Eyepieces for f4.7 dob

[alanjgreen]

1 minute ago, MSammon said:

I’ve been doing some research but on a steep learning curve. If I don’t go for the zoom, are these good for replacing the standard eyepieces? They seem good spec and price. 

https://www.firstlightoptics.com/baader-planetarium/baader-hyperion-68-degree-eyepiece.html

I would say "no good at f4.7" 

[Mike_S]

Why is that? I’ve heard a few using them and happy with them with the same scope?

[Ricochet]

The 34mm Maxvision Louis linked to is a great deal. The Maxvisions are just the old body design of the Explore Scientific 68° design so you're looking at €80 for a £200 eyepiece. If you don't want to go that long they also have a 28mm for €70. At shorter focal lengths the options you have at a similar cost to the Hyperions are:

• Explore Scientific 68°
• Explore Scientific 82°
• BST Starguider, 5, 8, 12mm (Celestron X-Cel LX/Meade HD-60 similar)
• Vixen SLV
• Baader Classic Ortho (probably ok)

[Mike_S]

Sounds good I will look for some of those second hand. Are the explore scientific better than Baader 68 degrees then?

[Mike_S]

The explore scientific 62 degrees look good value too 

[Ricochet]

1 minute ago, MSammon said:

Sounds good I will look for some of those second hand. Are the explore scientific better than Baader 68 degrees then?

The ES68° are better corrected in fast scopes but the Hyperions have longer eye relief if you have astigmatism and have to wear glasses to observe.

Second hand you should look out for the old versions as well, both the ES Maxvision and the Meade (Series 5000) SWA.

I have not used the 62° series and there are not many reviews to know if they should be recommended or not.

[Mike_S]

Or what about Televue 50 degrees plossls? How do we know what is designed for fast scopes as most of them don't mention focal ratio? 

[alanjgreen]

12 minutes ago, MSammon said:

Or what about Televue 50 degrees plossls? How do we know what is designed for fast scopes as most of them don't mention focal ratio? 

All Televue eyepieces are tested down to f4. All ES eyepieces are tested down to f5.

Those APM 100 degree eyepieces are great in dobs  and well priced. The 5mm is on sale at 199 euro at the moment on the APM website  - I am tempted myself on that offer...!

The problem with the 50 degree plossls is that it will be like looking down a straw and if your scope has no tracking then you will be manually nudging continually. If you buy wider 82 or 100 degree then yes they cost more but much less nudging needed and the usage of them is so much more relaxed  

[Mick J]

Spotted some Maxvision on eBay, may be helpful.

[Mike_S]

Okay super!

[Mike_S]

What else are tested to F4? Max vision and APM? 

[alanjgreen]

1 minute ago, MSammon said:

What else are tested to F4? Max vision and APM? 

No other manufacturer states f4 compatibility as far as I know

[James]

I own a 10" f/4.7 scope and have used various eyepieces over the years, whilst I've now settled on Pentax XW's (took a while to save for them) I use 7mm, 10mm XW's and a 24mm Panoptic. I was quite happy using Baader Hyperions, the 8mm worked well for me. I used the 31mm Aspheric for a time and was happy with the views - the standalone eyepieces are slightly better than the zoom option but the last time I checked the difference wasn't huge.

If you want the perfect "tack sharp" views across the entire field of view you'll need to spend/invest in eyepieces like the Tele Vue's or the Pentax XW's (the ES ones are quite nice too) but they all cost. If you don't have the cash now (and most of us don't/didn't when we set out, or now for that matter!) then there are a variety of options that give very good views. There's an old saying with eyepieces - you can have any two of the following: Good, Cheap, Widefield. I think the boundaries have blurred a little over the years but it still holds true to some extent

I tried for a while to get the widest views I could in terms of focal length but for me I was not happy with the view with eyepieces longer than 32mm in focal length. Similarly from the other end I've not really found I can go below 5mm, even 5mm pushes things a bit on most nights. I settled on the 24mm Panoptic as it is a wide enough field of view (M81 & M82 fit in it) and the background is darker in a 24mm eyepiece than a 32mm.

If the edges of the field of view concern you then you can go for eyepieces with a lower field of view like 68 degree ones. If you want the widefield view of say an 82 degree or more then you really will need to look at the offerings from Tele Vue..

