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Anyone have an ES ED127 with 2.5" Hexfocus?

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#1 thekubiaks

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Posted 14 January 2020 - 12:59 PM

And for bonus points, do you have the ES (Explore Scientific) .7x focal reducer. I am trying to determine the correct backfocus for the reducer and am getting conflicting information. Thanks!

#2 TrustyChords

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Posted 14 January 2020 - 01:29 PM

And for bonus points, do you have the ES (Explore Scientific) .7x focal reducer. I am trying to determine the correct backfocus for the reducer and am getting conflicting information. Thanks!

I just got the ES ED127 FCD100 CF. I do not have the focal reducer yet.

 

I'm using a DSLR: Canon ESO Rebel 3 1100D, and for imaging in prime focus the correct backfocus is achieved by using both of the provided extensions and adjusting the focuser about halfway.

 

Also keep in mind that if you ever plan to use a 2x barlow (edit: for imaging), you'll need an additional 2-inch extender.


Edited by TrustyChords, 14 January 2020 - 01:30 PM.

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#3 thekubiaks

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Posted 14 January 2020 - 01:59 PM

Explore Scientific tech support now says the back focus for the focal reducer is 55mm, that is more in line with my findings. It was quite a hair puller trying to get focus with bad back focus data

#4 Master_Shake

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Posted 15 January 2020 - 03:08 AM

The backfocus is 55mm that is from the glass, not the M24 adapter.  You'll have to add about 3mm to it.


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#5 thekubiaks

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Posted 19 April 2020 - 12:11 PM

The backfocus is 55mm that is from the glass, not the M24 adapter.  You'll have to add about 3mm to it.

2.69mm to be exact.   Thanks Master Shake for discovering this difference in measurement points, I lost a bunch of data in the corners due to elongated stars.  So, to clarify, the focus point is 2.69" behind the front face of the FFFR, it is not the face of the FFFR

 

My image train is ASI1600MM (6.5) > EFW(20) > T2-T2(2) > ZWO 11mm ring (11) > M42 Rotator Agena (12.5) > 1.18mm spacer rings (1.18) >  FFFR (2.69)  = 55.87mm   In my EFW, I have both ZWO filters that need 1mm and Astronomik filters that need ~.5mm of spacing past 55mm.  I think 55.87mm is close enough.  YMMV.


Edited by thekubiaks, 19 April 2020 - 04:27 PM.


#6 Master_Shake

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Posted 19 April 2020 - 07:58 PM

The backfocus is 55mm that is from the glass, not the M24 adapter.  You'll have to add about 3mm to it.

For anyone else reading this in the future: 

 

I called Explore Scientific and they said the 55mm (or 56mm if you are using an EFW) backspacing starts from "A" in the photo and adds 2mm to "B".  

 

pE8Sdr9l.jpg



#7 Master_Shake

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Posted 19 April 2020 - 08:58 PM

2.69mm to be exact. Thanks Master Shake for discovering this difference in measurement points, I lost a bunch of data in the corners due to elongated stars. So, to clarify, the focus point is 2.69" behind the front face of the FFFR, it is not the face of the FFFR

My image train is ASI1600MM (6.5) > EFW(20) > T2-T2(2) > ZWO 11mm ring (11) > M42 Rotator Agena (12.5) > 1.18mm spacer rings (1.18) > FFFR (2.69) = 55.87mm In my EFW, I have both ZWO filters that need 1mm and Astronomik filters that need ~.5mm of spacing past 55mm. I think 55.87mm is close enough. YMMV.

Ahh.. Didn't see this message before I PM'd you.

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