Edge HD 14 - Shooting at 3910mm Celestron EdgeHD 14" · MeridianSkyAstronomy · ... · 38 · 1604 · 3

MeridianSkyAstronomy 4.21
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Starting a forum for the Celestron Edge HD 14 as there appears to be somewhat limited information in general for users.
Wondering if anyone could share their setup, tips or processes for shooting at 3910mm

Current setup

Edge HD 14
AP 1100 GTO AEL
ASI 6200mm
OAG
Moonlite Litecrawler
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laperuz 0.00
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Hi Starguy!
I do pretty much all my imaging using the 14". I did some at native F/11 for a while. Switched to F/7.7, really like the added FOV and shorter exposures. However, I'll probably switch back for doing small galaxies. The important thing here is to us OAG, not the guidescope as you'd invariably face differential flexture issues. Otherwise, I am routinely getting 0.3-0.5 arc-sec guiding with pretty round stars. I love the MesuMount 200 I bought directly from Lucas Mesu back in 11/2012. To me the EdgeHD 14 and this mount are match made in heaven.

My setup:
EdgeHD 14
MesuMount 200
QHY268 Pro-M
Celestron 0.7X Reducer
QHYCCD QHYCFW3-M
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BenoitSchillings 0.00
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Using a paramount ME with my c14 edge. I replaced the tube by a carbon tube to avoid focus drift.

Using an old FLI DF2 for focusing, and a ZWO2600 duo camera for the main imaging.


– benoit
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jhayes_tucson 26.84
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I imaged with an Edge 14 for about 2 years locally here in Oregon and then for about 5 years remotely at DSW.  The single most frustrating aspect of imaging with any Celestron telescope is the focusing system.  I wound up consulting for Celestron to develop a new high precision focuser and we built a prototype that worked extremely well.  Celestron wound up using my design in their RASA scopes but unfortunately, they decided not to put the design into their Edge scopes—mainly for cost reasons.  That photo-type Edge system that we built is still running trouble free in Norther New Mexico.  So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).   This system is really good and the only small disadvantage is that you have to run a wire through the pupil.  If you curve it, the diffraction effects are very minimal.

As others have pointed out, you must guide through the telescope.  The very best way to do that is with an Innovation Foresight ONAG.  This allows on-axis guiding but more importantly it allows real-time focusing.  The Edge telescopes have aluminum tubes, and a secondary with a high optical magnification factor which means that they are very sensitive to temperature changes.  It only requires a change in temperature of about 0.7C to pull the focus outside of the depth of focus (also called the critical focus zone).  I had very good success using ONAG with SkyGuard for guiding and for real time focusing.

Finally, you need a good mount.  I had my C14s on an Astsro-Physics 1600, which is a mount that can easily handle a 20” telescope and it was hell for stout.  It was a bit of over-kill but you won’t get far with a C14 on a flimsy mount.

For more information, you might watch my presentation on long focal length imaging in the AIC archives:  https://adamblockstudios.com/articles/secrets-long-focal-length-imaging-john-hayes

If you check out my AB page, you can find a lot of images that I took with my C14s.  You’ll see that if you do it right, you can get really good results.

Good luck with it!

John
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laperuz 0.00
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John Hayes:
So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).


I actually have good focusing done by locking the main mirror and using MoonLite focuser at the back.
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jeffreycymmer 0.00
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I use my Edge14 at F11 primarily for planetary nebulae.  Results are extremely dependent on seeing conditions.  I have not been able to autofocus for this reason and have to rely on a bahtinov mask.  I use a Celestron off-axis guider and a Lodestar X2 guide camera which has always found guide stars.  I also use the scope with an Astro-Physics CCDT67 telecompressor to shoot around F7 when the need arises.
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rimcrazyph 4.72
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I can't add much to what @John Hayes had to say as far as the most perfect setup one could want for a C14.  His work with a C14 is what the rest of us aspire too!  That being said, the setup he mentions works just perfect but it is pricy.  I just started imaging with my C14 this past spring.  I shut down for the summer but I'm in the process of putting things back together for the fall.  (Phoenix has had 113 continuous days OVER 100F this summer, and we are still having weeks on end over 100F.  Tough to cool a camera to -10C when it is 40C at 10pm).  My C14 is set up on my AP1600AE mount, which is the bomb.  

