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Celestron OAG to ZZWO ASI6200MM with EFW - plumbing help please

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#1 Linwood

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Posted 22 October 2020 - 11:25 AM

I'm getting close to pulling the trigger on an ASI6200MM Mono, and struggling to understand how the plumbing might work.

 

From OTA Side of a C11 Edge HD: 

 

- Custom adapter (I already have) from 3.28" OTA to OAG

- Celestron OAG

- M48 Male OAG adapter (came with OAG) 
- M54-M48F Adapter (comes with EFW) 

- 5mm Sensor tilt adaptor with camera; I think it has M54 threads?

- EFW Filter wheel (can the tilt attach directly on the scope side?)

- Camera with 5mm tilt off moved to front

 

Forget backfocus for a moment, is this how all the plumbing would actually fit together?  Most ZWO documentation that includes the EFW also include their OAG, but I'd rather keep the 50% wider prism in the COAG. 

 

To fix backfocus for now would just get some different length M48 extensions. 

 

I also assume the M48 OAG adapter is going to vignette, so eventually I could replace it with a custom piece directly to the tilt adapter?  

 

But will the above actually connect together properly? 

 



#2 bobzeq25

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Posted 22 October 2020 - 11:53 AM

I'm getting close to pulling the trigger on an ASI6200MM Mono, and struggling to understand how the plumbing might work.

 

From OTA Side of a C11 Edge HD: 

 

- Custom adapter (I already have) from 3.28" OTA to OAG

- Celestron OAG

- M48 Male OAG adapter (came with OAG) 
- M54-M48F Adapter (comes with EFW) 

- 5mm Sensor tilt adaptor with camera; I think it has M54 threads?

- EFW Filter wheel (can the tilt attach directly on the scope side?)

- Camera with 5mm tilt off moved to front

 

Forget backfocus for a moment, is this how all the plumbing would actually fit together?  Most ZWO documentation that includes the EFW also include their OAG, but I'd rather keep the 50% wider prism in the COAG. 

 

To fix backfocus for now would just get some different length M48 extensions. 

 

I also assume the M48 OAG adapter is going to vignette, so eventually I could replace it with a custom piece directly to the tilt adapter?  

 

But will the above actually connect together properly? 

It's just a question of matching the threads.  You may or may not need additional thread adapters, it's a _lot_ easier to work this out with he pieces in your hands.  But it won't be impossible to match the threads.

 

The big problem with the Celestron OAG (which I own) is spacing a flattener or flattener/reducer.  Many have short spacing requirements.  I got a flattener that has a spacing spec over 100mm, unusual.  I needed just about every mm to make the Celestron OAG work.

 

To take advantage of that prism you need a guide camera with a fairly large chip.  I use a 174.


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#3 Linwood

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Posted 22 October 2020 - 12:03 PM

It's just a question of matching the threads.  You may or may not need additional thread adapters, it's a _lot_ easier to work this out with he pieces in your hands.  But it won't be impossible to match the threads.

 

The big problem with the Celestron OAG (which I own) is spacing a flattener or flattener/reducer.  Many have short spacing requirements.  I got a flattener that has a spacing spec over 100mm, unusual.  I needed just about every mm to make the Celestron OAG work.

 

To take advantage of that prism you need a guide camera with a fairly large chip.  I use a 174.

I have the ASI174 and use it now, and it works nicely, which is one reason I am hesitant to shift to the 8mm prism on the ASI OAG. 

 

The EdgeHD Reducer on the C11 keeps the same backfocus with or without, which is very handy, since I only need one set of plumbing.

 

The reason I am asking the questions is it is less than obvious what threading (and if it is adequate to hold the weight) is on the EFW and the Tilt Adapter, since they go elsewhere in the examples from ASI.



#4 bobzeq25

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Posted 22 October 2020 - 12:10 PM

I have the ASI174 and use it now, and it works nicely, which is one reason I am hesitant to shift to the 8mm prism on the ASI OAG. 

 

The EdgeHD Reducer on the C11 keeps the same backfocus with or without, which is very handy, since I only need one set of plumbing.

 

The reason I am asking the questions is it is less than obvious what threading (and if it is adequate to hold the weight) is on the EFW and the Tilt Adapter, since they go elsewhere in the examples from ASI.

