Author Topic: Stacking filters?  (Read 9507 times)

Eric Castro

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Stacking filters?
« on: December 26, 2017, 07:34:28 PM »
Sorry if this is a Dumb question:

Is it feasible to have more than one filter on your optical train to pile, not including a filter wheel or similar merchandise (which wouldn't pile 2 different ones) ?

For cases, do you have one 1.25 or two" filter on the eyepiece plus a single 2 inch on a barlow?



Lawrence Paez

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Re: Stacking filters?
« Reply #1 on: December 30, 2017, 04:15:03 PM »
Possible but not practical or particularly useful. See similar thread that started a few days earlier.

Kapil Majmudar

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Re: Stacking filters?
« Reply #2 on: December 30, 2017, 10:18:05 PM »
It's a good question, well posed. Yes, you can. Some filters even have female threads on the eye side. I've tried it with 2 narrowband filters with different passbands. It didn't get me much and no improvement, for sure.
There's nothing stopping you and you'll certainly not damage anything. Give it a shot.  "Freedom is something that dies unless it is used." -Hunter S. Thompson

grateganir

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Re: Stacking filters?
« Reply #3 on: December 31, 2017, 02:09:03 AM »
If there's a thread, it is possible indeed. I've regularly did that with my neutral filters, and I also do that with polarizing filters. I've also found that you can make cheap O-III-s better by stacking two of them from a different manufacturing series. As for cheap filters sometimes theres a little shift in the band passed, this may result in a somewhat narrower transmission. But unless you don't already have the filters, it's not really worth the hassle.

Edit: an O-III and a UHC together may also result in a narrower O-III bandpass, as a UHC is in fact allows O-III and H-ß lines.

alnepensa

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Re: Stacking filters?
« Reply #4 on: January 04, 2018, 06:38:20 PM »
I have heard on another forum that stacking two like narrowband filters will result in narrower band. I tried two 7nm Ha filters and appeared slightly better S/N. Supposedly the stack is at the cost of transmission though, although it did not seem to make much transmission difference in my night vision eyepiece.

Paul Woodrow

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Re: Stacking filters?
« Reply #5 on: January 08, 2018, 07:17:10 AM »
Quote
If there's a thread, it is possible indeed. I've regularly did that with my neutral filters, and I also do that with polarizing filters. I've also found that you can make cheap O-III-s better by stacking two of them from a different manufacturing series. As for cheap filters sometimes theres a little shift in the band passed, this may result in a somewhat narrower transmission. But unless you don't already have the filters, it's not really worth the hassle.

Edit: an O-III and a UHC together may also result in a narrower O-III bandpass, as a UHC is in fact allows O-III and H-ß lines.


Actually, an OIII and a Lumicon UHC together will just be an OIII with a similar passband width but with a slightly lower peak transmission. The long wavelength cutoffs of both the UHC and OIII are fairly similar, while the OIII will effectively superimpose its blue wavelength cutoff onto the UHC. What you will get will pretty much be a similar bandwidth lower peak transmission (around 83%) OIII filter. Thus, stacking these filters makes little sense. Clear skies to you.

Jomega Ceo

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Re: Stacking filters?
« Reply #6 on: January 08, 2018, 08:19:49 AM »
Quote
Quote

. As for cheap filters sometimes theres a little shift in the band passed, this may result in a somewhat narrower transmission.


Actually, an OIII and a Lumicon UHC together will just be an OIII with a similar passband width but with a slightly lower peak transmission. The long wavelength cutoffs of both the UHC and OIII are fairly similar, while the OIII will effectively superimpose its blue wavelength cutoff onto the UHC. What you will get will pretty much be a similar bandwidth lower peak transmission (around 83%) OIII filter. Thus, stacking these filters makes little sense. Clear skies to you.

Yes, that is why I mentioned that it is valid for the cheap filters only, when the manufacturing process is not so strict and there may be shifts in the transmitted bands (and not manufactured in the same run). Naturally, for more expensive ones, where there's a rigorous testing process, the filters transmit the same bandwidths near exactly. (edit: of course we are talking about a few nm's of difference, so I agree that generally stacking these filters makes no sense)

revenade

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Re: Stacking filters?
« Reply #7 on: January 08, 2018, 04:40:18 PM »
I've heard of people stacking the Baader Neodymium with the Baader Contrast Booster filter for planetary viewing.

jumphindnore

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Re: Stacking filters?
« Reply #8 on: January 09, 2018, 11:35:17 PM »
Speaking of planetary viewing, stacking planetary color filters for different combinations of effects is probably more useful than stacking nebula filters... IF you're the sort of person that likes to use those filters properly in the first place...

aththrilnalo

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Re: Stacking filters?
« Reply #9 on: January 10, 2018, 07:54:12 AM »
Quote
I've heard of people stacking the Baader Neodymium with the Baader Contrast Booster filter for planetary viewing.

I do that with my C102 Achro to reduce the color on bright objects. It works well.

Gregory Plummer

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Re: Stacking filters?
« Reply #10 on: January 11, 2018, 03:23:49 AM »
Quote
Speaking of planetary viewing, stacking planetary color filters for different combinations of effects is probably more useful than stacking nebula filters... IF you're the sort of person that likes to use those filters properly in the first place...

I'd have thought so too. I think you would need a decent aperture size (150mm plus?) to properly use stacked Wratten filters without diminishing the light significantly.

I have seven (Celestron) Wratten filters including a 0.9 Neutral Density filter. The Baader Contrast Booster filter is probably a bit like a milder Wratten 12 Deep Yellow.

The coloured ones are:

12 Deep Yellow: Minus blue filter. Improves contrast.
21 Orange: Contrast filter for blue and blue-green absorption. Longpass filter blocking visible wavelengths below 530 nm.
25 Red (Tricolour A): Used for colour separation and infrared photography. Longpass filter blocking below 580 nm.
56 Light Green.
58 Green (Tricolour B): Colour separation.
80A Blue: Colour Conversion. Raises the colour temperature.

Not sure if I know how to use them properly though lol.

massgisttesci

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Re: Stacking filters?
« Reply #11 on: January 11, 2018, 11:36:27 AM »
Quote
Quote

I've heard of people stacking the Baader Neodymium with the Baader Contrast Booster filter for planetary viewing.

I do that with my C102 Achro to reduce the color on bright objects. It works well.
I believe the Baader Contrast Booster filter was specifically designed for achromatic refractors.

http://www.firstligh...ter-filter.html