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Explore Scientific FCD-100 Field Flattener

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#1 theocerboneschi

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Posted 23 February 2018 - 01:04 AM

Hi Everyone, 

 

I just purchased an Explore Scientific FCD-100 102 (4 inch) and I'm looking for a good field flattener and potentially a focal reducer to shoot with an A7S (full frame).

 

The ones sold by  ES won't work for me as they all have a focal plan on 45mm and I need 55mm, which seems to be the standard. 

 

After looking online, it doesn't seems like there are many options that fits the bill and and I somewhat settled one Stellarvue 0.8x FR/FF.  That said they don't mention if it will cover a full frame sensor. Anybody has experience? 

 

If not my last option would be their large sensor FF without any FR. 

 

Any other options I should consider? 

 

Thanks!!

 

 



#2 ZL4PLM

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Posted 23 February 2018 - 03:25 AM

thats the one I have on my 102 and its very good 

 

can't comment on the full frame though 



#3 ThermalSeeker

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Posted 23 February 2018 - 06:56 AM

I have the ED102CF and went with the Stellarvue SFF3-3FT-48 but upgraded to a 3" Moonlite focuser.  The Stellarvue SFF3-25-48 may also be a choice worth considering that it is designed for 2.5" focusers.  I can't comment on the reducer/flattener combo you are interested in.  I recommend calling Stellarvue directly and speaking to Vic for the most accurate response.



#4 theocerboneschi

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Posted 23 February 2018 - 03:00 PM

Thanks for the inout everyone. 

 

I called High Point Scientific and they confirmed a few points:

 

  • Stellarvue SFFR-102 won't cover a full frame sensor
  • Stellarvue Large photographic Field Flatteners will cover a full fired (obviously) but won't thread on the Explore Scientific focusers.
  • the Hotech FF should cover a full frame.

I went with the Hotech, especially since it's on sale and will keep you all updated on results!



#5 Star Stalker

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Posted 01 March 2018 - 02:15 PM

The AT 2" Flattener is a good full frame flattener.  I use it on my Orion 80T CF/f6, svt90r and 115/f7 and even on my C8 sct with no noticeable stretch in the corners.  Keep the 57mm distance to sensor accurate and stars will remain round. 



#6 Lead_Weight

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Posted 01 March 2018 - 02:22 PM

I’m using the SFFR-102 on my ES102 FCD100. I don’t have a full frame sensor, I’m using the ZWO ASI1600MM-C micro 4/3 sensor. Seems to work good. Flat image to all corners. You can see pics on my astrobin. With your full frame you might experience something different.

Edited by Lead_Weight, 01 March 2018 - 02:23 PM.


#7 View2

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Posted 18 March 2018 - 11:57 PM

I've got the ES127 with a 3" FT focuser. Oddly enough yes does not make field flattener for their own telescopes I don't even know if they make an f8 and don't understand the logic there. I thought about stellarvue .8 x 3 in. Waiting to hear feedback from people. Hard to find a matching field flattener for this thing

#8 theocerboneschi

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Posted 27 March 2018 - 11:24 AM

Hi everyone, 

 

So I FINALLY got clear skies and took my first few shots on the FCD-100 102 with the Hotec FF. 

 

Stars looks sharp on every corner but I get insane vignetting!

 

I'm wondering if the FF has anything to do with this or if the vignetting is due to the extensions (delivered with the scope) I had to add to be able to focus. 

 

This is "corrected" with flat frames:

 

54380787642__AC1C2131-7968-496B-9499-40599F02C47D.jpg

 

Anybody as experience?



#9 Lead_Weight

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Posted 27 March 2018 - 11:57 AM

Hi everyone, 

 

So I FINALLY got clear skies and took my first few shots on the FCD-100 102 with the Hotec FF. 

 

Stars looks sharp on every corner but I get insane vignetting!

 

I'm wondering if the FF has anything to do with this or if the vignetting is due to the extensions (delivered with the scope) I had to add to be able to focus. 

 

This is "corrected" with flat frames:

 

attachicon.gif 54380787642__AC1C2131-7968-496B-9499-40599F02C47D.jpg

 

Anybody as experience?

Are you using the stock Focuser? I have this issue on mine, and I’m using a 2” Moonlite Focuser with the ASI1600. It’s a larger sensor, but not full frame. After discussion with ES and Moonlite it turns out the Focuser draw tube is too small for the sensor size and causes vignetting like you see. They tell me a 2.5” or 3” drawtube focuser should eliminate this issue, or I should use a smaller sensor. I’m about to sell the 2” one I have, which seems more appropriate for visual than photography.



#10 theocerboneschi

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Posted 27 March 2018 - 12:28 PM

Are you using the stock Focuser? I have this issue on mine, and I’m using a 2” Moonlite Focuser with the ASI1600. It’s a larger sensor, but not full frame. After discussion with ES and Moonlite it turns out the Focuser draw tube is too small for the sensor size and causes vignetting like you see. They tell me a 2.5” or 3” drawtube focuser should eliminate this issue, or I should use a smaller sensor. I’m about to sell the 2” one I have, which seems more appropriate for visual than photography.

Thanks for the input.

 

I'm using the stock focuser but the FCD-100 version comes with a 2.5" focuser, not 2". Maybe this is not enough for a full frame though...



#11 Lead_Weight

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Posted 27 March 2018 - 12:42 PM

Thanks for the input.

 

I'm using the stock focuser but the FCD-100 version comes with a 2.5" focuser, not 2". Maybe this is not enough for a full frame though...

Yeah, I have the FCD-100 as well. 2" is definitely not enough, but I didn't know this before getting it. This hobby seems to be more trial by error than anything else. The Moonlite guy suggested the 2.5, and even the 3" version to be safe, but the cost between the two is astronomical. Since their 3" version is only sold with their computerized Nightcrawler focuser.

 

Anyhow, all this is to say, it might be too much to use full frame for that focuser. Which is odd, as it's sold for imaging, and is fairly wide field at 102mm. You might just call ES and see what they say.

 

I will add too, that although not ideal to have some vignetting, it's not unordinary. And, it can be corrected with flats. So you might try creating flats at different ADU values to test how much of a flat you need for your particular situation. Push your flats to the point that they start over correcting, then back off just a bit so that it's fully corrected.




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