1.25" vs 2"

[ChrisEdu]

The C11 comes with a 1.25" visual back and EP. However, the C14 has a 2" set-up. I have seen that a 2" set-up can be used on the C11, so, the question is, is it worth it? Does a 2" EP / visual back set-up provide a significant gain / advantage over a 1.25"?

[riklaunim]

C11 has actually a ~3" SCT thread (+ the standard ~2" SCT thread reduction). 2" EP can give you widest fields (for example Erfle eyepieces - WO SWAN and their cheap clones). If you want to use the f/6.3 reducer then the 1,25" eyepieces may suffice.

[ChrisEdu]

So, what would use the ~3" thread?

In terms of the FOV, does this mean that, for example, 68 degrees on a 2" appears as more than on a 1.25"?

[riklaunim]

1,25" maximum is around 20 mm at 70 deg FOV, while 2" may have that 70 deg FOV even at around 38-40mm (Erfle/SWAN) or 50mm 51 deg GSO SuperView Erfle

[ChrisEdu]

1,25" maximum is around 20 mm at 70 deg FOV, while 2" may have that 70 deg FOV even at around 38-40mm (Erfle/SWAN) or 50mm 51 deg GSO SuperView Erfle

So, ultimately, given any FOV, like for like, the 2" will appear bigger? (not sure if I have phrased that particularly well). By bigger, I don't mean that the object appears bigger, rather the 'view' in the eyepiece appears larger in size.

[riklaunim]

The magnification will be smaller (like 38mm vs 20 mm EP), but you will also see more sky. The 2" allows you to see more sky at even lower magnifications than 1,25" would allow. For eyepieces at short focal length 1,25 vs 2" doesn't means much.

[ChrisEdu]

So, the most benefit is at lengths like 25mm+?

[riklaunim]

For C11 if you want decent-big FOV for "big" DS objects you will probably need those 2" EP or f/6.3 reducer for 1,25". I'm using only 20 mm 1,25", but with reducers (now with the 0,5x Optec NextGen reducer - before imaging the object).

[m.tweedy]

Go for the 2 inch diagonal. You can always put 1.25" eyepieces in it but not the other way round. I often use my 50mm 2" celestron eyepiece and it gives lovely views. Of course now I have the ethos's I need the 2" diagonal.

Remember in a previous thread I mentioned this

First Light Optics - MoonLite CS Dual Rate SCT Crayford Focuser for large 3.25 inch thread for a totally unrestricted view with a 2 inch diagonal

[John]

I think a 2" diagonal would make a lot of sense in a C11. The standard 1.25" diagonal is rather cheap and cheerful as you have found so you will want to upgrade that soon and you might as well go for a 2" one.

The wider field of view is the benefit that the 2" format brings - the 1.25" eyepieces being limited by the internal diameter of their barrels. In one of the the pictures you posted of your new scope showed the standard 40mm 1.25" plossl that came with the scope - that will have a field of view of around 43 degress. A 40mm eyepiece in the 2" format can have a field of view of 72 degrees and so it will show a lot more sky. Translate that into true field of view (how much of the sky you actually see through the scope) and the 40mm 1.25" will give a magnfication of 70x and show .61 degrees of sky wheras the 40mm 2" I mention would also give 70x but show just over 1 degree of sky - nearly 70% more.

Of course you will need to budget for 2" filters when you start to consider those as well

[ChrisEdu]

cool - that's cleared things up for me, thanks.

[AztecastroMcJ]

Think it may be worth adding 2" star diagonal and nice widefield EP at some point,

or like Rik has said u can also use reducer with 1.25" EP.

Personally i would rather have nice widefield scope to complenent C11,

the standard 1.25" 40mm (43AFOV) TFOV is 36.8 arc mins which is around 0.6 degree TFOV

enough to fit Full moon and most objects

if u used say 2" 40mm swan (70AFOV) u could get 60 arc mins which is full degree TFOV

both above would give 70x mag with 4mm Exit Pupil,

for comparison a 2" 31mm Axium/luminos or Tevelue Nag with 82 AFOV would still give TFOV of 54.47 arc mins

but at higher mag of x90 and smaller Exit pupil 3.1mm

u can check true fov's here

http://www.12dstring.me.uk/fov.htm

the 9x50 finderscope has around 5.8 degree fov

James

[ChrisEdu]

Personally i would rather have nice widefield scope to complenent C11,

Shh!!! You never know who might be listening!

I did mention getting another scope when I upgrade the mount - well, if I don't sell the CG5, it would be a shame to leave it empty! I think I got away with it but time will tell!

[m.tweedy]

Personally i would rather have nice widefield scope to complenent C11,

James

A WO Megrez 90 would (does) look good.

You will then be pushing the limit for the mount. The NEQ6 PRO just copes with that load.

[AztecastroMcJ]

Very nice Michael

hopefully have something similar in few years lol

do u have or use fastar btw ? another option for widefield ofcourse

[ChrisEdu]

Nice!

[m.tweedy]

To complicated. Have not yet taken an astro image despite having all the gear (and no idea) yet.my Primary objective is to have the C11 and 90 for contrasting views of the same object. For imaging I have the Astrotrac set up (but again not used yet)-hoping that will change from Saturday as going to Mauritius for 2 weeks. The C11 did not fit into the hand luggage so have packed astrotrac and WO66 instead.

[ChrisEdu]

The C11 did not fit into the hand luggage so have packed astrotrac and WO66 instead.

You need to buy the lady in your life a larger handbag then!

[m.tweedy]

You need to buy the lady in your life a larger handbag then!

Thought of that. Gillian's hand luggage is full with my eyepieces and camera lenses:D:D

[ChrisEdu]

Thought of that. Gillian's hand luggage is full with my eyepieces and camera lenses:D:D

Then you need a bigger handbag!

[m.tweedy]

Then you need a bigger handbag!

my own plane is the only thing that would hold everything I REALLY want to take with me

[m.tweedy]

Anyway we digress. I strongly recommend an ADM top rail as they are so versatile and can attach virtually anything you want from tube rings as I have my 90 on to camera adaptors .

MDS Camera Mount

a telrad was a must have for me.

[ChrisEdu]

Yeah - trying to get hold of a Telrad is like finding a certain Libyian ex-leader! I have been told they might be available from tomorrow or the start of next week - the Telrad that is!

[ChrisEdu]

Anyway we digress. I strongly recommend an ADM top rail as they are so versatile and can attach virtually anything you want from tube rings as I have my 90 on to camera adaptors .

MDS Camera Mount

Ok - so where do you start with that lot? Which bit is the top rail? Looking on their website I'm not sure which bit is which!

[m.tweedy]

MDS Dovetail Bar