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1 1/4" or 2" Star Diagonal upgrade for 8SE?

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#1 dgerow

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Posted 08 April 2012 - 07:33 PM

It seems it is now time to upgrade the Star Diagonal that was supplied with my 8SE. I have begun to upgrade my my EP's so guess I need to decide what size EP's to purchase,1 1/4 or 2". I received my first "better" EP a couple days ago. Couldn't justify spending $360 for Televue so went with a 10mm 68 degree Baader planetarium. WOW, what a difference. I can't believe how nice the wider FOV is. The Baader will fit in either a 1 1/4" or 2" diagonal. So just looking for opinions and guidance from the Experts on what is the best direction to go with the diagonal. I will be staying with the middle price EP's, looking to purchase a 24mm 68 degree Explore Scientific next. Thanks

David.

#2 Maverick199

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Posted 09 April 2012 - 04:30 AM

I had bought a Celestron 2"-1.25" Diagonal which I use at times. Mine needs to be threaded to the rear cell as I use the 2"-1.25" only with Celestron's Focal reducer.

I also bought Astrotech's 1.25" dielectric diagonal which works pretty well with all my eyepieces, including the 8mm Baader Hyperion. In the stock diagonal, this eyepiece could not be seated properly and was loose.

Btw, since you are looking at ES, may as well try out their 82 deg. which are very good.

#3 Midnight Dan

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Posted 09 April 2012 - 06:15 AM

Hi David:

Nearly all 2" diagonals come with a 1.25" to 2" adapter so you can use either size eyepieces in them. When shopping for a diagonal, get one with a dielectric coating. They will have high reflectivity, but more importantly the coating resists scratching so you can clean it with less worry. Also, for the 8SE its best to get an SCT threaded diagonal so it screws directly to the rear cell of the OTA. That way it will be short enough so that it won't hit the base when pointing towards zenith.

-Dan

#4 dgerow

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Posted 09 April 2012 - 07:32 AM

Thanks Guys, So I should upgrade my diagonal? Which would be more advantageous a 1 1/4" or 2" diagonal? By the way I really can justify the Televue EPs, just can't afford them. Thanks again.

#5 Bob Griffiths

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Posted 09 April 2012 - 08:16 AM

I use like using a 2 inch diagonal,,,so I say go for one...

BUT do a little research on this forum about clearance issues with 2 inch diagonals and the base of the scope "some" 2 inch one are too long and may required Eddies or Rons rail solutions...

I own a 8i (earlier model of the 8SE) and with Rays brackets (not an option for your 8SE) have no trouble clearing the base (with room to spare) using my Denkemier S1 2 inch diagonal...

Bob G.

#6 Midnight Dan

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Posted 09 April 2012 - 09:06 AM

If the cost is not a problem, I agree with Bob ... go for it. I just find it to be a much more stable connection to the scope which holds my heavier eyepieces more securely. After using the 2" diagonal for a while, the 1.25" kind of looks wimpy on the 8SE! :grin: I think the 1.25" diagonal is a more appropriate size for the smaller SCTs.

-Dan

#7 Widespread

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Posted 09 April 2012 - 02:36 PM

Much wiser and more experienced folks than I have already spoken, but here's 2 yen from someone who has thus far stuck to 1.25" format on my 8SE.

Like many new 8SE owners, I loved just about everything about my scope except the limited TFOV, which in stock form is only about 0.8 degrees.

So I added a 6.3 focal reducer, which gives me a TFOV of about 1.2 degrees. That's enough for most, but not all, tasty targets.

I considered going to a 2-inch digonal. But the 8SE cannot fully take advantage of a 2" diagonal due to the 8SE's 38mm internal tube. So even with a 2" diagonal, my maximum TFOV without vignetting problems would be about 1.5 degrees. And good 2" EPs cost big bucks. If you're gonna spend that much on EPs, you might as well get a good quartz dielectric diagonal. By this point, you're talking about a substantial chunk of cash. The kind of cash that will buy a whole telescope.

So I spent $179 total and got an Orion ST80. With my 24ES68, it gives a TFOV of about 4 degrees, and it rides beautifully on the 8SE mount. It gave views of the Venus/ Pleiades event, for example, that my trusty 8SE just can't provide. And the ST80s short focal length transforms my existing EPs into completely different beasts; it's like getting a whole new set of EPs.

If cost is no issue, by all means get a nice 2" diagonal and some good long-FL widefield EPs. I just wanted to point out that there is more than one way to skin the old TFOV cat. As an additional and significant bonus, my chosen method of feline flensing also gives me a good little grab-n-go GoTo scope for camping trips and quick winter peeks.

