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.7 Antares reducer method

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#1 GOLGO13

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Posted 23 February 2020 - 12:17 PM

I wanted to provide an update on a successful method of reduction I've found. My 6 inch F4 newt came with a 2 inch to 1.25 inch adapter which has threads for 2 inch accessories. Screwing on the .7 Antares reducer onto this adapter allows me to use 1.25 inch capabilities with extra reduction. I've been using my Tele Vue 40mm Plossl afocal using the Tele Vue Envis adapter which provides .7 reduction of it's own. Then added to the .7 antares works well.

 

I've found this works especially well for situations where you need more FOV such as the Rosette Nebula with my 6 inch F5 refractor. It's not perfect across the entire field of view, but it's decent. I have not tried this much for normal unfiltered or long pass filtering. Though I did last night and had a very nice view of M81 and M82. M82 is actually quite good with Night Vision.

 

See the .7 reducer attached to the 2 inch to 1.25 inch adapter below:

 

20200223 111127

 


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#2 slavicek

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Posted 23 February 2020 - 10:22 PM

My experience with the focal reducers is that they use up even more back focus of the telescope, so sometimes I just cannot focus the setup anymore. And I also get into vignetting problems. Here I'd use the 55mm TV Plossl instead of your 40mm + 0.7 reducer setup. But hey, whatever works! Just my 2c.



#3 GOLGO13

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Posted 23 February 2020 - 11:16 PM

The combination of the reducer and afocal with the 40mm places the focus in a very normal position.

I agree a 55mm plossl and 2 inch filters would do the same. But for me I am currently all 1.25 inch and monetarily that will be the case for awhile.

#4 bobhen

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Posted 24 February 2020 - 08:15 AM

Since I got my intensifier 4 years ago, I’ve been using the 2”, .7-reducer just like that.

 

Here's my optical train with the reducer. 

 

Bob

 

Attached Thumbnails

  • IMG_00551.jpg

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#5 GOLGO13

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Posted 24 February 2020 - 09:12 AM

Bobhen. If you ever ran into an issue with focuser travel, using it afocal would solve it. 

 

This 6 inch F5 I have won't come to focus prime using a 2 inch diagonal. And for sure it doesn't work prime with the .7 reducer. However, this is not a problem because I can use afocal using the above method.

 

But I can do prime using a 1.25 inch diagonal (using my baader prism). So afocal widens the capability if focusing is an issue. 

 

Turns out with the 6 inch F4 newt, it's kind of the opposite issue on focusing. There is so much back focus that using afocal gets a little crazy. It does work, but I have to pull out the extensions a little and it's already a tall stack. So using prime is a better way to go with the 6 inch F4 newt.

 

This all kind of reminds me of binoviewing situations. It's nice to get a system where you have multiple options for different scopes to come to focus.


Edited by GOLGO13, 24 February 2020 - 09:16 AM.


#6 bobhen

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Posted 24 February 2020 - 10:36 AM

Bobhen. If you ever ran into an issue with focuser travel, using it afocal would solve it. 

 

This 6 inch F5 I have won't come to focus prime using a 2 inch diagonal. And for sure it doesn't work prime with the .7 reducer. However, this is not a problem because I can use afocal using the above method.

 

But I can do prime using a 1.25 inch diagonal (using my baader prism). So afocal widens the capability if focusing is an issue. 

 

Turns out with the 6 inch F4 newt, it's kind of the opposite issue on focusing. There is so much back focus that using afocal gets a little crazy. It does work, but I have to pull out the extensions a little and it's already a tall stack. So using prime is a better way to go with the 6 inch F4 newt.

 

This all kind of reminds me of binoviewing situations. It's nice to get a system where you have multiple options for different scopes to come to focus.

The 6" F5 that you have will most likely come to focus using prime focus if you replace the original focuser with a GSO 2" focuser.

 

I swapped out my focuser for the GSO with my 102 mm F5 and others have done that with their 120mm F5 refractors. All of these 102, 120 and 150mm F5 achromatic refractors are made by Synta . I know that CN poster, Vondragonnoggin has a Synta 120 F5 and 150 F5 that he uses with NV and the GSO focuser.

 

My 2 other scopes that I use with NV (a Tak TSA 120 and a Mewlon 210) come to focus with the .7 reducer without modifications.

 

The GSO is a better focuser anyway.

