12" bintel dob EP selection.

[vespine]

Ok well I'm thinking more about getting the bintel 12" dob and have read a bit about the stock eyepieces you get not being crash hot so was wondering what people's thoughts were specifically to this scope..

The eye pieces you get are (and their mag):
32mm (2") 46x $79.00
15mm (1.25") 100x $49.00
9mm (1.25) 166x $49.00

=$177

I figure I can probably afford a few hundred more dollars so was wondering what the best way to spend that on upgrading eyepieces would be. Unfortunately there are so many of the things I can't quite get my head around it yet!!

1st thing I thought is upgrade to the Bintel SuperView 30mm (2") $99.00
and buy an additional Bintel Barlow 2x (2") $99.00

Could you then forgo the 15mm plossl? Anyone have any idea what the view through a barlowed 2" 30mm superview would compare to a standard 15mm 1.25"? I'm quite stumped on this one. Would you be better off sticking to the separate 15mm, even the cheapo one? or would the better 2" give a better view even with the cheapish barlow?

Then for the same price you could instead get: Meade Series 4000 Super Plössl 32mm (1.25") $99.00

But for the astro-newby do you reckon the 2" bintel would be better? Being a newb I don't think I'd be very "sensitive" to edge discoloration or distortion or the other "cheap EP issues", I kinda figure that the 2" would probably give a superficially better view, what do others think?

I've been playing with a borrowed el-cheapo 700mm refractor and found that about 175x (4mm) is the mag I was using the most for star clusters and whatever else I could find. (but the barlow is a plastic PoS, completely useless) So I figure the 9mm EP is the one I'd be using a lot but I didn't really manage to find any galaxies or nebula other then the faintest smudges, (which is what i'm hoping to see more of in 12") so what magnifications are common for those objects?

As for the 9mm ep the choice is:

Meade Series 4000 Super Plössl 09.7mm (1.25") $89.00
Meade Series 5000 Plössl 09mm (1.25") $145.00
Meade Series 5000 Ultra Wide Angle 08.8mm (1.25") $285.00
Tele Vue Plossl 11mm (1.25") $145.00

the 5000 UW meade is probably a little on the expensive side but is the ultra wide REALLY good? and would it perform with a barlow? Or is 340x not realistic? (even with good viewing conditions?)

If 340x is the very extreme range of mag for the 12" f5 dob (extreme range is good to have I guess) and the 5000 ultra wide is very good at native 166x, I could see my self using this eye piece a lot and therefore would consider spending a bit extra on it. 5000UW +30mm superview +barlow = $483 or $306 more then the standard ep package. I'd have to tighten my belt for a few weeks but not impossible...

If 340x is way overboard, then the choices are the teleview 11mm which barlowed would give 272x, a much more comfortable figure and would only set me back an extra $166 over the standard package.

or the 4000 super plossl which would give 309x with barlow and be only $110 over.

Am I really making amountain out of a molehill for a newby? Should I just shut up and get the standard EPs and see what I think before I start to worry so much? If you've made it this far through my too lenghtly post, I'd really appreciate any opinions

[ving (David)]

for the price the televue plossl offers really good performance...

if you could ditch all the EPs that come with the telescope and trade them for televue plossls (if you have a fair amount of extra cash) or meades (if you have less) then you'd be better off.

galaxies: start wide (32mm EP) and work your way down. you will hit a point wher you will get a combo of best brightness and magnification...

you will probably find that you will want a widefield EP at some stage too. the superview is good as a finder EP (for hunting down galaxies etc) but it wont be sharp to the edge (or even near it at f5 i believe). good widefields cost bucket loads for f5 scopes.

[janoskiss (Steve H)]

The eyepieces that come with your scope will do nicely. The only thing you might want to add is a 2x barlow and, if you want even more flexibility, a 12mm GS plossl. If you get a 2" GS barlow, get the ED model rather than the achromatic one. (Don't know if Bintel stocks these, but they were $110 from myastroshop.com last time I checked.) In the 1.25" barlows I'd go with either the Meade #140 apo, or the Televue 2x.

