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Svbony Camera Backspacing

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#1 garblivet

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Posted 05 December 2021 - 08:49 PM

I have Svbony SV305 and SV105 cameras.  I'm wanting to use them with a 0.5x reducer but am having a hard time finding 1.25" extension tubes.  They will be going into a 1.25" focuser.   I have a couple of eyepiece extensions but will have to do some cutting to get the 55mm backspacing.  That's not a problem, but would rather not do it if it's not necessary.  Am I just completely missing something?  Thanks.

 



#2 vidrazor

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Posted 05 December 2021 - 09:39 PM

Why not just mount the 1.25 mount on 42mm or 48mm extension tubes?


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#3 garblivet

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Posted 05 December 2021 - 10:05 PM

I had thought about doing that, but I think I would still be past the 55mm backspacing.  I'll have to measure the 2" to 1.25" adapters again when I get home from work.  I'll have to buy more extension tubes either way, and was hoping to have the ability to keep the camera/reducer combo set up. 

 

Edit to add:  Also, the reducer is 1.25".


Edited by garblivet, 05 December 2021 - 10:09 PM.


#4 vidrazor

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Posted 05 December 2021 - 11:10 PM

I had thought about doing that, but I think I would still be past the 55mm backspacing.  I'll have to measure the 2" to 1.25" adapters again when I get home from work.  I'll have to buy more extension tubes either way, and was hoping to have the ability to keep the camera/reducer combo set up. 

Edit to add:  Also, the reducer is 1.25".

Well, there are kits available in both 42mm and 48mm sizes that have various size rings that may have the individual or combined distance needed. If you needed finer sizes than 5mm, you can try contacting a supplier like Agena Astro that may be able to help you find specific thickness spacers.


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#5 garblivet

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Posted 06 December 2021 - 12:02 AM

I do have the M48 extension tube kit you referenced for my ASI533 and coma corrector.  But... What I hadn't thought of was just getting a c mount to M42 adapter and an M42 adapter for 1.25" filters (c mount for SV305, cs for 105, iirc).  I was stuck on the idea of needing to have the 1.25" reducer on the end of a 1.25" tube.  I'd imagine the reducer would have to be recessed in the M42 tube so it doesn't interfere with the 2" to 1.25" focuser adapter?  Any issues you can think of doing it this way?  I appreciate the help!  You got my brain going in the right direction. 

 

I'm setting up my CEM25P and Orion 130ST for my daughter (6) to do EAA with on her own, with a little oversight of course.  This was the last piece that I couldn't figure out.



#6 vidrazor

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Posted 06 December 2021 - 01:08 AM

I'll assume you Orion is something you already have at hand, and I suppose you want to throw the reducer due to the small sensor on the SV305 (I just picked up a Pro for lunar, planetary and even some DSO work), so you're using something like the SVBONY or similar 1.25 reducer. and you need longer back focus distance? So the C to 1.25 adapter that came with the SV305 is not an issue. Perhaps I'm missing something, but if you just use, say, 2 inch extensions and screw on a 2 inch to 1.25 mount and stick the reducer in that, wouldn't you have what you need? Or do you need the extension ahead of the reducer between it and the SV305?


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#7 garblivet

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Posted 06 December 2021 - 02:07 AM

I'll assume you Orion is something you already have at hand, and I suppose you want to throw the reducer due to the small sensor on the SV305 (I just picked up a Pro for lunar, planetary and even some DSO work), so you're using something like the SVBONY or similar 1.25 reducer. and you need longer back focus distance?

 

Yes, exactly, to all of the above.  I'd be getting the pro if I didn't already have the non-pro version.  Maybe for my daughter's b-day if she sticks with it.  Have you been able to use it yet?

 

So the C to 1.25 adapter that came with the SV305 is not an issue. Perhaps I'm missing something, but if you just use, say, 2 inch extensions and screw on a 2 inch to 1.25 mount and stick the reducer in that, wouldn't you have what you need? Or do you need the extension ahead of the reducer between it and the SV305?

Everything I have and have measured (with digital caliper) gives me more than the 55mm required for backfocus.  But I'm also looking to be able to go beyond 55mm based on this post - https://www.cloudyni...305/?p=11405279 where the member said they had to go to 70mm out.  I could just get a 25mm 1.25" extension (reducer would be 55mm from the sensor) but was looking for more spacers in smaller increments, as well.  What I really need to do is stop getting lost in the sauce and just get the 25mm 1.25" extension and see if it works or not.  But the idea I was thinking earlier:

 

C mount to M42 on the SV305:

https://www.amazon.c...e/dp/B0812QPHWN

 

Then the M42 extension tubes.