Just some thoughts

Best thing to do is to get out there and try them to see what you do/don't like. That way you'll know what to save your Christmas/birthday money for  Took me about 6 years..

James

 

[Louis D]

Just now, alanjgreen said:

No other manufacturer states f4 compatibility as far as I know

Even though not stated, based on forum feedback, other high end eyepieces do well in fast scopes.

By all accounts, the 3.5mm to 10mm Pentax XW eyepieces do great in fast scopes as well.  The longer ones have field curvature even in slower scopes.  The Nikon NAV-SW and NAV-HW are also supposed to be pretty good in fast scopes, though I have no experience with either.

[Mike_S]

Okay great I will look at all of these. So if I find some high end, would you say wider the better and ideally 68 degrees and above?

[bingevader]

10 hours ago, Louis D said:

@bingevader I didn't intend to flame you. ?

Amused rather then scorched, don't worry.

The Hypreions are also better in slower 'scopes, not sure how they'd fair in yours.

[Mike_S]

Woo so just read Pentax XW and the XL zoom are States on FLO to work down to F4 and F4.5. Sounds good.

[emadmoussa]

Explore Scientific. Well corrected EPS for a fast scope. 

[bingevader]

The Maxvision 28mm might be an option if they're still around.

[John]

When you use really well corrected wide angle eyepieces (eg: Tele Vue, Pentax) in a fast newtonian such as an F/4.7 the optical errors caused by the eyepiece are much diminished or at least substantially reduced compared to lesser quality eyepieces so thats nice. The irony is though that you can now see the optical issues that a fast newtonian has, namely coma, which affects the outer 50% of the field of view. Stick to eyepieces with apparent fields ot 70 degrees or less and the coma should not be too intrusive. When you get to 82 or 100 degree eyepieces, coma can become annoying an a coma corrector becomes desireable.

 

[Mike_S]

Great i am know building more fundamental knowledge to help with future decisions. 

Do you know of any differences in quality between Pentax and Televue?

[Charic]

I advise folk to play safe with their telescope, try not to exceed their/your expectations or that of the telescope.

If you look on the telescopes data plate, there’s often two numbers printed, the Focal Length and the Aperture, and if not already printed the Focal Ratio, derived from dividing the focal length by the aperture so in my case 1200/200=6. The numbers printed on the data plate are invariably rounded for convenience.

If you take an eyepiece that matches the focal ratio, you will have chosen an eyepiece that, given the right viewing conditions, will provide a suitable high power eyepiece, matching the capability of the telescope. I  try forget the fact that my scope has the ability to reach x400 power?
I’ve had x375 on the Moon, but its just too high a power for most practical uses on this scope, often providing a degraded image on anything else.

For your low power eyepiece, limits can still dictate as what’s possible and/or practical.

If your opting for a bright exit pupil of 7mm, your own dilated eye should closely match 7mm to get the maximum use from the exit pupil.

In less than perfect conditions, say early evening, a 7mm exit will appear bright, not much different to what your seeing with the naked eye, just not magnified. But if your pupil can only dilate to 6mm  or less, then you may well have issues later?

Later has arrived? still using the same exit pupil, only its much darker at your perfect site,  but technically  your image should be darker, because your own 6mm entry pupil has reduced the aperture from the 7mm exit pupil of the scope, so even though using the same setup, your not getting the full amount of light as before, a reduction in aperture has taken place, followed by a reduction in contrast, therefore the image looks, may look darker.

The reverse is similar, by having too small an exit pupil, the image will be even darker, and you may even experience further issues, in trying to align your eye to the axis of the smaller exit pupil in order to  just see the image.

Here’s How I would choose a low power eyepiece. You don’t need to be too precise, but my average dilation is 4.9mm, confirmed by a laser optometrist. Ive rounded up to 5. Therefore 5x(focal ratio) = 30. It just so happens that the Skywatcher 32mm Panaview, (which was highly recommended by @rwilky) arrived before I studied the theory that I now follow, but its close enough for my needs, and  this eyepiece does provide a very good view.

If I were to buy a new telescope tomorrow, or just advising someone else,  looking at the scopes data plate will provide my first two eyepieces, one for high power, one for low power, and anything in-between  or just outside is a bonus, based on your experience/desire and the capability/ability of your setup up.

