Celestron 8" Edge HD SCT OTA

Discuss Celestron telescopes
Post Reply
User avatar
smp United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3401
Joined: Sat May 11, 2019 10:34 pm
4
Location: NH, USA
Status:
Offline

Celestron 8" Edge HD SCT OTA

#1

Post by smp »


Hi folks,

I'm considering the purchase of a Celestron 8" Edge HD SCT OTA.

First of all, I am a visual observer. Would this SCT be good for visual use, or is it one of the OTAs designed primarily for imaging?

I already have the Celestron 6" SCT OTA that I purchased almost a year ago. It performs well optically, but I've been frustrated with the amount of image shift when doing the last bit of back-and-forth with the focus knob trying to get optimum focus. Will I get the same image shift issue with the Edge HD 8" SCT OTA?

I see that some folks opt to purchase the Feather-Touch focuser replacement for the focus knob on Celestron SCTs. Does this address the image shift issue? Or does the image shift come from the mechanics inside the OTA? I'd hate to spend an additional $300 for my 6" or for a new 8" and find that the focuser is nice but doesn't fix the issue I have!

Thanks for any thoughts, comments, or advice you may have.

smp
Stephen
- - - - -
Telescopes: Questar 3.5 Standard SN 18-11421; Stellina (EAA)
Solar: Thousand Oaks white light filter; Daystar Quark (chromosphere) Hα filter
Mounts: Explore Scientific Twilight I; Majestic heavy duty tripod
Local Club: New Hampshire Astronomical Society
User avatar
Bigzmey United States of America
Moderator
Moderator
Articles: 8
Offline
Posts: 7548
Joined: Sat May 11, 2019 7:55 pm
4
Location: San Diego, CA USA
Status:
Offline

TSS Awards Badges

Re: Celestron 8" Edge HD SCT OTA

#2

Post by Bigzmey »


Stepping up to 8" is definitely a good move. You will go deeper on DSOs with still compact and lightweight scope. HD or vanilla for visual, I been agonizing over this for a while. It seems that opinions are fairly split on forums. Some saying "little improvement not worth the price" and some comparing HD vs plain to APO vs achro in refractors.

For myself, I figured out that if I ever need to replace my plain 8" SCT I would go with plain 9.25" SCT. It has different optics which delivers image quality closer to HD and gather ~30% more light than 8" SCT.

As for the focuser shift it does come from the fact that you are moving primary mirror while focusing. It seems that extend is vary from OTA to OTA. My newer OTA has hardly any. If it is an issue I would just get a helical focuser for the diagonal for fine focus adjustments.
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
User avatar
Lady Fraktor Slovakia
Co-Administrator
Co-Administrator
Articles: 0
Offline
Posts: 9860
Joined: Mon Apr 29, 2019 9:14 pm
4
Location: Slovakia
Status:
Offline

Re: Celestron 8" Edge HD SCT OTA

#3

Post by Lady Fraktor »


For some reason my reply disappeared...
The CGE dovetail is a Losmandy style though slightly different.
Look at posting #6 for a diagram of how it will fit in the plate.
https://www.cloudynights.com/topic/4995 ... ce-or-not/
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
The only culture I have is from yogurt
My day was going well until... people
Image
User avatar
Lady Fraktor Slovakia
Co-Administrator
Co-Administrator
Articles: 0
Offline
Posts: 9860
Joined: Mon Apr 29, 2019 9:14 pm
4
Location: Slovakia
Status:
Offline

Re: Celestron 8" Edge HD SCT OTA

#4

Post by Lady Fraktor »


To help get rid of the focuser shift focus towards the object and if you go to far bring the focus further back and focus towards again.
It helps take up some of the shift while focusing.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
The only culture I have is from yogurt
My day was going well until... people
Image
User avatar
smp United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3401
Joined: Sat May 11, 2019 10:34 pm
4
Location: NH, USA
Status:
Offline

Re: Celestron 8" Edge HD SCT OTA

#5

Post by smp »


Lady Fraktor wrote: Mon Sep 16, 2019 7:13 pm For some reason my reply disappeared...
The CGE dovetail is a Losmandy style though slightly different.
Look at posting #6 for a diagram of how it will fit in the plate.
https://www.cloudynights.com/topic/4995 ... ce-or-not/
I got your reply to my dovetail question over in the Mounts Forum - thanks very much, Gabby!