 

And the reducer would sit in this:

https://optcorp.com/...-filter-adapter

 

Then the 1.25" focuser adapter.
 



#8 vidrazor

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Posted 06 December 2021 - 10:10 AM

Yes, exactly, to all of the above.  I'd be getting the pro if I didn't already have the non-pro version.  Maybe for my daughter's b-day if she sticks with it.  Have you been able to use it yet?

 

Everything I have and have measured (with digital caliper) gives me more than the 55mm required for backfocus.  But I'm also looking to be able to go beyond 55mm based on this post - https://www.cloudyni...305/?p=11405279 where the member said they had to go to 70mm out.  I could just get a 25mm 1.25" extension (reducer would be 55mm from the sensor) but was looking for more spacers in smaller increments, as well.  What I really need to do is stop getting lost in the sauce and just get the 25mm 1.25" extension and see if it works or not.  But the idea I was thinking earlier:

 

C mount to M42 on the SV305:

https://www.amazon.c...e/dp/B0812QPHWN

 

Then the M42 extension tubes.

 

And the reducer would sit in this:

https://optcorp.com/...-filter-adapter

 

Then the 1.25" focuser adapter.
 

No I just got it 2 days ago and clouds came in as soon as I got it LOL. I'm completely new to the planetary thing and I'm trying to understand ASTRODMX, which is the only program I've found that works with the SV305, but has essentially zero documentation, so I'm trying to figure out what kind of settings I need for planetary, as well as lunar. DSO seems pretty straightforward because I can just control the camera with Ekos.

 

So is the distance you need is not between the reducer and the sensor? Did you get the small C to 1.25 adapter ring, along with the 1.25 extension ring with the SV305, like the ones shown below? Can't you just screw the reducer to the C to 1.25 ring and mount that to a 1.25 eyepiece mount and go out from that with 42mm or 48mm rings?

Attached Thumbnails

  • rings.jpg

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#9 Borodog

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Posted 06 December 2021 - 10:46 AM

First, wrong forum, but I'm sure this will get moved shortly, so no harm done.

 

Second, back to basics. What reducer are you using? With what scope? What exactly are you trying to accomplish?


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#10 garblivet

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Posted 06 December 2021 - 08:13 PM

No I just got it 2 days ago and clouds came in as soon as I got it LOL. I'm completely new to the planetary thing and I'm trying to understand ASTRODMX, which is the only program I've found that works with the SV305, but has essentially zero documentation, so I'm trying to figure out what kind of settings I need for planetary, as well as lunar. DSO seems pretty straightforward because I can just control the camera with Ekos.

 

So is the distance you need is not between the reducer and the sensor? Did you get the small C to 1.25 adapter ring, along with the 1.25 extension ring with the SV305, like the ones shown below? Can't you just screw the reducer to the C to 1.25 ring and mount that to a 1.25 eyepiece mount and go out from that with 42mm or 48mm rings?

Of course the clouds came.  haha.  I'll have to look at ASTRODMX.  Have you tried it with Sharpcap?  I was going to try using StellarMate for my daughter's setup.  Hopefully that'll work. 

 

I'm looking to get the distance between the sensor and reducer.  I did get the C mount to 1.25 adapter ring and the 20mm extension with the camera, but it's not enough to get the 55mm backfocus for the reducer.  I don't think I made that very clear earlier.  Sometimes I get run over by the struggle-bus when trying to put my thoughts into coherent sentences.  Thanks for hanging in there.  haha.  I did go ahead and get a 25mm 1.25" extension tube on order. 
 



#11 garblivet

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Posted 06 December 2021 - 08:21 PM

First, wrong forum, but I'm sure this will get moved shortly, so no harm done.

 

Second, back to basics. What reducer are you using? With what scope? What exactly are you trying to accomplish?

Ah.  Thanks.  Mods, please place in the appropriate forum when you get a chance. 

 

I'll be using a Svbony 0.5x focal reducer, though I'm open to suggestions on a better cheap 1.25" reducer.  The scope is an Orion Spaceprobe 130ST.  Reaching prime focus was no issue with my ASI533 on it, so I'm hoping it will be fine with the SV305.  If not, I'll use a Meade ETX-80.  All I'm trying to do at this point is get the right backfocus for the reducer on the SV305.  Svbony says you need 55mm... but I'd like the ability to make adjustments in distance between the sensor and reducer.  (Man... I should have started this thread with that... words are hard)



#12 vidrazor

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Posted 06 December 2021 - 10:39 PM

Of course the clouds came.  haha.  I'll have to look at ASTRODMX.  Have you tried it with Sharpcap?  I was going to try using StellarMate for my daughter's setup.  Hopefully that'll work. 

