Any reason to get a 6in over an 8in SCT?

[b16707]

Hi all, new the forums! Hoping to get some advice. Been debating on getting an 8in ota (on an avx) for 1:1 swap with my CPC800 which im hoping to sell off but was wondering what are some opinions on getting a 6in purely for visual use?  My primary concerns that made me decide to try to sell the CPC800 was overall weight of the mount+ota assembly. Understand that a 6in would give me dimmer objects.

Would that be it though? Dimmer objects when doing visual?

I really do like the size and weight of the 6in. Most people have said 8in is the standard and you shouldnt go lower however. Everytime I find myself settled on the 8, i find myself also start teetering back to the 6.

[Knighty2112]

The C8 is pretty light. I don’t have any issues with the weight all, and if your putting it on an AVX Mount it should handle it easily.

[Minhlead]

I personally wouldn't go with the 6" if I could afford the 8". That is to say If your use is strictly visual I doubt the 8" will make much of a different since 8" on planets is quite small it self. 

[emadmoussa]

6 inch is lighter, but the 8" extra  light gathering capability is worth the extra weight - still fairly portable. 

[Luna-tic]

40 minutes ago, Minhlead said:

I personally wouldn't go with the 6" if I could afford the 8". That is to say If your use is strictly visual I doubt the 8" will make much of a different since 8" on planets is quite small it self. 

The 8"  mirror is 35% larger than the 6" in area, and has significantly better views. All other things being equal (price, mainly), the only way I'd take a C6 over a C8 would be if transporting it was the prime consideration. The C8 is fairly lightweight, but quite a bit bulkier than the C6.

[b16707]

Thanks all for the replies! Still seems like 8 is a winner.

2 hours ago, Minhlead said:

I personally wouldn't go with the 6" if I could afford the 8". That is to say If your use is strictly visual I doubt the 8" will make much of a different since 8" on planets is quite small it self. 

but then the 6 would make the planets even smaller no? 1500mm vs 2000+ mm. 

 

[Sunshine]

I agree, other than portability issues, I would always choose the 8", aperture is king.

[celestron8g8]

If you are wanting to observe and want to do WF imaging the 6” would be a great choice if your not having aperture fever . You can always use a barlow and a good EP for planet viewing as well as DSO  viewing . Yes an 8” would be better if it’s convienant for you but if it’s not a 6” is a good choice . Remember it’s your choice  and you you choose what is best for you ! 

[Stu]

 

3 hours ago, Luna-tic said:

The 8"  mirror is 35% larger than the 6"

I make it 77% larger, approx 52 square inches vs 28.2 square inches

Ultimately only you can decide which suits your needs best, but it comes down to a basic decision over how important portability and speed of setup are to you. The C8 will give significantly better, brighter images with more resolution when the seeing permits, but is heavier and will take longer to cool down.

Havng had a C8 Edge before, I thought it was an excellent balance between size and performance, very useable. The planetary performance was very good, showing good detail and nice colour in the various features on Jupiter for example. Collimation and cooling are key to showing good detail.

I found the C8 to be surprisingly good on DSOs too. The field of view is big enough to fit most of them in and the additional resolution over the 6” will be worthwhile on globular clusters for instance, resolving more stars and showing greater detail generally.

That said, the best scope is the one you use the most. My best scope is a 4” frac for this reason, I use it very frequently. If you think you would setup and use the 6” a lot more because of its lighter weight and quicker cool down then don’t feel obliged to opt for the bigger aperture, just get the scope you will use.

[ollypenrice]

I've had SCTs of 8, 10 and 14 inches. They get better with aperture but not, in my view, simply because of light grasp. They also gain in resolution, which is perfectly well in keeping with theory. However, I feel that SCTs exaggerate the consequences of the theory. I find them inherently slightly soft, optically, and this is far more prevalent in the smaller apertures. I wouldn't even call the 14 inch soft at all. If I compare a 3 inch apo with a 5 inch apo I don't see the same kind of differences in crispness that I see when comparing SCTs with a comparable percentage difference in aperture. In other words I think SCTs improve with aperture more than other systems, at least with regard to the mass produced ones. (I've observed with a 5 inch hand made SCT by Ralf Ottow. It was like a refractor.)

I can't say a small SCT would really tempt me. How about a Mak? They are small but give very crisp views?

Olly

[Chris]

I'm not sure swapping a CPC for an AVX for visual would be worth it. I've had both and there isn't that much portability difference, maybe the AVX is a lighter if you break it right down, but then you've got more setup with more components to put together, polar aligning, balancing counter weights, weird eyepiece position once setup etc Unless you're planning DSO imaging I don't personally think it's worth it.

But if you do, go for the 8"

[newbie alert]

A 8 inch on a avx is a highly portable outfit.. a cpc is a totally different beast portability wise....

[Demonperformer]

I started with a 6" sct and subsequently upgraded to an 8".

If I could go back, would I go straight to the 8"? Probably. The planetary views are much better with the 8" ... plus even when you sell the 6", the total cost is always going to be more than buying the 8" alone.

Was I ever disappointed with the views through the 6" at the time? No. The views met (and exceeded) my expectations.

On balance, I would say go for the 8". (But I don't think you will be disappointed with the results if you choose the 6".)

 

[Rob]

I've owned 2 x C8's in the past. I only used a Vixen GP (for visual) which is the same as a EQ5. It was fine on there. i will say though thats the max weight for that mount.

An AVX or HEQ5 with a C8 is perfection!

Rob

[michael.h.f.wilkinson]

7 hours ago, Minhlead said:

I personally wouldn't go with the 6" if I could afford the 8". That is to say If your use is strictly visual I doubt the 8" will make much of a different since 8" on planets is quite small it self. 

