Good eps for sw 300p

[todd8137]

hi all i want to no what would be the best eps for the sw 300p as i have a couple uwa that are not good at all, sw20mm uwa the coma is so bad ,and the antares speer-waler 18mm is the same .so what would be good eps for my fast f5 scope so if you have this scope what are the eps you have tried and work well cheap or exspensive ones or just point me in the right direction as waste in money is a pain,the ep kit a got on a scale of 1/10 i would say is a 5 the rev photo kit ,so what do you have with your 300p ? and what works well?

cheers

[AWR]

Hi Todd,

I really like my TV 35mm Panoptic in my 300p. It seems to spend most of the time in the focusser whilst I'm using the dob. It's great for hunting out galaxies and the like. I got mine for £240 in the sale a few months back but they seem to be going for around £290 now.

At the other end my 9mm TS planetary is good and I've used a WO 6mm SPL which was also great, but after my experience with the very fine panoptic, I'm saving for a TV Delos.

Andrew

[Austin]

I just recently purchased a skywatcher extra flat 27mm e.p, it had mixed reviews. I got to use it last week on comet garradd and was pleasantly suprised. It gave a nice crisp view, with a lot less coma than expected. I also have a couple of u.w.a e.p's, the 6mm gives an awesome view of m13 and m57 - for the price!

[Moonshane]

be aware that coma is a feature of the primary mirror and nothing to do with eyepieces. all newts have coma, the faster ones more than the slower ones.

you can only see coma with good quality eyepieces otherwise it's fault in the eyepieces you can see as the coma is masked.

anyway, I am selling a 11mm Televue Plossl for £50 which always worked well in my 12" dob on planets, giving (I think) 136x magnification and 272x if barlowed in your scope.

this will be sharp to the edges. not a wide field at 52 degrees but all 'perfect'.

[John]

All Tele Vue eyepieces are designed and tested (individually !) to work well down to a focal ratio of F/4 so those are always a good bet in a fast scope. They range from the Plossls which you can get for around £50 used up to the Ethos range which cost in excess of £400 each.

Other very well corrected eyepieces would include the Baader Genuine Orthos, William Optics UWAN's / Skywatcher Nirvana's, Pentax XW's and more, depending on your budget.

It sounds from your post that you like a wide angle of view but you dislike astigmatism (not coma, as Shane says that a scope induced issue). You may need to invest a bit to achieve both.

[Bas van Krieken]

You might want to give this thing a try before buying more expensive EP's. Designed specifically for the SW dobsonians:

SKY-WATCHER Coma Corrector (2") for Newtonian Reflectors

[MjrTom]

Be careful not to confuse coma with astigmatism.

As Shane said coma is the product of the parabolic shape of the primary.

Astigmatism can be either the telescope (i.e pinched optics) a badly designed eyepiece or lastly your own eyes.

Coma is quite easy to correct, astigmatism is less so.

[todd8137]

Be careful not to confuse coma with astigmatism.

As Shane said coma is the product of the parabolic shape of the primary.

Astigmatism can be either the telescope (i.e pinched optics) a badly designed eyepiece or lastly your own eyes.

Coma is quite easy to correct, astigmatism is less so.

thanks i did mean that really ,yes will look in to it

[todd8137]

thanks for all your replys so far uwa are not really my thing they were a blind buy they work ok in the 90 mm frac,(speer walers/sw uwa 20mm) but not that great on the 300p,so we will see how it goes

[Austin]

Cheers mark and shane, i'm easily confused these days! good advice

[Moonshane]

aren't we all??

[halo1234]

Just to add a question to this thread. On this OTA If you were to pick 3 EP's what mag/mm would you go for?

Thanks

[Moonshane]

as the scope is f5, I'd be looking to retain an exit pupil of 5mm so for me I'd consider something giving magnification of 60 = 25mm, 100 = 15mm and 170 = 9mm. if you added a decent 2x barlow you could then also have 120x, 200x and 340x. This range would suit almost all circumstances (but you can always have more).

the choices now are budget, width of field, 1.25" or 2", eye relief etc etc. It's a complex subject.

