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Will a Celestron C6-A-XTL Support a 2 inch Diagonal?

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#1 JMW

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Posted 09 January 2020 - 01:57 PM

I was trying to figure out if a 6 inch SCT has a visual back big enough for a 2 inch diagonal.

Just considering ideas for a short travel scope.



#2 junomike

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Posted 09 January 2020 - 02:11 PM

It will support a 2" via the SCT-threads on the rear of the OTA.

An SCT VB or SCT Diagonal will be required.

Also, what's the reason for wanting a 2" Diagonal (curious)



#3 Astro-Master

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Posted 09 January 2020 - 02:18 PM

If you do decide to use a 2" diagonal I'd get the Baader 2" click-lock visual back, rather than the screw on visual back.   That way a regular star diagonal will work instead of a SCT screw on diagonal.


Edited by Astro-Master, 09 January 2020 - 02:22 PM.


#4 andycknight

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Posted 09 January 2020 - 02:19 PM

I don't have a C6, but I do have a C90, C5, and C8.

 

All 3 will work and focus at infinity with my SCT Threaded Celestron 2" diagonal and eyepieces. However many eyepieces will vignette not showing the very edge of the FOV especially on the smaller scopes. (Note the C90 required a £10 SCT adapter ring).

 

The second problem is balance. It is surprising how much a 2" diagonal and eyepiece will unbalance a scope. This is fine if you have the ability to fully adjust the balance bar (like on my C8). But the C5 and C90 only have short dovetails. So they either require weights fitted on the front or upgrading with a longer dovetail.

 

Regards

 

Andy.


Edited by andycknight, 09 January 2020 - 02:20 PM.


#5 JMW

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Posted 09 January 2020 - 02:20 PM

My eyepiece collection  is almost all 2 inch. 

 

 

[Edit}

Actually I do have a set of 1.25 inch eyepeice pairs for my Lunt 100mm binoculars in my 2nd eyepiece case that I wasn't thinking about when I asked the question:

 

     Panoptic 24mm, ES 20mm and 16mm 68 degree, Nagler 13T6, 9T6 and 5T6.

 

I own the C11 EdgeHD but I was looking for something more compact to take on a plane. I was thinking about flying with my SVR90T which size is perfect for carry-on. I thought the C6 would be another option.

 

I need to read more about the C6 and see what works well with it. I think the diameter of the C8 would be too much to fit on a carry-on.


Edited by JMW, 09 January 2020 - 02:36 PM.


#6 aa6ww

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Posted 09 January 2020 - 02:24 PM

I have a C6 and it will take a 2" diagonal just fine. I tried that on my scope but didn't like it. There was too much going on, in the back of my scope to make it practical. Awkward balance issues, too much eyepiece for the size of the back of the scope. The views were nice, I never noticed vegetating but I knew on the lower FL eyepieces it was there..
My scope seems to be much happier using a 1.25" with quality 1.25" eyepieces. The scope seems perfectly balanced, visually and mechanically, just using the 1.25" 68 deg and 82 deg eyepieces.

Its nice that you can use both, just in case.

...Ralph
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#7 SeattleScott

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Posted 09 January 2020 - 09:41 PM

A focal reducer could give you the FOV you seek without a heavy diagonal and eyepiece.

Scott
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#8 MrRoberts

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Posted 10 January 2020 - 10:02 AM

For my C-6 I added the Baader CL/SC adaptor and their 1.25" prism diaganol, along with a C- .63 FR.

When mated with my 13 Ethos or MOD 3 NV ep's the views are nothing short of stunning.

I did not find any appreciable gain in using 2" ep's in this scope.

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#9 mclewis1

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Posted 10 January 2020 - 11:32 AM

My eyepiece collection  is almost all 2 inch. 

 

[Edit}

Actually I do have a set of 1.25 inch eyepeice pairs for my Lunt 100mm binoculars in my 2nd eyepiece case that I wasn't thinking about when I asked the question:

 

     Panoptic 24mm, ES 20mm and 16mm 68 degree, Nagler 13T6, 9T6 and 5T6.

 

I own the C11 EdgeHD but I was looking for something more compact to take on a plane. I was thinking about flying with my SVR90T which size is perfect for carry-on. I thought the C6 would be another option.

 

I need to read more about the C6 and see what works well with it. I think the diameter of the C8 would be too much to fit on a carry-on.

Jeff,

 

I'd suggest sticking with the 1.25" gear for travel, it really makes things easier. I'd take the Pan 24, the 13 and 9mm T6 (and maybe the 5 if the destination has good stable skies and the planets will be visible). Add an SCT f6.3 reducer with the 24mm Pan for the widest fov. Beyond the fov offered by the 24/reducer or similar combos I find vignetting starts to become noticeable. The 13mm T6 is my all time favourite eyepiece in my C6 (and other scopes for that matter).

 

The C6 is just barely airline travel "legal". It's smallest dimension the ~7" diameter ota with a minimal soft case will just pass if checked with the fit tool (smallest dimension of 9"). Most airlines will allow you a little more wiggle room but a C8 with a case is often a favour too far for some airlines (especially if you end up on a regional type of aircraft with smaller bins). Make sure that your cap on the corrector end fits nice and tight (so it can't easily to be displaced) as this is your primary protection for the corrector from any pressure on the secondary mirror holder.

