Edge HD 14 - Shooting at 3910mm

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

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.

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

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

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

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

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

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?

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

FlyDogAstro:

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

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