Celestron C6-S GT XLT

[GuillermoBarrancos]

Well,

I finally did it and ordered the Celestron C6-S GT XLT.

Got a really good deal with a Swedish store (as astronomy equipment is way overpriced here in Norway).

So I could order from them 40% cheaper and they remove the 20% VAT to compensate for the 25% Customs tol fee.

With some future accessoires I should be able to turn this nice scope into a decent Astro imaging platform.

Guillermo

[russ]

Well done on your new purchase…..it's a great scope, you'll be very pleased. And sounds like you got a good deal too.

[GuillermoBarrancos]

Yes I ordered the Celestron C6-S GT XLT, extra plosl 6mm eyepiece (next to the standard 22mm), T-ring for Canon and Red Dot Finder for less than 8000 NOK, incl shipping.

Ofcourse I will have to pay 2000 NOK to customs. But it's still a lot cheaper than the 14.000 NOK they are charging here in Norway (without the 3 extra accessoiries).

How is colimnation on these C6's by the way?

[russ]

Mine needed a small tweak on arrival. But held it's collimation very well there after. SCT collimation is very easy to do, much easier than Newtonian collimation. You can replace the collimation screws with Bob's Knobs to make it easier still.

[GuillermoBarrancos]

I forgot to order a colimnation tool.

Are there other ways to do collimation, or are you forced to use the special tool/laser to do it properly?

[russ]

hehe that's the beauty of SCT collimation........no tools needed

Here's a link to an excellent guide:

http://legault.perso.sfr.fr/collim.html

And check the diagram in this article, it's really helpful for knowing which screw to turn and which way:

http://home.comcast.net/~astrophoto/Articles/Collimation.htm

[GuillermoBarrancos]

Excellent thanks! That should be a piece of cake.

[russ]

[GuillermoBarrancos]

Another question. The C6 can handle 2" eyepieces as well right? With an adapter ring?

As for future proofing, later buying expensive eye pieces and filters, I think it's wiser to buy 2" ones. So you can use them on more scopes in the future.

And oh... Is there no focal reducer for the C6 ??

The official Celestron F-reducer seems to be for all their CST's, except the C6!

[russ]

There's a small problem with the C6. It does have a standard SCT thread at the rear, so will take a 2" visual back no problems and also accept the Celestron f6.3 reducer. But the rear opening is stopped down to 1.5", so a widefield 2" eyepiece will just vignette. And this is probably why Celestron don't list the C6 as a compatible tube for the reducer.

It's something i found out the hard way myself when the scope arrived, i had grand plans for the C6 and this scuppered them to a certain extent.

[GuillermoBarrancos]

EDIT:

The vignetting will only be a problem with wide field 2" eyepiece for viewing right? What amount of mm 2" eyepiece will vignetting become visible?

But I see that the 1.25" eyepieces go up to 40mm these days? Should be enough for quite a wide field isn't?

The Focal reducer works fine then? Without problems for photography. Or will it cause vignetting problems there too then?

I saw there are some third party f6,3 reducers with flattening available for SCT's?

[russ]

I think it depends what you want to do with the scope. The Celestron reducer still works fine and a smaller sensor camera won't have an issue either. I did find my Moonfish 30mm Ultrawide vignetted horribly, so that was probably the point where the reduced opening played its part. But the 26mm 70deg was fine. Which maybe all you need.

A 1.25" 40mm Plossl will give a true FOV of 1.14deg but a 26mm 2" 70deg will give a true FOV of 1.23deg. So still worth going the 2" route.

It's a mighty good scope, really is. Although at the time I decided to swap my C6 for an ED100. For me personally it was a great move as i found the ED100 performed just as well on all targets as the C6 but had no real limitations. I used the 0.63 reducer i bought for the C6 on the ED100 to bring it's FR down from f9 to f5.7.

[GuillermoBarrancos]

I think it depends what you want to do with the scope. The Celestron reducer still works fine and a smaller sensor camera won't have an issue either. I did find my Moonfish 30mm Ultrawide vignetted horribly, so that was probably the point where the reduced opening played its part. But the 26mm 70deg was fine. Which maybe all you need.

A 1.25" 40mm Plossl will give a true FOV of 1.14deg but a 26mm 2" 70deg will give a true FOV of 1.23deg. So still worth going the 2" route.

It's a mighty good scope, really is. Although at the time I decided to swap my C6 for an ED100. For me personally it was a great move as i found the ED100 performed just as well on all targets as the C6 but had no real limitations. I used the 0.63 reducer i bought for the C6 on the ED100 to bring it's FR down from f9 to f5.7.

Ok. That's not so bad and to workaround with I guess.

So with my Canon 400D I will get vignetting (even without the reducer?).

But if I later install a CCD camera. I won't have any vignetting issues at all anymore?

[russ]

I'm trying to rack my brain as to whether i got vignetting with the 300D at prime focus? But really can't remember for sure.....sorry!

[GuillermoBarrancos]

I just talked with the guy from the store.

The 1.5inch (3,75cm) opening in the back. As long as the camera sensor size is within the barrel opening size it won't cause vignetting.

I just checked and the sensor size of the Canon 400D is 2,22cm by 1,48cm.

So it should be ok then.

He said that the large sensor cameras will have problems with vignetting as their sensor size is larger than the barrel opening of 1.5inch.

And if I buy a standard CCD camera later on. Those sensors are even smaller.

I guess we will see how it goes.

[GuillermoBarrancos]

Oh and before I forget. Are there special filter adapters I can place between the T-ring and the scope tube thread?

As with the Canon T-ring I can directly connect my Canon 400D body to the back of the scope (directly on the thread).

But it started me thinking how to use filters in such a setup.

[russ]

I bought a 2" visual back for the scope and a 2" nosepiece for the T-ring. The filters just screwed into the 2" nosepiece. Or you could just buy a CLS clip-on filter for the Canon, which fits directly into the camera. But personally i would add the 2" visual back so you can open up the max aperture on the scope.

[GuillermoBarrancos]

I saw some filter adapters and was indeed wondering if they would be screwed just in between. But I guess that's indeed so.

What I also wondered. With the camera directly mounted against the back of the scope.

You are basically always imaging with a standard magnification of the telescope F-length ?

What would the standard magnification be when imaging then? As eyepieces are not used.

I always wondered how those calculations are done with imaging.

And what you do if you want to magnify an object for imaging? Guess it will change your camera setup significantly, with all kinds of issues that come with it?

[GuillermoBarrancos]

Bahhh.... I went for the C8 instead.

It's much more future proof. And the hole is 2inch. So I can go for higher field of view. Including Focal reducer/flattener.

He had a very very good deal on the C8.

Just have to wait with my accessories till next month hehe.

But I think that's more than worth it. The C8 seems to have gotten really good reviews for both Viewing as being a very good imaging platform.

[GSTEVENS]

I went to buy the C6-SGT XLT today, but the sales guy talked me out of it. Tried to sell me the C8, I know bigger is better when it comes to scopes but the price is 50% more. I thought the C6 was a good value for the money and the mount is excellent. Now I'll just have to think about it some more.

Enjoy your C8, let me know how you like it and what eye pieces and other accessories you get.

G.