Another which one?

Zuts · #1 25-03-2007, 09:31 PM

Maybe someone can help me. I want to buy a new scope and basically have narrowed it down to two choices.

Celestron 11 inch, CPC GPS
Meade 12 inch LX90 GPS

If i had the money i would get a meade lx200R or god forbid a rcx400, but these are far too expensive for me. The image quality of the new meade richey chretians sound superb but alas they are way too expensive.

(1) Meade lx90 gps. A full 12 inches but the mount is not really suitable for long exposure photograpy even with a super wedge. It is far lighter than those on the LX200R's. Also the price is around 5600 bucks in Oz.

(2) Celsestron CPC. A decent mount. Top of the range celestron alt az mount and 4999 in oz.

I am thinking of the celeston because it is a bit cheaper and probably more versatile. I am sure the optics in both are superb (at least i hope so). Still the extra aperture of the meade means about 20% more light so it is a hard choice to make.

What do you guys think?

iceman (Mike) · #2 26-03-2007, 06:25 AM

12" SCT is pretty serious.. it's a long focal length meaning wide field views are almost impossible given the f/10 focal ratio.

Is your primary interest in photography or visual?

Does it have to be a fork mount? Does it have to be an SCT?

For pure visual, the fork mounts are great.. easier to setup and align.

Zuts · #3 26-03-2007, 10:10 PM

Quote:

Originally Posted by iceman

12" SCT is pretty serious.. it's a long focal length meaning wide field views are almost impossible given the f/10 focal ratio.

Is your primary interest in photography or visual?

Does it have to be a fork mount? Does it have to be an SCT?

For pure visual, the fork mounts are great.. easier to setup and align.

I have a 12 inch dob, so whatever i buy i would be dissapointed if its light gathering power was not at least around that of my dob. I guess i miss out on good views of open clusters but should still be able to see orion et al in the field of view with my 16mm nagler 3048 / 16 = 190 by and 82 / 190 = .43 degrees. Maybe i would need a lower power nagler?

A good eq6 mount with goto costs a packet and may not be stable with a 12 inch dob. I also like the idea of a sct as far as observing angle is concerned and basically have always wanted a large aperture scope on a driven goto mount. So at the moment fitting a argo navis doesnt cut it as i still have to move the scope and i dont think an eq6 would be very stable with a 12 inch dob, for viewing, maybe photography would be ok..

There is no such thing as a 'last' scope but i am hopefully thinking this will be my last scope and in the future i will want to do photography.

This is why i am thinking of the celestron which has a better mount than the lx90gps. I am assuming it has a better mount and that the eqivalent meade one is the lx200r which is far more expensive.

Do you reckon i would be dissapointed with the 1 inch less aperture, around 19% maybe.

Anyway it is hard to know which one to buy.

Thanks Paul

iceman (Mike) · #4 27-03-2007, 07:09 AM

The 12" dob is great, you'll notice some drop off in light gathering and probably a loss in portability, grab n go etc when you move to a motor driven mount, SCT etc.

Not to mention the wide field, contrasty views offered by a newt.

I can see the desire to get a motor driven mount, but have you considered getting an EQ mount for your dob, if you want tracking? Have you considered getting an Argo Navis for your dob, which in effect gives you goto (except it's push-to)?

Ambermile · #5 27-03-2007, 07:18 AM

I'd go look in the for sale section and home in on that NS11GPS and all those other lovely bits of kit included...

Arthur

Zuts · #6 27-03-2007, 10:42 AM

Quote:

Originally Posted by Ambermile

I'd go look in the for sale section and home in on that NS11GPS and all those other lovely bits of kit included...

Arthur

That looks really nice, but i dont need all the photography stuff just yet. Also I can get a new CPC 11 for 4999 and then maybe look at getting some second hand stuff when i am ready.

Zuts · #7 27-03-2007, 10:51 AM

Quote:

Originally Posted by iceman

The 12" dob is great, you'll notice some drop off in light gathering and probably a loss in portability, grab n go etc when you move to a motor driven mount, SCT etc.

Not to mention the wide field, contrasty views offered by a newt.

I can see the desire to get a motor driven mount, but have you considered getting an EQ mount for your dob, if you want tracking? Have you considered getting an Argo Navis for your dob, which in effect gives you goto (except it's push-to)?

I was sort of asking whether i would notice much difference between the 11 and 12 SCT's.

I did consider an ago narvis but it wont track. I really want to keep something in the FOV and just watch it without having to bump the DOB.

I was considering a celestron advanced so i can get an eq6 mount (clone) and maybe use the mount for a lighter APO as well. But I dont think an eq6 driven mount would be suitable for my big dob for viewing, maybe for photos. A real stable eq mount/goto/driven for a big dob would be around 4000 dollars and that is nearly the price of the SCT after i sell my DOB?

Narrower field of view is a problem with any SCT but if i get a 40 mm widefield or a field reducer will i overcome this problem to some extent?

Can anyone help with my points above and tell me if i am really off the mark.

