Celestron Edge 8 HD focuser upgrade options? - Forums

Topic starter

Apr 9, 2025 · Edited: Apr 9, 2025

Hey folks,

Hope you’re all well and (if you live here) have been enjoying some of the recent clear spells over the UK!

I’ve recently taken delivery of an Edge 8 and looking for options/advice on upgrading the focuser…would greatly appreciate any help or experience from other users (or indeed, anyone who wants to chime in).

I’m considering options for both the focus knob or at the visual back and would be interested in viewpoints as to the relative advantges/disadvantages of both solutions.

Also for context, the Edge would be used mostly for imaging, but would be using it for occasional visual too.

Thanks in advance for any help and have a great day!

Cheers,

Steve

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Jan Erik Vallestad

Apr 9, 2025

Hi there!

I've been using mine with the ZWO EAF focuser on the focus knob. I don't really see any issues with mirror flop or focus changing throughout the session. Quite often I find focus is pretty close between sessions as well. Moving the focuser will shake the mirror a tiny bit, but it doesn't take long to settle.

I looked into adding a focuser to the visual back as well but realized that it would create problems with backfocus, especially if you want to have additional accesories in the image train.

Here's how mine is set up, EAF on the opposite side unfortunately:

FWIW I've also used the Gemini focuser with it and it works just as well as the ZWO focuser.

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ScotiaAstro

Topic starter

Apr 9, 2025

Hi there!

I've been using mine with the ZWO EAF focuser on the focus knob. I don't really see any issues with mirror flop or focus changing throughout the session. Quite often I find focus is pretty close between sessions as well. Moving the focuser will shake the mirror a tiny bit, but it doesn't take long to settle.

I looked into adding a focuser to the visual back as well but realized that it would create problems with backfocus, especially if you want to have additional accesories in the image train.

Here's how mine is set up, EAF on the opposite side unfortunately:

FWIW I've also used the Gemini focuser with it and it works just as well as the ZWO focuser.

That’s awesome Jan, thanks!

Yes, I was thinking of any potential back focus issues too and at least the focus knob option doesn’t really interfere with that.

Appreciate you sharing your experience and your EDGE photos are beautiful!

Thanks again and best wishes from Scotland!

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Himanshu Pandey

Apr 9, 2025

I have the same experience with my edge 8. It is much more resistant to temperature changes than my refractor and I don't need to autofocus it a few times across a night. I don't have a handle on how bad the mirror flop is with my particular unit but find that performing an auto focus after a meridian flip and slew/recenter gets me back on track. I sometimes have failures associated with the flip and following auto focus run and suspect it is mirror flop that has caused the shift in focus to be too far off the threshold for auto focus to work.

I use celestron's focus motor which is a more coarse than the ZWO unit but it performs well for the telescope family it was made for.

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Brian Diaz

Apr 9, 2025

Hi , eveyone

i use primalucelab essato 2 , best option to avoid mirror shift
and any problems with the secondary mirror

Brian

Jan Erik Vallestad

Apr 9, 2025

That’s awesome Jan, thanks!

Yes, I was thinking of any potential back focus issues too and at least the focus knob option doesn’t really interfere with that.

Appreciate you sharing your experience and your EDGE photos are beautiful!

Thanks again and best wishes from Scotland!

Yeah, once I got it all set up I was pleasantly surprised that I didn't see any issues with focusing. However I forgot to mention how I've set up my focus routine which probably is of some importance.. I run AF on startup, meridian, every 2 degrees temp change and every two hours. This is probably a bit overkill if I'm being honest, I added the 2 hour one a few months ago because the temperatures may be very stable but it still may need a slight re-focus from time to time.

Thank you for the compliment!

I love Scotland!

Kind wishes returned from Norway!

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Eddie Bagwell

Apr 9, 2025

I have a ZWO EAF with SCT kit installed on my C11 and 9.25 SCTs and both work great. Easy to install. I don't have to worry about back focus issues when using a reducer in the image train.

C11 pictured

Kyle Goodwin

Apr 9, 2025

I definitely think that to achieve good results with the scope you need to have the mirror locked to minimize mirror flop. That means an external focuser. There are options like the Moonlite focusers which allow the reducer to recess inside the focuser alleviating backspacing issues and well as thin focusers like the Esatto or Leo which solve the problem by just not taking up so much space.