And, thanks again for the pointer to that CN topic. Much appreciated!

smp
Stephen
- - - - -
Telescopes: Questar 3.5 Standard SN 18-11421; Stellina (EAA)
Solar: Thousand Oaks white light filter; Daystar Quark (chromosphere) Hα filter
Mounts: Explore Scientific Twilight I; Majestic heavy duty tripod
Local Club: New Hampshire Astronomical Society
User avatar
smp United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3401
Joined: Sat May 11, 2019 10:34 pm
4
Location: NH, USA
Status:
Offline

Re: Celestron 8" Edge HD SCT OTA

#6

Post by smp »


Bigzmey wrote: Mon Sep 16, 2019 7:08 pm Stepping up to 8" is definitely a good move. You will go deeper on DSOs with still compact and lightweight scope. HD or vanilla for visual, I been agonizing over this for a while. It seems that opinions are fairly split on forums. Some saying "little improvement not worth the price" and some comparing HD vs plain to APO vs achro in refractors.

For myself, I figured out that if I ever need to replace my plain 8" SCT I would go with plain 9.25" SCT. It has different optics which delivers image quality closer to HD and gather ~30% more light than 8" SCT.

As for the focuser shift it does come from the fact that you are moving primary mirror while focusing. It seems that extend is vary from OTA to OTA. My newer OTA has hardly any. If it is an issue I would just get a helical focuser for the diagonal for fine focus adjustments.
Thanks very much, Andrey! Much appreciated. Oh, no! Now you've given me even more to agonize about! :lol:

smp
Stephen
- - - - -
Telescopes: Questar 3.5 Standard SN 18-11421; Stellina (EAA)
Solar: Thousand Oaks white light filter; Daystar Quark (chromosphere) Hα filter
Mounts: Explore Scientific Twilight I; Majestic heavy duty tripod
Local Club: New Hampshire Astronomical Society
User avatar
smp United States of America
Inter-Galactic Ambassador
Articles: 0
Offline
Posts: 3401
Joined: Sat May 11, 2019 10:34 pm
4
Location: NH, USA
Status:
Offline

Re: Celestron 8" Edge HD SCT OTA

#7

Post by smp »


Lady Fraktor wrote: Mon Sep 16, 2019 7:18 pm To help get rid of the focuser shift focus towards the object and if you go to far bring the focus further back and focus towards again.
It helps take up some of the shift while focusing.
Great tip, Gabby - thanks very much! I'll give that a try next time I get out with the C6.

smp
Stephen
- - - - -
Telescopes: Questar 3.5 Standard SN 18-11421; Stellina (EAA)
Solar: Thousand Oaks white light filter; Daystar Quark (chromosphere) Hα filter
Mounts: Explore Scientific Twilight I; Majestic heavy duty tripod
Local Club: New Hampshire Astronomical Society
stewe
Articles: 0

Re: Celestron 8" Edge HD SCT OTA

#8

Post by stewe »


smp wrote: Mon Sep 16, 2019 7:43 pm
Bigzmey wrote: Mon Sep 16, 2019 7:08 pm Stepping up to 8" is definitely a good move. You will go deeper on DSOs with still compact and lightweight scope. HD or vanilla for visual, I been agonizing over this for a while. It seems that opinions are fairly split on forums. Some saying "little improvement not worth the price" and some comparing HD vs plain to APO vs achro in refractors.

For myself, I figured out that if I ever need to replace my plain 8" SCT I would go with plain 9.25" SCT. It has different optics which delivers image quality closer to HD and gather ~30% more light than 8" SCT.

As for the focuser shift it does come from the fact that you are moving primary mirror while focusing. It seems that extend is vary from OTA to OTA. My newer OTA has hardly any. If it is an issue I would just get a helical focuser for the diagonal for fine focus adjustments.
Thanks very much, Andrey! Much appreciated. Oh, no! Now you've given me even more to agonize about! :lol:

smp
Hi there,

I agonized about the same thing some time ago, and after reading way too many posts about comparisons, I decided to acquire a C9.25 for visual instead of the C8 SCT or C8 Edge. If I also wanted to do astrophotography (at f/2), I would have opted for the 8" Edge, mainly because it is lighter (and its field is somewhat flatter). I have to admit that I have never had the chance to compare the two scopes side by side, but experts say that there is extremely subtle if any difference in the image quality visually (apart from the brighter image of the C9). Still, I can tell you that I did not regret my decision: the C9 is a superb scope, and for visual, aperture is (almost) always a winner. As a former 6"-scope owner, I am still amazed every time to see how GCs are resolved into thousands of pinpoint stars. The Moon and the planets are also amazing if the scope is well collimated and the seeing is good. I read that Damian Peach, a renown planetary astrophotographer uses a C9 after trying many different scopes, you might want to check out his blog to read more about the C9: http://www.damianpeach.com/c925review.htm . I use my C9 with an AVX and it is just fine for visual observation. I solved the (slight) mirror shift issue by attaching a Skywatcher dual-speed Crayford focuser to the SCT thread at the back of the scope. It costs a fraction of the price of the Feathertouch. Also, with its fine focuser, mount vibrations due to focusing diminished almost entirely. NB. the focuser adds some focal length, and the C9 effectively becomes an f/11 scope.

