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Which (BST) eyepiece next?


JulianFR

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I know there's lots of threads about eyepieces (one of which I started) so apoliogies for starting another... but I would appreciate some advice about eyepiece selection, specifically around BSTs.

I have a Skywatcher 200/8" f6 Dob with the stock SW 10mm and 25mm eyepieces and I bought a 6mm and a 15mm Celestron Omni plossls. I use the 25mm SW mostly (at the moment at least) and it seems pretty good. I'm less  convinced by the 10mm quality-wise and haven't used it much. As for the Celestrons, I like the 15mm though the eye-relief isn't great for me... but the 6mm I find really difficult to use, almost uncomfortable to peer into for more than a few minutes at a time. Anyway, the point of this post is....

After reading's Robin's excellent overview at http://www.swindonst...s/eyepieces.htm I decided to splash out on the BST 8mm. And it's amazing compared to my existing eyepieces. I can stretch to a second BST but the question is which makes most sense given my existing eyepieces?:I would like to get most use from it so the lower mag 25mm or perhaps 18mm would probably be most used. But then when I need a higher magnification for planets etc the better quality of the 5mm BST would easily trump my existing Celestron 6mm. So, which one?

Any advice and thoughts on which choice? I know it's probably subjective and a matter of choice but I would really value your collective opinion.

Thanks, Julian
 

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As you said if you bought the 25mm it would be used the most. It is a big step up from the stock eyepiece.

I dont know the focal length of your scope so it might be giving you too much mag but you could always barlow your 8mm and turn it into a 4mm for planets?

Its all subjective at the end of the day and depends what your goal is... i.e. upgrade to higher quality eyepiece.... or fill in the gaps you have in your collection.

I have loads of eyepieces now. Including a full set of Meade 4000 super plossls. However the only ones i use are the 25mm and 12mm BST's they are just sooooo much better than my other eyepieces :)

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Thanks for your quick replies all.

The focal length is 1200mm.

I'm not entirely sure on my startegy yet... on balance I think at this very early stage in my observing career I would prefer to fill in the gaps between my current favourite eyepieces (excluding my new BST 8mm): that is, the SW 25mm and the Celestron 15mm. I certainly want to choose a new one that I would use most often (to make best use of the BST's quality), so I guess that suggests lower rather than higher magnification,

I haven't factored in getting a Barlow as well. Any recommended size/make?

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what do you feel you are missing? you have a half decent 25mm, a decent 15mm and a good 8mm. are there any targets that don't fit in the field you have available? although not available as a BST, maybe a 32mm Plossl would be a good next buy as this gives the widest field in a 1.25" eyepiece.

BUT don't buy to fill gaps, buy to suit purpose. think about what you cannot see well enough currently and then suit that.

if you don't have a Telrad or right angle corrected image finder, I'd recommend them before another eyepiece personally.

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Personally I'd want something to take advantage of good seeing conditions. A 5mm would just be about right, especially with Jupiter season upon us.

With what you have now, the 25mm is ideal for wide field, the 15mm for deep sky and the 8mm for globulars and planetary nebulae. For planets the 6mm and 5mm would be a nice combination. I wouldn't bother filling gaps, other magnifications won't really add to what you have already.

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Either 12mm or 18mm depends on what you want from the next one. The 18mm would give a more magnification then your present 25mm and not really a lot less field of view.

Having said that I would probably go for the 12mm, 100x in your scope and a view of just over 1/2 degree will get quite a bit in. Jupiter will be good at 100x and the 8mm you have will give 150x which will be good on Saturn. Mars may need more.

So working on the planets: The 8mm for Saturn, get a 12mm for Jupiter then save for a 5mm for Mars.

The logic is as good as any :grin: :grin: :grin:

I bought the 12mm and the 18mm as my first two. I then bought the next two then the final two.

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Thanks everyone for the helpful advice. This is such a great forum for novices like me.

I've decided to go with the 18mm BST as I expect to get lot of use from it. I would like to gradually switch to this make, so for Christmas and birthdays I'll add the 12mm and the 5mm to my gift wish lists.