 

Bob



#7 GOLGO13

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Posted 24 February 2020 - 10:53 AM

The 6" F5 that you have will most likely come to focus using prime focus if you replace the original focuser with a GSO 2" focuser.

 

I swapped out my focuser for the GSO with my 102 mm F5 and others have done that with their 120mm F5 refractors. All of these 102, 120 and 150mm F5 achromatic refractors are made by Synta . I know that CN poster, Vondragonnoggin has a Synta 120 F5 and 150 F5 that he uses with NV and the GSO focuser.

 

My 2 other scopes that I use with NV (a Tak TSA 120 and a Mewlon 210) come to focus with the .7 reducer without modifications.

 

The GSO is a better focuser anyway.

 

Bob

I agree that is an option, but I would rather not spend more on this one. It's possible the focuser on it is either the same or worse on back focus.  It does have a different than stock focuser on it which is fairly nice. It's a William Optics with a digital one:

 

paf-wo-fddgsynw-2.jpg



#8 Jeff Morgan

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Posted 24 February 2020 - 11:16 AM

My Antares 0.7x is a key piece of equipment and gets heavy use. Threads onto the end of the ScopeStuff 2” C-mount adapter (m48 thread).

 

My measurements showed approximately 12mm of additional inwards focuser travel is required.

 

By coincidence during the building of my Dob (pre NV days a.k.a., the Dark Ages) I cut the truss tubes 1/2” too short and compensated for it with a focuser riser. Removing the riser and I was good to go with the reducer. 
 

Gavster has posted about screwing it on the bottom of a 55 Plossl in afocal mode with good results. 



#9 Shelldawg

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Posted 24 February 2020 - 11:35 AM

I will just add that I just got both a .7 and .5 Antares FR and used .7 this weekend with success screwing it into the bottom of my TV eyepieces (e.g., 55 plossl) and then adding my filters to it and then using the TV-TNVC adapter to my Mod3c at the end .... it worked in my 80mm and 102mm refractors and my 12" Imaging Newt. In the  80mm I had HH, Flame, and Orion in the same FOV and could see them all without averted vision...LOL! I did not try it in my 30" yet - I kind of forgot to do so.  But nebulae such as Heart, Soul, etc were perfectly framed in the 102 with it and the .7 also provided less scitilation with the faster optics. 

 

Shelldawg



#10 Shelldawg

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Posted 24 February 2020 - 12:54 PM

here is that pic - Orion overexposed - it looked way better in the EP but this is a good reference for FOV

 

posts wideFOV_Orion_HH_Flame.jpeg

 

and a few others from the night - Soul and Heart used the .7 reducer on the 102 and the Jellyfish and Monkey Face are from the 30" no reducer - All afocal with TV 55 plossl I will upload in separate



#11 Shelldawg

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Posted 24 February 2020 - 12:55 PM

heart with reducer 

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  • Heart copy.jpg


#12 Shelldawg

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Posted 24 February 2020 - 12:59 PM

Monkey face in the 30" w/TV plossl and Astronomik 6nm Ha filter - - ok looks like I can't upload all these at once so I will stop for now. 

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  • monkeyface_30inch.jpeg


#13 Shelldawg

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Posted 24 February 2020 - 01:02 PM

HH & Flame in the 12" Newt 

 

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  • HH_Flame_12inch copy.jpg

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#14 BJS

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Posted 26 February 2020 - 06:05 PM

Instead of an extension tube, i use a GSO comma corrector with my 6"f4.  It helps to clean up the image with the 55mm TV.  Its not perfect but it makes it better.  I also place a .7x reducer on the bottom to make it even faster!  Great for the North American or Andromeda galaxy...really large objects.  I could have used it at WSP last week but i had my 10"f3.3 instead...i could have used the extra fov for Eta Carina.



#15 GOLGO13

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Posted 26 February 2020 - 06:51 PM

BJS... do you have to use any spacing with the GSO coma corrector? Any experience with this would be helpful.



#16 BJS

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Posted 27 February 2020 - 09:00 PM

I use a one inch spacer between the top and the bottom parts of the gso.
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#17 Peregrinatum

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Posted 27 February 2020 - 09:25 PM

GSO CC needs 75mm of backfocus, I have one and for the price it's pretty decent:

 

"Back-focus spacing requirement is 75mm with a tolerance of +/- 5mm."

 

https://agenaastro.c...-corrector.html




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