Happy contemplating!
User avatar
Bigzmey United States of America
Moderator
Moderator
Articles: 8
Offline
Posts: 7548
Joined: Sat May 11, 2019 7:55 pm
4
Location: San Diego, CA USA
Status:
Offline

TSS Awards Badges

Re: Celestron 8" Edge HD SCT OTA

#9

Post by Bigzmey »


stewe wrote: Mon Sep 16, 2019 9:27 pm
smp wrote: Mon Sep 16, 2019 7:43 pm
Bigzmey wrote: Mon Sep 16, 2019 7:08 pm Stepping up to 8" is definitely a good move. You will go deeper on DSOs with still compact and lightweight scope. HD or vanilla for visual, I been agonizing over this for a while. It seems that opinions are fairly split on forums. Some saying "little improvement not worth the price" and some comparing HD vs plain to APO vs achro in refractors.

For myself, I figured out that if I ever need to replace my plain 8" SCT I would go with plain 9.25" SCT. It has different optics which delivers image quality closer to HD and gather ~30% more light than 8" SCT.

As for the focuser shift it does come from the fact that you are moving primary mirror while focusing. It seems that extend is vary from OTA to OTA. My newer OTA has hardly any. If it is an issue I would just get a helical focuser for the diagonal for fine focus adjustments.
Thanks very much, Andrey! Much appreciated. Oh, no! Now you've given me even more to agonize about! :lol:

smp
Hi there,

I agonized about the same thing some time ago, and after reading way too many posts about comparisons, I decided to acquire a C9.25 for visual instead of the C8 SCT or C8 Edge. If I also wanted to do astrophotography (at f/2), I would have opted for the 8" Edge, mainly because it is lighter (and its field is somewhat flatter). I have to admit that I have never had the chance to compare the two scopes side by side, but experts say that there is extremely subtle if any difference in the image quality visually (apart from the brighter image of the C9). Still, I can tell you that I did not regret my decision: the C9 is a superb scope, and for visual, aperture is (almost) always a winner. As a former 6"-scope owner, I am still amazed every time to see how GCs are resolved into thousands of pinpoint stars. The Moon and the planets are also amazing if the scope is well collimated and the seeing is good. I read that Damian Peach, a renown planetary astrophotographer uses a C9 after trying many different scopes, you might want to check out his blog to read more about the C9: http://www.damianpeach.com/c925review.htm . I use my C9 with an AVX and it is just fine for visual observation. I solved the (slight) mirror shift issue by attaching a Skywatcher dual-speed Crayford focuser to the SCT thread at the back of the scope. It costs a fraction of the price of the Feathertouch. Also, with its fine focuser, mount vibrations due to focusing diminished almost entirely. NB. the focuser adds some focal length, and the C9 effectively becomes an f/11 scope.

Happy contemplating!
Good to hear Steve! Even with my 8" SCT getting 9.25" is tempting. Sharper optics and a bit more light in still manageable package. Going from 6" to 9.25" is no brainier. Unless you can handle 11". :D Used prices of 9.25" and 11" are about the same. 11" gathers twice more light than 8", so more logical choice for me. But 30lb weight of 11" is a bit more than I like to handle and I need to get a beefier mount. 9.25" has sharper optics, weigh ~20lb (my mounts can handle it) but gathers only ~30% more of light. Decisions, decisions. :lol:
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
stewe
Articles: 0

Re: Celestron 8" Edge HD SCT OTA

#10

Post by stewe »


Bigzmey wrote: Mon Sep 16, 2019 10:18 pm
Good to hear Steve! Even with my 8" SCT getting 9.25" is tempting. Sharper optics and a bit more light in still manageable package. Going from 6" to 9.25" is no brainier. Unless you can handle 11". :D Used prices of 9.25" and 11" are about the same. 11" gathers twice more light than 8", so more logical choice for me. But 30lb weight of 11" is a bit more than I like to handle and I need to get a beefier mount. 9.25" has sharper optics, weigh ~20lb (my mounts can handle it) but gathers only ~30% more of light. Decisions, decisions. :lol:

Exactly, C11 would have been even better, but would have required a significant step up with the mount (talking $$), plus portability using a small car is a must for me.
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

Return to “Celestron telescopes”