#8 Rob Stemple

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Posted 09 April 2012 - 06:13 PM

Hey Widespread. I just purchased a focal reducer online. (I'm waiting for it to come in.) As you are still using the stock diagonal as well, do you have any clearance issue with it?

#9 Widespread

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Posted 09 April 2012 - 07:23 PM

Hi Rob,

Yes, I'm using the stock diagonal. I've used a TV Everbrite 1.25" on it, and it was a bit brighter, or maybe just "whiter". Anyway, it was incrementally more pleasing. I stayed with the stock 1.25" because I thought I would soon go to 2" format, but have thus far gone 6.3FR and ST80 :)

To your main question, NO, I could not quite get full zenith clearance with the 6.3FR/ stock diagonal combo on my 8SE. I could get to maybe 87 degrees altitude, but I wanted zenith. So I installed a Ron's Rail (with help and encouragement from Dan, Bob and Maverick), and now clearance is no problem. (You can Google Ron's rail (or search the forum); sorry, I've never posted a thread link.)

HOWSOEVER, with the Ron's Rail installed and the OTA pushed forward for clearance, the 8SE is front heavy. I could tighten my altitude nut, but thus far have simply omitted my dew shield. It works fine; I was THIS CLOSE to replacing my stock diagonal with a Denk PS1 before I went low-budget with the ST80 (hey, if I'm gonna go 2", I'm gonna go whole hog).

Enjoy your 8SE! Mine became more grab and go after Midnight Dan taught me to hug it with my cheek against the HC, and dance it out the door.

Best,
David

#10 Rob Stemple

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Posted 09 April 2012 - 07:53 PM

Thanks David. I'll have to keep that in mind for when I attach it.

For now, my viewing area is not what anyone would consider a good location. So, until I find a better spot, I'm fine with only being able to go 87˚.

Yeah..... Found that "Dance out the door" on my own! :)
The first time I took it out the door, and the HC slammed into my face! I learned to beat to the punch by putting my cheek on it. The next mod that I'm doing to mine, is to add a Velcro strap to the mount. that should fix that little issue. ;)

#11 Rob Stemple

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Posted 09 April 2012 - 07:56 PM

87&#730:.????????

I'm guessing the BBE code here doesn't take kindly to bitmap degree symbols?

That is suppose to be "I'm fine with only being able to go 87 degrees". :smashpc:

#12 dgerow

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Posted 09 April 2012 - 09:05 PM

Thanks to all. After much debate I decided to go with the 2" diagonal. I ordered the GSO quartz dielectric mirror. Found it at Scopestuff for $119. You guys are the best at helping me spend more(all) of my money. For some reason the wife doesn't want me to ask you guys any more questions. I don't get it.??

David

#13 Midnight Dan

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Posted 09 April 2012 - 10:22 PM

Your wife is obviously a person of superior intelligence. Didn't take her long to figure out that what we do best here is spend other people's money! :grin:

In case you're looking for the Ron's Rail thread, here it is: http://tinyurl.com/39gcpl8

-Dan

#14 dgerow

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Posted 09 April 2012 - 10:39 PM

Thanks Dan.

#15 NorskeBob

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Posted 10 April 2012 - 09:32 AM

Good choice I purchased the same - GSO 2" Diagonal for SCTs. The 2" diagonal will expand your choice in eyepieces.

#16 UncleMossy

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Posted 10 April 2012 - 10:33 PM

Also, for the 8SE its best to get an SCT threaded diagonal so it screws directly to the rear cell of the OTA. That way it will be short enough so that it won't hit the base when pointing towards zenith.

-Dan


With the diagonal screwed directly to the rear of the OTA are you still able to rotate it for more comfortable viewing angles or do you have to leave it in one position?

#17 Tel

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Posted 11 April 2012 - 04:55 AM

Hi Jim,

A very warm welcome to CN and to this Nexstar forum ! :bow: :bow:

Yes, in exactly the way your 8SE's 1.25" visual back fits and loosens by means of its screw threaded, locking flange ring, most conventional SCT 2" diagonals do the same.

You merely dispense with the 1.25" visual back and screw the 2" diagonal directly to the back of your 'scope. Then, if it happens to be in an awkward position for viewing, just slacken the ring and re-orientate the diagonal to make the viewing more comfortable, re-tightening the ring once the appropriate angle has been reached. The 2" diagonal also has, as I'm sure you already know, normally a further adapter at the eyepiece holder end so that you can fit either 1.25" or 2" eyepieces.

