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C6 Eyepieces/Barlow/Diagonal - My Recommendation...

Astro Tech Celestron Eyepieces SCT Visual
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#26 Dave Bush

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Posted 05 October 2023 - 12:00 PM

Thank you.

You're welcome.  One thing though, in the photo I shared, that diagonal is the prism one but the Maxbright mirror that I am using looks the same (with out the Baader button emblem).


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#27 wachuko

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Posted 05 October 2023 - 12:10 PM

You're welcome.  One thing though, in the photo I shared, that diagonal is the prism one but the Maxbright mirror that I am using looks the same (with out the Baader button emblem).

Cool, that photo works.  Just wanted to see how it went together.

 

On the diagonal, you are correct... Baader diagonal is backordered everywhere.  Only looks available directly from Baader.

 

So looks like I have to wait anyway... 

 

But I did place the order for the 18 mm eyepiece.  Went with Celestron since B&H had it for US$129.

 

Thanks again.


Edited by wachuko, 05 October 2023 - 12:22 PM.


#28 Doug Culbertson

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Posted 05 October 2023 - 12:27 PM

Unfortunately Baader will not ship directly to the United States. Teleskop Service in Germany shows the T2 Maxbright in stock. Shipping is a bit pricey but it’s available. Even with $30 shipping it’s only around $220 at the current exchange rate. https://www.teleskop...T2-threads.html

Astro-Physics also shows it in stock, but it’s $275. https://www.astro-physics.com/bp1a

#29 wachuko

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Posted 03 November 2023 - 09:33 AM

Everything arrived!  The difference in size for the diagonal, is significant.  Wow.

 

Baader vs Stock-1.jpeg

 

Baader vs Stock-2.jpeg

 

Can't wait to try it out tonight. 



#30 Dave Bush

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Posted 03 November 2023 - 12:36 PM

Everything arrived!  The difference in size for the diagonal, is significant.  Wow.

 

attachicon.gif Baader vs Stock-1.jpeg

 

attachicon.gif Baader vs Stock-2.jpeg

 

Can't wait to try it out tonight. 

Yes, the housing is larger than the typical 1.25" diagonal.  Baader has well constructed stuff.  Looking forward to hearing how it works for you.

 

I spend easily 80% of my time with just the 18mm in my scope.  Not a thing to complain about.


Edited by Dave Bush, 03 November 2023 - 12:37 PM.

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#31 wachuko

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Posted 03 November 2023 - 12:49 PM

We saw Saturn last night!  First time for me.  This was with the stock diagonal as I had not installed the new Baader diagonal.  So I can't wait to test this setup!

 

Must confess, all done manually... I have not taken the time to learn how to track with my GOTO mount.  Need to take the time to practice that because doing it manually, if I want to look really close, everything moves out of sight very quickly.  You all know that, but it is all new to me, hehehehehe...

 

Thank you again for the recommendations!


Edited by wachuko, 03 November 2023 - 12:50 PM.

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#32 RCLARK28

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Posted 03 November 2023 - 02:11 PM

We saw Saturn last night!  First time for me.  This was with the stock diagonal as I had not installed the new Baader diagonal.  So I can't wait to test this setup!

 

Must confess, all done manually... I have not taken the time to learn how to track with my GOTO mount.  Need to take the time to practice that because doing it manually, if I want to look really close, everything moves out of sight very quickly.  You all know that, but it is all new to me, hehehehehe...

 

Thank you again for the recommendations!

Outstanding!

Nothing wrong with using the stock diagonal until you have time. Learn your hardware and enjoy it. Get as many practice sessions as you can. Enjoy your new adventure!! Proceed at your own pace and ask questions here.

Clear skies.


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#33 25585

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Posted 03 November 2023 - 02:26 PM

1500mm is a good FL. How neccessary is an Evolution mount for a C6 OTA? I like Evolutions, but not non-replaceable batteries, so a SE might be better?



#34 Dave Bush

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Posted 03 November 2023 - 03:03 PM

1500mm is a good FL. How neccessary is an Evolution mount for a C6 OTA? I like Evolutions, but not non-replaceable batteries, so a SE might be better?

