Best solution for BIG low power EP on 120mm refractor??

[Wurzil]

Hi all - another EP question from me!

I own the celestron OMNI xlt refractor (lucky me - theyve sold out on FLO!) and in a month or so (cashflow depending) I want to add a nice big wide-angle low power eyepiece for scanning the stars, open clusters etc.

Firstly, does anyone know if the R&P focuser on my scope will take a 2" star diagonal? If NOT, is replacing the focuser with a crayford 2" an expensive, difficult procedure.

If SO, can anyone recommend a decent 2" diagonal and 2" EP to give me nice wide views (at a nice price ).

If its not really possible (or too expensive) to go with a 2" solution on my scope, what is the biggest, widest, bestest solution for me on 1.25"?

Ive found this on the cloudy nights forum:

"The largest field stop in a 1.25" eyepiece can be a 32mm 50 degree, a 24mm 68 degree, a 20mm 82 degree, or (currently) a 13mm 100 degree eyepiece.

For a 2" eyepiece, the largest field is obtained with a 41mm 68 degree, or a 55-56mm 50 degree, etc."

If I have to stick woth 1.25" is it better to have a 1.25" 32mm 50degree EP or a 24mm 68degree one?

The reason for all this is that I saw one of those 2" 'handgrenades' on youtube for the first time yesterday and I really like the idea of them (I WANT ONE NOW!!!)

Thanks in advance (as always)

gotta love this forum

Warren

[John]

The Omni 120 should take a 2" diagonal with no problem and it's a worthwihile move because i) it gives you access to 2" eyepieces (obviously !) and ii) you can still use your 1.25" eyepieces as the 2" diagonals come with an adaptor.

The 1.25 inch format will always be limited in the size of field it can give by the physical diameter of the barrel. The widest 1.25" eyepiece I ever used was a 20mm Widescan III which had a whopping 84 degree FoV - a wee bit wider even than the famous Naglers. These don't come up for sale that often though.

If you go for a 2" diagonal you could use a 38mm Panaview which gives a 70 degree FoV and would work just great with your scope:

Skywatcher - Skywatcher PanaView 2" eyepieces

[russ]

Well the good news is your scope has a 2" focuser already fitted. So unless you find it unpleasent to use, should be no reason to change that.

There are loads of 2" diagonals around. The Revelation Dieletric 2" is well priced for £75. Or if that is too much, there are standard coated models around for £35.

As for the eyepiece, the Swan clones should work well with an f8.3 scope and they are well priced around £45-50. Available in 26mm, 32mm and 38mm sizes.

Russ

[John]

Well the good news is your scope has a 2" focuser already fitted. So unless you find it unpleasent to use, should be no reason to change that.

There are loads of 2" diagonals around. The Revelation Dieletric 2" is well priced for £75. Or if that is too much, there are standard coated models around for £35.

As for the eyepiece, the Swan clones should work well with an f8.3 scope and they are well priced around £45-50. Available in 26mm, 32mm and 38mm sizes.

Russ

Good point on the Swan clones Russ - I've often wondered if they are the same as, or very similar to the Panaview's internally - the spec is very similar

On diagonals, I've owned some quite expensive ones (Tele Vue Everbrights) and lower cost ones and it's one item where you don't seem to get noticably better performance the more money you spend, or a least I didn't think so. My best 2" diagonal now is an old Japanese Meade with a standard mirror - it cost me £25 used !.

[russ]

On diagonals, I've owned some quite expensive ones (Tele Vue Everbrights) and lower cost ones and it's one item where you don't seem to get noticably better performance the more money you spend, or a least I didn't think so. My best 2" diagonal now is an old Japanese Meade with a standard mirror - it cost me £25 used !.

That's my feeling too John. I have a Moonfish Dielectric now only because it came up for a silly price on Ebay. Otherwise my bog standard Skywatcher 2" was fine.

I've always thought the Panaview and Swan clones were one in the same eyepiece.

Russ

[Wurzil]

easy peasy then!!

I take it then that the plastic assembly on the end of my focuser (the part that the 1.25" barrell from the diagonal slots in) just screws off and can be replaced with an assembly which takes a 2" barrell (does this come with the diagonal??).

I like spending money before Ive got it!

thanks for the quick replies guys

Warren

[russ]

I take it then that the plastic assembly on the end of my focuser (the part that the 1.25" barrell from the diagonal slots in) just screws off and can be replaced with an assembly which takes a 2" barrell (does this come with the diagonal??).

hmm that doesn't sound familiar, i wonder if the Optcorp picture showed a different version of the focuser???? The 1.25" diagonal should go into a metal 2" - 1.25" adapter. The adapter is held in place by two locking thumb screws?? With the adapter removed, the 2" diagonal goes straight in the focuser and those two thumbs screws hold it in place.

Russ

[Wurzil]

Ill have a play with it when i get home from work I think. (and look in the instruction book). Ill post here later.

The focuser tube is definitley metal, but the adapter that the diagonal goes into, im pretty sure is plastic (with thumb screws). hmmmmm

[John]

Ill have a play with it when i get home from work I think. (and look in the instruction book). Ill post here later.

The focuser tube is definitley metal, but the adapter that the diagonal goes into, im pretty sure is plastic (with thumb screws). hmmmmm

It should look like this (different colour):

http://www.astronomie.be/Jan.Simons/images/orion80edcrayford.jpg

All the adaptors are metal.

[Wurzil]

Hi john and Russ - Ive just got home from work and yes the adapter parts are metal and the 1.25" bit does come off (I was being stupid) and leaves a nice 2" hole for the bigger star diagonal - so its all good.

Now all thats left to decide is how low do i want the mag?? Maybe I shouldnt get the lowest mag, maybe I should get the 32mm and not the 38mm.

Thanks guys

w

[Wurzil]

I take it by SWAN clones you mean clones of william optics SWANs?? Any idea where I can get these from for about £50 please, Ive checked FLO, Modern astronomy, rother valley optics and a few others but cant see any.

another thankyou in advance

w

[Wurzil]

hmmm ived found one but its on scopes and skies

Adler Optik Adler Optik Skarp 38mm 2" fit 5 element SWA Eyepiece

[John]

hmmm ived found one but its on scopes and skies

Adler Optik Adler Optik Skarp 38mm 2" fit 5 element SWA Eyepiece

It's the same type of eyepiece I think. If you do buy from there I would suggest you phone the order in so that you can check the stock level before you order.

[russ]

I've just ordered 4 bits from S'n'S. Phoned first to confirm stock. One item was out of stock and i considered not ordering it from there. But in the end i placed the order for all of it with them. The 3 In-stock items arrived the next morning and the out of stock item arrived yesterday. I placed the order on Monday....no complaints. Just need to handle S'n'S differently.

Russ

[russ]

Opticstar and Astronomica also do those eyepieces but they want £60 plus P+P, which is a lot more than S'n'S or Pulsar and not far off the Panaview from FLO.

[Wurzil]

Thanks Russ - Its going to be next months purchase anyway, as this month i'm buying my HR Planetary EP from modern astronomy. I think Ill do what you suggested and phone S&S before ordering, if they havent got it in stock then Ill just bite the bullet and buy one of the more expensive ones. Thanks for all the help matey.

PS - I never could find those paradigms you suggested from that seller on e-bay, but it doesnt matter now as Im getting the HR planetary instead!!

Thanks again

Warren