2" Explore Scientific 2x vs 2" Luminos 2.5x

[jasondvd79]

Hi I recently purchased a Skywatcher Dobsonian 200p and am really torn between the 2" Explore Scientific 2x Focal Extender and the 2" Luminos 2.5x barlow.

Would really appreciate any advice.

Thanks in advance. 👍🏻 

[JeremyS]

Just a thought: a 2-inch Barlow is a bulky heavy beast. higher mags, such as used with Barlows, are usually obtained with 1.25 inch eyepieces.

Of course, you might have other reasons, like imaging……

[jasondvd79]

Part to do with imaging and as planning to buy a few 2" eyepieces I don't want to regret not having the option to double them.

I'm sure I'll benefit from using a counter weight of some sort though.

[John]

The ES Focal Extender will have less, or no, impact on focal position, field of view vignetting and eye relief, which the barlow will impact to some extent.

As @JeremyS says though, 2 inch barlows / extenders are bulky things and can create quite a lot of stress on the focuser as well as scope balance.

 

Edited December 30, 2021 by John

[Louis D]

Make sure to buy a telecentric 2" magnifier if you're insistent on using widest field 2" eyepieces in them.  Otherwise, you'll get severe vignetting that actually looks more like a hard cutoff of the field like a smaller field stop.  That said, I would just get an affordable 1.25" Barlow for starters since it's rare to double up 2" eyepieces except for those which are 2" due to being huge like the ES-92 and ES-100 series.

[jasondvd79]

@John @Louis D @JeremyS

Thank you as I have now realised I was making a newbie mistake, I will now revert back to 1.25 route and maybe look at having 1x 2" eyepiece for use on its own.

I'm glad I posted on here now as I don't have the knowledge you guys clearly have so thank you.

I do want to buy a good 1.25 Barlow in that case and have been looking at the following:

1. Explorer Scientific focal ext. 1.25 2x

2. Tele Vue 2x

3. Vixen 2x Deluxe Barlow

Also in terms of eyepieces the main ones I have been considering the most are the following:

1. Explorer Scientific 68 and 82 degrees

2. Baader Morpheus and HYPERION

3. APM Ultra Flat Field Eyepieces 65°

My idea is to buy 1x 2" 33mm and 3x 1.25 maybe a 10mm, 18mm and 25mm for example.

Any thoughts or advice would be massively appreciated!

Sorry its so long winded 😫

[Louis D]

I recently picked up a used ES FE 2x, but haven't had a chance to try it out under night skies.  It would probably be best for a 24mm/25mm eyepiece to avoid vignetting.  If I ever get a chance to try it out, I'll report back on it.

I've had a TV 2x for over 20 years.  It certainly works well, but isn't spectacularly better than other vintage options.  It's certainly high priced today.

Since the Vixen isn't sold (or ever been sold) in the US, I know nothing of it.  It might be very good based on my experience with Japanese made Barlows.

If you follow the used market, my vintage favorites are the following Japanese made Barlows:

Orion Deluxe: very long (not an issue for Newts), but the cleanest image with no light scatter even at highest powers.

Meade 140 APO (3 elements): Mid length, basically identical to the TV with just a hint of scatter at highest powers.

Celestron Ultima/Parks Gold Series/Orion Shorty Plus (3 elements): Again, basically identical to the Meade and TV, but short and compatible with refractors.

All three of these regularly show up in the US for under $50 in the astro classifieds.  Similar performance new generally runs over $100.

The only modern Barlow I own is the GSO ED 2" 2x which is great for general usage, but it is not at the same level of polish as those above.  There is noticeable scatter at high powers, so I generally use it with a Tele Vue Panoptic Barlow Interface to make a poor man's 2" 2X Powermate.  I then use my 2" low power eyepieces in the combo just for fun some nights to change things up.

I also have the Orion 2" Deluxe 2x which is very long, but similar to the 1.25" version in scatter.  However, it is incompatible with the TV PBI, so it's not very useful with long focal length 2" eyepieces unless you live with the hard vignetting.

I have no idea if any of today's Chinese or Taiwanese made 1.25" Barlows have the same level of polish as the vintage Japanese Barlows I mentioned above.  Perhaps others have compared them to yesterday's best.  Starting out, I'm sure some of them would work well enough even if not being at the highest levels of polish.

