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RASA 8 + Quad BP Filter?

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#1 cuivienor

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Posted 20 February 2019 - 11:34 PM

So I am considering another purchase for nebula imaging. I currently use an ASI1600MM-C, Astrodon 3nm filters, and a 350mm f4 lens or an f7 reduced EdgeHD 800 scope. I am in Tokyo, so a super white zone, it's terrible.

 

I have a 294MC Pro sitting around pretty much unused, so I am thinking I could put it to good use, after I saw the Triad Ultra from OPT being release. The problem with the filter is that it only works for f4 or above without too much bandpass shifting.

 

So I've been wondering whether a broader pass band filter like this one http://sightron.info/quad-bp-filter/ could work with the RASA 8 - in which case I could use that as a light bucket, which I could use in parallel to my main setup to capture OSC images... Or would other filters work well? Such as the Idas NB1? That one seems to kind of ignore SII....

 

Also, what is needed in addition to the RASA 8 to add a 48mm filter in the light path?

 

Any ideas/advice?

 

Thank you!

 

Yannick



#2 Wintermute

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Posted 22 February 2019 - 07:46 PM

It seemed to do pretty well at F/2.2.

https://www.cloudyni...d-asi294mc-pro/



#3 rockstarbill

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Posted 22 February 2019 - 11:12 PM

Also, what is needed in addition to the RASA 8 to add a 48mm filter in the light path?

 

A filter made to work with the RASA8 which this is not. 

 

Seriously people need to read the white paper for this scope. No offense, but the tolerances it is designed for does not leave much room. 



#4 APshooter

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Posted 23 February 2019 - 12:01 AM

I believe there's only one light pollution filter made for the Rasa 8, one made by Celestron.  It's 46mm. 

 

Bandwidth issues aside, you could install the Starizona filter drawer and change out a 2" filter that way.  That's what I'm using on mine with Baaders 2" narrowband filters.  The caveat is you have to use a short backfocus camera like the ZWO 1600MM or 294MC.  Unfortunately no one yet makes a notch filter like the triad that works at F2.

 

 

The Light Pollution Imaging (LPI) Filter for the 8" RASA blocks light from some of the most common sources of light pollution between 400-700nm (i.e., the visible spectrum), including high- and low-pressure sodium-vapor streetlights, mercury-vapor streetlights, and natural airglow caused by oxygen in the atmosphere. Unlike some light pollution filters, the LPI filter blocks only specific areas of the spectrum instead of wide regions. This helps to maintain image brightness and color balance. In addition, specific wavelengths associated with emission nebulae, such as H-a(656nm), H- (486nm), OIII (496nm and 501nm), and SII (672nm), are highly transmitted, ensuring minimal loss of image brightness for those objects. 

 

For the triad:  Since the filter has extremely narrow band passes, telescopes with focal ratios faster than f/4 will move transmission off band. Telescopes with focal ratios between f/2.9 and f/3.9 are compatible with Triad Ultra, with lower transmissions. Telescopes with focal ratios faster than f/2.8 are incompatible with the Triad Ultra filter.


Edited by APshooter, 23 February 2019 - 12:08 AM.

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