ZWO often has really detailed mechanical drawings of this and that, buried near the end of the documentation, often available online.



#5 MikiSJ

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Posted 22 October 2020 - 12:16 PM

I have the Celestron C11 EdgeHD and using the parts included with the Celestron OAG was able to mount an ASI294MC-Pro with no backfocus issue. The one advantage not talked about too much is that there is an addition OAG connection that allowed me to mount up the Celestron diagonal with the OAG making changing from the ASI to an eyepiece a non-issue. (Need to refocus, but...)


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#6 Linwood

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Posted 22 October 2020 - 05:56 PM

Kudos to Daniel at Woodland Hills.  I gave up waiting for Agena, saw WH had not only it but the 7x filter holder, and he pulled it all out of the boxes to make sure the plumbing worked the way we thought, spent a lot of time with me doing it, and is even as I write this boxing it up to go out UPS.  I should be within 0.6mm of the right backfocus also. 

 

I am confident now that will solve all my problems, my guiding will be under 0.2", my post processing skills will take a quantum leap and I'll actually understand what local normalization does (not yet I don't, but as soon as the box arrives I am confident), plus all the clouds will clear out and the stars and nebula will be much brighter.  waytogo.gif

 

(Please do not correct my presumptions at least for 24hours, allow me blissful optimism!). 


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#7 Lead_Weight

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Posted 23 October 2020 - 01:55 PM

Best of luck with the COAG, I’d like to hear how it goes. I have the same setup, but the ZWO OAG and 174 and 6200MM, and have not had an issue finding a guide star. YMMV.



#8 Linwood

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Posted 23 October 2020 - 01:58 PM

Will do. 

 

Slight change -- Woodland Hills changed my order to 2" Mounted filters instead of 50mm unmounted due to availability.

 

Am I going to have vignetting issues because of that? 



#9 nfotis

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Posted 25 October 2020 - 04:52 PM

I don't expect vignetting problems with the C11, it's not like a fast refractor.

N.F.

#10 Linwood

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Posted 29 October 2020 - 06:15 PM

I just want to put some closure to this.  I got the ASI6200, EFW, and have it in use with the Celestron OAG.  I did a brief trial run last night.  I did not get my filters yet (UPS Next day didn't make it). 

 

So here's the first light, it is just 14 x 60s subs with no filter.  I was having a lot of guiding issues at first (mostly wind, some tuneup issues), so I had taken a bit more than twice that much but had to throw them away.  I'd actually throw all of them away if they weren't really the first light with it.

 

M15.jpg

 

That's a quick integration and background extraction and preview stretch, no real processing, no noise reduction.

 

I thought the night was cloudy, but looked outside about 10pm and say clear skies, and grabbed stuff and put it together ... wrong.  I had it at 156mm instead of 146.5, about 10mm long.  I was pleasantly surprised that despite that I did not see a lot of distortion at the edges.  I was also pleasantly surprised that focus looked uniform and I didn't have to fiddle, at least yet, with the tilt adapter. 

 

What I am less happy with is the vignetting.  I am not sure if it's the C11 + FR (contributed by the wrong backfocus?) or if the current 48mm link from the OAG to the EFW.  I'm kind of thinking at least some is that piece, I need a different sort of connection there.

 

What did I learn: 

 

You cannot connect the tilt adapter that comes with the camera to the front of the EFW.  It looks like it should, but no holes align, and both are thin female threads (in theory I could use the M54 male spacer as a connector but that would be too insecure). 

 

So what I have is: 

 

Camera (Tilt removed for spacing reasons) -> screwed to EFW -> M54-M to M48F adapter to Celestron M48M OAG Adapter.

 

What I think I want is a M54 -> Gerd CTU -> M54 -> OAG with two precise parts custom made.  This will go from 48mm to 54 mm (outside) path and may reduce the vignetting.

 

Now that I've had some time with it, I'm thinking if I get a small refractor (which I'm trying hard to find) I will actually use the Celestron OAG anyway -- keep the light path the same from it to the camera, and just get a part made for the front.  That way I'm using the same basic stuff (and same guide focus distance).  The COAG really works nice. Last night on another shot I had only about 3 usable guide stars in frame -- the ZWO OAG has 1/4 the real estate, so I might have had zero with it.