[Louis D]

As far as eyepieces, do you have astigmatism in your eye?  Check your eyeglass prescription for CYL or cylinder.  If it exceeds 1.0 diopter, you might want long eye relief eyepieces at lower powers so you can wear your eyeglasses at the eyepiece.

If astigmatism isn't an issue, there are many good options including the ES-68/82 lines.  There are also the Nirvana 82 and their other brandings if you want ultrawides.  The UFF line at 18mm and below is also a good choice.

If astigmatism is an issue, the Morpheus line is better corrected than the Hyperion line.

The 24mm APM UFF is a good choice whether or not you have astigmatism.

The 30mm APM UFF is an excellent choice for a near widest field 2" eyepiece whether or not you have astigmatism.

The APM UFF line is now sold under many other brands as well.

I wouldn't buy an 18mm and a 25mm.  They're just too close in power with your Dob.  If you don't get the 2" eyepiece, get the 25mm and skip the 18mm.

If you do get a 30mm 2", I'd skip the 25mm and 18mm and get a 12mm to 16mm eyepiece for general mid-power viewing.

Lastly, I would get a 5mm to 8mm eyepiece for high power viewing.  With a 2x Barlow, you can get some higher/highest powers with the mid and higher power eyepieces.

[Mr Spock]

Here's the two I have and shows the difference in size between 2" and 1.25". 

The Meade Apo is great - but only available used. I believe ENS Optical has one in stock. The 2" is similar to this one FLO has https://www.firstlightoptics.com/barlows/skywatcher-ed-deluxe-2x-two-inch-barlow-lens.html

For me, both are excellent quality. On test I find the Meade to be consistently around x2.35. With the 2", adding a 35mm extension tube turns it into a x2.5. 

The ES looks pretty good quality too https://www.firstlightoptics.com/barlows/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

[John]

I was loaned one of the Explore Scientific 1.25 inch 2.x focal extenders a few years ago to compare with the Tele Vue 2.5x Powermate that I had at the time. The ES focal extender compared very well indeed quite honestly.

Personally I like the way that these devices (compared to barlow lenses) have much less, or no, impact on the point where eyepieces reach focus (important if your focuser has limited travel), don't tend to vignette the field edges when used with eyepieces with close to the maximum field stop size, and don't extend eye relief.

I don't use barlows or extenders much these days but have kept a Baader 2.25x barlow which are basic but quite good optically, for occasional use.

 

[jasondvd79]

Thanks guys.

I'm very close to purchasing 1st eyepiece and the 2 I have narrowed it down to 2 which are:

1 APM XWA 13mm 100 degree at £207

2 Baader Morpheus 17.5 at £190

I have heard and read lots of good things about both, I'm also aware the APM has less eye relief.

I think I would consider buying both in time but can only afford 1 for now.

Any advice as to which one or even if you think I'm making a mistake etc. would be much appreciated!

Edited January 1, 2022 by jasondvd79
Typo

[jetstream]

2 hours ago, jasondvd79 said:

Any advice as to which one or even if you think I'm making a mistake etc. would be much appreciated!

Just curious what you want to observe for the mentioned 2 eyepieces? If DSO is on the menu how dark are your skies? Filter use? or lunar/planetary?

[jasondvd79]

3 hours ago, jetstream said:

Just curious what you want to observe for the mentioned 2 eyepieces? If DSO is on the menu how dark are your skies? Filter use? or lunar/planetary?

 

[jasondvd79]

Aim is to eventually view most things but sooner rather than later I would like to view and photograph the Moon, Saturn and Jupiter just using Smartphone with attatchment.

Very aware I can't get great photographs this way but want to get my little one to enjoy it too.

I understand the 100 fov might sound like overkill but my logic behind that is the need to move  the scope less.

I was advised as im in the UK we only have very few nights of the year that something like a 6.5mm would give any real use and generally we benefit more at the 10mm and above mark year around due to our conditions, so figured the APM 13mm was a good option as could barlow to 6.5 on the few occasions that I would get rather than spent alot on dedicated 6.5mm option.

Only have a Moon filter at the moment but will look into filters further.

As I'm in London not sky isn't that great however I am planning to go out of London to to achieve much better views.

I genuinely don't have the knowledge in knowing how these particular 2 ie 13mm and 17.5mm would work for me (with barlow or FE included) but theory was to try and spread the range so for example having those 2 then adding a 25mm and a 2" 32mm.

