Jump to content

Narrowband

2 inch diagonal, should I shouldn't I?


Recommended Posts

Hi I've commented on this a few times before in other posts but I've decide to make my own.

Ive read countless reviews on the subject of upgrading to a 2 inch diagonal on a C6 is it worth it do you see enough of a fov increase to make it worth it?

So before I make this purchase I would like to here everyone's opinion on this and personal experience.

I currently own a Celestron Nexstar 6SE and after acquiring a Ethos 13mm i feel the stock diagonal isn't sturdy enough it does the job but if I'm going to upgrade I mite as well have all basis covered.

Heres one I've seen which I think should fit directly into my 6se again opinions welcome -

http://www.rothervalleyoptics.co.uk/altair-astro-lightwave-2-dielectric-diagonal-sct-fit.html

Richard

 

 

Link to comment
Share on other sites

  • Replies 59
  • Created
  • Last Reply

Looks like the right one for your scope, looks a nice bit of kit and a sensible price for a 2" Dialectric, i would do a little reading up on using 2" EP`s in the C6, not sure if they might vignette  on some focal length`s

Link to comment
Share on other sites

I think it's only worth getting a 2" diagonal if you're going to use 2" eyepieces. I got a Quartz coated 2" diagonal and honestly I do not see any difference when using my 1.25" EPs compared to the standard celestron one. 

That said, that using the 2" diagonal with 2" EPs like my 17mm ethos or 31mm nagler, the views are a little bit brighter than on the 1.25" diagonal through a 2"-1.25" adapter, but not any more FOV... The onr thing I do like about the 2" diagonal is the fact that my one screws directly onto the back of my 8SE and so there no chance of the ep & diagonal slipping out... it can only rotate on its axis and ep fall out if not tightened... and believe me, with those EPs, I make sure they are tightened in place. :-D

 

 

Link to comment
Share on other sites

34 minutes ago, nightfisher said:

Looks like the right one for your scope, looks a nice bit of kit and a sensible price for a 2" Dialectric, i would do a little reading up on using 2" EP`s in the C6, not sure if they might vignette  on some focal length`s

I have heard there are some vignette on some of the lower focal lengths ie 28-32-40 but anything below is minimal enough and of course depends on how much you can tolerate.

My 6se does have a field stop around the 24mm 68 degree mark or a 32mm plossl.

So any 2 inch eps above the 24mm is a bad idea but below that I don't believe I should have a problem?

Richard

Link to comment
Share on other sites

57 minutes ago, MarsG76 said:

I think it's only worth getting a 2" diagonal if you're going to use 2" eyepieces. I got a Quartz coated 2" diagonal and honestly I do not see any difference when using my 1.25" EPs compared to the standard celestron one. 

That said, that using the 2" diagonal with 2" EPs like my 17mm ethos or 31mm nagler, the views are a little bit brighter than on the 1.25" diagonal through a 2"-1.25" adapter, but not any more FOV... The onr thing I do like about the 2" diagonal is the fact that my one screws directly onto the back of my 8SE and so there no chance of the ep & diagonal slipping out... it can only rotate on its axis and ep fall out if not tightened... and believe me, with those EPs, I make sure they are tightened in place. :-D

 

 

I think the one I've selected above should screw in directly to my scope as well.

I would be limited FOV wise but for me if there's a brighter image then that sounds great ? 

Ensuring my eps are save and secure is a biggie for me and considering I plan on purchasing a couple more ethos it just seems like the logical step.

Richard

Link to comment
Share on other sites

Are you missing anything with a 1.25" that you do not or cannot see now, but know or think you will be see with a 2".

Using Jupiter it is the same in a 15mm ES82, a 15mm 2" and a 15mm Ortho. All with different supposid fields of views. In effect is a 2" going to actually deliver any more.

One other thing is go look at a 2" eyepiece. I have one @20mm, it is big about 1/3 the size of a 6SE OTA. Showed it to a friend one day who had asked about 2" eyepieces, he could not believe it. The 2" box is next to the TV plossl's (all boxed) and I could easily fit 4 TV plossl boxes in the 2" eyepiece box and they would still rattle around. The simple comparision is a coke can, a 2" eyepiece is about the same size, just heavier (all that glass).

Link to comment
Share on other sites

From some of the reviews and comments I've read apparently they can yield a brighter image in a C6 as long as I don't push the magnification to low coupled with the apparent FOV this does check out on a few equations and sites I've tried to figure this out on.

It does seem like a hit and miss thing some people swear by it others say it's to much trouble for how much optically you gain?

Surely a brighter image and a slightly more apparent FOV can't be a bad thing coupled with I can use the same diagonal for 1.25" and 2" eps gives some flexibility there?

Richard

Link to comment
Share on other sites

34 minutes ago, John said:

I think a 2" diagonal is a sensible move if only to provide a more secure base for the 13mm Ethos. I'm not sure the views will be improved but your peace of mind might be :icon_biggrin:

Thank you John I appreciate your vote of support ?

