Long Perng and Guan Sheng Eyepieces

[Globular3]

Hi All,

I've been looking for a good quality 1.25" high power eyepiece for my 80mm f/5 iOptron Refractor to use for planetary and double star resolving.

The choice so far is a 6mm eyepiece (good eye relief and sharpness) and a 2.5x ED barlow. This will give 167x (2-2.4x dia of lens in mm) which is around the practical maximum. I have a 3x barlow that I got with the scope and could get 200x if seeing permitted, but this is not essential.

I was looking at Guan Sheng for the 2.5x barlow and Long Perng for the 6mm Planetary eyepiece. I also thought I'd get a Guan Sheng or Long Perng erecting 90° diagonal.

Does anyone have any views on these products? (I've heard that Long Perng manufacture for Williams Optics)


Thanks,

Glob.

[dannat]

i heard somewhere the long perng ep's are the same as william optics spl's, of which i have the 6mm, very nice ep at a pretty low price, its no nagler but i really like the ER and less fov doesn't worry me, it is sharp almost right to the edge

[toyos]

I have a couple of WO's wide-angle ep's which I don't use anymore. The images start to blur halfway from the centre, and near the edge the images look worse than any ep's I've ever come across.

[Prickly]

The pick of the guan sheng barlows is the 2 inch 2x barlow.
I find that is quite a good barlow.

I would easily choose this above the guan sheng apo barlows (by a significant margin). Having said that Ive not tried the 2.5x barlow only the 5x.

Cheers
David

[Chippy]

The Long Perng eyepieces are similar to the WO SPLs (and may come from the same factory) but they are definitely not "the same". I've had a look at both. They are similar design and size but the WO are lighter and look like they have a superior finish IMO. I haven't looked through either eyepiece though!

I am also interested to hear from someone who has looked through the Long Perng version (or even better - compared with the WO version).

[Globular3]

Thanks Dannat,

I'll consider the 6mm WO eyepiece.

By the way, is that a plossl you've got?

Regards,

Glob.

[Globular3]

Thanks toyos,

I'll know not to go for the low power eyepieces.

Regards,

Glob.

[Globular3]

Hello Prickly,

Thanks for the advice. I can only use the 1.25" OD eyepieces.

Over the last few days, I've reassessed my needs and a 5x barlow may be better regards the power that I need for the moon and planets.

What didn't you like about The Guan Sheng 5x barlow?

Regards,

Glob.

[Chippy]

Not necessarily low power. I believe it is some of the SWANs (Super Wide) that have a bad rap. The UWANs (Ultra Wide) are generally well received, as are the SPLs and others. Toyos may be able to confirm the exact EPs he had issues with?

[Globular3]

Hi Chippy,

Thanks for this info.

It's not so easy to decide on these eyepieces.

I do like the Skywatcher brand eyepieces, so maybe I'll stick with the cheaper one's.

Anyhow, I'll think it over some more.

Regards,

Glob.

[VK2KR]

Hi Glob

I have been using the WO 6mm eyepiece with my iOptron and the GSO diagonal. The GSO diag is far better than the one that was supplied with the scope. The ep is brilliant for this scope, good eye relief and contrast.
It is about at the limit for this scope ie 6mm with 2x barlow as anything more
is just fuzzy. I was hoping to pick up a 3mm LP ep due to the cheaper cost compared to the WO version for comparison and complete my ep travel set for this scope.

The apparent field is less than other eyepieces, but for planetary work of no consequence.

The 6mm ep is great for lunar observations, and I have the 12mm WO for better contrast on nebula.

You will not go wrong trying these on your scope as they are much better for planetary viewing than the generic plossels.

regards

Alex

[dannat]

Glob, i think WO spl are a plossl type design, the swan ep's which i have the 9mm are not as good as the spl's . THe 20mm is ok but the 9mm ER is a bit tight and the view suffers near the edge of the field.

[Globular3]

Hi VK2KR,

Thanks for the comments on the higher price eyepieces. I guess I needed reassurance that the extra money is going to make a difference. By the way, is your iOptron scope the refractor, mak or newt.? Also, is the GSO diagonal a prism or mirror type and is it normal star or correct image?

Regards,

Glob.

[Globular3]

Hi dannat,

Thanks for this advice. I'm interested in the lower focal lengths, so I don't think these problems with the 9 & 20 mm ep's will affect me. It's good to know though as others will possibly read this forum at some time. The lower field of view in some 6 mm ep's shouldn't be a problem either as I intend it for high detail work such as splitting double stars, planetary detail and the moon.

Regards,

Glob.

[pneuman]

I'd probably steer clear of the GSO 5X -- I've heard from a couple of sources (online and offline) that it's not brilliant, with internal reflection that makes it essentially unusable for observing the Moon in particular. Here's one review that compares the 2.5X and 5X (it doesn't label them as GSO Barlows, but they definitely look like the GSO models from the photos):

http://www.astromart.com/articles/article.asp?article_id=600

I also have the 2" 2X ED GSO Barlow and I'm quite happy with that, though I guess that doesn't help you much if you can only use 1.25" models.

