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Astrophotography Modification Advice Needed

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#1 Greenleafs91

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Posted 03 April 2020 - 03:16 PM

So was reading up on the astromods for canons (I have a T3i) and there was basically the full spectrum and the one where you just take out the ir/cut filter LPF 2. I was looking to get the 2nd option but was confused if just taking out the LPF 2 without replacing it with another filter would make it better or worse in terms of image quality, ability to autofocus or achieve infinity focus. I was also concerned when I read somewhere that if I don't premeasure some parts and put it back close to the exact "micrometer" position or something like that, it might screw stuff up in terms of the camera's ability to focus. I keep seeing Gary Honis's name but not sure if his instructions account for those things. 



#2 mmalik

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Posted 03 April 2020 - 03:26 PM

Read here...; 'Removed LPF-2' is recommended. Spring mounted Canon sensor would need to put in the same position to preserve orthogonality or moved forward a bit to preserve auto-focus (not needed for AP). Instructions here.... Regards


Edited by mmalik, 03 April 2020 - 06:12 PM.


#3 Greenleafs91

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Posted 03 April 2020 - 06:18 PM

Awesome. I took a look at the instructions. Very nice. Questions:

 

1) I guess it's not too different between the canon models since I have a T3i?

2) I was wondering though if it'll affect my ability to use my camera lenses and apo telescope? I heard that some of the mods make it so that I won't be able to use camera lenses or need extra equipment for Apo telescopes. 

3) For LPF-2 removed only, you mentioned moving sensor forward 1/2 to 3/4 turn beyond stock position. Could you elaborate more on that? I'm guessing you mean the "turn" of the screwdriver? Also "forward" as in bringing it closer to the LPF-1 sensor? 

 

BTW thanks for all the advice. 

 

Read here...; 'Removed LPF-2' is recommended. Spring mounted Canon sensor would need to put in the same position to preserver orthogonality or moved forward a bit to preserve auto-focus (not needed for AP). Instructions here.... Regards



#4 mmalik

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Posted 03 April 2020 - 06:26 PM

1) Correct

 

2) and 3) are the same. You need to move the sensor (assembly) forward to maintain auto-focus for your lenses. Note: You are not moving LPFs per se since they 'are' part of the assembly.

 

 

Regards


Edited by mmalik, 03 April 2020 - 06:29 PM.


#5 Greenleafs91

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Posted 03 April 2020 - 08:38 PM

I see. But as in "forward" you mean the whole sensor + filter assembly towards the actual front of the camera correct? And that is achieved by screwing each of the measured screws that hold the assembly in place 1/2 a turn? 

 

1) Correct

 

2) and 3) are the same. You need to move the sensor (assembly) forward to maintain auto-focus for your lenses. Note: You are not moving LPFs per se since they 'are' part of the assembly.

 

 

Regards



#6 mmalik

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Posted 03 April 2020 - 08:45 PM

Correct; spring mount points move whole assembly (sensor + LPFs) and yes it needs to be moved forward. Regards


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#7 Greenleafs91

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Posted 03 April 2020 - 08:49 PM

Promise last question. Do you know if the amount moved forward depends on each individual camera? I'm just not sure how I would know how much to move it or how precise (0.1 vs 0.001 cm or mm etc) it has to be. 

 

Correct; spring mount points move whole assembly (sensor + LPFs) and yes it needs to be moved forward. Regards



#8 mmalik

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Posted 03 April 2020 - 09:31 PM

More important is marking the original (default) position of each of 3 anchor points. Once you get to the default mark, then you can move forward from there. Keeping default is recommended for AP; lens use will need you to move forward to preserve auto focus. Most Canon are the same in terms of how much forward you move. Regards


Edited by mmalik, 04 April 2020 - 12:19 AM.

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#9 Greenleafs91

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Posted 03 April 2020 - 09:47 PM

More important is marking the original (default) position of each of each of 3 anchor points. Once you get to the default mark, then you can move forward from there. Keeping default is recommended for AP; lens use will need you to move forward to preserve auto focus. Most Canon are the same in terms of how much forward you move. Regards

Gotcha. Assuming AP = with a telescope and not a lens. 



#10 mmalik

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Posted 04 April 2020 - 12:22 AM

AP = with a telescope and not a lens. 

Correct.


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