I'm very aware that this might also seem like trying to run before you can walk but I guess I'm trying to buy once rather than less quality then wanting to upgrade making it far more expensive in the long run.

I hope all that makes sense and massively appreciate all the help from you guys as I'm a complete novice. 

[Mr Spock]

The 17.5mm and 13mm are good sizes for a x2 Barlow. They add the equivalent of 8.75mm and 6.5mm which gives a good spread - x69, x92, x137, x184 - perfect.

If you are worried about nudging too much, have you considered an EQ platform?

The only issue I find with x2 Barlows is you end up duplicating magnifications at some point. 

[jasondvd79]

@Mr Spock I litterally just read you asking that same question in another post 😆 I would love one however I not only wouldn't be sure which one would work best for my set up but think a little pricey for me at the moment but definitely a valuable option.

[John]

I guess the risk is that you might not like the 100 degree eyepiece experience ?

Personally I enjoy them a lot but I know they are not everyone's "cup of tea".

The Baader Morpheus seems to be popular with everybody who uses them.

In terms of overall performance the two will be pretty much the same I reckon. The 13mm XWA will be a big chunk to have hanging out of a barlow or focal extender of course although the Morpheus is also quite sizeable.

 

Edited January 1, 2022 by John

[jasondvd79]

Yes agree might be quite alot of weight with both attached, here is a question that will possibly REALLY expose how much of a newbie I am 😄 but my thought was to buy a substantial sized magnet and of course depending where you positioned it at the opposite end it would balance the scope in what I thought would be a time and effort efficient solution?

Is this when someone slaps the back of my head and says are you crazy! 🤣

[AstroKeith]

12 minutes ago, jasondvd79 said:

Yes agree might be quite alot of weight with both attached, here is a question that will possibly REALLY expose how much of a newbie I am 😄 but my thought was to buy a substantial sized magnet and of course depending where you positioned it at the opposite end it would balance the scope in what I thought would be a time and effort efficient solution?

Is this when someone slaps the back of my head and says are you crazy! 🤣

Magnetically attached weights are a good solution. There are even some sold commercially specially for the purpose. (Pricey though!)

[John]

I use a magnetic weight counterbalance approach on my 12 inch dobsonian. The tube is aluminum though so I have attached a magnetic strip to the tube and have a couple of weights that I can use in 2 positions depending on the top end load and the angle at which the scope is pointing - the closer to the horizon, the more counterweighting I need:

 

 

[jasondvd79]

So it's actually a thing! and I escape being astronomically slapped 🥳

I'm not gonna lie @John I'm slightly impressed 🤣 that's a serious bit of kit!

Is counter weight strip etc. available to buy or something you have built?

Looks good. 👍🏻

[Mr Spock]

Magnetic knife strip?

[jetstream]

4 hours ago, John said:

The 13mm XWA will be a big chunk to have hanging out of a barlow

+1 ^^^

Very heavy setups ie my binoviewers can de collimate my dobs enough to cause loss of detail past half racked out. My truss dobs are very sturdy as are the Moonlights...

[cajen2]

5 hours ago, jasondvd79 said:

@Mr Spock I litterally just read you asking that same question in another post 😆 I would love one however I not only wouldn't be sure which one would work best for my set up but think a little pricey for me at the moment but definitely a valuable option.

Your post and requirements are very similar to mine (I think it was my post that you're referring to) and remarkably, I came up with the same two makes of EP as you. The only problem is availability on both.

I'm seriously considering buying a tracking platform (https://www.firstlightoptics.com/equatorial-astronomy-mounts/asterion-ecliptica-light-tracking-platform-for-dobsonian-telescopes.html) and this one's price isn't much more than some of the EPs mentioned. I've decided to get one EP first, then later the platform, being old and poor.....😉

 

 

 

[John]

3 hours ago, jasondvd79 said:

So it's actually a thing! and I escape being astronomically slapped 🥳

I'm not gonna lie @John I'm slightly impressed 🤣 that's a serious bit of kit!

Is counter weight strip etc. available to buy or something you have built?

Looks good. 👍🏻

@Mr Spock has made a logical deduction - it's a magnetic kitchen knife strip. A few quid from e.bay. I had a couple of weights left over from an old telescope mount.