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Focal Reducer Problems

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#1 dlwmacgregor

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Posted 28 September 2020 - 06:52 AM

I had my first opportunity to try out my new 0.5 focal reducer.

It did not go well.

 

It is an SVBony 0.5 focal reducer part number F915A.

I just checked the SVBony site and this is not the one they are selling now - that part number is F9154A.

I also just read that mine should be avoided because it is garbage.

 

Now the question is did I use it wrong or is it really no good?

 

I screwed it into the bottom of my 25 mm eyepiece and put the eyepiece into the diagonal and tried to refocus.

I can't describe what I saw because I don't know exactly what it was but it wasn't a smaller image of the moon.

Did I use it right?

Let me know so I can tell SVBony.

Thanks

 

Doug

 



#2 SeattleScott

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Posted 28 September 2020 - 11:28 AM

The problem is you are trying to use it visually with an eyepiece instead of with a camera.

Scott

#3 dlwmacgregor

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Posted 28 September 2020 - 11:45 AM

The problem is you are trying to use it visually with an eyepiece instead of with a camera.

Scott

Shouldn't I be able to use it with an eyepiece like I do with a Barlow?



#4 SeattleScott

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Posted 28 September 2020 - 04:09 PM

No. These are designed to reach focus with cameras, not eyepieces. They are only remotely sharp in the center of the field. Fine for low res, small sensor cameras.

Scott
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#5 MitchAlsup

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Posted 28 September 2020 - 04:32 PM

Shouldn't I be able to use it with an eyepiece like I do with a Barlow?

It all depends on the back focal distance of the reduced, and the field stop position in the EP relative to the threads in the barrel.

 

When the FS of the EP is at the BF distance of the reducer, the EP will deliver a focused image.

Otherwise, its nadda gonna work.



#6 SeattleScott

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Posted 28 September 2020 - 04:48 PM

Consider your reducer costs $20 on Amazon. A reducer designed for photo or visual use, like a 0.63x SCT reducer, costs $90-160.

There can be issues too depending on what scope you use it with. Let’s say you have an 8” F6 Dob. Now you just made the light cone F3? Absolutely brutal on eyepieces. Now a F10 SCT wouldn’t be so bad, which is why you can buy a visual reducer for a SCT. But to get one that is suitable for visual use costs a lot more money. And isn’t as aggressive. 0.5x is really aggressive and really intended for EAA, not visual, and not necessarily AP.

So bottom line, if you are visual only and have a refractor or reflector, give up on the reducer idea to get a wider view. If you have a SCT or Mak you can get a wider view with a reducer. But one good enough for visual use will cost several times as much.

In your defense, I see that this is being advertised as being for photo or visual use, which is very misleading.

Scott

Edited by SeattleScott, 28 September 2020 - 04:52 PM.


#7 dlwmacgregor

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Posted 28 September 2020 - 05:54 PM

It all depends on the back focal distance of the reduced, and the field stop position in the EP relative to the threads in the barrel.

 

When the FS of the EP is at the BF distance of the reducer, the EP will deliver a focused image.

Otherwise, its nadda gonna work.

Huh?

I'm a newbie.

Thanks.



#8 dlwmacgregor

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Posted 28 September 2020 - 05:56 PM

Consider your reducer costs $20 on Amazon. A reducer designed for photo or visual use, like a 0.63x SCT reducer, costs $90-160.

There can be issues too depending on what scope you use it with. Let’s say you have an 8” F6 Dob. Now you just made the light cone F3? Absolutely brutal on eyepieces. Now a F10 SCT wouldn’t be so bad, which is why you can buy a visual reducer for a SCT. But to get one that is suitable for visual use costs a lot more money. And isn’t as aggressive. 0.5x is really aggressive and really intended for EAA, not visual, and not necessarily AP.

So bottom line, if you are visual only and have a refractor or reflector, give up on the reducer idea to get a wider view. If you have a SCT or Mak you can get a wider view with a reducer. But one good enough for visual use will cost several times as much.

In your defense, I see that this is being advertised as being for photo or visual use, which is very misleading.

Scott

I wanted it to do double duty (visual and camera) (please see my signature for equipment).

I was intending to get an f/6.3 reducer (a good one) somewhere down the road.

 

If it can only do cameras that's OK.


Edited by dlwmacgregor, 28 September 2020 - 06:01 PM.


#9 SeattleScott

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Posted 28 September 2020 - 06:10 PM

Your camera is fairly small sensor so that should work. More moderate resolution, not a low resolution EAA camera. A $20 reducer might not do justice to your camera. Also your camera is really more of a planetary camera so there wouldn’t be any point in using the reducer for planetary. You can try some DSO with it using the reducer though.

Scott

Edited by SeattleScott, 28 September 2020 - 06:16 PM.


#10 dlwmacgregor

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Posted 28 September 2020 - 06:18 PM

Your camera is fairly small sensor so that should work. More moderate resolution, not a low resolution EAA camera. A $20 reducer might not do justice to your camera. Also your camera is really more of a planetary camera so there wouldn’t be any point in using the reducer for planetary. You can try some DSO with it using the reducer though.

Scott

Thanks Scott.



#11 Rutilus

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Posted 29 September 2020 - 04:53 AM

I wanted it to do double duty (visual and camera) (please see my signature for equipment).

I was intending to get an f/6.3 reducer (a good one) somewhere down the road.

 

If it can only do cameras that's OK.

When I bought my SCT telescope it came bundled with loads of extras including the SCT focal

reducers f/6.3 and f/3.3. I have been using them for visual use with all my refracting telescope and they work 

really well.  The pick of the bunch for me is the now defunct f/3.3 FR.

Using the FR on my 80mm refractor I get a field of view of 8.5 degrees, and had superb views of comet Neowise

back in July. I made an eyepiece with the f/3.3 reducer, and it works superbly with my 6 inch f/8 refractor.

Here is a couple of photos.

Attached Thumbnails

  • fr-cn.jpg


#12 dlwmacgregor

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Posted 30 September 2020 - 10:05 AM

I contacted SVBony about this reducer and at first they said that the T-adapter that comes with the camera was no good  for the telescope I have which I found strange.

When I told them which scope I had they said the 20mm T-adapter was OK.

 

They also asked me what the back focus of the scope was and I sent them the Celestron chart.

 

https://www.celestro...-celestron-scts

 

SeattleScott - I was actually planning on using it more or less only for lunar shots, since the FOV of the 25mm EP is too narrow and I didn't want to buy a new EP just for that.

 

I'll give it another shot but the forecast for the next 7 days doesn't look promising.

 

They also gave an explanation on why the F9115A reducer isn't listed on their web site any longer, while the F9154A is...

 

the F9115A originally is Brand VITE. finally it changed the brand into SVBONY.
when I upload the F9154A to the website, the F9115A is still VITE brand.  that's why I didn't update it to the website.




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