Looking again at my scope, The calculated focal ratio of f/6 suggests  that I choose one 6mm Eyepiece for my high-power  requirement, providing x200 magnification ( note here, x200  matches the scopes aperture(mm) for a simple rule of thumb).

For my Low powered eyepiece its 6x(my entry pupil).

Therefore I have in my collection a 6mm Eyepiece providing x200 power with an exit pupil of 1mm, and a 32mm Eyepiece providing x37 and an exit pupil of 5mm.

For my eyes alone, an exit pupil of less than 1mm or greater than 5mm are not really desirable or practical due to the effects they produce.

My 32mm will provide an exit of  @5.333333333333333  (using eyepiece/focal ratio ) which is close enough, but there’s no hard fast rule, the choice is yours alone, but its highly unlikely that I’ll need anything longer than 32mm just for now, and having already exceed my 6mm by two focal lengths, I’m complete in my focal length collections. But I would suggest again calculating or physically measuring your entry pupil and based on the focal ratio, choose accordingly.

I also use a 5mm and 3.2mm so have already have exceeded my own theory for eyepiece selection, but eyepieces can and do become sets, and if that range exceeds my theory, I’m not going to discount them, I’ll just use them, as and when for what they are, and hope for the best.

Given good seeing, at least one of my eyepieces will prove to be the right one for the occasion at the time of viewing, if not, then its time to go back in.

The eyepieces in my signature work extremely well for my eyes on an f/6 scope. For your f4.7 ratio, your going to need to accept there will be some aberration towards the edge of your field of view, but possibly (should be ) perfect on axis. This is due solely to the nature, principles and  design of a Newtonian telescope, especially  more notable on faster scopes ( @John mentioned earlier ).
The wider your field of view, the more noticeable things can appear, but can be corrected, by the nature of  the eyepiece design, or by the addition of corrector lenses.

Although I have discounted TeleVue (Delos) eyepieces for my scope, for reasons explained in other threads, a second hand TeleVue may make for a good eyepiece as their personally tested to f/4.

Who'd have thought that just  buying a simple eyepiece was fraught  with so many issues!

[Mike_S]

Thanks I am now looking for used Televue Delos or Nagler or Pentax XW. I could end up with anything but at least I’m learning what’s what.

[Mike_S]

If I buy new I think it will be Baader Hyperion. I don’t want to be stuck with crap eyepieces. I’m even thinking that with the Baader zoom at least I will learn what magnifications I use and if i want more field of view then I can go for a 70 degrees ish Pentax or Televue in the future. The reviews for the Hyperions in fast scopes are more good than bad.

[Charic]

34 minutes ago, MSammon said:

I don’t want to be stuck with crap eyepieces.

Only you will know whats best AFTER you have tried an eyepiece for yourself.  Often, It's  the only way!
On paper, just about any eyepiece will have its moment in the right scope, dependent on that scope being setup correctly and under  conditions  which allow for observation. 

You also mention Delos Nagler and Pentax. The Delos were ok, but not outstanding on my scope, but I would imagine they would be of some benefit on a faster scope, like your f/4.7

One member here ,John,  goes out of his way to report  and review on eyepieces far and wide to help us mere mortals, especially when were first starting out.
If I'm not mistaken,John would rate the Delos quite high, but the Pentax even higher, but that's his own opinion based on his skills of observation, the equipment he owns and all possibly dependent  on the viewing conditions. Only the end user can realise if any given eyepiece is actually right for them by testing it.

Its the reason I bought and sold my Delos. I still believe their excellent,  but on the right scope? They made no difference to what I see at present using existing eyepieces, but I could not have known that without trialling them myself. I knew from day one that a  Tele Vue eyepiece was the brand to get, a Plössl of some description and a decent scope. Well I've had them all and the only one that remains is the decent scope! Not that the eyepieces were in any way at fault, their just not required on my f/6 scope, and down to my personal preference/choice. It would have also been a very expensive collection of eyepieces, given that, for a fraction of the price, my main Starguiders do exceptionally well.

Whatever you do/choose, if it's wrong, it was for the right reason, at least you made the test. If its right, you may buy more from the same stable?
Not only that, any decent, expensive or  premium eyepiece you purchase, that does not satisfy your own need, will no doubt sell on to the next enthusiastic buyer, the cycle goes on!