That being said my Phoenix skies in the fall/winter/spring time are Bortle 6 - 7.  I found a few things.  As @John Hayes mentioned, you need to guide a C14 with some type of OAG or in his case ONAG.  I tried 3 different guide scope/camera combinations and I could not make any work successfully.  (Stars would not be round and I was getting streaks). I switched to an OAG setup.  I have a Moonlite Compact focuser specifically for SCT's but you can't fit a Moonlite on the back AND use an OAG.  There is not enough back focus to do that.  I have two focusers on my C14.  My Moonlite on the center back and a Pegasus Cube Zero that drives the C14 focus knob.  I use the Moonlite for visual use and imaging planets and the moon.  You don't need to guide for either of those targets.  I use the Pegasus to "center" the Moonlite focus point and then I lock the mirror and only focus with the Moonlite.  This keeps things tight as for planets as you like to shoot around the meridian to keep your imaging through the least amount of atmosphere.  With the mirror locked you get little to no movement and with my AP1600AE in most cases I can shoot well past the meridian without having to do a flip.  Depends on what is up and where but with the AP you can push it.

For DSO photography with my C14 in Phoenix under my Bortle 6-7 skies like I mentioned, I found I cannot use my C14 without the 0.7x reducer.  The problem is when you are guiding with an OAG and you are at F11 mode, unless you are shooting right in the heart of the Milky Way, it is quite difficult to get enough stars to guide.  In fact at F11 I was finding it next to impossible to even find objects because I could not get enough stars to plate solve after a go-to.  I use the Celestron 0.7x reducer.  With that, I'm now shooting F7.7 and have a wider FOV.  The combination of a wider FOV and the brighter stars due to the shorter focal length I can plate solve with no issue.  I can make very large pointing models.  I use the Celestron OAG designed for the C14 and I use an ASI174MM as my guide camera.  I shoot using NINA and I autofocus with the Pegasus Cube.  Now, since I am using the Pegasus I obviously have an issue because the mirror is not locked.   I have found so far, that tends to not be a huge issue, most likely because I have my C14 on an AP1600AE mount.  When I pass the meridian I always do a plate solve to repoint and an autofocus so after a flip, I have "fixed" the mirror flop and because my AP tracks so well I don't have much correction even with the flop.  (My C14 Edge HD is relatively new, purchased only a few years ago from B&H Photo)  I shot M27 last May and it came out quite nice I think.  The other thing to think about is if you wish to use a Hyperstar with your C14 as I would like down the road, you cannot use the setup @John Hayes mentions because the secondary focuser is replaced with your Hyperstar so you need something like the Pegasus Cube Zero to focus your image.  Now however, with a Hyperstar you are shooting at F2 so you have boatloads of light over a very wide FOV so plate solving and pointing is a non issue.  Guiding with a guide scope/camera at F2 should also work well but I have not tested this as I currently do not own the Hyperstar adapter.

Lastly, if you have nice dark skies where you have your C14 I would go ahead and try guiding OAG at F11 and see if it works.  Since you have an AP100AE your capabilities are very similar to mine.  Down the road, I would like to duplicate @John Hayes setup but there are a few more things I want to try first.   Since we both have AP mounts with the absolute encoders, we should be able to use DecArc models and just bypass guiding all together.  I was just at the point of trying this out earlier this year when summer hit hard and fast and I had to take down my setup.   It is one of the first things I want to try once I get things back up and running.  With an AP mount I really think for most things, we should not have to guide at all but that remains to be seen.

CS
Phil
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jhayes_tucson 26.84
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Ian Gorin:
John Hayes:
So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).


I actually have good focusing done by locking the main mirror and using MoonLite focuser at the back.

Agreed.  That will work well if you have sufficient back working distance.  However, an external focuser won't work with an ONAG because it eats up too much of the 5.75" available from the rear of the baffle nut to the focal plane.  