 

When I travel with my C6 I go with a 32mm Plossl, focal reducer, and 13 and 7mm T6s. This seems to cover all my needs for larger objects down to planetary viewing. The eyepieces with a diagonal all fit into a small bag that I can tuck in just about anywhere in my luggage (checked or onboard) and not have to worry about the additional size and weight.


Edited by mclewis1, 10 January 2020 - 11:33 AM.


#10 JMW

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Posted 10 January 2020 - 01:50 PM

I have a Stellarvue case that is sized correctly for airline travel. I believe it will handle the 7 inch diameter tube. It came with my SVR90T.  I could probably fit the SVR90T on one side and the C6 on the other if I wasn't worried about weight. My wife would have to carry the FTQ mount, eyepieces and diagonals and Nexus DSC. The Gitzo 5541LS tripod would go in a checked bag. We are going to condo in Maui for 14 nights later this spring and am considering my options for flying with astronomy gear.

 

I know the aperture of the C6 will beat the SVR90T. But the wide fields of the SVR90T are fantastic and it will do well at 180 or 252 power with my Nagler 3.5 and 2.5mm T6. Seeing could possibly be great but my biggest goal will be southern objects not available from the latitude of my home in Reno.


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#11 Ihtegla Sar

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Posted 11 January 2020 - 04:42 AM

I have been considering the C6 for air travel as well. To Hawaii, coincidentally. From my research its the largest aperture that will legally fit in a carry on. I will probably just use 1.25 eyepieces and my focal reducer that I got with my C8. My favorite 2" eyepieces (the ES92s) are as big and heavy as the C6. Well, not really, but almost. So the 1.25" eyepieces would be a lot more convenient than lugging along a big 2" diagonal and eyepieces.

#12 mclewis1

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Posted 11 January 2020 - 09:31 AM

Jeff,

 

Thinking specifically about a Hawaii trip this spring and given that the planets won't be up until well after midnight and won't get very high even by sunrise I initially thought you should go for the wider field refractor. But with the deep sky stuff in Lupus and Centaurus it might make more sense to go with more aperture and spend some time with the globulars and irregular galaxies that cover the area. This all assumes you can work from good dark skies (so not downtown Kikei or Kahaluhi lol.gif ), have really good southern horizons, and be able to comfortably work between midnight and 3am. Will you be able to travel "up country" (up Haleakala for example)? If so that would really take care of the horizon and dark skies part ... just dress warmly.

 

I might also bring a pair of reasonably sized binoculars for the Crux area.

 

If your wife is carrying the mount plus eyepieces and such for the sake of marital harmony I'd definitely go with the 1.25" stuff ... lol.gif



#13 andycknight

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Posted 11 January 2020 - 12:04 PM

Ihtegla Sar, on 11 Jan 2020 - 09:42 AM, said:

[snip...] So the 1.25" eyepieces would be a lot more convenient than lugging along a big 2" diagonal and eyepieces.

Fellow amateurs have often laughed at me for still using 0.965" eyepieces. But one of the reasons I like them is because you can fit a diagonal and several eyepieces into a very small space (The only problem is that the decent ones are only available on the second hand market and therefore it can take a while to obtain a reasonable set of focal lengths).

 

So if I am using either my C5 (or C90) on vacation, I often carry a set of 0.965" eyepieces. If I want to also have a wider FOV, then I'' take a 1.25" diagonal (the .965 adapter fits inside) and just one low power 1.25" eyepiece. (Another good option is the f6.3 reducer corrector to expand the FOV)

 

For the OP:

 

While not obviously quite as good as the C6... Perhaps you should also consider a Celestron C5. It is both of smaller diameter and shorter length than the C6 and is therefore a better fit for carry-on luggage, since it allows a little more padding around the tube.

 

My C90 goes much further in that I can fit the tube, a [camera] tripod and accessories into a small backpack. This makes it very portable and great for travel. However (obviously) its main limitation is the 90mm aperture.

 

Regards

 

Andy.


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#14 JMW

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Posted 11 January 2020 - 04:12 PM

I dug up an old thread on a C6 being used on the FTQ mount. Looks like it is a good match. I piled 7 inches of books in my Stellarvue case that I use for the SVR90T refractor. The case closes without issues. I don't have enough room for the SVR90T and C6 in the same case.

 

The question I will have to ask myself is will I want to use the C6 when not flying. I have an 8 inch f/6 newtonian on a quality Dob mount and we that and a TEC 140 on a DM6 on trips with our travel trailer. The SVR90T is for when we want to go wide field and for very easy grab and go. I already have a C11 EdgeHD for visual or imaging at f/10, f/7 or f2.

 

The other piece in the mix is I will be able see dimmer objects using my SVR90T paired my PVS14 night vision gear afocal using my 2 inch eyepieces. I don't think the C6 is up to handling the heavy weight compared to the 2.5 inch focuser on my SVR90T.

 

Planetary won't be my main focus in Hawaii since I can do that at any latitude. Of course the seeing may temp me to give the planets a look.


Edited by JMW, 11 January 2020 - 04:15 PM.



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