Eyepieces for f4.7 dob

[DRT]

I would advise against buying new for your first few upgrades. You will simply lose money finding out what works for you.

Astro kit is generally well looked after as we all tend to be quite careful with our precious optics. You will be able to pick up second hand TV or Pentax EPs for about 2/3rds of the retail price in perfect condition and in their original boxes. When you want to sell them you will get your money back and really your only outlay is the cost of the postage.

Watch the classifieds section here on SGL, AstroBuySell UK and even Ebay (but be more careful there).

[Mike_S]

Thanks. Why not Televue Plossls and just cope with narrow field of view? The prices are very good? Are they still top quality and tested to F4? Surely true field of view won’t be bad if I use the 25mm? Works out just over 1 degree. Is that enough for most deep sky objects? 22mm Nagler works out around 1.5 degrees and 31mm Nagler around 2 degrees in my scope. 

[DRT]

The Tele Vue Plossls are excellent and are tested in the same way as their other ranges.

What is it that you want to be looking at?

[DRT]

Here is the difference in FOV between the Baader 31mm and a TV 25mm Plossl

http://astronomy.tools/calculators/field_of_view/?fov[]=42|327|||1||&fov[]=42|56|||1||&solar_system=moon

[Mike_S]

just everything really. I’ve got enough eyepieces for now I suppose. I’ll have to see what problems the cheap ones bring so I know what I want. At least I have learned a lot.

[DRT]

OK - let's start at the beginning:

1. What  scope do you have?

2. You say you have 4 eyepieces - what type/brand are they?

[Charic]

8 minutes ago, MSammon said:

Why not Televue Plossls and just cope with narrow field of view?

Why not indeed! But it often depends on the view and the target you desire. Looking at the Moon through my 70° Panaview makes the Moon look awfully small, such is the amount of 'space' and field around the target.

My first attempt with a Tele Vue Plössl put me right off as I was so used to 60°, and the difference is/was very apparent to me, not only that,  the eye relief was extremely short on the 8mm that I was trialling.

That said, the longer focal length eyepieces should have better eye relief.

Having said that, one of my £9 Revelation Astro (GSO) eyepieces, is in my opinion,  just as good as the Tele Vue gave, but look at the price difference! Surely that can't be right can it?  but the proof is in the pudding as they say.
Again I'm comparing my f/6 to a much faster f/4.7. The premium eyepieces may fare better, but without testing them..........?

I  did eventually try the 8,11 and 15mm Tele Vue eyepieces, and although their at the other extreme of the focal length  range to what your actually needing just now, I still believe in my Revelation Plössl's over the TV's, yet I don't actually need them? but thats the situation I'm in at the present moment in time. They were my plans, I stuck to them, this is the result.
I  favour the BST's, but had always promised myself and thought at the beginning that I/we had to have a Plössl  somewhere in our collection? 

[Mike_S]

20 minutes ago, DRT said:

OK - let's start at the beginning:

1. What  scope do you have?

2. You say you have 4 eyepieces - what type/brand are they?

254x1200 Orion SkyQuest Dobsonian. 

10 and 25mm Supers (they came with the scope). 

4 and 12.5mm no branders. 

Mind the image from left to right from smallesg to largest. The no branders are very narrow field of view. The 10 and 25mm seem better. Also have a cheap X2 Barlow that works.

thanks for your help

 

 

[Charic]

23 minutes ago, MSammon said:

I’ll have to see what problems the cheap ones bring so I know what I want.

The problem here exists due to the speed of your scope being f/4.7. Not  just a cheaper eyepiece!
Not every eyepiece needs or warrants an expensive corrector system, as not all scopes require correction, only the real fast ones, especially Newtonians, but some folk live with the issue?! 

 Like I said, given the right scope, right eyepiece,  most eyepieces will  work just fine.

Have you considered a coma corrector, to help correct the off-axis aberration  itself, then you could use just about any eyepiece that you like or fancy.
Again, Tele Vue have their 'Paracorr' product which should alleviate the issue. 

[Mike_S]

No I haven’t. I’ve only just got the scope last week. So far my main issue is field of view. It might be that i just save up for naglers. It’s very difficult to decide what sizes though. I think it’s because the field of view in my current eyepieces are very small though. I’m not sure if they are below 50 degrees. Edit: the supers are 50 degrees, don’t know about the others. 

[bingevader]

I've been avoiding saying any decent plossl as you'd originally asked for wider views.

But as you've been saying, maybe play with the ones you have a bit more to find out what bugs you about them and what you'd like to replace them with.

In that time, start saving!

Someone else has already talked about saving and taking 6 years to get to where they are now eye piece wise.

Mine has been a similar journey.

Yours might take a bit of time with your faster 'scope.

Have fun!

[Mike_S]

Thanks it’s looking like the first clear sky tonight since I have had my scope so i will have a proper play. It took me a few weeks of going back and forth in my head with my scope but in the end this forum really helped. It’s going to be the same with the eyepieces. Learn what i need First for a few weeks or more.

[Charic]

Since your EP image appeared, I'd say a BST Starguider would better those in your collection even on a f/5 (rounding up your f4/7).
Several folk here are using  10" scopes at f/5  with Starguiders and getting great results.  Try one. If there's still an issue, get it refunded, or get a corrector and try again. 

Earlier I was just thinking strictly f/4.7.

