American Association of Variable Star Observers (AAVSO)
Sun, 04/07/2024 - 23:32

My Brother and I are planing to move his Celestron Edge C-14 to NM for remote observing. He has quite a few NEOs and a comet (hug-bell) to his credit and I’m a complete newby looking to get involved in observing variables. 

I’m tasked with the hardware and a wondering if someone would review this image train before I pull the trigger on purchase. This will be primarily used for photometry.  


Item                                                                 Backfocus in mm

Edge C-14

Focal reducer 0.7

2” adaptor for 3.3” focal reducer threads                        2.0

Esatto 2” robotic micro focuser                                     67.0

M56 to M54 adaptor with step ring                                 4.0

Askar M54 back focus adjustor                                     18.0

M54 to M68 tilt plate (included with camera)                   5.0

ZWO M68 - L Off axis guider bolts directly to EFW       17.5

ZWO EFW 2”X 7                                                            20.0

ZWO ASI6200 MM pro camera                                     12.5

Total Backfocus                                                            146.0


The guiding camera will be the ASI124 mm mini i was planning on using the Sloan g r i and Cousins b v r filters with Clear glass in the last position.  OK?

One last thought, the CGE pro mount is showing its age and finding even a replacement Dec motor cable is neigh impossible. An appropriate mount recommendation would also be welcome. 

thank you 

Bruce Bell

American Association of Variable Star Observers (AAVSO)
Re: C14 Image Train review


I'm using a similar arrangement: C14 (classic, not Edge) with a Starizona focal reducer, 2" Esatto, and QHY268M w/filter wheel (no guider). My one comment is with respect to focus: with my C14, the difference between cold winter focus and warm summer focus exceeds the total travel limit of the 2" Esatto focuser. I end up using the mirror focus knob as a coarse focus adjustment that is only moved 3 or 4 times a year as the seasons change. "Everyday" focusing is done with the Esatto. I have a little Arduino board running a stepper motor to the mirror focus knob via a 3:1 reduction belt drive.

(I get away with no guider because I've got the scope on a 10 Micron GM2000 mount, which does a fantastic job.)

I also suggest that you do some kind of a vignetting analysis (if you haven't already done so). The 2" throat of the focuser may end up being a source of vignetting across that sensor because of the distance between the sensor and the point where the imaging path first necks down to 2".

- Mark


American Association of Variable Star Observers (AAVSO)
Mark, thank you.  Your…

Mark, thank you.  Your comments about the focuser concern me more than any potential vignetting.  I’m really not familiar with how the edge differs from your C14. I would have thought 15mm of travel in the focuser would have been more than enough to compensate for temperature differences. I guess that’s where my inexperience shows. 

just curious, what is the backspacing on your C14?   Esatto is adamant that this focuser is right for the Edge hd c-14 . I obviously need to do more research. 


American Association of Variable Star Observers (AAVSO)
C14 backspacing with Starizona IV SCT reducer

The Starizona IV SCT reducer has an advertised backfocus distance of 90.3mm. This reducer actually inserts into the Esatto focuser tube (way different from the way the reducers work on the Edge optics, as I understand it), so the Esatto isn't part of the backfocus distance. I did find, through experimentation, that I needed to adjust that backfocus distance by several mm in order to get best image quality. The Esatto is a great focuser; I've had zero problems with it.

The focus sensitivity to temperature is a function of a bunch of material things like composition of the mirrors and what the tube is made of. Using low-thermal-coefficient-of-expansion materials probably makes a huge difference, but my old C14 was acquired second-hand (I received it "as is"), and it shows pretty significant focus changes with temperature. (Each SCT I've owned has had its own unique thermal quirks.)

- Mark

American Association of Variable Star Observers (AAVSO)
I use the AstroPhysics…

I use the AstroPhysics 1100GTo with absolute encoders and low temperature lube. It just works. Have not realigned it for three years. Can carry 110 LBs.  An old fashioned C16 might ride on it. It hauls around a 12" SCT like a toy. The 1600GTO is likely over-kill for the little C14. 



Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)
C14 Edge f/7

Hi, I am running since 2022 an C14 Egde HD at f/7 in my observatory in my backyard over here in Belgium.

I have a C14 with a Carbon tube and never focus. For photometry it is not really needed to have pinpoint stars. I also do not autoguide as I have an ASA DDM85 direct drive mount, which can provide round stars for any target I observe in Belgium. I use a QHY600M CMOS camera in 4x4 binning. It is efficient enough to stay below 120 s for most of the targets. It has the same sensor as your ZWO ASI cam. I am not sure though you can run it in 4x4 binning mode. IT would help to keep storage needs for the images under control. I average 700 to 1000 images a night each about 7.5 MB (in 4x4bin mode).

I would also go for a better mount than the CGE. SInce ASA is no longer producing mounts for the amateur market a mount like a 10 micron 2000 would be an option. No autoguider would be needed any more.


Josch (HMB)


American Association of Variable Star Observers (AAVSO)
Josch thank you. I’m getting…

Josch thank you. I’m getting the message about the mount. In transporting the CGE Pro I managed to break the housing on the Dec cable. Not the end of the world, but trying to find a replacement…..? Well not a scenario you want if you’re setting up for a remote hosting site. In the race car world, we always took spares. Not happening with this mount. So we are looking at 10 micron, planewave, and paramount. I like the idea of direct drive. 

now you must need to focus once in a while? Are you using anything special? 


Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)
Focusing manually

Hi Bruce,

as said I have only focused manually the scope in 2021 once before I started a session. Since then I did not focus any more due to the Carbon tube of the C14 Edge HD.

Of course it is simpler if the scope is at reach in my backyard. I have another scope remotely in Chile and there I use a FLI Atlas focuser, but also there I hardly ever focus.

I would go for a planewave or 10 micron mount as they are fast mounts and you can observe several stars simultaneously one after the other like I do for time series.