Whats the word for it?

[Bluenosebatty]

Im really sorry if this may sound silly.....especialy when ive been readin this site for 12 months now and i should know! but whats the word used to describe the "blurr"around the outer edge of the view threw a EP? I had chance to test my 32mm panaview last night and altho it give clear in the centre of the EP the stars around the edge were streaks/blurr of light, it was annoying really because i was trying to find M31 and because every star was like this when scanning the sky it was a pain to find in the EP, simply why is it like this? Is it to do with thr size of my scope or is the panaview known for this?

Thanks

Mark.

[LukeSkywatcher]

I think this is called "coma". To correct it and make the view sharp right the the edge of the EP you need a coma corrector or maybe a field flattner.

I really am not sure because it nothing i really worry about as a visual type of astronomer.

[pvaz]

If you own a fast scope, that's one with a focal ratio less then f/6, then you'll experience that with most wide field EPs. The only solution is to get better corrected wide field EPs or stick with standard designs such as plossls or orthos.

[ollypenrice]

I don't know your EP at all but we have a fast (F4.1) Newtonian 20 inch with a mirror of 'OK but very ordinary' quality. A TeleVue Nagler or Panoptic gives a very acceptable view without a corrector so I suspect that better EPs really do make a difference.

However, is your scope well collimated?

Olly

[Bluenosebatty]

Cheers for the advice guys. I

Have a £250 px dob f5 i believe,

I had a 200p and used a 32mn GSO and it was beautiful! Clear and crisp.

So could anyone with the same size scope recommend a low power ep that will work well with my f5 250px?

I dont feel i can live with the views i was getting last night it was annoying!

Saying that though it gave stunning views of the moon around 1am.

Thanks again

Mark.

[Bluenosebatty]

(dont know where that pound sign come from lol!!)

[Moonshane]

there are a few things at work possibly. assuming your scope is well cooled and collimated accurately then the next most likely is astigmatism. this is usually an aspect of the eyepiece (although poor quality or poorly supported optics can suffer from this too - unlikely in your scope) and this effectively hides the coma which will be there. I don't get astigmatism in my 26mm Nagler but you will probably in your Panaview.

however, I do get coma in my f4 (and to some extent my f5) newtonian unless I use my coma corrector.

I am lucky to have a 26mm Nagler and a Coma corector and this creates the effect of looking through a f8 scope

[Bluenosebatty]

Hi olly,

Yes pal its collimated very well, would this effect the outta edge if it wasnt even tho i was still getting a clear view around the centre?

...i carried the scope out on two occasions first time i checked the mirrors with my laser collimator and it was well but after a while (this is still when it was light so didnt look through the EP) it started clouding so i carried it back in, i wonder if the mirrors slightly moved on the second carry out?........mmm got me thinkin now as i didnt check second time around.

[russ.will]

Yup, that sounds much like my experience of the 32mm Panaview in my F5 200p and worse still, in in my F4,9 300 FlexTube. In the 200p, I only tended to use it as a finder, but with the 1,5x increase in focal length of the 12" Dob, it was getting used a lot more. I replaced my BST Explorers with Explore Scientific 82deg EPs, because they were suffering too, albeit not quite so badly. Based on the very positive experience of my 18mm ES82, I've ordered the 2kg hand grenade that is the 30mm ES82. Not a Televue, but then nor is the price...

Russell

[Bluenosebatty]

.....looks like il be replacing this sometime soon then, see how long i can cope with it.

I Dont really want to be spending another £100+ on a coma corrector. Shoulf of done my homework...ar well we live and learn.

[rory]

so a 32mm panaview eyepiece suffers coma in a 200p f/6 . interesting. i was looking at these as a future buy , but not now.

[pvaz]

I had the agenda astro 32, 15 and 10mm and all suffered from this on my f/6. Upgraded to televue EPs and that fixed it. Skywatcher Nirvana EPs are the cheapest well corrected wide field EPs. I never tried one myself but have seen side by side comparisons by experienced astronomers and they rate them very well against Naglers.

[pvaz]

Agenda=agena*

[Moonshane]

the problem with cheaper wide fields is that you may not benefit from a coma corrector as you probably cannot see the coma due to aberrations (which are normal at the budget end).

[crazyjedi]

Most of the time if a 2 inch low power EP costs as little as the Panaview there is a good reason for it. Faster scopes are rather unforgiving of EP's. My 24mm Expolre Scientific works well with my F5 scope but cost more than a Panaview. When it comes to EP's you usually (but not always) get what you pay for. There are some bargains to be had out there but usually an average price gets you average glass

[russ.will]

the problem with cheaper wide fields is that you may not benefit from a coma corrector as you probably cannot see the coma due to aberrations (which are normal at the budget end).

Quite. In the case of the Panaview, the astigmatism masked the coma, although I am surprised people are finding it that bad in an F6 scope.

Russell

[Bluenosebatty]

So it Looks like the panaview is going to the classified section,....thanks for all your advice! Just need to ask then can anyone recommend to me through experience of actualy using, a good low power ep that will work well in a f5 scope?.... £100 tops, i spent £250 on eps last week, i know that might not sound alot but to tell the wife im spending another £200 wont go down to well with her when were trying to plan and pay for my 5 year olds birthday party as well as save for florida, now i know im not going to get a telvue for that but i just want somethin thats half decent and will gives me good clear view in terms of the £s spent.

Thanks!!

[russ.will]

That only leaves second hand as the Panaview probably is one of the best long focal length, wide angle EPs up to £100.

[Bluenosebatty]

Dag namit!!

So really buying a fast f ratio 250px scope only leaves me with the option of buying the better more expensive eps in order to get satifactory views, i had a 200p with a set of GSOs and was happy...what have i done?! Ha, what have i got myself i to hehe!!

[pvaz]

John is probably one of the members that has tried more EPs. Here is his side by side comparison of the 3 of the best wide field EPs available;

http://www.google.pt...YfMWNK00pc1-PcQ

The nirvana 28mm 82º retails for 245 new and you can try and post a wanted add.

[Bluenosebatty]

Thank you very much! Il have a nose at that,

Mark.

[russ.will]

...what have i done?! Ha, what have i got myself i to hehe!!

Nothing that hasn't happened to most people before...

Low price, wide field of view, sharp edge to edge. Pick two, forget the other one.

Russell

[jimmyjamjoejoe]

The next price step up from the panaviews is around £130 for the hyperion aspheric or skywatcher aeros etcetc.

Like you, i couldnt quite live with the edges of the panaview, though the large field was nice since it was the first wide ep i tried. I got the aspheric 31mm and love it to pieces. The effect is still there but really barely noticable unless you're really looking for it, cant recommend it enough.

Panaviews are highly sought after and you should have no trouble getting most of your money back for it.

[pvaz]

Hyperions may be better, it's another EP I never tried myself, but I have seen similar threads reporting similar experiences with Hyperions on fast scopes.

[Moonshane]

if you don't really need the wide field you'd be hard pressed to beat a TV 32mm Plossl. I use mine all the time when doing lunar, solar and travel observing. if I didn't have a 26mm Nagler I'd use it more at home too.