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Celestron Astro Fi 5 (5" SCT)

SCT Beginner CMOS
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#1 TomParis

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Posted 02 October 2022 - 07:21 AM

Dear Cloudy Nights guys,

 

I just ordered a Celestron Astro Fi 5" Schmidt-Cassegrain as my first (second) telescope.

Well the first one was an ES 102/714 Apo + ES PMC-EIGHT EXOS 2 but I returned them because of the W10 wifi problem of the PMC-EIGHT (and the APO had a faulty focuser). However, I could play around with them for a while and noticed that in my apartment and on my recessed balcony the proportions and handling of the scope and mount were already on the limits of what's possible.

After some research I then decided to get a Celestron Evolution C8 which is quite portable for it's aperture but the prices in Germany have skyrocketed a few month ago. I told myself that I would wait until they're cheaper but in the meantime some big South American river shop decided to put a nice Celestron Astro Fi on offer in their shop.

 

It has many shortcomings compared to a C8 but at 460 € I hope it'll be nice to play around and maybe get some more experience with telecopes. I have read about baffle tube diameters when I tried to find out about good eyepieces for the C5 (and hopefully C8 later on). Celestron website says 27 mm for C5/C6 and 37 mm for the C8.

I think I now know which eyepieces I can use for the C5 (1,25" 24 mm/68° should be around the maximum) but I am not sure if I can use every camera.

According to the astronomy tools calculator a 294 sensor with its big pixels would be great for both the C5 and C8. Also 571 and 533 could be fine. But what about the sensor diamter? What's the maximum diameter for a sensor without obstruction? Any recommendations for nice cameras for EAA?

 

Regards from Berlin

 

Markus



#2 bmcclana

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Posted 02 October 2022 - 08:09 AM

The C5 doesn’t have a very big illuminated field. The baffle tube is about 1”. I would expect a 533 sensor might be OK at F/10, but reduced to f/6.3 would probably need flats due to vingetting.

I would stay with a 533 or smaller chip.

#3 TomParis

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Posted 02 October 2022 - 08:15 AM

Okay thanks. What about bigger sensors. Could I just set a ROI for the area of the chip that gets light? I really have no idea if that's possible or if it makes sense. So small ROI for the 533, 294 or 571 chip but when I get a C8 everything could be used, right?



#4 alphatripleplus

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Posted 02 October 2022 - 08:42 AM

Okay thanks. What about bigger sensors. Could I just set a ROI for the area of the chip that gets light? I really have no idea if that's possible or if it makes sense. So small ROI for the 533, 294 or 571 chip but when I get a C8 everything could be used, right?

From reading other users experience with a sensor as large as the 294, you will still get vignetting on a C8 operating at f/6.3. With a large sensor camera and a SCT, you will probably want to use flats to remove the vignetting. Using ROI has the same effect as cropping - you are giving up some of the real estate associated with a large sensor.



#5 bmcclana

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Posted 02 October 2022 - 08:47 AM

I think the 533 works well with an 8” SCT, but the larger chips will give the bigger FOV.

On the C5 you can always crop or use an ROI with the larger chips.

What works is really up to you.

#6 TomParis

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Posted 05 October 2022 - 02:35 PM

Thank you! That helps a lot.


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