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Moving from Mono 814M to OSC ASI2600mc using RASA 11"

Astrophotography
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#1 davidpuglia

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Posted 17 October 2021 - 11:31 AM

I've been using a Starlight XPress 814M for 7 years on a C14 Hyperstar and recently a RASA 11" with very good results.  I recently moved to Northern Arizona in a Bortle 4 area.  I've ordered a ZWO OSC ASI2600mc and will be using the RASA 11".  I use the Starizona filter drawer and trying to determine what LP filter I should use with this new combination.  The IDAS NBZ LP filter was recommended since it was designed for fast f2 systems that will not result in spectral shift but I can't find any in stock on this planet.  I'm now looking at the Opotolong L Extreme LP filter.  Not sure if it works well with fast f2 systems.  Does anyone have experience with this combination?  I've also seen posts from folks that live in Bortle 4 areas and they don't use LP filters with their OSC cameras.  Any advice appreciated,  Thanks


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#2 pyrasanth

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Posted 17 October 2021 - 12:18 PM

I replaced the clear stock filter on my RASA 11" with the Astrodon/Celestron LPR filter which works really well. I use this in combination with the Optolong Lenhance filter and with the ASI2600MC pro is a potent combination. Whilst it is advised not to use more than 1 filter I've not found any descernable reason to remove the LPR filter so it stays in the RASA all the time. It is useful as when I remove the LE-enhance filter I have the LPR filter still in place for normal OSC imaging.  

 

You may need to adjust the 2600 tilt plate, I found that my camera needed to have the tilt plate plate optimised to dial out the tilt. It is easy to build a laser collimator to do this- see my thread "ASI6200 tilt correction" which works just as well for the 2600.

 

The larger the sensor the more demands are put on the camera components. If you get severe tilt then the first port of call in my opinion would be to invest in Precise Parts adaptors that replace the Celestron stock camera fittings. I would, if you go down that route, purchase the adaptors that screw over the camera atachment mount on the corrector plate  thus avoiding issues like the Baader UFC plate, if used, is left rocking on the top of an existing Celestron LPR filter which sits high in the filter mount. I would not initially try and adjust the RASA lens tilt until you are sure you have eliminated camera tilt and an orthagonal check of the camera mounting adaptors has been performed.


Edited by pyrasanth, 17 October 2021 - 12:25 PM.

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#3 davidpuglia

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Posted 17 October 2021 - 12:54 PM

Thanks @pyrasnath - I was looking at the Astrodon/Celestron LPR filter and I'm going with your recommendation.  Interesting that with 2 glass surfaces you don't have any back focus issues as Celestron states you can't have 2 in the image train.  BTW - I had to modify the tilt on my 814M for the RASA 11 and that camera has a small 1" sensor.


Edited by davidpuglia, 17 October 2021 - 12:58 PM.

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#4 stargzr66207

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Posted 17 October 2021 - 06:02 PM

You're gonna love the 2600MC Pro!  It is super sensitive (I was using a Starlight Express 694C, and have found that what used to take a 6 minute sub to capture, I now can equal with a 3 minute exposure, using the 2600MC Pro).   Being able to use shorter subs means less lost time when you have to reject subs for one reason or another.

 

Ron Abbott


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#5 RogeZ

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Posted 17 October 2021 - 06:37 PM

Check astroblender’s video on the RASA and L-extreme.
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#6 davidpuglia

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Posted 17 October 2021 - 08:23 PM

@Vanguard - thanks.  So the L-extreme is a no!  Great video.



#7 RogeZ

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Posted 17 October 2021 - 09:30 PM

You are welcome Lift Off :)


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#8 Wiser

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Posted 18 October 2021 - 02:38 PM

It's possible to use a dual narrowband filter at F/2, if the bandwiths are not too narrow, something like 12 nm. With my C11 + Hyperstar 4, my STC dual narroband filter works well with a QHY 294c. Cyclops Optics, where I purchased this filter, stated compatibility somewhere at their site.


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#9 RogeZ

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Posted 18 October 2021 - 04:30 PM

The NBZ works very well at f/2.
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