I'm looking to get the distance between the sensor and reducer.  I did get the C mount to 1.25 adapter ring and the 20mm extension with the camera, but it's not enough to get the 55mm backfocus for the reducer.  I don't think I made that very clear earlier.  Sometimes I get run over by the struggle-bus when trying to put my thoughts into coherent sentences.  Thanks for hanging in there.  haha.  I did go ahead and get a 25mm 1.25" extension tube on order.

I'm working with an Astroberry setup on a Raspberry Pi4, so AstroDMX is the only game in town. I'm not a fan of subscription software either.

 

OK then, would an eyepiece projection adapter work? I just got one one for lunar and planetary, and this one's 42mm threaded, you can stick the reducer inside the narrower 1/25" shaft and adjust it's position. If need be it may need an extension, if you have an old eyepiece around you can take apart you can screw it to the reducer so you'd have a little more positioning leeway to get the proper back focus distance. You can use a 1.25 to 42mm adapter to screw it onto the SV305 and screw the other end to the scope, or vice-vesa as needed, which may negate needing an extension on the reducer. This way you can have any back focus distance you want by moving it in the shaft and tightening the retaining screw to keep it in place. The 1.25" narrow shaft is 1" long, and as you can see the retainer screw is at the top end.
 

Attached Thumbnails

  • eyepiece adapter.jpg

Edited by vidrazor, 06 December 2021 - 10:57 PM.

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#13 garblivet

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Posted 06 December 2021 - 11:29 PM

Nice.  I think it would depend on the length of the 2" barrel, but I'll definitely look into it.  There may be some out there with the dimensions I'm looking for.  Thank you!

 

Edit to add:  I wonder if this would work... screw in the 2" to 1.25" tube with the reducer at the end and adjust spacing with the SV305's 1.25" extension moving in/out...  I may just buy it anyway for my OCAL collimator.

 

https://www.amazon.c...38850548&sr=8-1


Edited by garblivet, 06 December 2021 - 11:37 PM.


#14 Tapio

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Posted 06 December 2021 - 11:53 PM

I guess the nominal 0.5x reduction is then achieved with 55mm distance.

Here is an older thread which might be useful
https://www.cloudyni...er-comparisons/
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#15 garblivet

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Posted 07 December 2021 - 12:27 AM

I guess the nominal 0.5x reduction is then achieved with 55mm distance.

Here is an older thread which might be useful
https://www.cloudyni...er-comparisons/

Good thread.  I missed that during my searches.  Thanks!  I'm hoping the 55mm is all I'll need and won't have to vary anything.  But since I'm trying to be cheap for the time being on this setup, who knows.



#16 vidrazor

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Posted 07 December 2021 - 10:37 PM

Nice.  I think it would depend on the length of the 2" barrel, but I'll definitely look into it.  There may be some out there with the dimensions I'm looking for.  Thank you!

Edit to add:  I wonder if this would work... screw in the 2" to 1.25" tube with the reducer at the end and adjust spacing with the SV305's 1.25" extension moving in/out...  I may just buy it anyway for my OCAL collimator.

https://www.amazon.c...38850548&sr=8-1

You may want to peruse these accessories pages and see if something in there may be useful for you.
 


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#17 garblivet

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Posted 08 December 2021 - 02:37 PM

I'll check it out.  Thank you!



#18 garblivet

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Posted 23 December 2021 - 11:41 PM

Just an update, if anyone stumbles across this during a search for the same subject....  I found a 20mm c-mount extension on ebay.  Both ends are c-mount, but the SV305 comes with a 5mm c-mount to 1.25" adapter and a 20mm 1.25" extension tube. (camera - 20mm c-mount - 5 c to 1.25" - 20mm 1.25" - reducer)   According to Svbony on an amazon Q&A response, the 20mm is all that is needed to reach 55mm.  Another member of the forum disassembled his SV305 and measured 7mm to the sensor from the shoulder of the camera housing.  If that is the case, then the thread section on the camera (5mm) makes the starting point 12mm and an 18mm extension is what is truly needed.  A 15mm c-mount extension and some 1mm spacers may be next on the shopping list.  When I finally get a chance to try the 20mm c-mount tube out, I'll post an update. 


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