[jjjnettie]

The 3x barlow that comes with the Ioptron scope is next to useless.
I use a GSO 2x barlow, while not of the highest quality, it does the job well enough.
I also suggest changing your finderscope. I've put a 9x50 right angle finder on mine little 80mm refractor and it makes the scope a joy to use now.
The diagonal isn't much chop either, if you can spare the cash, buy a mirror diagonal. You can get all of the above quite cheaply from www.andrewscom.com.au.

[Globular3]

Hello pneuman,

Thanks so much for the article from astromart.com.:D (Link above in quote)

I agree with you, they do look like the GSO barlow lenses (also, they're made in Taiwan too!)

It has given me loads of help in the decision about the barlow (I'd buy the 2.5x now) as well as answering some questions. I'll summarise this below to help future readers.

1. The 5x barlow is no good for the moon otherwise, both barlows are good.

2. Barlow lenses work well within the low to mid eye relief range. They both increase the eye relief of the eyepiece used however, long eye relief eyepieces may be rendered unusable.

3. TELEVIEW POWERMATES are NOT barlow lenses even though they increase the magnification the same way as a barlow. THEY'RE DIFFERENT in that a POWERMATE WON'T CHANGE THE EYEPIECE EYE RELIEF. This is why POWERMATES CAN BE USED WITH LONG EYE RELIEF EYEPIECES.

4. Parfocal barlow means, focus the eyepiece WITHOUT the barlow. Remove the eyepiece, PUT IN THE BARLOW AND SAME EYEPIECE AS BEFORE, NO NEED TO RE-FOCUS.


All the best from,

Glob.

[Globular3]

Hello jjjnettie,

Thanks for endorsement of the GSO barlow. I really feel that it is the right choice now.

Thanks for the advice about andrewscom.com.au. I can underline your point about them being cheaper to buy from as I've already purchased there a couple of times.

By the way, do you like the mirror diagonal more than the prism type? I thought the prism may be better due to 100% reflection and no need to realuminize. What do you think??


Cheers,

Glob.

[Prickly]

Hi Glob3,

What dont I like about the guan sheng 5x apo barlow. Hmmm- well I was being very polite about it.

I use it for accurate 3 star alignment. Nuff said.

There is only one solution as far as Im concerned for a 5x barlow. Thats televue powermate.

Cheers
David

[Globular3]

Hi Prickly,

Thanks for the advice. I'll get the 2.5x barlow.

Regards,

Glob.

[VK2KR]

Hi Glob

After I found out how nice the 80mm refractor was I spent more $
on upgrades ( I think Jjjnettie has as well with hers?). The diagonal is the
1.25" mirror type (suffient for my needs) however the plastic focuser had to
go and was replaced by a Crayford (dual speed) from Andrews. This
upset the balance so a set of tube rings and a dovetail were next
to get the appropriate balance point. A cheap red dot finder replaces the
useless one that came with the scope and the only option needed
now is the LP 3mm ep. I have yet to use the webcam imaging with the unit
but will try it out this spring when it is warmer outside. (any hints
and tips jjjnettie????)

I know it sounds as if it is overkill for what appears to be a cheap scope
but the optics are worth it and the 80mm unit is a bargain.

I find it to be the perfect take away unit and have the 17ah battery
for powered use if needed for tracking.

I have thought about trying to find a 100mm mak to see if it performs
as well as the refractor, so will check out Andrews website again soon.

Oh BTW, like others I found the scopes inbuilt level to be WAY OUT
and popped it off and releveled and reglued it, so much easier to
get a good setup now.

regards

Alex

[Globular3]

Hello VK2KR,

Alex, sorry for the delayed reply - work commitments have been overwhelming lately.

I'll look forward to hearing how the LP 3mm ep goes. How will you connect the webcam to the scope?

I'm using a car jumpstarter and 12V DC power supply that I got on the internet from OO.com.au in Sydney. A bargain for $39.95 and the 12V cable (supplied) fits the iOptron "Cube" mount too. So I didn't need to buy the cord from the telescope manufacturer. :)

The 100mm mak sounds interesting. A longer focal length will be really great for the planets.

Thanks for the other tips as well.


All the best,

Glob.

[jjjnettie]

I really need to put rings on my scope too.
What size did you end up getting?
I use the Gstar Ex camera with my setup and I'm more than happy with what I can get out of the little scope.
I bought myself 2 small pocket levels and use them to level mount and dovetail.
At Astrofest I had a night of horror with the handcontroller. It just wouldn't work properly. Slewing sideways, telling me that Jupiter wasn't due to rise for hours when I could see him high in the sky etc etc.
The next day I deleted all my data, site info, coordinates etc and reset the lot. I haven't had any trouble since.
Just thought I'd let you know that in case you ever have the same problem.