[halo1234]

Thanks Moonshane. You're right the subject is far to complex for me. I guess I have a 2'' focuser so I assume 2'' EP's are better in most instances. I guess the down side is the added costs associated with larger EP's & Filters. I've also read wide or ultra wide can struggle on fast scope. Reading above it also seems that is would be wise to pick up a comma corrector. My last scope was a SCT so things were a little different then.

[John]

What 2" eyepieces can deliver is the wide angle views at low / medium powers. The 1.25" size is fine for medium and high power and most folks own a combination of the two sizes for this reason.

There are wide and ultra wide angle eyepieces that perform very well with fast scopes but they are harder to design and make and therefore cost more.

Coma is an issue with fast newtonians but you can only see it with the above rather expensive, wide field eyepieces - otherwise the eyepiece distortions mask the coma !. I use the expensive eyepieces in my 10" F/4.8 newtonian and there is some coma showing but frankly I've not found it bothersome so I've not invested in a coma corrector.

[Moonshane]

I agree with John. I sold a f5.3 scope and bought an f4. the difference is coma is dramatic at f4. the f5.3 was there but not 'ugly'. I never felt the need to buy a CC at f5.3 so I bet you'll be fine without one. with the f4 though the difference in using Televue Paracorr is large.

given the choice with an f5 between a couple of eyepieces of good quality or a coma corrector (they are not all adjustable and the Baader and Skywatcher ones look a bit fiddly having to be unscrewed etc every time you change an eyepiece) I'd get the eyepieces (or a good barlow) every time.

in terms of filters, I went with 2" as they can then be used on both (you can put a filter in the 2" to 1.25" adapter) but only have three (Oiii, UHC and Baader Neodymiun). Contrary to most advise I never use a moon filter when the moon is <50% illuminated but do use the Baader when the moon is brighter, even with the 16" there's no real need for a moon filter (as long as you don't want to chase faint fuzzies afterwards).

but you have only just got the scope! so don't rush into anything (with the exception of a Telrad - essential for me with a dob) and see how you go with supplied eyepieces (assuming there were some).

[halo1234]

Thanks guys for the great advice. You are correct I really want to minimize my spending & take my time. I do need a low power EP as the scope didn't come with one. Apart from that all I need is a red dot or laser & some cloud free nights.

Thanks

[jam1e1]

hi can recommend the meade 5000 swa where still available, else meade 5000 uwa eyepieces for a good price/performance comprimise. use these in sw250pds newt at ~f5. for low power around 40mm have the skywatcher aero which performs to a really good standard. as above take into other comments about astigmatism/coma.

For me, dont use coma corrector as hassle to attach and reattach when change eyepieces.

There are a couple stores still selling the meade 5k eyepieces so shop around for good price. Been using the meade 5k and SW Aero for around a year now and have no intention to upgrade/change as they suit my needs perfectly. Everyone has different expectations and standards they with to observe to, hence just remember to take that into account

To me most used are SW aero 40mm for low power wide views, meade 5k swa 28mm for medium power and meade 5k 14mm UWA for closer views of DSO.

hope that helps

[Moonshane]

threads like this just show what a delightfully varied bunch we are and also that there's scope (pun intended) for lots of different observing styles.

[Moonshane]

sorry - wrong thread!

[halo1234]

So for a low power EP for scanning & such. With a budget of say £70 what would you suggest?

I was thinking -

Revelation 30mm 2''

SkyWatcher UWA 80-deg 30mm 2-inch

William Optics SWAN 25 or 33mm 2'' (at a push or 2nd hand market)

Thanks

[John]

I'd avoid the low cost 80 degree eyepieces - you are asking for trouble with an F/5 scope - there is only so much correction they can do for the budget price. !.

I'd go for a 32mm SWA like a Skywatcher Panaview I think. If you can finde mor pennies then the Skywatcher Aero ED 30mm is a bit better corrected at the edges than the Panaview is.

[halo1234]

The Skywatcher Panaview seems like the way forward. I'm leaning towards the 32mm. Will see if one pops up 2nd hand. I suspect they're keeper, but will see.

[cyborg421]

My SW Panaview 32mm is a keeper - sorry!

Simon