I used the 8mm to view Jupiter and moons last night... It was quite breathtaking and I spent long minutes gazing through the BST quite comfortably to pick out as much planetary detail as possible. I was surprised just quickly they travelled through my field of view, so I had constantly to move the scope to match it (jerkily).

I'm going to search forums next for advice on condensation as it was pretty cold outside... And when I brought the OTA back inside my house everything was wet and the mirror was fogged. I'm concerned the liquid might stain or otherwise damage the mirror.

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My response is late as I have been away since my 25mm BST arrived, but for the record: I found the 8mm BST a HUGE improvement over the stock 9mm in every way. The 15mm is excellent and I tried the 25mm for the first time last time, interchanging with the stock 25mm to compare. Conditions were good/very good and although the 25mm was an improvement (better contrast and wider FOV) it was not significant like the 8mm v 9mm, but then I have read that quality of stock EPs do vary.

Ultimately I will get the 12mm and 18mm as they would fill what I am finding are gaps in optimum magnification between the EPs that I have, but I am in no rush and it is something to keep back maybe as a santa gift.

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The 25mm is comfortable and easy to use but I think the stock 25mm is not all that bad so comparisons are not going to be hugely striking. I find the 18mm gets a lot of use and although the magnification of the 12mm is more than one would use on many objects I'm always struck by just how good it is when I pop it in for a closer look. The 8mm and 5mm do a good job on planets but the 12, 15 and 18 are reputed to be the picks of the bunch.

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Thanks. Do you notice much difference between the 8mm and 5mm? I have the 8mm as mentioned at the beginning, but I was wondering if 5mm would be too much for the 200 in most seeing conditions. Or maybe that would just be the case with the extra oomph from a Barlow.

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I have the 5mm and have to say it gets little use. Perhaps I'm throwing a bit of a curve ball here but if  were you I would save up and get a 2 Inch wide angle lens. I can only speak from my own experience I bought a 31mm Hyperion aspheric and it is by far and away the most used lens in my case.

Speaking from experience the tendancy when you begin is to go for magnification and then try and fill gaps but in truth if I ever use more than 3 different lens in one night it is highly unusual.

Anyhows good luck with your deliberations - the one thing to remember with this hobby is it is a long term investment in both time and hardware so don't rush into spending lots of money if you don't need to.

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The 8mm is fine for now but at the start of next year (April) Mars is well placed and for that the 5mm will be of great use, you will get 240x and you will need it. So I would say do plan on the 5mm by the end of Janurary.

Immaterial of the eyepieces you have one will get used least, doen't mean it is pontless not having one, just the uses for it are more limited. But for Mars and to an extent Saturn a 5mm will be wanted.

Alan will happily sell you one of each, :grin: :grin: :grin: :grin: :grin: .

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I'd replace the low end if I was you.

Your current 25mm Plossl gives 48x, and shows 1.04 degrees of true field

An 18mm BST will show 66x and show 0.90 degrees of true field.  So it's comparable to a 25mm Plossl in terms of true field (shows slightly less) but spreads it over a wider view and with higher contrast (higher mag darkens the background).

A 25mm BST will show 48x and 1.25 degrees of true field.  The background brightness will be the same as your plossl but youll see a wider view.

When I had a 1200mm focal length scope I found the 18mm shows much better views than the 25mm.  I didn't care about the slight loss of true field (not many things are a full degree in width anyway) and did notice the increase in magnification and contrast and nice wider view.

If you think the background brightness of the 25mm plossl is acceptable then get a 25mm BST.  When barlowed it'd give you a nice 12.5mm as well.  Of course the 18mm would also give a nice 9mm :)

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Just to throw a spanner in the works, the 16mm and 24mm 68oMaxvisions are within a gnats whisker of the BST prices! You won't get much better for the money.

I have a Celestron X-Cel LX 5mm for the moon, planets and double stars for when conditions are good and it's fab. They come up second hand quite regularly in the Classifieds here (once you're over 50 posts), UK AB&S and a certain auction site (in fact there's one there now). Mine was £42.

My 32mm PanaView is one of my most used EPs and they go for about £50 second hand.