For me, the Evolution mount offers a couple things that I greatly appreciate.  First, stability.  Yeah, the C6 OTA would likely be OK on the SE mount but it's rock solid on the Evolution.  I can make fine focus adjustments with the stock focuser at higher powers with almost no vibrations.  Second, the clutches.  I've had an SE mount and being able to loosen up each axis and move the scope/mount manually is a great advantage.   Third, accuracy.  I'm getting more accurate GOTOs with the Evolution.  This is my second one and the difference is noticeable.

 

Regarding the battery issue yes, they are not easily replaceable but there are options (there have been some threads here on CN about it).  Of course, I've not read about anyone having them fail yet.  And, the SE mount, while it does have replaceable batteries, they're AA cells and the mount burns through them fairly quickly.  My set up, which is likely overkill, is that I power the whole setup with a Celestron Lithium PowerTank.  It keeps the internal battery topped off and then powers the mount.  


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#35 Dave Bush

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Posted 03 November 2023 - 03:05 PM

1500mm is a good FL. How neccessary is an Evolution mount for a C6 OTA? I like Evolutions, but not non-replaceable batteries, so a SE might be better?

Oh, and with the r/c and the Baader diagonal configuration as I've described above, the focal length is actually around 1040mm (1650mm without the r/c)


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#36 25585

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Posted 05 November 2023 - 04:29 PM

I have an Antares 0.63x reducer from a C8, but would be more tempted with a 2" visual back. Heavier eyepieces etc would need an Evolution mount I expect.



#37 Dave Bush

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Posted 05 November 2023 - 06:33 PM

I have an Antares 0.63x reducer from a C8, but would be more tempted with a 2" visual back. Heavier eyepieces etc would need an Evolution mount I expect.

The only problem with a two inch diagonal and two inch eyepieces on the C6 is that you immediately begin to lose aperture.


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#38 davidgmd

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Posted 05 November 2023 - 09:45 PM

The only problem with a two inch diagonal and two inch eyepieces on the C6 is that you immediately begin to lose aperture.

  
Do you mean vignetting? Isn’t that when the eyepiece “sees” a wider FOV than the back of the OTA can provide? Is that  the same as losing aperture when the exit pupil is larger than the eye’s entrance pupil?


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#39 Dave Bush

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Posted 05 November 2023 - 11:17 PM

  
Do you mean vignetting? Isn’t that when the eyepiece “sees” a wider FOV than the back of the OTA can provide? Is that  the same as losing aperture when the exit pupil is larger than the eye’s entrance pupil?

No, I'm referring to actual aperture reduction due to excessive back focus (beyond 200mm)  but, if you use an SCT style, screw-on two-inch diagonal, you may be OK


Edited by Dave Bush, 05 November 2023 - 11:18 PM.

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#40 areyoukiddingme

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Posted 06 November 2023 - 01:35 PM

Sounds like vignetting to me. The aperture of the baffle tube is the limit, and once you start increasing the field stop of the eyepiece beyond that, light drops off gradually, but eventually you'll see it.


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#41 25585

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Posted 06 November 2023 - 01:45 PM

Sticking to 1.25" is restrictive, but with a GOTO I guess its not so important. My widest is a 24 UFF, but other longer FL with less AFOV, are good too. I would piggyback a ST80 on a C6 Evolution as finder, or maybe use a Starsense.


Edited by 25585, 06 November 2023 - 01:46 PM.


#42 Dave Bush

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Posted 06 November 2023 - 01:54 PM

Sounds like vignetting to me. The aperture of the baffle tube is the limit, and once you start increasing the field stop of the eyepiece beyond that, light drops off gradually, but eventually you'll see it.

Indeed.  In addition to potentially losing aperture, you will get vignetting if the eyepiece's field stop exceeds the baffle diameter which, for the C6 is about 27mm


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#43 davidgmd

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Posted 06 November 2023 - 01:57 PM

Sounds like vignetting to me. The aperture of the baffle tube is the limit, and once you start increasing the field stop of the eyepiece beyond that, light drops off gradually, but eventually you'll see it.

  
Sorry for the basic questions. I’m not a whiz at optics…

 

Would that restriction reduce resolution the way a smaller aperture would? Or would it only cause vignetting (dimming in the outer field)?