Again, the challenge with the C14 telescopes is their sensitivity to thermal variations. The charts below explain the problem and show that the C14 is among the most sensitive telescopes to temperature changes.   Note that the smaller the delta-T value, the more sensitive the telescope is to temperature changes.  None of this matters if your environment is very stable but there aren't many locations that are stable to within a half degree C over long periods of time and it's possible to see a 0.5C in 3-10 minutes under many common conditions.  That's why I have never been a fan of OAG with the C14.  ONAG permits real time focusing but it also requires a precision focuser that takes up zero back focus like the SMFS system. 

Cassegrain Thermal Stability with Temperature 2-19-19.jpg


List of Telescope Sensitivity to Temp 2-19-19.jpg


- John
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AstroRBA 4.98
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Greetings from Bortle 8 Mississauga Ontario!

I've been shooting F11 3910mm on the Edge 14 for about a year now; I tried a bit of F7 with the Celestron reducer prior to that and didn't like the results.

I took the (very good) advise of John Hayes and got the Innovations On Axis Guider and the Optec Secondary focuser (I actually also bought a Hyperstar and have yet to use it and probably never will for a variety or reasons); The On Axis Guider is brilliant; especially so with the ASI6200 full frame camera; I wouldn't want to be trying to position a tiny prism outside of that big FF image window for Off Axis guiding.

I absolutely love long focal length astro work now and and I've just mothballed the wide field RASA 8 that I had set up in California in favour of another long focal length set up (not yet fully on line). I kind of feel like I've run out of wide field targets across all of my short focal length rigs (at least in the northern hemisphere anyway ! Lots of southern short focal work to do still with my travel scopes!). There seems to be an endless list of interesting long focal length targets to pick from; John Hayes highlights this well in the aforementioned presentation that he linked in his comment.

I'm using a CEM120 Mount on a permanent concrete mounted pier and I use a custom oversized Telegizmo 365 cover which provides perfect year round protection for the entire rig. I use a ladder to remove and recover the rig and can do either end now in a minute or two.

I prefer NB (mostly due to the aforementioned Bortle 8 horror zone that I'm in) and other than *constant* sub par seeing in my area; I'm happy with the results. But I also do RGB - I'm using a seven position filter wheel - LRGBSHO.

Balance carefully and double check polar alignment often - even with my permanent pier the otherwise tiny fluctuations due to temperature are noticeable at 3910mm; in fact EVERYTHING is noticeable at 3910 mm ! Calm and patience is an absolute MUST ! Many clear looking nights will end up being a total waste of time and effort - just be prepared for that!

Oh, and I suggest the Celestron metalic due sheild, and although I also have the dew ring installed, I suggest wrapping a few dew bands around the sheild instead; 

Good Luck and Good Hunting !

Pete
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jhayes_tucson 26.84
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Benoit Schillings:
Using a paramount ME with my c14 edge. I replaced the tube by a carbon tube to avoid focus drift.

Using an old FLI DF2 for focusing, and a ZWO2600 duo camera for the main imaging.


-- benoit

I did the same thing on my Edge 14 at DSW and I could measure the effect with the autofocus system.  Unfortunately, the CF tube made almost no difference in the thermal stability.  The problem with carbon fiber is that the lay of the fiber has a big effect on the thermal characteristics of the structure  and I don't think that the tube that I had (from Public Missiles) was well engineered with respect to the thermal characteristics.  It sure looked good though!   ))

John
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jhayes_tucson 26.84
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Oh, and I suggest the Celestron metalic due sheild, and although I also have the dew ring installed, I suggest wrapping a few dew bands around the sheild instead;


Pete,
I'm really glad to hear that your system is working well.  Your last bit of advice is absolutely spot on!   I'm working on a new presentation about the physics of dew prevention and in it, I show why the approach that you've recommended is so good.  With a dew shield about 1.5 times as long as it is around, you only need to uniformly raise its temperature by about 3C to prevent dew--and I'll show that calculation.

John
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MeridianSkyAstronomy 4.21
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Benoit Schillings:
Using a paramount ME with my c14 edge. I replaced the tube by a carbon tube to avoid focus drift.