Upgrading the 32mm to the 30mm superview is worth considering for $20 (but no more) but do not expect good edge performance from either EP in the fast Dob. The 30mm Superview works well in a 2" barlow (much better edge sharpness than on its own) and the extra field of view is nice, but the 15mm plossl will be more suitable for planets and faint fuzzies. So don't give up the 15mm, because it is a very useful focal length for deep sky and for planets in a barlow. Ditto 12mm.

Even if you decide to upgrade your EP collection later on, these basic EPs will come in handy when you are showing off the sky to your friends with dirty paws.

[ausastronomer (John Bambury)]

Vespine,

No your not making a mountain out of a molehill and your wise to ask the questions before you part with your hard earned cash.

The 2" 32mm FMC GSO eyepiece is a kellner design and useless in an F5 scope, it is woefull. I have no idea why it's packaged with the scope and not done away with. The 30mm GSO Superview is a clearly superior eyepiece in every respect and only a little more expensive. That is the eyepiece that should come packaged with these scopes from all retailers. It is not as good as the premium widefields but is pretty good and good enough to keep you going for a at least a couple of years into the future. I would pay $40 or $50 extra if necessary, to be able to get this eyepiece instead of the 2" 32mm GSO Kellner. The Superview is quite useable and a reasonable eyepiece, the Kellner is useless IMO.

The 1.25" plossls that are supplied with the scope are fair and you may be happy with them to get started. However in the whole scheme of things they are not great eyepieces, if you can get a credit from the retailer against those I would do that as well. For that scope with a Focal length of 1500 millimeters and a fast light cone at F5 I would be looking 2 get 2 decent eyepieces and a barlow as opposed to low/medium grade eyepieces that you are considering. The Meade series 4000 plossls are not much better than the GSO plossls and not worth the time and effort IMO. The Meade Series 5000 plossls are not great in a fast scope which is what you are considering buying.

If you're buying the scope from Bintel (a great dealer BTW, as is myastroshop)I would try to get a credit against all the normally supplied eyepieces and take a 30mm Bintel (GSO) Superview, a 17mm Orion Stratus and a 13mm Orion Stratus. I would couple these to a good 1.25" barlow like the Orion Shorty Plus, Meade #140 barlow or Televue 2x barlow. The Orion Stratus are about $180 each but offer 90% of the performance of a premium widefield at 40% of the price. They work fairly well in an F5 scope, or at least the 17mm, which I have tried does. If these options are outside your budget I would substitute the Orion Stratus eyepieces for the 18mm and the 12mm UO Optics HD orthos which cost about $125 each and offer superb image quality across a slighlty narrow AFOV of 45 deg. Another good option would be the 15mm and 11mm Televue plossls ($145) combined with a good 2x barlow. Again with the TV plossls the FOV is a little narrow at 50 deg, but like the UO HD orthos they offer superb image quality across the entire FOV.

CS-John B

[chunkylad (David)]

Hi Vespine and welcome

I agree with Steve. The 1.25" GS Plossl eps that you will get as standard with your Dob are of reasonable quality. The 30mm SV 2" ep likewise. Plossl eps are a great starting point for both planetary (in combination with a good barlow to boost focal length), and deep sky observing.

The problems associated with 'fast' reflectors - and I mean our F5 dobsonians - manifests itself when you try to get nice wide views. You tend to get little 'seagulls' where there should be pinpoints of light. This occurs "off axis", meaning the centre 50-60% of your field of view is in focus, and the remainder - the 'edge' of the field of view - is out of focus. The is due mainly to a condition called coma, inherent in fast designs. I find this distracting and unpleasant. The only way around this is to purchase high quality eyepieces. Eg Teleview Panoptics and Naglers and the like. No low-cost , wide angle eyepiece will be sharp to the edge. I stress again, this only becomes problematic when chasing nice wide views of those beautiful deep sky objects. After all, that's why I personally bought a 12" reflector in the first place.

