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8" Edge vs C 9.25


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1 hour ago, JeremyS said:

C9.25 would be better for visual. I have one ands it is lovely

Actually these are really nice scopes, and I have a question- how would the cool down compare between the 8"Edge vs the C9.25? One more- is there a difference with regard to seeing?

I'm looking at the C8Edge for imaging as well as visual. I'm also going to buy the Hotech SCT collimator as I can't stand the thought of collimating one of these with a star. The Edge series looks much more flexible with regard to precise collimation. Realistically though these scopes most likely hold collimation very well, I kinda got a twitch of OCD with regards to it however.

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7 hours ago, jetstream said:

Actually these are really nice scopes, and I have a question- how would the cool down compare between the 8"Edge vs the C9.25? One more- is there a difference with regard to seeing?

I'm looking at the C8Edge for imaging as well as visual. I'm also going to buy the Hotech SCT collimator as I can't stand the thought of collimating one of these with a star. The Edge series looks much more flexible with regard to precise collimation. Realistically though these scopes most likely hold collimation very well, I kinda got a twitch of OCD with regards to it however.

One problem with the Edge is that the additional optics block the baffle tube which I think slows cooling, and means you can’t use a cat cooler. You can buy after market fans for them which will help.

https://www.deepspaceproducts.com/product/temp-est-temperature-equilibration-system-for-telescopes---for-edge-hd-and-vented-standard-celestron-scts

I found that mirror flop can be an issue with collimation, just like many of the moving primary type scopes, although it seems to vary between samples. The Edge models have mirror locks which definitely help prevent this, and a good option is to add an after market focuser on the visual back so you can leave the mirror locked and precisely collimated.

Many people say that Edge optics are only necessary for imaging, but I found they also help give a flat field and sharp stars to the edges when using wide afov eye pieces.

I have had both an Edge 8” and standard 9.25, both very nice scopes. Cooling was always a challenge for me, and my seeing conditions often meant I only got the best out of them when I took them away camping when they stayed cool! The Edge is probably the better option as an all rounder, and particularly if DSO imaging is on the cards, the 925 would likely be preferable for lunar and planetary imaging as it is meant to be that bit better due to the slightly slower primary vs the rest of the range (f2.3 vs f2 if I remember correctly), plus the resolution gain of course.

I could be tempted by another 925 in future perhaps, but likely only if I moved to a better site. My 8” f8 dob gives better results for me now, but is much more cumbersome than an SCT and definitely not an imaging scope!

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The original question was around observations not imaging - however it sounds like the c9.25 is winning this one for visual use due to more light gathering power which is what I thought , thanks all 👍🏼🔭

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Yes the C9.25 is definitely better as a visual scope than the C8. More light gathering.

Gerry @jetstream mine holds its collimation very well, even after short car journeys (I have used it as an outreach scope). Star images are not as nice as in the TSA120, though 😬

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1 minute ago, JeremyS said:

Yes the C9.25 is definitely better as a visual scope than the C8. More light gathering.

Gerry @jetstream mine holds its collimation very well, even after short car journeys (I have used it as an outreach scope). Star images are not as nice as in the TSA120, though 😬

How do you find the mirror flop Jeremy? Both the 8 and 925 had it for me, and it did affect collimation which is why is used a secondary focuser.

Apologies for any diversion @Beardy30! Got carried away with other posts. I think a C925 would be a very good choice. Just bear in mind they are as long as a c11 pretty much due to the slower primary, perhaps a bit bigger than you may expect.

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Just now, Stu said:

How do you find the mirror flop Jeremy? Both the 8 and 925 had it for me, and it did affect collimation which is why is used a secondary focuser.

Apologies for any diversion @Beardy30! Got carried away with other posts. I think a C925 would be a very good choice. Just bear in mind they are as long as a c11 pretty much due to the slower primary, perhaps a bit bigger than you may expect.

Mirror flop is minimal, Stu. It’s worse in my C11 (arggghh .....there I go again destroying my frac credentials 😬), perhaps magnified by the longer FL. I have a secondary focuser on the C11, but it’s used exclusively for imaging anyway. I had anticipated getting one for the C9.25 but it’s just not needed. 

The other thing for @Beardy30 to consider is ease of mounting and dismounting the OTA if he needs to set up every time. If find the C9.25 acceptable, but not as easy as a traditional C8 mainly due to extra bulk rather than weight.

