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C11 with Starizona corrector (corrector already purchased) vs EdgeHD 11 with reducer?

Celestron EdgeHD 11" Equipment Buying Advice Planetary Nebula
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Rob Calfee avatar
Rob Calfee avatar
Hi, 

I’d like to go after smaller planetary nebulae in the future. I have a C9.25 with the Starizona IV corrector already. I’m thinking of a C11 because I already own the corrector, the targets are tinier, they will be in the center, and the cost is $2000 cheaper than the edgeHD 11. I’m using a CQ350. I’ve been researching some shots here on Astrobin and I’m on the fence. I mean, there are many more great shots with the EdgeHD version (more EdgeHD11s out there used for astro) but the ones I can find with the C11 and Starizona corrector look fine, too. Just wondering if the $2k is worth it. I know edge correction will probably be better and there are vents, but, still, seems like there is a law of diminishing returns here. 

Thoughts? 

CS,
Rob
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churmey avatar
churmey avatar
That corrector is very nice and does a great job with SCT’s. I’d be inclined, if it were me, to get a C11 and use the corrector vs the edge.  However, your preferred FOV of targets would have to come into play because the FOV difference between the C11/.63 corrector verses the Edge 11 @ F10 is pretty significant.
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Rob Calfee avatar
Rob Calfee avatar
The FOV isn’t that much different between the two when both use reducers. BUT…I would like a FL closer to 2000 than 1700. So there is a plus for the EdgeHD right there. 
Lynn K avatar
Lynn K avatar
I also use a non-Edge C9.25 with the Starizona F6.3 IV reducer/flattener. I also have a non-Edge C11. I have only used the older Starizona vIII on the C11.  I have compared the C11 to the C9.25 with the vIII, and didn't see significant difference, other that obvious magnification. 

I have a Edge 8, but only use it for visual. The wide field views or great with a Televue Delos eyepiece.

I do not use the Edge  8 for astrophotography,  because I see no advantage over the C9.25 withe Starizona VI.

BUT, the main disadvantage of the Edge is the limited Back Focus due the Celestron reducer being directly connected to the rear of the scope. You are mostly limited to using the primary mirror moving focuser.  With the Starizona,  I can insert it in the back of a attached focuser. I have used a Starlight 2" and an Optec Leo. I can even get a Pegasus Falcon rotater in the train with the Leo.

However, I mostly use refractors for imaging and use the SCTs very little.

Lynn K.
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andrea tasselli avatar
andrea tasselli avatar
If I were to get on (a C11) I'd rather go with the XLT with the Starizona reducer than the HD one. Much better bang for your money, I'd reckon.
Jeramie avatar
Jeramie avatar
I purchased my C11 XLT over the Edge, it was a similar question on cost/value for me. 

I use the Starizona LF and I get round stars to the edge (when well-collimated). I also saved a ton of money and that always helps.
Lorenzo Siciliano avatar
Lorenzo Siciliano avatar
+1 to the classical C11 and Starizona reducer-corrector. Take a look at my gallery and you'll see some examples.
Ciao
Lorenzo
knak avatar
knak avatar
I'm very happy with the XLT + LFII reducer.  But note the LF reducer is f7.4 and not f7 on the C11
GalacticRAVE avatar
GalacticRAVE avatar
If you are after planetary nebula, FoV does not matter, so go for the edge at native focal length. Matthias
Joe avatar
Joe avatar
Please also take a look at my C11+Starizona.
To be honest, an EAF is absolutely necessary. With my C11, I had to adjust the collimation of the secondary mirror and focus every two hours.
(Even changing the oil in the primary mirror to a heavier one didn't prevent mirror flop.)

The EdgeHD11 doesn't have such concerns, but you still need to periodically release the shift lock and use the EAF.
Please refer to the following user(Mr Martin) who has successfully installed a focuser on the back of the reducer for imaging.
With this method, you can effectively control everything wirelessly for long periods.

https://www.youtube.com/watch?v=JJQCS0xnGDM
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Philippe Germon avatar
Philippe Germon avatar
Without any hesitation : C11 XLT.

why?
  1. 2000$ price difference
  2. You already own a good quality reducer => no advantage here
  3. XLT optical parts (reducer, hyperstar) are cheaper too
  4. You may consider buying a used Hyperstar one day (mine costed me 600 €)=> then C11 XLT becomes a beast!
  5. Optically, if you consider to do planetary imaging, XLT is better. XLT has NO BACK FOCUS issues!!!!
  6. Cooling/temp : XLT is open vs EDGE HD closed/vents, etc => false debate and marketing argument. In reality, mirror needs 3 to 4 hours in summer to cool or warm to the ambiant temp. In winter, if stocked inside, mirror will need up to 6 hours moving from 20°C to 0°C (for example). Mostly, I get my C11 outside hours before seting it up to cool it. In summer, for planetary imaging, I even turn tube vertically and apply ice in a plastic bag on the secondary mirror side, then turn it secondary up, and apply ice in plastic bag on the secondary miror. This is a tip given by Damian Peach in a conference. So, IRL EDGE has no advantage.
  7. Planetary imaging : You only use a small part of the field of view. And sometimes, even when your collimation is very good, you see that the details are a little better on one side of the camera. And, here, EDGE correction is a disavantage.
  8. The 2000$ alows you to buy an Hyperstar, an IMX571 deepsky cooled camera or a very good barlow lens with a 662 camera and, obviously a good ADC


So, for me who is using C11 for 3 years now (and C8 too for 5 years), there is no positive point on buying an EDGE HD.

And if those words are not enough to convince you, check at my gallery. You don't "need" an EDGE HD.

One last thing to consider : when you 'll imaging with C11...you will soon sell the C9.25.

Have a clear skiy and good day.
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