There is a group of us about to purchase and evaluate a (new?) type of wide-angle eyepiece made especially for planetary viewing: http://www.iceinspace.com.au/forum/s...ead.php?t=7400
You will find your standard plossl eps that come with your 'scope adequate for planetary work, but pretty soon you may be wishing for a greater apparent field of view. That is, you will have more time to allow the target to drift across the f.o.v. before you need to nudge your dob.

When you are talking "extreme range" of you dob, do you mean maximum magnification? This figure is around 2.4 x aperture in mm, or around 720x for a 300mm aperture. But whether you can achieve this magnification in practice is totally dependant in the seeing conditions at the time. remember, more magnification can mean a larger image-scale (things look bigger), but at the cost of image sharpness, contrast and definition. High power eyepieces are for getting up close and personal with planets and Luna; and low power, wide angle eps are for most DSOs.

You will find that discolouration at the edge of the f.o.v. (chromatic aberration) is not such a problem with you reflector, than it is with cheaper refractors.

The above is meant as a guide to determiningg what type of eyepieces to buy. Other, more experienced users may offer better advice on what specific brands to buy. I like your sign off line: spend plenty of time at the eyepiece and this will help you learn about what you'd like to have in the future. Also, get together with other astronomers and look through as many eyepieces as you can, before committing your hard-earned $$$.

Hope this answers some of your questions without causing too much confusion.

Cheers

Dave W

[janoskiss (Steve H)]

I did not realise the 32mm 2" would be so bad at f5, John. I only tried it in the f7.5 ED80 and it was passable in that scope, similar to the superview.

[Starkler (Geoff)]

I think any talk of hanging Orion Stratus eyepieces out of barlows would necessitate the crayford focuser option, as the standard rack and pinion would be too sloppy with such weight hanging out of it.

[vespine]

wow, that's some great advice there! Thank you very much, brain still racing... A couple of things to add:

These were mentioned in one of the replies:
a 17mm Orion Stratus and a 13mm Orion Stratus.

I'm scouring the bintel website and can't find them, there's just bintel, meade and tele vue, am I not looking in the right place?

Originally Posted by janoskiss

but the 15mm 1.25" plossl will be more suitable for planets and faint fuzzies.

Could you clarify? More suitable then the 30mm 2" with barlow because? Sharpness of image or contrast or something else?

So seems like the Meade Series 5000 Ultra Wide Angle 08.8mm gets no votes? Better to start off with the orion or tele vue?

Originally Posted by Starkler

would necessitate the crayford focuser option

Yeah I was thinking for only $100 over the 'standard' I'd go the premium anyway.

[ausastronomer (John Bambury)]

Originally Posted by chunkylad

Hi Vespine and welcome

You tend to get little 'seagulls' where there should be pinpoints of light. This occurs "off axis", meaning the centre 50-60% of your field of view is in focus, and the remainder - the 'edge' of the field of view - is out of focus. The is due mainly to a condition called coma, inherent in fast designs.

Dave W

Dave,

I have quoted a little from your post. I just wanted to clarify something because what you have said is not quite correct, it is very close.

The little seagulls you get with cheap widefield eyepieces in conjunction with a fast telescope are more attributable to astigmatism and field curvature eminating from the eyepiece itself than from coma eminating from the primary mirror. The cheaper eyepieces are unable to eliminate those aberrations internally, when combined with a "steep angle of incidence" of the light cone. Those aberrations effectively "mask" the coma coming from the primary and overpower it so you dont see the coma itself. This is not always the case but true in 95% of cases. Premium eyepieces like Naglers, Panoptics and Pentax XW's are free of astigmatism and go a long way towards correcting for the coma eminating from the primary mirror, hence they can show pinpoint stars to the EOF even though there is coma inherent in the primary optic at EOF. Its all in here

https://www.willbell.com/tm/tm6.htm

This book is a great reference for anything "telescope and eyepiece optics". It is a timeless classic work, if your interested in what makes it all happen. Although it's getting a little dated, being wrtitten in the 1980's prior to the release of the more modern of the Nagler and Pentax designs, the physics doesn't change.

