Has anyone succeeded with unguided imaging at 3910 focal length?

This would be possible with the mirror locked and the OTA held in very firm rings such as those provided by software Bisque. The key would be rigidity of the OTA and very accurate polar alignment, balance and excellent sky conditions.

The stock Celestron orange rails are not very rigid and indeed rails may be a source of differential flexure.

The C14's biggest enemy is mirror flop and indeed the stock mirror locks may not hold the mirror firm enough so you may need to consider alternatives.

Protrack offered by Software Bisque through the SkyX & others can help improve the guiding accuracy.

I am using an AG Optical 14.5" at 2464mm focal length and can do up to 10 minute unguided exposures with my GM 3000 mount. Although, I typically expose for 3 minutes LRGB filters and 5 Minutes with SHO filters. I also use a 99 point model for the mount.

John Hayes:
The Celestron Edge14 has a good optical system but a very mediocre mechanical design.  The primary can move and the entire OTA is not super rigid.  You might get some useable results by imaging without guiding but why?  Guiding is easy and it guarantees that you won't have guide errors due to mechanical flexure or thermal issues.  Guiding will also greatly improve your image yield.  High quality sky time is valuable so don't throw some of it away by not guiding!

I can still remember years ago when a well known guy in this industry first started imaging from DSW.  He got a CDK14 and put it on a high-end mount with absolute encoders.  He decided to run it unguided and he had nothing but trouble.  Yes, he got a few decent subs but he threw out most of the data that he gathered.  He only lasted a couple of weeks before he flew back out to the observatory and retrofitted a guider on the system.  After that, the scope was useable.  Lesson:  Don't be that guy.

John

Thanks John - my understanding is that normal guiding won't work because of differential flexure problems.  The alternative, which I know that you use, is the ONAG from Innovations Foresight which doesn't come cheap.  If my ASA DDM 85 can succeed unguided then that would obviously be the best option - if not I guess I'll have to get the AMEX card out! I've got off axis guider that I could use, although past experience with a CX11 wasn't good as it struggled with finding a guide star.

Well…. yes…. I have access to a CDK24 on a 10micron GM4000 (Astronomy Club). This year I started using it for imaging. Not going into my technical  problems, but getting the first images out was work. At least now I am able to get pictures from it with 120s unguided. I would like to guide, but there might be a "backlash" issue with the mount (however, Baader told me that the 10m does not have a backlash?!?!?) and guiding kind of fails using PhD2 (maybe it is me not able to set up PhD2 properly using a 3960mm focal length and OAG)… So in short, yes, I get reasonable subs (120s) unguided, but not recommended. If technical issues are sorted I would definitely guide!
Rob

I don't find the reducer for my C14 Edge bad at all. I must have a good example. It produces good stars right to the field edge on the ASI2600 sensor. I don't use the ASI6200 on the reducer as field calibration begins to get a lot harder.

It is surprising how effective imaging deep sky objects is at F11 as well. I saw no issues with the trade off of having longer integration times. My first first light was at F11 and I was pretty much blown away at the extra detail seen from the increased image scale. However, I do favour the reducer as it helps mount equipment by moving all the connected devices away from the back plate of the C14- its weird shape can cause issues if you need to get devices close the back.

I use the ONAG on my C14, the mirror is locked with low profile mirror locks and I use the SMFS focus system. The SMFS, preserving the available back focus will allow me to fit a Falcon V2 rotator which will be fitted shortly to complete my system.

The OTA is held in the Paramount MX+ versa plate using Bisque rings which hold the OTA very rigidly.

I also find that using a CMOS camera I don't need very long exposures except for narrow band imaging so the aspiration of 20 minutes unguided, like a lot of others, I do question the need. If you can afford the outlay I would go for the ONAG- it really is a game changer especially at F11 where I believe guiding is a necessity and not something that can be negated in all circumstances. 

The ONAG can eat up back focus as it has 66-68 mm used by itself alone but by careful adaptor selection with the camera and filter wheel I'm at 128 mm leaving me enough back focus to add a rotator whilst still staying at the suggested 146mm (which according to Gaston is somewhat flexible depending on camera and conditions).