Celestron C6/8 SCT v Skymax 150/180 MAK for planetary observing - help please

[CAB]

I am looking to get a longer focal length scope for mainly planetary observing. Have an 80mm APO refractor for my widefield so that's covered but in my light polluted back garden would like to move on to something with more FL/mag for lunar and planets and double stars/clusters. Am looking for an easy to handle scope that will go nicely on my HEQ5 so I can use the tracking. My 10" dob lives elsewhere in a dark site so don't have access to that.

I am thinking that a 6" Cat might be a good option does anyone have experience of these scopes and any thoughts. I am thinking the C6 is an SCT which should cool quicker than the Mak but the Mak may have better contrast although I have read the C6 performs well due to its optics/coatings. The Skymax 150 is a longer FL so more suited to planets i.e. smaller FOV gives illusion that something is bigger even at same mag?

Also to throw something else into the mix would there be a big benefit of a C8 (as they are quite light to handle) or a Skymax 180 which is F15 which I think is best FL for planets but to be honest I keep reading things that contradict myself.

I am not too worried about cool down for SCT/MAKs as I am planning to keep the scope in the garage to help with that.

Anybody's thoughts or experience with these scopes most welcome please.

Many thanks, Cheryl

[dweller25]

Hi Cheryl, I do a lot of planetary observing with a C8 and used to own a Skymax 180. The 180 took a looooong time to cool down, the C8 takes a good hour but when it does the views are tremendous. I also have a 5" Takahashi Apo and there is nothing between it and the C8 !!!

[nightfisher]

I have a 180 pro mak, i dont find the cool down to be so bad, but i dont have central heating, much as i love my mak, if i were buying again, i guess i would go with the C8, due to being lighter and it still has a decent focal length

[CAB]

Thanks David/Jules

You both said what I was thinking and I decided to go with the C8 and have one on order!

Can't wait...

Cheryl

[gcraib]

Good for you, bet you are well excited!

Are you running all the scope on the same mount (HEQ5)?

have a couple of other questions:

What is the C8 or SW180 like with DSO's?

Can anybody explain the practical differences between SCT and maksutov cassegrain?

[Dunkster]

Nice choice Cheryl!

I have both the C6 and C8 and the C8 is noticeably better at clusters than the C6, resolving lots of stars instead of just fuzzy patches from my light polluted garden. All in a package that is only about 1kg heavier! I haven't had enough tries at planetary since I've had the C8 - unfortunately the weather just hasn't been that good

[rowan46]

The practical differences between an sct is primarily of cooldown when you get to 6" and above the sct cools quicker than a mak. the general consensus appears to be that a properly cooled mak gives better views. I am not an expert but I have never been able to tell any difference between a c8 and a skymax 180. if you take their magnification into account they appear to behave the same. I have a mate who collects cats he showed me a few types next to each other, at similar magnifications they are all much the same to my uneducated eyes and that included a klevstov.

[gcraib]

so unless you are an expert go for the SCT?

[gcraib]

I saw a C9.25 mentioned on here as a good all rounder, food for thought.

[Teslar]

I own a 180 Mak and sold a 6" SCT to buy it. I do keep it in the shed so no lengthy cool down. I don't find weight a problem and my NEQ6 handles it with easy. It really is an excellent scope though I did add a baader steel rack to improve focus. I prefer it to an orange tube any day

[Dunkster]

The C9.25 seems to strike a chord with owners, but here's some maths....

C8 provides approximately 1.9x the light collecting area of a C6 for an extra 25% weight

C9.25 provides approximately 1.3x the light collecting area of a C8 for an extra 60% weight

C11 provides approximately 1.4x the light collecting area of a C9.25 for an extra 32% weight

C11 provides approximately 1.9x the light collecting area of a C8 for an extra 110% weight

This takes into account (also approximately) the area of the secondary obstruction of each. Based on this, I ended up with a C8 because of it's grab-and-go "sweet spot" (read: SE alt/az mount) and a C11 for extended reach. The C8 packs a punch!

However, it should be noted that the focal ratio of the mirrors in the C9.25 are different which apparently makes collimating it easier. My SCTs seem to star test OK, so I've not bothered to collimate them so far.

[rowan46]

so unless you are an expert go for the SCT?

Basically yes it does after all have an inch of apparture over the skymax

[gcraib]

The C9.25 seems to strike a chord with owners, but here's some maths....

Now we are talking!

Can't beat a bit of mathematical analysis.

So the C8 gives a bit more for not so much, I was thinking about a C8 before. 9.25 is a fair size like but imagine the POWER!

Not sure if I get another scope I would want it to be another catadioptric though, was thinking 6" refractor. I suppose you can always use a focal reducer on SCT.

[gcraib]

Basically yes it does after all have an inch of apparture over the skymax

you mean the 9.25? or does the C8 have an inch over the SW180? (how?)

[rowan46]

you mean the 9.25? or does the C8 have an inch over the SW180? (how?)

the c8 is 8" that is aprox 200mm the skymax is 180 which works out at about 7"

[E621Keith]

I have the 150 and C6. I agree the Skymax takes longer to cool but it holds collimation better than the C6. Not that C6 was bad, in fact the C6 keeps it collimation quite well, but the Skymax is perfect out of the box and doesn't really need tweaking. If you keep the scope in non heated area and primary interest is planets than I'd pick the Skymax 150 over the C6.

C8 is 1 inch larger than 180 because C8 is 203mm while 180 is roughly 7 inches.

[gcraib]

Ah yes, general maths fail. How on earth could I have been thinking SW180 was 8", which is obviously 200mm!!!!!

So C8 is bigger but cools faster - interesting.

[nightfisher]

The C8 cools faster due to having a much thinner corrector, but it is said a maksutov has better contrast