CS-John B

[ausastronomer (John Bambury)]

Originally Posted by vespine

wow, that's some great advice there! Thank you very much, brain still racing... A couple of things to add:

These were mentioned in one of the replies:
a 17mm Orion Stratus and a 13mm Orion Stratus.

I'm scouring the bintel website and can't find them, there's just bintel, meade and tele vue, am I not looking in the right place?

These are only a fairly recently released eyepiece by Orion in the USA. They are not listed on the Bintel website but they are a special order that Bintel will get in for you from the USA, they cost about $180 each. If they generate enough demand in the future Bintel are likely to carry them as a standard line.

Originally Posted by vespine

Could you clarify? More suitable then the 30mm 2" with barlow because? Sharpness of image or contrast or something else?.

The 30mm GSO Superview barlowed 2X to 15mm, is a reasonably heavy combination that optically will be inferior to the 13mm and 17mm Orion Stratus or the UO HD orthos or a high grade plossl like the Televue. Despite what others have mentioned, IMO the GSO plossls are marginal at best and I would be setting my sights a little higher if you can afford it, if not the GSO plossls will have to do for the time being.

Originally Posted by vespine

So seems like the Meade Series 5000 Ultra Wide Angle 08.8mm gets no votes? Better to start off with the orion or tele vue?

I haven't used the Meade 8.8mm Series 5000 UWA but I have used the 14mm and and the Orion Stratus is a better eyepiece for $100 less IMO. The 14mm Series 5000 Meade UWA didnt impress me at all for a semi premium eyepiece. However, some colleagues in the USA advise me that the 14mm UWA that I used is the worst of all the Series 5000 UWA's and the other focal lengths in this series are a lot better. Nevertheless, I would be going with the Stratus at $180 or high grade plossls or orthos, unless you wish to pay top $$$ for Pentax XW's, Naglers, Panoptics or Vixen LVW.

Originally Posted by vespine

Yeah I was thinking for only $100 over the 'standard' I'd go the premium anyway.

Definately worth spending the $100 here and I suggested the Orion Stratus and barlow on the assumption you were buying the premium scope with the crayford focuser.

CS-John B

[janoskiss (Steve H)]

Originally Posted by vespine

So seems like the Meade Series 5000 Ultra Wide Angle 08.8mm gets no votes? Better to start off with the orion or tele vue?

It gets a NO vote from me. I looked through a 6.7mm UWA 5000 recently and I was most unimpressed. Lots of glare and scattered light.

The Stratus EPs are very good for the price. But acc to my measurements on the 5, 8 and 13mm, their focal lengths are about 10-15% longer than specified.

[vespine]

ok, so last question, what of the barlow. I can justify upgrading from a $50 or $99 ep to a $180ep but upgrade a $99 barlow to a $330? ouch.. Is a newb like me really going to appreciate the difference? or is the barlow the "weakest link in the chain" and quality REALLY makes a difference?

So you reccomend a 1.25" barlow which are a bit cheaper, is that you think a better option? Even though then I won't be able to barlow the 2" ep, and instead getting a 13mm and a 17mm? That gives me a range of 6.5ep+b, 8.5ep+b, 13ep, 17ep and 30ep. Where as with a 2" barlow and the same amount of EPs I can get 4.5ep+b, 9ep, 12.5ep+b, 15ep+b, 25ep, 30ep....

but you say the cheap barlow with the 30ep isn't going to be as nice as a 1.25" without barlow............. AARGH! If I had any hair, i'd be tearing it out..

ok, I really don't think I need any more replies, i think the verdict is I'm going to keep saving my money until I can get myself to a star party or something and actually check out some people's gear....