The BST Starguiders have 60° afov, and will be clearly different to what your used too. Just look at the size of the  eye lens on a Starguide!, that makes for pretty comfortable viewing and eye placement.

Give the Starguider a chance before you spend hundreds on a second hand premium. Buy then from First Light Optics here, the sites sponsor, or from ebay, where I originally bought mine, again, choices. 

[Mike_S]

I’ve got a Telrad though so I don’t need really need a finder piece anymore

[Mike_S]

Yea BST’s I have been recommended but I wasn’t sure what they’re like for faster scopes. Keep your thoughts coming if you like and I will take this in over a few weeks. I’ve only just learned how to calculate true field of view today so having fun with that. 

[DRT]

1 minute ago, Charic said:

Since your EP image appeared, I'd say a BST Starguider would better those in your collection even on a f/5 (rounding up your f4/7).
Several folk here are using  10" scopes at f/5  with Starguiders and getting great results.  Try one. If there's still an issue, get it refunded, or get a corrector and try again. 

Earlier I was just thinking strictly f/4.7.

That is very sound advice.

[DRT]

Brand new BST 25mm for £39.99 from a reliable Ebay seller ? 

https://www.ebay.co.uk/itm/1-25-25mm-BST-Explorer-Dual-ED-eyepiece-Branded-Starguider/161144826675?hash=item2584faeb33:g:yxQAAOxyXDhSe5pY

...and you will get about £30 back if you decide to sell it on  

[Charic]

........as for choices, try the 12 and 18mm Starguiders, both 60° afov, and both could be 2x Barlowed giving you  a combination of 6mm 9mm 12mm & 18mm. 

[Charic]

Before First Light Optics started selling the BST Starguiders (took their time ?) my allegiance was to Alan, at ebay, the same  link supplied by DRT above, but now both vendors are selling the same object, I'd vouch for either vendor, no issues.
Speak with these vendors, you wont know until you ask, its known that they both do and have  special deals, be straight, tell them what you want, hear their advice, make your opinion, pay your money,  its that simple.  I have the full set of Starguiders, no need to get any more except  the one that does not exist at present, but either way, one vendor will produce the goods at the right price, not necessarily the advertised price, go on, try your luck, Flo or e-bay, Flo or e-bay.............There are of course other outlets and ways to obtain these eyepieces, also their are other branded eyepieces, but physically the same eyepiece, about 7 brands last time I searched?
Again..........its just a choice !

[Mike_S]

Awesome thanks. Should my no name barlow work with them still? It seems to work fine with what I have got. Awesome those BST’s are only £49 and FLO we’re recommending me for them for the refractor I was going to buy but good to hear they should still be okay on mine. They will be better I’m sure. 

Are their smaller ones okay as well such as the 8mm or lower for planetary?

[Charic]

Barlows just like eyepieces, some are favoured some are not. Just try it with any newer eyepiece, if your happy, then nothing to change.
I have two, Skywatcher Deluxe and a Meade #140, both work fine for my needs, although the Meade may be favoured more by other folk. With the Deluxe, I generally remove the lens cell and screw this straight onto an eyepiece, giving me about x1.6 Barlow, that is, using the Barlow lens without its body, just the cell attached to any Starguider.

The 8mm was my first and favourite for several reasons, the 12mm has become the second, but I will use them all.
Going with the focal ratio on your scope, the 5mm would match, the 8mm will improve the detail, but the target image may appear smaller, but with the same field of view. I would say better start with something a little higher, then work from there. A 5mm will work, but its only a 5mm, 2xBarlow that, and a 2.5mm will give you problems. 2x Barlow an 8mm, will give you 4mm, still useable, but you'll probably find using the 8mm straight or the 12mm better on your Planetary searches. Im sure my best view was from the 5mm (would need to look back) but I've never had the same conditions since, so its been almost a one shot, once in a lifetime, moment  for me to see the perfect pencil dot of a shadow, the shadow of the moon Io ( pronounced 'Eye Oh') passing over Jupiters surface during what's known as a Moon transit, and is still clearly etched in my mind.

If you went for the 12mm and used your Barlow, that should cover your planetary option................?

[Ricochet]

46 minutes ago, MSammon said:

Are their smaller ones okay as well such as the 8mm or lower for planetary?

The 5, 8, 12 and possibly 15 are suitable for your scope. It is the longer 18 and 25 that do not work so well in fast scopes. 

[Mike_S]

I think i need more experience to decide on exact sizes but I think an 8 and 18 would be good for now.  With 10” aperture in U.K. skies I’ve heard max useful magnification is aroubs X250?

[Mike_S]

8 minutes ago, Ricochet said:

The 5, 8, 12 and possibly 15 are suitable for your scope. It is the longer 18 and 25 that do not work so well in fast scopes. 

Sorry just seen this. If that’s the case then  i might just try the 5 and the 8 as it’s the smaller ones I need to replace First. My 25 is more useable.

[Charic]

2 minutes ago, MSammon said:

I think i need more experience to decide on exact sizes but I think an 8 and 18 would be good for now.  With 10” aperture in U.K. skies I’ve heard max useful magnification is aroubs X250?

Use your telescopes aperture in millimetres  as your guide to power(magnification) , you wont go wrong!

As long as your conditions are favourable, and  your scope  is correctly setup, collimated and cooled to ambient, your scope will provide 250x magnification.
You will and can exceed this, but almost guaranteed 250 is doable (when conditions allow )