Using an old FLI DF2 for focusing, and a ZWO2600 duo camera for the main imaging.


-- benoit

That sounds like a fairly straight fwd mod. How has it helped focus and where does one get a carbon fiber tube?
Any pictures?

Somewhat related - I have not noticed any flexure yet using the dovetail connection on the scope (I upgraded to Losmandy bars) but have seen 14s with large rings. Has anyone used them or had a similar experience
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jhayes_tucson 26.84
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Benoit Schillings:
Using a paramount ME with my c14 edge. I replaced the tube by a carbon tube to avoid focus drift.

Using an old FLI DF2 for focusing, and a ZWO2600 duo camera for the main imaging.


-- benoit

That sounds like a fairly straight fwd mod. How has it helped focus and where does one get a carbon fiber tube?
Any pictures?

Somewhat related - I have not noticed any flexure yet using the dovetail connection on the scope (I upgraded to Losmandy bars) but have seen 14s with large rings. Has anyone used them or had a similar experience

As I said, a CF tube didn't help my system much (if at all) but if you want to try it, here's the only supplier that I currently know about:  https://carbonscopetubes.com/Celestron_C14_Tubes.html.

I believe that Public Missiles got out of the telescope tube business so this may be your only option.  My guess is that they operate like Public Missiles use to and only actually fabricate tubes after they accumulate enough orders to make it worth their while.   Call them to see where they stand.

John
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MeridianSkyAstronomy 4.21
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Thank you for the information John
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BenoitSchillings 0.00
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scope.jpg

and a result. sq_lum.png

John. I got my tube made custom. Also, you need flexure connections with the dovetail plates.


I also do have many images taken with the edge at https://www.astrobin.com/users/BenoitSchillings/

Maybe a good show of what a c14 can do would be this image of M64 :

https://www.astrobin.com/full/e2gnys/0/

About your questions : You still do need to focus, even with the carbon tube, the combination of Pyrex optics and carbon tube is not totally athermal, but still need to refocus maybe every 5 degres.

I do have two dovetail on my OTA, and I never notice any obvious flexure, I would think that the rings are overkill.

I have used the scope using a zwo motor on the focuser, and this is usable, but I do prefer a separate focuser and locking the mirror.

Yes, one more thing. I modified the secondary assembly and do have the secondary actuated by 3 piezo pico-motors. I do use this both to do remote collimation but also for high speed guiding. I could also focus with this if needed. Each step of the piezo motor is 30 nanometers.

-- benoit
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BenoitSchillings 0.00
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A few more things... I did a number of experiments with cooling fans, the stock C14 doesn't have fan (maybe it changed) and pushing air thru the vents certainly helps getting to an ok thermal state. I use to have an open tube C14, this was a success... I may go back there sometimes with the edge.


Here is a photo of the extreme c14 :-)   c14_1.jpg
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MeridianSkyAstronomy 4.21
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That looks incredible!
My location its not too bad for keeping the scope temp at equilibrium but I have noticed its very common for focus to change from night to night and often exceeds the limited focus travel of the Moonlite Lightcrawler and requires a recalibration.

When calibrated I find the Lightcrawler focuser/rotator works quite well throughout the night, the only problem is calibration requires unlocking the mirror to operate the manual focus which is problematic for remote operations

Anyone seen a device that automates mirror locking?
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hawkranch 0.00
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Greetings, I use my Edge C-14 full focal length with a Moonlite focuser, an Askar OAG, ZWO 294MC camera and a Losmandy G-11 mount. Guiding will an ASIAIR averages about .7. If I have trouble finding a guide star I rotate the Moonlite focuser (very easy to do) and can quickly find one. Also I shoot planets with just the guiding of the Losmandy mount and a Player One Uranus C color camera.  I'm very happy with the results and not to brag but to reassure you I have received two top picks of the three shots I've posted so far on Astrobin. Also I have TEMP-est fans installed for thermal issues. Hope this is of some help! Also for planets collimation has to be dead on.
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jhayes_tucson 26.84
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Benoit Schillings:
scope.jpg

and a result. sq_lum.png

John. I got my tube made custom. Also, you need flexure connections with the dovetail plates.