[Globular3]

Hello jjjnettie,

Thanks for the info on re-entering the hand controller site stats. I'll remember this in case its needed. My hand controller (#8402) needs to be repaired so I'll be without my scope for a while I guess. When I get things operational again, I'll probably take an avi file video with a webcam at the eyepiece. Anyway, that's in the future. The 80mm scope looks like it has some coma, do you notice any? Also, do you know if collimation adjustments are possible with the iOptron refractor?

By the way, do you know if Sirius Optics is open since the Qld. Astrofest. I've been trying to contact them (via email) for a few weeks and can't get through for some reason?


Regards from,

Glob.

[Screwdriverone]

Hi Glob,

To throw in my two cents, I have a GSO 2.5x APO barlow which cost me $69 about 6 months ago and a 3x ED GSO barlow which I bought 1 month ago for $49.

The ED one leaves the APO one for dead in my opinion, less colour fringing and much better views. For a cheapie, the 3x ED GSO is very good value. I havent seen any others in action, but these ones I have and thats my findings. Certainly, the quality jump on my Jupiter photos has indicated this from the 2.5 up to the 3x, easier to focus too.

Just thought I would weigh in if it helps.

Chris

[Globular3]

Hi Screwdriverone,

Thanks very much for this advice (see below).



I was going to buy the APO 2.5x GSO barlow as I thought it (apochromatic) would be better than the ED glass 3x version however, your description Chris has persuaded me otherwise.


All the best from,

Glob.

[jjjnettie]

I'd be ringing up Sirius Optics and having a chat in person.
Emails can be sent by accident to the trash bin and this can be misconstrued
as being ignored.
Cheers,
Jeanette

[Globular3]

Hello jjjnettie,



Yeah, that's a good idea.


Thanks Jeanette.


Regards from,

Glob.

[Chippy]

Yep, that's happened to me a few times with suppliers, and I DON'T have a hotmail (or similar) email account. If you're using hotmail the chances of being "filtered" are very high. Give em a call.

[Globular3]

Thanks Chippy,

I'll call the dealer.


Regards,

Glob.

[dazastar]

Firstly, get rid of that hideous diagonal they supply with the ioptron refractor. (Yes I have one too). I took it apart only to find it uses a plastic prism, yeeech no wonder the image viewing was so ordinary. Get a GSO proper star diagonal for around the $30 mark and see an instant improvement. Then you can get a descent EP and actually notice a difference.

[Globular3]

Hi dazastar,



My current 90° diagonal is an old 1.25" Celestron which is not threaded for filters, so I was going to buy a GSO 90° diagonal (correct image type). However, Andrews advised me about the fine line that runs down the centre of some of the prisms. This line can act as a diffraction grating and cause the image to be spoilt as a result. The assistant got a brand new one out of the box for me to see and sure enough, there it was (it looks like one of the crosshair lines for an illuminated eyepiece). Since I've used an illuminated ep before, I know how they can effect the image and so wanted to avoid this purchase. Well maybe I'll try again later and see if I can get a good GSO one (as the Long Perng 90° diagonals are ~ $79.00).

By the way, how's your GSO diagonal in terms of this line? If there is a line, do you notice any effect from it?


Thanks,

Glob.

[dazastar]

I've had this discussion with Luke (At Andrews) before, you want a 1.25 star diagonal not a correct image prism. Prisms are not for astronomy as a general rule. They do have a GSO right angle star type diag there....avoid prisms like the plague.

Mine has made a big difference over all, worth the cheap investment in my opinion.

BTW I also just recently replaced the cheap plastic focuser for a metal 2" one using a conversion kit I found on the net. I got mine from scopestuff.com. There are other vendors out there that sell them too. (my experience with scopestuff could have been better, had to chase them up with emails etc)

[jjjnettie]

I put a 10-1 GSO focuser on mine. It certainly added a bit of weight to the whole assembly. But worth it, well and truly worth it.
I just drilled new holes in the OTA to fit it. One day I'll fill the old holes and pretty it up again.

[VK2KR]

Hi JJJnettie

The rings I used were 90mm that I obtained from Bintel, along with a long dovetail to help balance the scope. A picture attached if it works. The reason is because the Crayford focuser is so much heavier than the original plastic one and the balance pont is near the focuser.

Glob - I finally got the LP 3mm from Luke at Andrews, nice and 'similar' to the Williams Optics, but far to much for this tiny scope, even the ED80 that I have and will try it out on the 12" dob later if conditions allow. CA was very evident and focusing difficult even with the dual speed. What I did find surpising is that I also obtained the LP 8-24mm zoom, and within its limitations, a very nice eyepiece to use with the Ioptron and save room in the travel case.

At least viewing was reasonable last night after the rain.

regards

Alex
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