The diagonal I've chosen will fit straight into my 6se won't it I won't need anything extra to secure it?

Richard

Link to comment
Share on other sites

9 hours ago, Richard Hather said:

Hi I've commented on this a few times before in other posts but I've decide to make my own.

Ive read countless reviews on the subject of upgrading to a 2 inch diagonal on a C6 is it worth it do you see enough of a fov increase to make it worth it?

So before I make this purchase I would like to here everyone's opinion on this and personal experience.

I currently own a Celestron Nexstar 6SE and after acquiring a Ethos 13mm i feel the stock diagonal isn't sturdy enough it does the job but if I'm going to upgrade I mite as well have all basis covered.

Heres one I've seen which I think should fit directly into my 6se again opinions welcome -

http://www.rothervalleyoptics.co.uk/altair-astro-lightwave-2-dielectric-diagonal-sct-fit.html

Richard

 

 

I don't think 2" diagonal itself will introduce any vignetting, your main concern with a 2" diagonal in a 6SE should be if the diagonal clear the mount base when the scope is pointing near zenith.

The picture in your link is kind of puzzling, a 2" diagonal with SCT fit should like the stock 1.25" focuser, i.e. with female SC thread directly mounted on C6's rear port, like this one

http://www.teleskop-express.de/shop/product_info.php/info/p87_TS-Optics-SC-thread-2--Star-Diagonal---99--Quartz---Compression-Ring.html

Link to comment
Share on other sites

Because of the longer optical path in a 2" diagonal, you'll have to shift your mirror forward to reach focus.  As such, you'll introduce a bit of spherical aberration into the system since the 6SE was probably optimized with a 1.25" diagonal's light path in mind.  You'd probably be hard pressed to detect the additional SA visually.  If you want to use large, premium eyepieces like the 27mm+ Panoptics or ES-68 eyepieces, 17mm+ Naglers or Ethos, all ES-92, ES-100, or ES-120 eyepieces, etc., you'll need a 2" diagonal.

As far as vignetting, the human eye is very forgiving as long as the view doesn't trail off to completely black at the edge.

Link to comment
Share on other sites

I think if I were to recommend/suggest any type of up grade in a diagonal it would be to try a prism, not just any prism but a Baader Zeiss.

After reading an article found when simply Googling telescope diagonals, best diagonals, prism vs mirror diagonal.

Read this one in paticular.

https://www.cloudynights.com/articles/cat/articles/mirror-vs-dielectric-vs-prism-diagonal-comparison-r2877

My Zeiss just arrived and no you will not gain any light, nor a brighter image with a 2" anything on an SE6.

Link to comment
Share on other sites

7 hours ago, YKSE said:

I don't think 2" diagonal itself will introduce any vignetting, your main concern with a 2" diagonal in a 6SE should be if the diagonal clear the mount base when the scope is pointing near zenith.

The picture in your link is kind of puzzling, a 2" diagonal with SCT fit should like the stock 1.25" focuser, i.e. with female SC thread directly mounted on C6's rear port, like this one

http://www.teleskop-express.de/shop/product_info.php/info/p87_TS-Optics-SC-thread-2--Star-Diagonal---99--Quartz---Compression-Ring.html

This is what I dont understand about this product it clearly states being a SCT diagonal but the pics don't add up I've messaged the supplier so we will see what they say?

Concerning clearance of the mount I guess I will find out when I purchase the item but it should do the length of the scope is a lot less then a 8se and plenty of people use 2" diagonals on those so we shall see.

Richard

Link to comment
Share on other sites

7 hours ago, Louis D said:

Because of the longer optical path in a 2" diagonal, you'll have to shift your mirror forward to reach focus.  As such, you'll introduce a bit of spherical aberration into the system since the 6SE was probably optimized with a 1.25" diagonal's light path in mind.  You'd probably be hard pressed to detect the additional SA visually.  If you want to use large, premium eyepieces like the 27mm+ Panoptics or ES-68 eyepieces, 17mm+ Naglers or Ethos, all ES-92, ES-100, or ES-120 eyepieces, etc., you'll need a 2" diagonal.

As far as vignetting, the human eye is very forgiving as long as the view doesn't trail off to completely black at the edge.

All makes perfect sense Lois apart from shifting the mirror forward which I understand but isn't something I've ever heard of anyone doing and isn't something I really want to do?

Richard

Link to comment
Share on other sites

38 minutes ago, Richard Hather said:

This is what I dont understand about this product it clearly states being a SCT diagonal but the pics don't add up I've messaged the supplier so we will see what they say?

Concerning clearance of the mount I guess I will find out when I purchase the item but it should do the length of the scope is a lot less then a 8se and plenty of people use 2" diagonals on those so we shall see.

