Decent high-power eyepiece for an ST80?

[Principal-Kohoutec]

Hi there, I'm back for more advice.

I recently upgraded my old 60mm refractor to a 80mm skywatcher and I'm very happy with how it performs on star clusters and some of the brighter deep sky objects. Miles better than what I was using. However I'm really keen to get a decent high power eyepiece especially as Jupiter and Mars are coming into view. I've tried using the 10mm with the barlow but personally I don't think they're up to much. Not bad but I think I can do better. Can anyone suggest a good eyepiece, maybe a 4mm or 6mm or some eyepiece-barlow combination considering that x160 is about the limit for this scope?

Thanks and clear skies to all

Will 

[RikM]

With the ST80 being an f/5 achromat, high power is not it's strong point. I think the ST80 is a great performer for the price and really good eyepieces do make the most of it. For high power I use a Pentax XW 10mm with a Televue 2.5x barlow to give the equivalent of quite a nice 4mm eyepiece but even so, it isn't wonderful. High power planetary views really need more than 400mm focal length. The ST80 is great for sweeping starfileds and large nebulae at low power with dark skies.

[Qualia]

Ay, it's just as Rik says. A 3" f/5 is not an ideal planetary scope. Being of such a short focal length, it relies on very short focal length (FL) eyepieces to gain significant magnification. A longer FL telescope allows one to use longer FL eyepieces, which in turn gives more eye relief making viewing a more comfortable possibility.

As you'll appreciate, magnification is equal to the telescope's FL divided by the EP's FL. So, if I wanted to enjoy Jupiter, for example, at around an average night's viewing of 160x to 200x, I'd need an eyepiece of around 4mm and less. I often view Jupiter, Saturn and the Moon, for example, with over 200x, so if this were the same for you, we'd need FL EP's around 3mm or so.

But all is not lost:

You could purchase:

• a zoom eyepiece of decent quality of between 3-6mm (a TV could be picked up for around £250)
• a decent Barlow which in effect helps double your EP collection whilst giving you the choice of buying a little longer FL eyepiece (I know you haven't enjoyed this experience, so perhaps count this one out)
• a 60º+ apparent field of view EP of around 3mm to 4mm which due to its wider field will be easier to track your object
• an ortho of around the same focal length. 

However, just looking at the numbers, I figure that if you want to do some serious planetary viewing, you will be pushing your system and eyes. This is not to dump on your scope in any fashion, you have a beautifully crafted wide-field scope and these telescopes can look at planets all the time but I think it is always helpful to the soul and mind to have reasonable expectations of what is realistically possible.

Personally, if it me and I was looking at the general price of eyepieces to telescope ratio, it might be an interesting proposition in the long run to see if you could pick up an 8" f/5 secondhand? I feel that getting over 6" and working around 200x + is where planets like Jupiter really take off. That way you'd have a lovely wide-field which could double as a decent white light solar telescope (with the correct filters in place) and a cracking DSO and planet buster

[ronin]

The ST80 will get to 80x and then I think more problems will become apparent (CA). That means a 5mm eyepiece and being f/5 I would avoid a plossl, that means something like the BST Starguider or Celestron X-Cel.

80x will show Jupiter nicely but Mars will be a small red disk. To see Mars you relayy need at least double and more, 160x-200x and the ST 80 is not going to give that.

A 4mm might be usable but there are no real inexpensive 4mm on the market, and I will bring your attention back to the word "might" as I personally doubt it.

[bomberbaz]

Having owned an ST80 I fell into the same trap trying to overgun the mag and the views were appalling, as mentioned horrible CA at higher mag. The best use able mag I got out of it was using a 12mm unbranded plossl with a decent 2x barlow. Erm think thats x66.

I did try using a BST 8mm plus barlow but it was awful. So I would go along with a 80x being the most you would get out of it using a 5mm.

So if you really wanted to spend some cash. You could do much worse than to go for a celestron x-cel 5mm, good eye relief and decent optics too. I believe the BST are very good too but the cost of a celrstron isn't that much more...

[Naemeth]

As others' have said, high power is not the ST80's strong point. I think you might be better off with another OTA for high power.

[jonathan]

I've never got into using a Barlow lens, I only have the ones that came with the ST80 and 150P, not particularly good.  It's on my shopping list to buy something like the Baader.

I have used a previous generation Celestron X-Cel 10mm with my ST80 but found that it was very sensitive to seeing conditions and light pollution, 25mm is usually the best for me with this scope, although I've never tried 12mm or 14mm so they may be fine too.

[bomberbaz]

I've never got into using a Barlow lens, I only have the ones that came with the ST80 and 150P, not particularly good.  It's on my shopping list to buy something like the Baader.

I have used a previous generation Celestron X-Cel 10mm with my ST80 but found that it was very sensitive to seeing conditions and light pollution, 25mm is usually the best for me with this scope, although I've never tried 12mm or 14mm so they may be fine too.

25mm Jonathan, thats 16 mag. Bet you get some great wide field views with that, must be around 4 degree of sky!

However at the OP, I would also consider getting another OTA for your deeper views of the night sky. If you want to get a frac for ease of use and money is tight, I got myself a Skywatcher Evostar 90 as a grab n go with focal length of 900. Its a little gem and will easily do planets and some reasonable DSO's. Best I had was to slap a 5mm into it and that and thats x180. (Mind you it was a quality EP, not sure how a cheaper one would respond).

I cannot find just the OTA anywhere though, although the mounted AZ3 model comes in at around 125 pounds, you would surely get 40 for a brand new mount, something to think about maybe......

PS. If you look for one, don't confuse with the ED DS Pro otherwise you'll get a price shock, hehe.

[Principal-Kohoutec]

Thanks for all the input. 80x would be perfectly fine for my uses (I was using a recycled binocular eyepiece in my old scope and it was actually pretty decent, gave roughly the same value). Wide star-fields were what I got it for plus the portability. The scopes worth it just for pleiades!  £250 is way out of my price range though - probably go for a 5mm or something, I don't need that much eye-relief.