whereas my Astrodons are.

There is a lot of lying about performance in this game by sellers. Hence the vital need to get info from those who have used them with no financial connection.

Don Goldman has posted images using an N11 filter. Have a look through his image gallery and you'll see some.

3nm narrowband set sounds awesome with an F3 scope and a sensitive Proline 16803.

Greg.
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Old 09-10-2011, 02:41 PM
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Quote:
Originally Posted by gregbradley View Post

3nm narrowband set sounds awesome with an F3 scope and a sensitive Proline 16803.

Greg.
How accurate would the 3nm window be at F3 I wonder?

Mike
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Old 09-10-2011, 05:29 PM
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All is explained here Mike.

http://www.astrodon.com/Orphan/astro...arrowband/#h11

Go down to

What About Using Narrowband Filters with Faster Optics?



Bert
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Old 09-10-2011, 06:41 PM
jase (Jason)
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Quote:
Originally Posted by avandonk View Post
Finally I have decided to go for broke literally and get the full set HA,OIII and SII with 3nm spectral width. I am more interested in 'real' nebula colours than artificial pallettes. This may change with time.
Good stuff Bert. I think you'll find you'll be doing narrowband imaging much sooner than expected. I had the pleasure of remotely operating a 16" ASA working at F/3.6. The scope sucked in photons like there was no tomorrow, alas it was located under moderately light polluted skies of Houston, Texas. Combination of sky glow and the speed of the scope made it extremely complex to do any RGB work. Narrowband made it bearable though major gradients continued to exist and made for considerable processing effort. The scope is currently being moved to rural skies so I'm hoping the set up will deliver considerably improved results. Whatever you can do to control local lighting will be to your advantage. Not much you can do about the greater sky glow, other than take your set up to darker skies. If you have the opportunity to do so, I'm certain the data from this set up will be nothing short of remarkable.
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Old 10-10-2011, 09:22 AM
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Quote:
Originally Posted by jase View Post
Good stuff Bert. I think you'll find you'll be doing narrowband imaging much sooner than expected. I had the pleasure of remotely operating a 16" ASA working at F/3.6. The scope sucked in photons like there was no tomorrow, alas it was located under moderately light polluted skies of Houston, Texas. Combination of sky glow and the speed of the scope made it extremely complex to do any RGB work. Narrowband made it bearable though major gradients continued to exist and made for considerable processing effort. The scope is currently being moved to rural skies so I'm hoping the set up will deliver considerably improved results. Whatever you can do to control local lighting will be to your advantage. Not much you can do about the greater sky glow, other than take your set up to darker skies. If you have the opportunity to do so, I'm certain the data from this set up will be nothing short of remarkable.
The whole new system is a bit of a leap into the dark Jase. The only real unknown is the F3 optic. The PL 18603 will really show any failings in the optical train. I am sure I can tame it by using a well designed dew extension shield to fit the existing one. A laser cut aperture to trim any edge effects may also be needed. This will give a slight loss in speed.
This will have the effect of limiting light not contributing to the image even entering the optic and having it being scattered to add to 'sky glow' and 'background'.

The PLC PWM temperature controller I currently use for my Peltier fridge would make a very good thermostatically controlled heater controller to keep the whole optical system at a constant temperature +/- 0.1C. As the system is sealed convective air currents would not be a problem at equilibrium.
The dew shield will be held at a few degrees above ambient to minimise convective currents as is current best practice. Lack of seeing at a FL of 600mm with 3" per pixel should not really be a problem.

I am still trying to think what else I have not thought of.

Bert
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Old 10-10-2011, 05:44 PM
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The main thing I would want to be assured of Bert is round stars to the corners of a 16803 chipped camera. Once you've got that then you are laughing.

I wonder if there are any more example images. I remember Massimo posted some in the AP Yahoo Group about 6 weeks ago. I'll see if I can find them. I can't remember what camera he used though.

Greg.
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Old 10-10-2011, 05:54 PM
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I found it:

http://tech.groups.yahoo.com/group/ap-ug/message/56383

And here are the 2 images he posted using a Microline 11002 camera.

The first image shows nice round stars, the 2nd shows some small amount of coma in the corners.

11002 chip is the same width as 16803 but half as long. I think its a good guide as to what to expect with a 16803 flexure issues not included. It seems pretty close to being spot on. Perhaps the spacing is not quite right.

> The images has been taken by Gino Bucciol and Giovanni Paglioli.
> In spite of the fact that the seeing was not good and there was the moon the
images below are fine ( Roland like them very much).
> The links below are for:
>
> - image of gamma cygni taken in August in South Italy
> with Veloce Rh200 F/3 covering 4 degrees field.
>
>
http://www.officinastellare.com/zoom...llare.com/ima\
ge/resize/id/737/width/930/height/410
>
> Image data are as follows:
> NEW Veloce RH200 image. Sadr region (IC1318)
> H-alpha light, sum of 10 minutes sub exposures (total 60 minutes). FLI imaging
train (Microline 11002-M full format 24x36 mm camera, CFW-2-7, Atlas focuser).
> Mach1 GTO mount.
> Full Moon (99%) at 60 degrees.
>
> and this second one concerning North America area:
>
>
http://www.officinastellare.com/zoom...llare.com/ima\
ge/resize/id/735/width/930/height/410
>
> Image data:
> Veloce RH200 image. Cygnus region (NGC7000 and IC5070)
> H-alpha light, sum of 10 minutes sub exposures
> FLI imaging train (Microline 11002-M full format 24x36 mm camera, CFW-2-7,
Atlas focuser).
> Mach1 GTO mount.
> Full Moon (99%) at 60 degrees.

Greg.
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