I sold my 6" F/8 Newtonian (a real planet killer, that one) to fund my C8 more than 22 years ago. I have never regretted that move. Mine is also on a Great Polaris mount (which is better than the EQ5 clone), and it does visual better than the 6" scope I had before: far better views of globulars, nebulae, galaxies, and even planets. In the latter case there is more detail, but the contrast at the same exit pupil is slightly less in the C8. The only advantage of the 6" F/8 is that if I fitted it with a bigger secondary and a 2" focuser, I would get a wider maximum field of view. The C6 doesn't even get you that, due to narrower internal baffles. The C8 is also a very capable planetary imaging scope

 

This also shows how much detail moments of good seeing give at the EP.

I suspect the main issue with the CPC800 is the fact that the fork and OTA are typically lifted as a single unit. I set up in three (quick) stages:

1: Set up tripod

2: Attach mount to tripod

3: Attach OTA to mount

Each of the units is easily handled.

[mikeDnight]

10 hours ago, b16707 said:

Hi all, new the forums! Hoping to get some advice. Been debating on getting an 8in ota (on an avx) for 1:1 swap with my CPC800 which im hoping to sell off but was wondering what are some opinions on getting a 6in purely for visual use?  My primary concerns that made me decide to try to sell the CPC800 was overall weight of the mount+ota assembly. Understand that a 6in would give me dimmer objects.

Would that be it though? Dimmer objects when doing visual?

I really do like the size and weight of the 6in. Most people have said 8in is the standard and you shouldnt go lower however. Everytime I find myself settled on the 8, i find myself also start teetering back to the 6.

It will be ighter, more compact, will cool faster, is easier to mount and will therefore likely be used more often as the urge takes you. A 6" is a powerful instrument and is not a dim scope by any stretch of the imagination. The only down side in my experience is that for visual SCTs just don't give sharp star images, so definition is not generally as good as Maksutovs Cassegrains, Newtonians or refractors. Having said that, its still better to have a scope you'll use more often than one that looks impressive but just sits around doing very little. Aperture is not everything!

[paulastro]

I've spoken to Ade Ashford on occasions re the Celestron 6inch and he is very impressed with all the examples he has owned or used, at least three of four of them.  Ade has told me that the ones he has used have had the best optics of any SCs he has used - and he has used a lot over the years!  There were fears at first that when the Celestron SCs production went from the USA towards the East that standards may fall.  Clearly, at least for this scope the opposite appears to be  true.

 

[Rob]

I have to say out of my 2 C8's the older USA built black tube with Starbright coatings was much, much sharper over the far east one!

[Minhlead]

10 hours ago, b16707 said:

Thanks all for the replies! Still seems like 8 is a winner.

but then the 6 would make the planets even smaller no? 1500mm vs 2000+ mm. 

 

It would. But then again, for visual use, I dont think you'll see much differences. For imaging, I'd go for the biggest aperture that vudget allowed but for eye-only I think 6" is sufficient

[ollypenrice]

5 hours ago, Minhlead said:

It would. But then again, for visual use, I dont think you'll see much differences. For imaging, I'd go for the biggest aperture that vudget allowed but for eye-only I think 6" is sufficient

For imaging what, though? Planets, for sure, like aperture but deep sky seems rather indifferent to it in my experience. 5.5 inches of refractor gave me these:

Olly

[Stu]

6 hours ago, Minhlead said:

It would. But then again, for visual use, I dont think you'll see much differences. For imaging, I'd go for the biggest aperture that vudget allowed but for eye-only I think 6" is sufficient

I can't agree with that. For sure, seeing conditions have an impact on high power views as aperture increases, but you get significant resolution gains at the same time which will be easy to see at the eyepiece. Aperture is, if anything, more important for visual.

[Chris]

13 hours ago, newbie alert said:

A 8 inch on a avx is a highly portable outfit.. a cpc is a totally different beast portability wise....

I take it you've owned both as I have? If so it's interesting how we have concluded such different views. 

[ollypenrice]

55 minutes ago, Stu said:

I can't agree with that. For sure, seeing conditions have an impact on high power views as aperture increases, but you get significant resolution gains at the same time which will be easy to see at the eyepiece. Aperture is, if anything, more important for visual.

Way more important. Totally agree (for deep sky.)

Olly

[newbie alert]

52 minutes ago, Lockie said:

I take it you've owned both as I have? If so it's interesting how we have concluded such different views. 

Not owned a cpc but yes a avx 8 inch sct..

I've got a 10 inch meade on a fork mount..i know which I'd rather pick up!

[Chris]

9 minutes ago, newbie alert said:

Not owned a cpc but yes a avx 8 inch sct..

I've got a 10 inch meade on a fork mount..i know which I'd rather pick up!

ok, in that case lets look at some figures as you seem to be comparing a 10" SCT to an 8".

Total telescope kit weight of a CPC800 is 19kg, and the 10" Meade is 29.5kg. Comparable?

Now lets look at both the AVX and CPC versions of the C8:

The AVX 8"SCT is 27kg all in with counterweight, so more overall weight than the CPC800 by 8kg. Stripped down the AVX I found a bit lighter to setup, but definitely more time consuming to setup. 

I've owned both these exact telescopes, I vouch for this in real life as well as the weight figures I've obtained from the net. 

I would go for the AVX if interested in DSO imaging, but for visual and planetary/lunar, the CPC is just so much easier to setup and and a lot more comfy to observe with. conversely I repeat I wouldn't go for the CPC800 for DSO imaging, even on a wedge, I'd go for a EQ mount.