 



#11 anismo

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Posted 29 October 2020 - 06:20 PM

Nice result. M48 would be causing that vignette. I thought ZWO has M68 connection as an option all the way. If not M54 would be fine (I use M54 at the OAG end in mine)  



#12 Linwood

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Posted 29 October 2020 - 06:55 PM

Nice result. M48 would be causing that vignette. I thought ZWO has M68 connection as an option all the way. If not M54 would be fine (I use M54 at the OAG end in mine)  

No, the hole on the EFW on both sides is M54 (-F toward the scope). 

 

Oh, I forgot, the mounted 2" filters vignette also even more.  I posted some photos of them vs an open hole (I didn't have the unmounted ones at the time) here: 

 

https://www.cloudyni...2#entry10611755

 

So I would definitely suggest not buying mounted filters.



#13 Linwood

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Posted 30 October 2020 - 01:27 PM

As an aside to this - I was considering a refractor, like the NP101is.  That allows 68mm from the end of the field flattener.  I've been fiddling around with all sorts of possibilities, and if I can get two zero-effective-length attachments from precise parts I could connect using the COAG, but without any tilt adapter at all. 

 

So the COAG is not looking good in terms of being useful for both the C11 and a refractor, too deep. 



#14 SilverLitz

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Posted 30 October 2020 - 05:43 PM

I would expect you would have a vignetting issue with an EdgeHD 11 even without M48 adapters.  Edges seem to be optimized for up to APS-C.  Even without the vignet, the stars will get weird beyond APS-C per the whitepaper.  Though Celestron talks about a 42mm image circle, their whitepaper says it is only diffraction limited out to ~28mm (2/3 of the 42mm), and the spot diagrams don't look good at 15mm & 20mm radius.  The best of the Edge lot seems to be the 925, but it will still be suspect at full-frame edges.  The 925 is diffraction limited out to ~38mm, and its spot diagrams look significantly better.

 

Are you using the Celestron Lg SCT Adapter V2 or only the parts that came with the Edge and COAG?  The normal connection between the Edge and the COAG, Adapter Plate, restricts the light cone to 38mm, at 146mm from the sensor.  This would give vignetting problems even for Micro 4/3.

 

See the spreadsheet I created regarding Edge Lightcones:

https://www.cloudyni...el-spreadsheet/


Edited by SilverLitz, 30 October 2020 - 05:50 PM.


#15 Linwood

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Posted 30 October 2020 - 07:08 PM

I would expect you would have a vignetting issue with an EdgeHD 11 even without M48 adapters.  Edges seem to be optimized for up to APS-C.  Even without the vignet, the stars will get weird beyond APS-C per the whitepaper.  Though Celestron talks about a 42mm image circle, their whitepaper says it is only diffraction limited out to ~28mm (2/3 of the 42mm), and the spot diagrams don't look good at 15mm & 20mm radius.  The best of the Edge lot seems to be the 925, but it will still be suspect at full-frame edges.  The 925 is diffraction limited out to ~38mm, and its spot diagrams look significantly better.

 

Are you using the Celestron Lg SCT Adapter V2 or only the parts that came with the Edge and COAG?  The normal connection between the Edge and the COAG, Adapter Plate, restricts the light cone to 38mm, at 146mm from the sensor.  This would give vignetting problems even for Micro 4/3.

 

See the spreadsheet I created regarding Edge Lightcones:

https://www.cloudyni...el-spreadsheet/

So short answer is so far I haven't noticed, but I perhaps have enough other problems that I haven't noticed.  smile.gif

 

The other night with my first try I had a lot of vignetting with the M48 threads, but I think that will get better when I fix it.  I also screwed up and was at 156 instead of 146 (too big of a hurry when I looked outside and it was clear and quickly put everything together).   These are the far corners and edges of a single frame.  I can see distortion on the edges, but it's not awful and that's at 10mm too long.  So ... I don't know. 

 

corners.jpg

 

I'm in the middle of getting set up now to try again, I got my LRGB + NB filters, so going to see if I can get anything at all, but will look at the edges.  Though I have to go outside and brave the mosquitos to focus the OAG since I moved it.  If you don't hear anything for a few days send out a search party.