Drawbacks ?

Well on the standard 8SE mount it adds more weight which may require a little OTA rebalancing, (probably by sliding it further forwards within the mount shoe) but then you will almost invariably have to do this anyway to ensure the larger 2" diagonal clears the base of the mount. And, if it so happens that there is still not sufficient clearance between base and diagonal which prevents access to the Zenith, then you may have to add an extra length of dovetail rail, (Ron's Rail).

Don't let this put you off though ! 2" diagonals are a joy to use !

Hoping this helps.

Best regards,
Tel

#18 UncleMossy

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Posted 11 April 2012 - 10:41 PM

Thanks Tel.
you're always quick with a good answer.

I'm enjoying being able to rotate the diagonal now that i've started using a chair. it looks like it would be worth my while to get a 2" diagonal but i'm not sure if the screwing/unscrewing is a viable long term solution for me. so i think i will trade zenith for useful device and get a baader click lock adapter.
http://agenaastro.co...sct-thread.html
along with either the GSO dielectric or the william optics carbon fiber dielectric.

i can always wait for the zenith sky to move into view.

jim

#19 Tel

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Posted 12 April 2012 - 06:33 AM

Hi Jim,

Thank you for the compliment ! :bow:

In any event, if you're using you're 8SE on its normal Alt./Az. mount, I would have thought that no rotation of the diagonal is particularly, if at all, necessary, unless you're thinking that you'd, say, perhaps have to rotate the larger 2" diagonal body through ca.90 degrees to allow the OTA to reach of the Zenith and avoid contact with the base of the mount, assuming of course, the length of forward movement of the dovetail rail has been exhausted. (?)

Where otherwise do you envisage a need to rotate it ?

Best regards,
Tel

BTW: Alternatively, there's always the possibility of installing a "Ron's rail" !

#20 Arctic_Eddie

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Posted 12 April 2012 - 06:56 AM

Jim
Aluminum threads tend to gall and stick. You can lessen the problem by rubbing a little beeswax into the threads. Candle wax will also work. Be sure to remove the excess particles with a small brush.

#21 Widespread

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Posted 12 April 2012 - 09:23 AM

Thanks Tel.
you're always quick with a good answer.

I'm enjoying being able to rotate the diagonal now that i've started using a chair. it looks like it would be worth my while to get a 2" diagonal but i'm not sure if the screwing/unscrewing is a viable long term solution for me. so i think i will trade zenith for useful device and get a baader click lock adapter.
http://agenaastro.co...sct-thread.html
along with either the GSO dielectric or the william optics carbon fiber dielectric.

i can always wait for the zenith sky to move into view.

jim


Televue makes a Shorty version of their refractor-style 2" Everbrite diagonal. They are expensive (I think about $270), but they do combine short length with the ability to easily rotate the diagonal.

Best,
David

P.S. I sold the two Orion Expanse EPs (9mm & 20mm) that came with my new ST80, bringing the effective cost (incl. rings, dovetail bar, finder and diagonal) to $114. Sweet!

#22 dgerow

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Posted 12 April 2012 - 07:38 PM

The new 2" GSO arrived today. What a beautiful piece. Midnight Dan is right. The OTA actually looks a lot tougher now, the 1 1/4" does make the OTA appear quite wimpy. Even if I see no improvement I'll still look better looking.

David

#23 Widespread

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Posted 13 April 2012 - 09:00 AM

Congratulations! That looks like a nice diagonal at a great price!

Not that you need any more encouragement, but in explaining my cosmic wimpout <grin>, I omitted mention of one big advantage your 2" 8SE has over my 8SE (1.25")/ ST80 combination: NEBULAS.

At very low magnifications (e.g. 35mm Panoptic), the much greater light grasp of the 8SE should give you sufficient brightness to make good use of "nebula filters", such as the UHC Narrowband.

Guang Sheng's new jingle: "See great DSOs, with your GSO"
(Sung to the tune of, "See the USA, in your Chevrolet")

When the groans subside, you may carry on.

#24 cpl43uk

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Posted 13 April 2012 - 09:19 AM

Dumb question so sorry in advance for asking, but if i have an 2" diagonal, would i see any difference in using a 1.25" eyepiece or is the view exactly the same as if using a 1.25" diagonal?

Thanks

#25 Midnight Dan

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Posted 13 April 2012 - 12:54 PM

Hi Chirs:

Not a dumb question at all. No you won't see any difference when using a 1.25" eyepiece.

-Dan






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