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RASA 8 and filters

astrophotography beginner
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#1 Marcelofig

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Posted 18 April 2019 - 03:08 PM

I'm thinking about getting a RASA 8, but I was wondering if I could use the 1.25" filters I already have.

 

I know I can't use a filter wheel, that's pretty obvious from the design of the RASA, but can I put a 1.25" filter in front of the camera (ASI 1600MM)? In the pictures and videos there are always using 2" filters.

 

Thanks



#2 perki14

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Posted 18 April 2019 - 03:33 PM

I have wondered this as well and I couldn't find a lot of data on this topic searching cloudy nights. I bought the RASA 11 and did some testing both with a 1.25 inch filter and no filter presents vignetting with the ASI1600MM. I think the difference in vignetting between no filter (or a larger filter) and the 1.25 inch filters is minimal if any. I don't have any test pictures available at the moment - I will try to add some later. The image circles are a bit different in size between the RASA 11 and RASA 8 so I don't know if that will make that big of a difference. The ASI1600mm came with this nifty filter adapter that threads into the spacer provided with the camera and will accept a 1.25 inch filter. This makes sure the filter gets as close as possible to the sensor. 



#3 APshooter

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Posted 18 April 2019 - 05:22 PM

I will try using my 1.25 in Astrodons in the Starizona filter drawer and see what vignetting I get. I've been wanting to try this for a while now. On Monday it looks like the rain is going to stop and give me an 8hr window, so I will test then and report back.

If the filter drawer slider is too far away, I have another idea that might work.

Edited by APshooter, 18 April 2019 - 05:23 PM.


#4 barrettlboehm

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Posted 02 May 2019 - 09:15 PM

APShooter, did you find a way to adapt the 1.25” into the 2” slide?  Do you have any pictures you can share?



#5 APshooter

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Posted 03 May 2019 - 12:13 PM

I did make a foam spacer to experiment with the idea and did a test on M81.  Here's the holder I made as well as the M81 image.  Frankly it was just a quickie image and I wasn't all that pleased with it, but I've always struggled with RGB imaging.  Placing 1.25" filters that far from the chip in the 2" filter holder created a large vignetted doughnut, so I ended up cropping just the central portion of the image.  Oh, and in case you wanted exposure details, it was 30 minutes of each channel, RGB, 60 seconds for each sub.

Attached Thumbnails

  • 20190503_112828.jpg
  • M81_combo_DBE CN.jpg

Edited by APshooter, 03 May 2019 - 12:15 PM.

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