#16 anismo

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Posted 30 October 2020 - 10:08 PM

My friend uses Edge11 with QHY600 (same chip) and mounted Chroma 50mm filters with M54 adapters and his result seems fine . The scope is slightly out of collimation (it is remote so will take time for him to adjust) but the result looks fine IMO

 

https://www.astrobin...t70j/0/?nc=user


Edited by anismo, 30 October 2020 - 10:09 PM.


#17 Linwood

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Posted 02 November 2020 - 09:16 AM

The weather is still fighting me, but I actually got 3 subs each filter on my first narrow band attempt with the COAG and EFW7x2.  I did a quick channel combination of the result with no processing (so lots of noise and background) just to see what the corners looked like.  I also this time did a proper set of flats for each filter and my corners brightened right up.  It's vignetting because I still have that 48mm section in there (pending getting a M54 section from Precise Parts), but it's not cutting off entirely.

 

The stars on the sides are pretty round (so at 18mm from center); on the corners not so much.  This is with the focal reducer, which I assume makes it a bit worse.  And I'm still 1.5mm long as I do not quite have the right pieces to hit 146mm. 

 

I THINK however, that the stars in the corners are fairly symmetric, which I THINK means the sensor is not tilted.  Certainly the left/right edge does not show much if any tilt (I see maybe a tiny amount more oval on the left side). Which would be good, as I'm thinking of ignoring the whole tilt adapter thing at least as a first pass. 

 

nb.jpg

 

Now I'm trying to figure out if I can use the COAG on a NP101is (which I plan to order this morning), which has much less room.  I'd love to have only one OAG and it with a large prism.

 

I suspect @SilverLitz, that the 9.5 does better in the corners as you point out, but my skills at capture and post processing are such that screwups there will hide the flaws in the corner stars from the C11 for a while.  wink.gif

 

I'm obviously banking on Florida winters to have less clouds than the late summer (haven't seen much "fall" so far).   I was really hoping to get more practice in last night.



#18 dhaval

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Posted 02 November 2020 - 01:46 PM

I have a C11 EdgeHD + QHY600M and Chroma 2in mounted filters (Anis was referring to me in one of his posts). I don't use a reducer, so I am imaging at 2800mm FL and native F10.

 

Here's my quick take on the set up - I do see some vignetting with the mounted filters - BUT, I am OK with it. I am going to crop it out anyways. I am primarily going to be imaging galaxies, PN, etc. and I will have enough FOV to not worry about the edges.

 

I am using a QHY OAG - much smaller than the Celestron OAG, I am using ASI174MM though. Guiding hasn't been a problem so far - I have been finding a guide star, almost always. That being said, I am under Bortle 1-2 skies. 

 

I don't seem to have tilt issues, however, I have noticed some issues with stars on the edges. I can't put a finger on whether that is due to spacing or just the fact that my scope is very slightly out of collimation - that will obviously have to wait till I can make a trip out to the observatory, which might be later this month. If I had to bet though, I would say it is spacing. Again, the cropping will help, so not worried about it as much (the star cluster that Anis provided the link to, clearly demonstrates that I can crop heavily if I have to and it won't show any aberrations at the edges). 

 

CS!



#19 Linwood

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Posted 02 November 2020 - 02:32 PM

Here's my quick take on the set up - I do see some vignetting with the mounted filters - BUT, I am OK with it. I am going to crop it out anyways. I am primarily going to be imaging galaxies, PN, etc. and I will have enough FOV to not worry about the edges.

I get that.  I'm just a bit paranoid in that I know later when I do want to crop, I'll want something in an area where the edge is messed up, so I want all the data pixels I can to try to outsmart Murphy. 

 

Guiding hasn't been a problem so far - I have been finding a guide star, almost always. That being said, I am under Bortle 1-2 skies. 

That's just plain cruel.  bawling.gif



#20 andysea

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Posted 02 November 2020 - 04:00 PM

Just saw this thread. I use the Celestron OAG with my RC and the ASI 6200+FW combo. I made an adapter that provides my correct back focus. I am sure that Precise parts can make this adapter, it has the dovetail connection for the OAG and the M54 thread on the FW side.

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