Upgrading from a 1.25" to a 2" diagonal. Any benefits?

[icmoon]

Hi all,

Does anyone know if I would gain anything from using a 2" diagonal in place of the 1.25" that came with the scope and would I still be able to use my 1.25" Hyperions with an adapter? I ask this simply because I've been offered a good 2" diagonal at a very good price. Am I trying to run before I can walk, bearing in mind I have yet to use this scope?

many thanks again

Simon.

Celestron NextStar Evolution 9.25 with Starsense Autoalign and three Hyperions, 13mm 17mm, 21mm. (31mm 2" Hyperion on it's way) 2"star diagnonal, numerous filters

[YKSE]

Yes, you can still use 1.25" Hyperion in 2" diagonal, since most 2" diagonals do come with a 2" to 1.25" reducer.

The biggest gain with 2" diagonal is that you can use 2" eyepiece with 46mm field stop for widest True Field of View (TFOV), such as 42mm Vixen LVW, 41mm Panoptic or 40mm Skywatcher Aero, these low-power eyepieces are very useful in observing extended DSO with filters in your f10 scope.

Hyperions are not small eyepieces, it feels also a little safer in a 2" diagonal than a 1.25" one, the little drawback is the increased light path of 2" diagonal, which makes your scope working more like a f11 than f10.

[glowjet]

If it is a good quality diagonal, for example, Williams diagonals in particular, have a built in stop when using Hyperions in the 2" mode, so the 1.25 nose piece does not reach the mirror, some other diagonals may not have this facility, it is worth checking, as an adapter stop ring for the Hyperions can be obtained from FLO, to stop any damage taking place.  As far as I am aware 2" diagonals with the larger mirror have the advantage, especially when used with 1.25 eye pieces  

[icmoon]

Many thanks for that info guys. Would I also need to get a new visual back?

And John, it was/is a Williams diagonal.

Cheers

Simon.

Celestron NextStar Evolution 9.25 with Starsense Autoalign and three Hyperions, 13mm 17mm, 21mm. (31mm 2" Hyperion on it's way) 2"star diagnonal, numerous filter

[YKSE]

Yes, you need an adapter,  SC thread to 2" for using 2" diagonal in your SCT.

I can warmly recommend Baader's Clicklock SC adapter, not cheap, but very secure and easy to handle, especially in cold weather, or using filters in diagonal.

Since you're going to have the 31mm eyepiece, the nosepiece of the 31mm can be connected to this SC Clicklock, the combination becomes this Clicklock extension , can be very handy should you get a Newt (Dob e.g.).

[Jim78154]

Using the 1 1/4" eyepieces in the 2" diagonal will defeat the purpose of using the 2" diagonal. You will still have the 1 1/4" format field stop in the light train. Also, what focuser are you going to use? A 1 1/4" focuser will do the same thing. Next you will need to change out all of your eyepieces for 2" format and your filters as well. Just as a chain is only as strong as its weakest link a light train is only as wide as its narrowest constriction. Well, that's not actually true because of the conical nature of the segments in the light train, but I'm sure that you get my point.

[John]

Using the 1 1/4" eyepieces in the 2" diagonal will defeat the purpose of using the 2" diagonal. You will still have the 1 1/4" format field stop in the light train. Also, what focuser are you going to use? A 1 1/4" focuser will do the same thing. Next you will need to change out all of your eyepieces for 2" format and your filters as well. Just as a chain is only as strong as its weakest link a light train is only as wide as its narrowest constriction. Well, that's not actually true because of the conical nature of the segments in the light train, but I'm sure that you get my point.

Hi Jim,

The original poster (Simon) has a 2" eyepiece on it's way to him though, according to his signature. The 2" diagonal will be needed to use that eyepiece and will still allow 1.25" eyepieces to be used via the adapter.

He may well need to invest in 2" filters though, if they are to be used with the 2" eyepiece.

[Dave In Vermont]

I will also give a nod to the William Optics 2"/1.25" Diagonals. I have three of them myself - all in use. And I love the 'stop' they have to help prevent an eyepiece striking the mirror. Tough as they are. They are also quite easy to disassemble for cleaning when, and if, they should require cleaning.

I'd also add another adapter to the list for 2" to 1.25" - the Antares Twist-Lock. Considerably less expensive than the Baader offering. Here's one described & imaged:

http://www.scopestuff.com/ss_adp4.htm

Best wishes,

Dave