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#44 Dave Bush

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Posted 06 November 2023 - 01:57 PM

Sticking to 1.25" is restrictive, but with a GOTO I guess its not so important. My widest is a 24 UFF, but other longer FL with less AFOV, are good too. I would piggyback a ST80 on a C6 Evolution as finder, or maybe use a Starsense.

Using my configuration I'm getting about 1.5º with the 24mm which, for me, is wide enough.  But yeah piggybacking an ST80 is a way to go wider.


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#45 areyoukiddingme

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Posted 06 November 2023 - 02:02 PM

  
Sorry for the basic questions. I’m not a whiz at optics…

 

Would that restriction reduce resolution the way a smaller aperture would? Or would it only cause vignetting (dimming in the outer field)?

I have the very same question. . . 

 

My 2 cents is that if the eyepiece field stop is exceeding the size of the baffle tube, then you are ultimately both experiencing vignetting and effectively a loss of aperture.

 

Presumably, the eyepiece is gathering light across the field stop, and then focusing it at the exit pupil. If the edges are cut off, then you are losing light, hence the loss of aperture interpretation.

 

But the two seem to be separable in other instances. e.g., using an eyepiece that exceeds the size of your dilated pupil is effectively losing light and stopping down the aperture of your scope, but you won't subjectively see dimming (i.e. vignetting) at the edge of the field of view.

 

Seems to me that the SCT case is probably best interpreted as vignetting for that reason, but I am open to further information. . . 


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#46 davidgmd

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Posted 06 November 2023 - 02:17 PM

I have no idea if this is correct… My naive assumption was that if the eyepiece field stop gathers all the light that the baffle tube can deliver, you won’t have an aperture reduction effect. You’re getting all of the light the scope can deliver, but it won’t fully illuminate the periphery of the eyepiece. Yes? No? Nonsense?

  
The last few posts had me wondering further. I take Dave’s post to mean that the extended back focus means that some of the light coming from the baffle spreads out enough by the time it reaches the eyepiece that some of it is blocked by the field stop?


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#47 Dave Bush

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Posted 06 November 2023 - 02:56 PM

I have no idea if this is correct… My naive assumption was that if the eyepiece field stop gathers all the light that the baffle tube can deliver, you won’t have an aperture reduction effect. You’re getting all of the light the scope can deliver, but it won’t fully illuminate the periphery of the eyepiece. Yes? No? Nonsense?

  
The last few posts had me wondering further. I take Dave’s post to mean that the extended back focus means that some of the light coming from the baffle spreads out enough by the time it reaches the eyepiece that some of it is blocked by the field stop?

There is a difference in vignetting and aperture loss.  Read EdZ's initial post in this message.  He explains things pretty well and has examples from measurements he's made...

https://www.cloudyni...s/#entry4663549


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#48 areyoukiddingme

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Posted 06 November 2023 - 03:04 PM

Seems that EdZ's write up concerns back focus and what ends up with moving the primary to reach focus--and that's ultimately causing aperture reduction. 

 

But that still seems different from having an eyepiece located at the focal plane operating at full aperture, but the field stop exceeds the size of the baffle tube.

 

I don't know if my guess is right or David's regarding full illumination, however. 

 

While it might be true that all of the light that can reach the eyepiece is there, if that is still getting vignetted by the aperture of the eyepiece, then I suspect we are losing light.



#49 25585

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Posted 06 November 2023 - 03:13 PM

Seems that EdZ's write up concerns back focus and what ends up with moving the primary to reach focus--and that's ultimately causing aperture reduction. 

 

But that still seems different from having an eyepiece located at the focal plane operating at full aperture, but the field stop exceeds the size of the baffle tube.

 

I don't know if my guess is right or David's regarding full illumination, however. 

 

While it might be true that all of the light that can reach the eyepiece is there, if that is still getting vignetted by the aperture of the eyepiece, then I suspect we are losing light.

I thought vignetting would only reduce FoV, not light/aperture.



#50 davidgmd

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Posted 06 November 2023 - 03:22 PM

Thanks Dave for the link. That’s a great post that explains it well.


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