That's another 4 options! Not helping much and maybe you were hoping to get an nice full set of BSTs rather than the liquorice allsorts I seem to be collecting.  :grin:

Cheers

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Thanks. Do you notice much difference between the 8mm and 5mm? I have the 8mm as mentioned at the beginning, but I was wondering if 5mm would be too much for the 200 in most seeing conditions. Or maybe that would just be the case with the extra oomph from a Barlow.

In terms of quality I would say they are quite similar although physically the 5mm is a longer eyepiece (like the 12mm). It doesn't get a huge amount of use but it is comforting knowing that I have that extra reach when the object and conditions allow. I think my two most used eyepieces are the 12mm and 18mm although the 25mm is indispensable even if sometimes it is just for finding things.

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So I think the answer to this is probably obvious but a 2x Barlow with my BST 8mm would give me a 4mm .... Optically/quality-wise is there much difference between that and a 5mm? My assumption is that adding an external layer of optics (the Barlow), possibly of lower quality than BST's glass, would degrade quality. 

Are there stand-out Barlow brands/makers that would compliment good optics.

Thanks again to all ... l hadn't even considered the 2" ep option!

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As you say you would need a good quality barlow as the view will degrade.

People used to like the Tal 2x barlow, but they are unavailable now, Tal seemed to cease production, and you do not often see them for sale. When Tal shipped the retailers were all sold out again in days.

There was/is a Celestron one, just not sure what it was called, Celestron seem to produce 3 or 4 similar items and you have to work out the best. Check out Celestron Shorty Barlow.

The other is the TV, the Powermates are the best but you could get 2 (or more) BST's for a powermate.

One point about the idea of a 4mm and a 5mm they sound close but in a scope the 4mm may give a poor image and the 5mm a good image. When using the high magnification eyepieces then the result can vary on 1mm difference. If the BST's came in 4mm, 5mm and 6mm then the others as now, I would have one of each just so I was sure of one delivering a good image. One reason I like the Celestron X-Cel range is simply that they have a better selection at the lower end.

A 4mm in yours is 300x and that may be too much on any occasion, or perhaps once or twice a year (literally). That is why I said the 5mm would be good but agree that it may not be the most used eyepiece. From the BST range I would expect the 15mm and 8mm to be used most in your scope, the 25mm would be for finding things with the wider view. Thats just 3 eyepieces.

As a grab and go scope I have a 70mm and I have a half set of BST's these are 5mm, 8mm and 25mm. Owing to the size the 5mm gets used a lot. Just different circumstances.

For you the vast majority of time the 8mm will be all you need, but for things like Mars and even Saturn on a good night the 5mm may well deliver, but a barlowed 8mm may not. I don't have a problem - I don't have/use a barlow, prefer individual eyepieces.

If you have a 12mm then barlow that for 6mm and 200x. Just do not think a barlowed 8mm (4mm) will deliver the image you expect. What I would expect is:
Barlowed 12mm (6mm) giving 200x and a good view, want a bit more. Barlowed 8mm (4mm) too much and a poor view. Solution 5mm. It is called Sods Law, however willing to bet that is what would happen.

Anyway to some extent you have time to think about it, well until March when Mars is easy and it is closest the first week in April.

After Mars and Saturn drift away I would not expect you to use a 5mm much, so yes it would be a little used eyepiece. Just go back to the 8mm for the magnification and wait for the next time Mars+Saturn appear.

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Personally I would go for a high power eyepiece first. Have you thought about replacing your Celestron 6mm, which you find difficult to use, for a better quality 6mm with good eye relief.  It will get more use than a 5mm and give very nice views of Jupiter and Saturn when conditions allow, plus a bit less dob nudging. It's a pity BST doesn't do a 6mm, I probably would have got one when I was looking for a step up in mag from my 8mm not so long ago.

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JulianFR........ My choice next is the 12mm followed by the 25mm and then 2xBarlow. This will replace the stock 10mm & 25mm, although the stock 25mm K/MA is`nt that bad to use. That gives me  effectively 4, 6, 8, 12, 12.5,  & 25mm lenses,  giving magnifications of between 48x - 300x  ( thats pushing the limits of the telescope a bit) but staying within the 1.25" barrel size.  i`ll be happy  working between 48 x - 150x.. The barlow just saves buying the 4, 6  & 12.5mm  lenses &  keeps the same eye relief.

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