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#1 descott12

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Posted 04 February 2024 - 12:04 PM

Hello all,

I have done pretty well with a C8 at f10 with an SA-100 but I would like be able to go deeper and longer and my mount (to be replaced at some point) cannot guide at 2000mm.  My Celestron reducer does not work well due to bad CA.

 

My eventual goal is to get an Alpy 600 but in the meantime I would like to get a faster system. 2 options:

1) Add a Starizona 0.63 reducer.  I have spoken to their optics guru and he showed me charts with a C11 that shows that the CA is actually improved with the reducer vs native f10. Cost: 400 USD - kind of alot for just a reducer.

 

2) GSO 6 inch f/5 newt with an upgraded focuser. That would require a guide scope, another guide camera and and EAF.  Cost around 950 USD. Quite a bargain for all that I think. And I have never owned a newt so there will be a bit of learning curve.

 

The second option is more optimal (according to everything Robin has posted) and the Alpy would do better at f5 rather than f6/7  but I would really like to reuse my C8 and all its accessories and I like the camera hanging off the back much better.

 

Thoughts?? I know alot of people have had good luck with a reduced SCT so I am leaning in that direction. And I was told the reducer could be returned if it didn't work out well.

Thanks in advance.



#2 SeymoreStars

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Posted 04 February 2024 - 12:26 PM

Sounds like the reducer is the cost effective, safe solution.

 

Steve



#3 robin_astro

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Posted 04 February 2024 - 02:33 PM

Have you tried one of those cheap 1.25 inch reducers you mount on the camera nosepiece?  I know it sounds crazy and I personally have not tried one but I have heard more than once that they work better than the standard SCT reducers with the Star Analyser and it could be a very low cost route if it works.

 

Cheers

Robin



#4 descott12

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Posted 04 February 2024 - 03:30 PM

Have you tried one of those cheap 1.25 inch reducers you mount on the camera nosepiece?  I know it sounds crazy and I personally have not tried one but I have heard more than once that they work better than the standard SCT reducers with the Star Analyser and it could be a very low cost route if it works.

 

Cheers

Robin

Hmmm. I do have a el-cheapo 0.5 reducer. I will give a try.

 

Edit: I just realize that I won't be able use by OAG if the reducer is just in front of the SA-100... as it will still see an FL of 2000mm and I am sure I won't be able to get both focused.


Edited by descott12, 04 February 2024 - 03:34 PM.


#5 descott12

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Posted 06 February 2024 - 08:29 PM

I tried the 0.5 reducer and the CA was pretty bad. No surprise as I think I paid $30 for the thing. I did get to try out my new rotator and that thing is awesome! It makes getting a horizontal spectrum SO much easier.

 

Therefore, I am going to order the Starizona reducer and see how that works. I will report back.

 

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#6 descott12

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Posted 08 February 2024 - 01:04 PM

Have you tried one of those cheap 1.25 inch reducers you mount on the camera nosepiece?  I know it sounds crazy and I personally have not tried one but I have heard more than once that they work better than the standard SCT reducers with the Star Analyser and it could be a very low cost route if it works.

 

Cheers

Robin

Hey Robin,

The Starizona reducer has a 90.3 mm back focus. That is from the back of the reducer to the science camera sensor. Having an SA-100 in front of the sensor at some pooint doesn't change that distance does it? Or does the SA-100 take up some of the distance like a typical filter would? What about when I add a prism?

Thanks



#7 robin_astro

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Posted 08 February 2024 - 01:48 PM

I guess like a filter the optical path length will be slightly longer through the glass of the grating. Is the back focus distance that critical ?

 

Robin



#8 descott12

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Posted 08 February 2024 - 02:48 PM

I guess like a filter the optical path length will be slightly longer through the glass of the grating. Is the back focus distance that critical ?

 

Robin

Not sure but I was hoping to get a close to spec as possible. I am trying to limit the CA so I thought I should at least try.  I think I have it all worked out now with an OAG so I should be good go for some longer exposures. After looking at your web site,  I think there is still quite a bit I can try to achieve with the SA-100 before getting an Alpy.



#9 descott12

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Posted 21 February 2024 - 09:31 PM

Hello all. I received my new Starizona reducer/corrector today and was able to start playing with it.  It looks very good so far. No visible CA or fishtailing at all. I definitely need to look at it a little more closely but I am pretty happy with it so far.

Very well built. Not even in the same class as the Celestron reducer.



#10 robin_astro

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Posted 22 February 2024 - 08:54 AM

Sounds promising. It could be the solution to the problem of CA when reducing SCT for fast slit spectrographs like the ALPY too

 

Cheers

Robin



#11 descott12

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Posted 22 February 2024 - 12:53 PM

Sounds promising. It could be the solution to the problem of CA when reducing SCT for fast slit spectrographs like the ALPY too

 

Cheers

Robin

Yes, my ultimate goal is to get an Alpy to run with this setup.




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