Thanks Paul

iceman (Mike) · #8 27-03-2007, 11:03 AM

Get an EQ platform, as I mentioned above. It sits BELOW your dob (your dob sits on top of it) and it will give you tracking for up to an hour before needing a reset.

I used one for 18 months, and just sold it to rmcpb. I had my 10" dob on it. Petra (spacezebra) bought one for her 12" lightbridge.

Go to www.roundtableplatforms.com and have a look. They're great, and just what you need to keep the convenience and quick setup of a dob, with the beauty of tracking so you can just sit and look.

Combined with an Argo Navis, it would make your 12" dob complete, so you can spend more time looking at stuff and less time trying to find it.

ving (David) · #9 27-03-2007, 01:50 PM

sounds like these people are trying to turn you off getting a sct hey!

of course there is alot of wisdom in thier words. if you arent taking pic and you have a dob then a platform will track for you... you could consider AN and dobdriver or something like that too... I have seen a couple of 12" newts on eq6 mounts now and it seems quite stable. of course you either have to take a step ladder to stand on or chop the legs tho. in choping the legs tho you reduce the "foot print" and therefore the stability too...

of course you could go teh f10 sct and use a 6.6 reducer... not sure how good these work as i have not used one before

sejanus (Gavin) · #10 27-03-2007, 02:35 PM

Why not get a EQ6 with a C11 OTA?

I had that for a while - I miss it! It was great.

Zuts · #11 27-03-2007, 07:24 PM

Quote:

Originally Posted by sejanus

Why not get a EQ6 with a C11 OTA?

I had that for a while - I miss it! It was great.

I went to andrews today, they had a 9.25 cpc and it looked great and very sturdy. I am thinking i do want an sct!

I was looking at the advanced which is basically an C11 OTA on a cloned? EQ5 mount. Didnt look sturdy for the C11 but fine for the C9.25.

The EQ6 would be great but it and a C11 OTA would be more than the price of a C11 CPC. I guess the benefit of the EQ6 is that i dont have to get a wedge later on, and can mount something else on it. Still the CPC 11 is all ready to go.

I am torn between the extra sturdiness of the CPC C11 v the LX90 GPS 12 inch; and the extra inch of aperture of the meade re the celestron. Will this make a real significant difference does anyone think?

I have been thinking about some of the second hand C11's, LX200's but it always comes back to for the money you are spending how can you be sure the electronics and optics are fine. Usually the price diference is only 1500 bucks (which is a lot of money) and i get worried and think i would be better off getting a new one.

Thanks for everyones help so far.

Zuts · #12 27-03-2007, 07:37 PM

This may be going over the top; and its not really relevant to seeing things but

I am very fond of my 12 inch DOB but it looks like a water heater whereas the C9.25 CPC looked like a finely crafted watch.

Also i like the view through my DOB but

it is an open tube so the mirrors probably have dust, its probably not collimated to 100 % effectiveness, the mirror coating will deteriorate and reflect less light and like most dobs it has no XLT, UHTC coatings so

i am thinking that in general an 11 or 12 inch sct will outperform a 12 inch Bintel/GSO DOB?

iceman (Mike) · #13 27-03-2007, 07:46 PM

No, in fact it's the other way around. The newts have a smaller central obstruction than an equivalent SCT.

You can collimate a dob. You can clean the mirrors. Mirror coatings don't deteriorate for 10's of years if looked after properly.

You really need to get to a star party and look through some SCT's, and compare it to your 12" dob. Have you collimated your dob? Are you happy with the views through it?

Zuts · #14 27-03-2007, 10:28 PM

Yes SCT's have bigger obstructions but most are oversized so you get the full specified surface area, also the coatings help a lot. I have only looked through an eight inch celestron sct; about 10 years ago and was impressed coz at the time i only had a homemade (ground my own mirror) pipe mounted 6 inch newt. The obstruction would tend to make the image softer i guess?

I really should go an look through a big sct before making any purchase but need to find a star party. Maybe someone in sydney has one they set up in their backyard on a good night and could give me a peak

, i have a 11 and 16 mm nagler,5 mm vixen lv and an astronomic UHC filter they could look through.

I think my scope is reasonably collimated, i only do a simple star test and the image looks nice and round with a bright diffraction ring both in and out of focus but i am no expert and have only just returned to the hobby after a long absence.

Do you think i would be dissapointed with the view through an 11 or 12 inch sct in comparison with a dob, given that in general the average eye can only just notice a 10 % difference on bright objects? I mean how bad can an sct be?

iceman (Mike) · #15 27-03-2007, 11:31 PM

I'm not saying SCT's are bad, and I imagine you'd be well pleased with the view through them - just as you should be well pleased with the view through your dob.

I've looked through a number of SCT's over the past few years and I always prefer the view through a newt. Maybe it's just personal preference?

If you really want the convenience of a fork mount for simple tracking and goto, then by all means get an SCT - it will do just what you want.

I'm not trying to talk you out of it, just trying to offer an alternative point of view.

Can you make it out to SPSP in April? There'd be 100 SCT's to look through