I also do have many images taken with the edge at https://www.astrobin.com/users/BenoitSchillings/

Maybe a good show of what a c14 can do would be this image of M64 :

https://www.astrobin.com/full/e2gnys/0/

About your questions : You still do need to focus, even with the carbon tube, the combination of Pyrex optics and carbon tube is not totally athermal, but still need to refocus maybe every 5 degres.

I do have two dovetail on my OTA, and I never notice any obvious flexure, I would think that the rings are overkill.

I have used the scope using a zwo motor on the focuser, and this is usable, but I do prefer a separate focuser and locking the mirror.

Yes, one more thing. I modified the secondary assembly and do have the secondary actuated by 3 piezo pico-motors. I do use this both to do remote collimation but also for high speed guiding. I could also focus with this if needed. Each step of the piezo motor is 30 nanometers.

-- benoit

Benoit,
Yes, I completely agree that you need a flexure connection to the dovetail plane and my system was designed that way.  I'm glad that you had such a good experience with your move to CF and you've certainly produce some spectacular results.  My experience with the Custom Missiles CF tube was not similar and I suspect that it was due to either a material choice or layup issue in the way the tube was made.  I too modified may secondary mount but it was simply to provide a stable, zero-clearance, kinematic mount.  It could be removed and replace to within less than about 4 fringes of tilt across the pupil as measured by a PhaseCam.  I really like your pico motor approach.  I thought about doing something like that at one time but never tackled it.

John
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FlyDogAstro 0.00
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Ian Gorin:
John Hayes:
So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).


I actually have good focusing done by locking the main mirror and using MoonLite focuser at the back.
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jhayes_tucson 26.84
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Ian Gorin:
John Hayes:
So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).


I actually have good focusing done by locking the main mirror and using MoonLite focuser at the back.

Yes, that will work fine if you have enough room using OAG but you can't do that with ONAG and stay within the 5.75" specified BWD.   SMFS provides the ability to use whatever guiding system you want.

John
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BenoitSchillings 0.00
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this brings a good question… once  you lock the primary, what is actually moving that makes guidescope works so poorly ? 

I am actually doing a few test in the next few night, the measure the motion between the main scope and a guide scope… hopefully will get some clues.


-  benoit
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laperuz 0.00
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Benoit Schillings:
this brings a good question... once  you lock the primary, what is actually moving that makes guidescope works so poorly ? 

I am actually doing a few test in the next few night, the measure the motion between the main scope and a guide scope... hopefully will get some clues.


-  benoit

Benoit:
The main problem is that a small guidescope and a large C14 flex differently under changing temperature, scope orientation, etc. You're guiding using one optical system and imaging with another. That makes it inaccurate, resulting in oblong stars and other problems. It is OK with short FL like RASA but pronounced with full FL of 3-4 meters.
Ian
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rimcrazyph 4.72
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Ian Gorin:
John Hayes:
So now, the best way to achieve precision focus is to lock the primary mirror and add the secondary focus system from Optec (SMFS).


I actually have good focusing done by locking the main mirror and using MoonLite focuser at the back.

This is actually what I’ve wondered about. Assuming with my AP1600 and using DecArc modeling I shouldn’t need to guide. Removing the OAG I can then use my Moonlite and lock the mirror.  I’m not disputing the thermal focus issue but I’m also trying to attack one issue at a time. Before I spend 3k+ on a ONAG and Optec secondary focus system I’d like to see, in my urban Bortle 6-7 setting, how good/bad my C14 performs with the current system I have.
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BenoitSchillings 0.00
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One way that is a easier is to use a dual chip camera like the zwo. you can calibrate the focus to be the same across both chips (there is a fine control on the camera)… that way you can refocus using the guide chip and not have to interrupt the exposure. I do write my control software in python, if you write code, you may want to look at it. having ways to fine control the scope makes a big difference.

There might be a windows piece of software that will refocus dynamically based on the guide chip, but I did not check
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