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12 minutes ago, Beardy30 said:

I do like the look of the evo mount I must admit it’s built in WiFi and gadgets appeal to me for visual use although I wonder if an AVX mount maybe better in case I want to dabble in AP in the future 

Potentially useful review here:

https://astronomynow.com/2015/02/25/celestron-nexstar-evolution-9-25-review/
 

It says there is a three second damping time with the tripod at mid height. That’s ok but may be a little frustrating at high powers. Single arm mounts just can’t be as stable as dual, or a good alt az or EQ mount. It would be interesting to hear from anyone who has used this combo. For example the 8” SCT is often said to be a bit much for the SE mount, is the 925 similarly a bit much for the Evo or is it ok? I don’t know, others will be able to advise better. Next step up is the CPC but that is a much more cumbersome arrangement with the scope and mount as one unit.

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5 hours ago, Beardy30 said:

The original question was around observations not imaging - however it sounds like the c9.25 is winning this one for visual use due to more light gathering power which is what I thought , thanks all 👍🏼🔭

Hi James, I thought it might be enlightening to discuss collimation (and also cooldown) because these 2 issues can really mess with the views visually (and imaging).It can boil down to "getting a good one" possibly.

I would take a C8 with "better" optics (a "good one" ) that is collimated tighltly over a C9.25 that is mediocre any day. Of course a "good"C925 would be preferred if size and weight is not an issue.

I mentioned the Edge because if miscollimation appears or is there to start with, it has a very easily removable sec and with easy corrector adjustment should the sec need to be moved a bit to line up (not tilt).

Maks might have a longer cooldown and the SW Maks baffle might up the CO to about 30% from 23%. They are reputed to be sharp scopes if you can cool them.

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7 hours ago, Stu said:

Many people say that Edge optics are only necessary for imaging, but I found they also help give a flat field and sharp stars to the edges when using wide afov eye pieces.

Thanks for all the info Stu, it is stored and being processed in a very cold mind! (-52c with wind this morning)

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5 minutes ago, jetstream said:

Thanks for all the info Stu, it is stored and being processed in a very cold mind! (-52c with wind this morning)

Wow!!!! 🥶🥶🥶🥶 and I thought it was chilly here!

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53 minutes ago, jetstream said:

Hi James, I thought it might be enlightening to discuss collimation (and also cooldown) because these 2 issues can really mess with the views visually (and imaging).It can boil down to "getting a good one" possibly.

I would take a C8 with "better" optics (a "good one" ) that is collimated tighltly over a C9.25 that is mediocre any day. Of course a "good"C925 would be preferred if size and weight is not an issue.

I mentioned the Edge because if miscollimation appears or is there to start with, it has a very easily removable sec and with easy corrector adjustment should the sec need to be moved a bit to line up (not tilt).

Maks might have a longer cooldown and the SW Maks baffle might up the CO to about 30% from 23%. They are reputed to be sharp scopes if you can cool them.

I agree a good 8 is better than a poor 9.25 however I’d say collminate the 9.25 correctly 🤔. and a 9.25 on an equal footing out paces the 8” for visual due to having a bigger apature. 
 

Be good to know if a Mak 6” (150 pro for example) would perform better than a 6” SCT  in the right conditions I’d say it would even for dso (brighter ones) - I think we’d all agree the evo mount is quality for visual no doubt about it but I’m betting the sw 150 Mak on an eq5 goto would do just as good a job

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  • 1 month later...
On 06/02/2021 at 20:25, Beardy30 said:

I’d be interested to know people’s views on the 8” edge SCT vs the standard 9.25 SCT 

which would be better for visual observations- using the celestron Evo mount 

Hi! I have 9.25 SCT Evo mount. I highly recomend 2" diagonal with eyepiece 30mm +82º for visual observations.

DSO amazing. But try allways as possible go to non light pollution area, or far enough from city lights. Visual improves a lot!

Starsense autoaling will help you to find any star cluster and some times when seeing is good some faint galaxies too.

Only problem is OTA weight! 

Clear skies!

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  • 2 years later...

I need some help please re celestron 9.25 which I have already but considering edge HD8, I started about 6 months ago do AP with my William optics and definitely know it’s a great scope for AP, I went for a 9.25 as I was told it’s also good for AP When using a celestron 6.3 reducer I have tried it but know way as good as the William optics, so am i wasting my money considering an edge HD8?

I have read that the 9.25 would be better as more light and fainter objects for visual is better than edge8?

can I please have some advise just stick to the 9.25

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