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IDAS filters with narrowband filters. A question.

RobH

By RobH
in Imaging - Discussion

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RobH

RobH

Posted
Posted

Hi all.

Now I have a fast scope and am running an Atik 460EX binned 2x2, I find that my local skyglow/LP is limiting my luminance subs to no more than 5 minutes.

Obviously, this has an effect on my RGB subs too, but isn't a factor with narrowband.

If I put an IDAS filter ahead of the filter wheel, how will this affect my narrowband subs?

Will the IDAS increase imaging time for them, or cut out wavelengths that I need for NB imaging?

Cheers

Rob

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swag72

swag72

Posted
Posted

There's a thread http://stargazerslou...e-of-questions/ that I started about the self same thing. I had bought a 2" IDAS and fancied putting in the imaging train and leaving it there for all filters.

In the end, based in part on this thread, I decided to use it purely as a luminance filter, and so I went for a 1.25" in my filter wheel. A bit deja vu really as it was your filter that I bought!!!!

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Tim

Tim

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Need to get the bandpass graphs for the filters Rob, match them up, and overlay one filter line over the other.

Do you need longer than 5 mins Lum at 2x2 though? There isn't much in the universe that faint is there? :D

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steppenwolf

steppenwolf

Posted
Posted

Hutech do two versions of their LP filter now - perhaps the attached plot will help:-

Hutech IDAS Light Pollution Suppression (LPS) Filter plot

tokai1.gif

Hutech IDAS Narrow Band Nebula Photo-Visual (NBN-PV) filter Plot

nbn-plt.jpg

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RobH

RobH

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Thanks folks.

Yes Sara....it looks like I may have been a bit hasty getting rid of the IDAS!!

Tim.....it's the really faint background galaxies that I like to catch....I reckon the background can be the final icing on the cake for an image, so going very deep for a few subs is something I want to do.

Steve....from the look of those graphs Ha and OIII will be unnafected by the IDAS, but S2 will get a bit of a beating. TBH that doesn't worry me as I rarely shoot S2 anyway.

I think the thing to do is borrow a 2 inch filter and see how it works in practice.

Cheers

Rob

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RobH

RobH

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Do you want to borrow it again Rob...

Peter...

Sent from my GT-P7300 using Tapatalk HD

Hi Peter....you're a star.

I'd love to if that's okay. :smiley:

Let me have your paypal id and I'll send you the postage.

Cheers

Rob

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kirkster501

kirkster501

Posted
Posted

I have the 2" IDAS. So Rob, you thinking of putting this in front of the whole imaging shebang, i.e. in the nosepiece in front of the wheel? So the LRGB filters will sit behind it?

NUMPTY ALERT QUESTION>>>>> If that's so why would you need the "L" or IR filter in the filter wheel? Could you get away with just RGB? Or does the "L" filter do other stuff as well - i.e. ONLY let IR though?

I often get confused with the context of using filters; it appears some filters "filter out" a particular set of wavelengths (i.e LP filters) and allow the rest though. Some other filter types seem to "filter in" and only allow only the selected light though and block everything else! Most confusing to beginners moving up from DLSR!

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BlueAstra

BlueAstra

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Posted

I thought of using the Hutech IDAS instead of the L filter in my filter wheel, with my Baader RGB filters. Only problem when i tried it was that the IDAS wasn't par focal with the RGB filters. My focusser setup isn't reliable enough the use pre-programmed focus offsets, so in the end I abandoned it.

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BlueAstra

BlueAstra

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I used to use it like that when I had a 2" nosepiece on the end of my imaging train. The IDAS was screwed into the end of the nosepiece, which then slotted into the 2" drawtube on the end of the scope. However, in my new setup everything is screwed together, so the filter would have to take the weight of the OAG, FW and camera.

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RobH

RobH

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I have the 2" IDAS. So Rob, you thinking of putting this in front of the whole imaging shebang, i.e. in the nosepiece in front of the wheel? So the LRGB filters will sit behind it?

If that's so why would you need the "L" or IR filter in the filter wheel? Could you get away with just RGB? Or does the "L" filter do other stuff as well - i.e. ONLY let IR though?

That's the plan....2 inch filter in the nose and the rest behind.

This should make the luminance filter redundant as you say. If it proves to be a worthwhile system, then I'll remove the 'L' filter. I don't want to use an IDAS filter in the filterwheel as I'll still be daeling with the LP in my colour channels, so I may as well get rid of that too. What I want to see is any negative effect (or lack of) on my NB filters.

If there is a negative effect, I'll opt for putting an IDAS in the filterwheel and dealing with LP during processing.

Not having to do it in processing is better though as you need to be really careful to preserve good colour, and simply equalising the background isn't the way to do this.

I don't mind the filter not being parfocal as I generally check focus for each filter anyway, whether they claim to be parfocal or not.

Was considering giving it a bash tonight but it was my good lady wife's birthday and we've had a long day!

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steppenwolf

steppenwolf

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Posted

I currently leave my IDAS LP filter in the 2" nosepiece of my FR and take Luminance through my 'empty' ninth filter slot and this seems to work well - although I was appalled by some of the dust bunnies I captured a couple of nights ago and traced these to the IDAS filter which has now been suitably cleaned!

Sent from my iPhone from somewhere dark .....

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