Richard

I've just looked properly and I reckon the 2 gaps are designed to screw into 2 different size SCT visual backs eliminating the use of a female thread or maybe I'm missing something?

Richard

IMG_5762.PNG

Link to comment
Share on other sites

1 hour ago, Richard Hather said:

All makes perfect sense Lois apart from shifting the mirror forward which I understand but isn't something I've ever heard of anyone doing and isn't something I really want to do?

Richard

@Louis D was probably referring to the fact you'll have to crank the mirror forwards from where it would focus with a 1.25" diagonal using the focus knob !! Thereby introducing the possibility of some SA. I doubt he was suggesting you need to get the tools out...

I use a Baader Clicklock 2" and a 1.25" WO Durabright in our 8" EdgeHD from time to time. But the EdgeHD optics mean we don't suffer the risk of a little SA a 6SE might encounter with a 2" with the mirror cranked forwards...

Link to comment
Share on other sites

10 minutes ago, Racey said:

@Louis D was probably referring to the fact you'll have to crank the mirror forwards from where it would focus with a 1.25" diagonal using the focus knob !! Thereby introducing the possibility of some SA. I doubt he was suggesting you need to get the tools out...

I use a Baader Clicklock 2" and a 1.25" WO Durabright in our 8" EdgeHD from time to time. But the EdgeHD optics mean we don't suffer the risk of a little SA a 6SE might encounter with a 2" with the mirror cranked forwards...

Thank god for that i was starting to think this mite be more trouble then it's worth all I want is a couple of eps to full appreciate the 100 degree spacewalk feeling and a small collection of 1.25 eps for the gaps but I am aware that the 24mm 68 degree is the widest at lower powers I can go which I think the 20mm/21mm 100 degree eps should be ok any lower and I will have problems?

Richard

Link to comment
Share on other sites

18 minutes ago, Richard Hather said:

Thank god for that i was starting to think this mite be more trouble then it's worth all I want is a couple of eps to full appreciate the 100 degree spacewalk feeling and a small collection of 1.25 eps for the gaps but I am aware that the 24mm 68 degree is the widest at lower powers I can go which I think the 20mm/21mm 100 degree eps should be ok any lower and I will have problems?

Richard

I would have thought the mirror would need to move back a bit as the EP will be further back

Link to comment
Share on other sites

2 minutes ago, nightfisher said:

I would have thought the mirror would need to move back a bit as the EP will be further back

'Tother way I should think Jules, the 2" diagonal will have a longer light path so moving the mirror forward will shorten it up to compensate.

In terms of eyepieces, I used a 30mm 82 degree quite happily in my OMC140 (5.5" Mak), and even a 40mm 68 degree with a small amount of vignetting.

Link to comment
Share on other sites

5 minutes ago, Stu said:

'Tother way I should think Jules, the 2" diagonal will have a longer light path so moving the mirror forward will shorten it up to compensate.

In terms of eyepieces, I used a 30mm 82 degree quite happily in my OMC140 (5.5" Mak), and even a 40mm 68 degree with a small amount of vignetting.

Excellent stu I've read some good/bad experiences, maybe this is something I have to try and win or lose at least I know if it doesn't work.

So the SCT diagaonal above stu what's your opinion on it will it screw right into my SCT? Or do I need another adapter?

Richard 

Link to comment
Share on other sites

2 minutes ago, Stu said:

'Tother way I should think Jules, the 2" diagonal will have a longer light path so moving the mirror forward will shorten it up to compensate.

In terms of eyepieces, I used a 30mm 82 degree quite happily in my OMC140 (5.5" Mak), and even a 40mm 68 degree with a small amount of vignetting.

Yep, you can tell i have just woken up from a nap, i was just thinking in the simple (as always) sense that with the occular being moved back on the scope the mirror might need to follow it

The OMC 140 can be a cracking scope, just a shame the native focal length is so long, had they made these at 1500mm F/L it would have been a tad better 

Link to comment
Share on other sites

I too used an OMC-140 with a 2" back. The 42mm LVW I have did vignette; the baffle tube size of the OMC-140 is 32mm so not really suitable for that eyepiece.

The baffle tube size on the C6 is 27mm. This means a 2" eyepiece with a field stop larger than 27mm would be unusable due to vignetting. I would say therefore a 2" diagonal and eyepieces would be wasting money.

Link to comment
Share on other sites

2 minutes ago, Mr Spock said:

The baffle tube size on the C6 is 27mm. This means a 2" eyepiece with a field stop larger than 27mm would be unusable due to vignetting. I would say therefore a 2" diagonal and eyepieces would be wasting money.

I've found that you can exceed the baffle tube size in terms of eyepiece size without vignetting becoming immediately obvious. Eyes are not that sensitive to it (unlike cameras) so you can bend the rules to some extent.

I forget the exact number, but the 30mm 82 degree ES field stop will be in the order of 40mm and it did not show noticeable vignetting. With the 40mm TMB it was there but not horrible.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.