So when's the next one?

Thanks heaps for all the replies and advice so far, I certinally have been learning a LOT!

[Starkler (Geoff)]

I can understand your confusion as its surely an information overload

The 30mm gso is shall I say a mediocre eyepiece ok for its price, but I wouldnt be buying a $300 barlow just to accomodate such an eyepiece

Good barlows at a reasonable price include the Orion Shorty-Plus (remember the PLUS), and the Japanese UO 2 " barlow. Both cost around $150. Steve (janoskiss) got a jap equivalent barlow from Bintel and hopefully still carry them.

One option not yet mentioned is the Antares Elite 5 element eyepieces of which Steve recently bought a sample. Nobody in Australia sells this type at a reasonable price and they are a good cheaper alternative to the Televue plossls.

[janoskiss (Steve H)]

Originally Posted by Starkler

Good barlows at a reasonable price include the Orion Shorty-Plus (remember the PLUS), and the Japanese UO 2 " barlow. Both cost around $150. Steve (janoskiss) got a jap equivalent barlow from Bintel and hopefully still carry them.

Unfortunately not. It was a one-off Roger Davis special (BATSC leftover). The Stratus will probably vignette in the Shorty Plus. Antares 1.6x 2" barlow is a very good one (got it with the Elites).

[ausastronomer (John Bambury)]

Originally Posted by janoskiss

The Stratus will probably vignette in the Shorty Plus.

Steve,

Why ? The shorty plus has 26mm of clear aperture. In addition I have only recommended the 13mm and 17mm Stratus, these focal lengths should be fine with this barlow. If my 20mm Pentax XW with a 70 deg AFOV works ok in why would you expect the 13mm and 17mm Orion Stratus with a 65 deg AFOV to vignette.

CS-John B

[ausastronomer (John Bambury)]

Originally Posted by Starkler

One option not yet mentioned is the Antares Elite 5 element eyepieces of which Steve recently bought a sample. Nobody in Australia sells this type at a reasonable price and they are a good cheaper alternative to the Televue plossls.

Geoff,

If he is getting a credit on the normally supplied eyepieces he really needs to buy the replacements from the store he buys the telescope from IMO. Bintel dont carry these and the reason I didnt recommend them.

CS-John B

[Starkler (Geoff)]

Quite right John.

Oh well those could be a "go jump" option if Bintel wont offer a credit on the gs plossls

[janoskiss (Steve H)]

Originally Posted by ausastronomer

Why ... would you expect the 13mm and 17mm Orion Stratus with a 65 deg AFOV to vignette?

Because I'm pretty sure mine did. The clear aperture equation definitely does not tell the whole story. For example, the 15mm televue plossl vignettes in all barlows I've tried it in, including 2" barlows with huge 40+ mm clear aperture. OTOH, the older style 17 and 10.5mm TV plossl barlow fine.

[ausastronomer (John Bambury)]

Steve,

Thats very interesting, as you say going by the numbers it shouldn't, but I don't doubt what you saw. It can also depend on the F-Ratio of the primary optic. Short barlows are worse for vignetting than long barlows, regardless of clear aperture. In this case this could be the influencing factor. I will try Rod's 17mm Orion Stratus in both my 2X Shorty Plus and 2.5X TV Powermate when we are next observing together to check for myself. I will also try Scott Mitchell's 16mm Nagler T5 in the 2X Shorty Plus, I have it on loan at the moment, hopefully for another week or so.

CS-John B

[janoskiss (Steve H)]

John, if you can, try a televue 15mm plossl too. Why that EP refuses to cooperate with any barlow is a complete mystery to me (haven't tried it in any televue barlows or powermates though, but at least in 4 good non-TV barlows).