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Jan Erik Vallestad

Apr 9, 2025

Kyle Goodwin:
I definitely think that to achieve good results with the scope you need to have the mirror locked to minimize mirror flop. That means an external focuser. There are options like the Moonlite focusers which allow the reducer to recess inside the focuser alleviating backspacing issues and well as thin focusers like the Esatto or Leo which solve the problem by just not taking up so much space.

l disagree with that statement. I don't experience any issues by having the focuser on the focus knob while the mirrors are unlocked. I'm sure I've read that the older C8s may be more prone to those mirror flop issues than the E8HDs are though (correct me if I'm wrong).

I'm not using a reducer myself though and as long as I'm using the filterless OSC system on it I'm not really having backspace issues - but still, I've had only positive experiences so far despite having my own doubts before I actually started using it.

Jim Case

Apr 9, 2025

I have an 8 inch Meade LX200 ACF, which also has a locking mirror. I added a rotating R/P Feather Touch Focuser to the back and use a Starizona reducer that fits inside of the focuser with a ZWO EAF with a standard bracket. I believe it would work with your Edge, but I am not sure.

Kyle Goodwin

Apr 9, 2025

Kyle Goodwin:
I definitely think that to achieve good results with the scope you need to have the mirror locked to minimize mirror flop. That means an external focuser. There are options like the Moonlite focusers which allow the reducer to recess inside the focuser alleviating backspacing issues and well as thin focusers like the Esatto or Leo which solve the problem by just not taking up so much space.

l disagree with that statement. I don't experience any issues by having the focuser on the focus knob while the mirrors are unlocked. I'm sure I've read that the older C8s may be more prone to those mirror flop issues than the E8HDs are though (correct me if I'm wrong).

I'm not using a reducer myself though and as long as I'm using the filterless OSC system on it I'm not really having backspace issues - but still, I've had only positive experiences so far despite having my own doubts before I actually started using it.

I can't argue with your results, you seem to be getting excellent data based on your images. All I can say is that my experience when I had an EdgeHD 8 was not as positive.

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Jan Erik Vallestad

Apr 10, 2025

Kyle Goodwin:
I can't argue with your results, you seem to be getting excellent data based on your images. All I can say is that my experience when I had an EdgeHD 8 was not as positive.

Thanks, I'm getting more and more used to the telescope now. I don't doubt your experiences. It just goes to show that there will always be variations even with similar gear! I've had the same experience with the Celestron reducer. Many use it with good results but mine was horrible..

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Kyle Goodwin

Apr 10, 2025

Kyle Goodwin:
I can't argue with your results, you seem to be getting excellent data based on your images. All I can say is that my experience when I had an EdgeHD 8 was not as positive.

Thanks, I'm getting more and more used to the telescope now. I don't doubt your experiences. It just goes to show that there will always be variations even with similar gear! I've had the same experience with the Celestron reducer. Many use it with good results but mine was horrible..

The reducer is the reason I no longer have the scope. I didn't want to image at f/10, but the reducer was just terrible for me. Completely ruined the sharpness of the scope.

Jan Erik Vallestad

Apr 10, 2025

Kyle Goodwin:
Kyle Goodwin:
I can't argue with your results, you seem to be getting excellent data based on your images. All I can say is that my experience when I had an EdgeHD 8 was not as positive.

Thanks, I'm getting more and more used to the telescope now. I don't doubt your experiences. It just goes to show that there will always be variations even with similar gear! I've had the same experience with the Celestron reducer. Many use it with good results but mine was horrible..

The reducer is the reason I no longer have the scope. I didn't want to image at f/10, but the reducer was just terrible for me. Completely ruined the sharpness of the scope.

It has its drawbacks, but I've been enjoying it so far. It's not for capturing the faint stuff though so I completely understand that.

Mine seemed sharp enough (in the center at least) but this is a heavily stretched and calibrated stack of ten-twelve hours, just utterly hopeless..

(https://www.astrobin.com/forum/c/equipment-forums/celestron-edgehd-8/issues-with-sct-calibration-frames/?page=2)