John

4 hours ago, Louis D said:

I tried both ES-92s in a variety of Barlow/PBI/CC combinations tonight to view the moon with my 8" f/6 Dob.  The cleanest view would have to go to the Orion Deluxe 2" Barlow.  It was simply sharp across the field.  The GSO ED 2" Barlow was close behind, but caused (or failed to mask) a bit of field curvature and slight sharpness issues at the edge.  Adding the PBI to the GSO ED seemed to flatten the field, but introduced edge aberrations of some sort.  With no bright stars handy, further diagnosis will have to wait.  For the longest focal length eyepieces, there was definite field truncation with either Barlow alone, but the Orion was again sharper across the field.  The GSO+PBI eliminated the truncation, but the image wasn't as sharp across the field.

Adding the GSO CC into the mix (between the eyepiece and either Barlow) did nothing to sharpen the image of the Orion Deluxe with the ES-92s.  I would say the image was much better without it.  Results were similar with the GSO ED.  However, adding the GSO CC to either Barlow eliminated the field truncation seen with the longest focal length eyepieces.  It was acting a bit like a PBI, apparently.  I was undecided if the GSO ED + PBI was better than the GSO ED + GSO CC with longest eyepieces.  Going GSO ED + PBI + GSO CC would seem ideal, but again, the results were mixed with longest eyepieces and downright bad with the ES-92s.  I think there's just too much glass and too many interactions going on.

Screwing the GSO ED lens element directly onto the bottom of every eyepiece resulted in a sharp inner 50% and a dreadful outer 50%.  Literally all eyepieces turned to a blurry mush that couldn't be refocused in the outer 50%.  Highly NOT recommended.

My recommendation for the ES-92s would be to try to find a Japanese made Orion Deluxe 2" Barlow if you have a Dob and skip adding a CC to it for use with the ES-92s.  Barring finding the Orion or another vintage long 2" Barlow, the GSO ED is a decent alternative.  I'm not sure how much improvement a genuine TV Powermate would yield as I could see no significant image degradation introduced by the long Barlow.  There was a tiny bit introduced by the shorty GSO ED Barlow around the edges.  It was a subtle difference.    The 12mm ES-92 in particular did best with the Orion alone.  Adding either the PBI or GSO CC to the GSO ED led to less sharpness, so less is more in this case.  The good thing is that these Japanese 2" Barlows turn up for decent prices every once in a while on the used market because they are relatively unknown to today's astronomers.

For longest focal length eyepieces, the GSO ED + PBI worked best across the field and eliminated field truncation best.  However, central sharpness was again best in the Orion Barlow.  The gentler lens curves of the long Barlow seem less demanding on eyepieces even when a PBI was added to the GSO ED.

None of the combinations resulted in terribly finicky exit pupil issues.  The GSO ED, though, seemed to introduce more than the Orion, even with the PBI in place.

Interesting feedback Louis.

Is the Orion Deluxe 2" Barlow this one ?:

The upper barrel section looks very similar to the body of the Mk 1 Antares 1.6x 2 inch barlow, also made in Japan. I wonder if the manufacturer is the same ?.

Did you encounter any issues with eye positioning when using the barlows with the ES 82 eyepieces ?. You mention exit pupil but I wasn't sure if you meant it's position in relation to distance from the eye lens or something else.

A barlow lens usually pushes out the eye relief to some extent. For me the eye relief with the 12mm ES 92 was too long as standard and it's just about OK with the 17mm. Personally, I would not want the eye position moved further out with these eyepieces. I can appreciate that the glasses wearer might have different preferences though !

I've been reading Ed Ting's reviews for around a decade I think. He and Todd Gross used to be my "go to" websites for information and viewpoints on equipment.

Ed ran into some trouble over a review the he did on a piece of optical equipment which was rather negative. It turned out that he had not installed it according to the manufacturer's instructions and the manufacturer challenged him regarding the review. He published a correction but was rather shaken up by the incident so withdrew from posting reviews for a while. 

It's good to see that he is doing reviews and posting them on the web again.

24 minutes ago, globular said:

I've been working along the same lines... but at a slightly higher figure of 5mm max exit pupil because my skies are not that highly polluted.

My XW40 in my F/10.5 scope gives exit pupil of 4.8mm and looks great to my eyes in my garden.  So that seems to fit.

If John finds 21mm Ethos and 31 Nagler are the limit then I guess that means he must be using scopes around the F/6 mark and/or more polluted skies.

My scopes are F/5.3, F/6.5, F/7.5, F/9 and F/9.25.

My skies are probably not bad for the edge of a large town and with two major cities within 15 miles of me. I've seen the Horsehead Nebula from my back garden when things have been at their best.

Most of my faint target observing is with the 12 inch F/5.3 dobsonian. The other scopes are refractors from 100mm to 130mm and I don't often use the 21 Ethos or 31 Nagler with those. The exception is the 31 Nagler in my Vixen ED 102mm F/6.5 refractor when I want to observe the whole of the Veil Nebula.

I really liked the Aero ED 40 but I decided to have a bit of a clear out a couple of months back and the 30mm and 40mm Aero ED's were not getting much use so I let them go to new homes.

It's not the eyepiece. My skies have some moderate light pollution so I find that using more magnification helps darken the background sky. I've owned a number of eyepieces of 40mm and even 50mm focal length but always ended up using the shorter FL ones more. I'm a bit of an occularholic though so sometimes get tempted to try longer ones again if one pops up at a good price

If your diagonal is made of plastic, an upgrade may be well worth while.

On eypeieces, a BST Starguider 5mm eyepiece is good quality, has longer eye relief than a plossl, a wider field of view and will give you 133x magnification.

Seeing the Cassini Division is quite possible with a 102mm scope but it is not easy and the seeing conditions need to be at least moderately good for it to be seen. The low altitude of Saturn currently does not help matters either.

I saw it as well ....... through a telescope

Got about 10 minutes before I got clouded out

15 minutes ago, vlaiv said:

Problem of course being that one can't get new Aero ED 40mm - it is just unavailable wherever I look.

 

I should have sold mine for more then !

3 minutes ago, johnturley said:

Thanks John

Is the quoted 68 degree APFOV of the Aero ED genuine, it looks very compact compared to the Panoptic especially in the 40 mm focal length.

I would probably however more likely go for the 35 mm as a replacement for the Baader Aspheric 36mm, may however wait until Rother Valley Optics showroom re-opens (hopefully sometime in the spring), so that I can look at one before deciding whether to purchase.

John 

I didn't measure the AFoV of the Aero ED40 but it sure looked like a 68 degree AFoV to me. I have Pentax XW's, a 24mm Panoptic and a couple of Delos eyepieces with AFoV's around this figure and the Aero ED40 seemed to offer something very similar.

I found the Aero ED 40 a really nice eyepiece even in my F/5.3 12 inch dob. Not perfect but surprisingly well corrected across the field of view for a relatively low cost super wide 2 inch.

I recently sold it though because I find that I just don't use that longer focal length under my skies. The 31mm Nagler and the 21mm Ethos work better for me with regards to background sky darkness and DSO contrast. Hugely more expensive though and much heavier eyepieces.

For the £60 or so that the Aero ED 40 cost me pre-owned it was a great performer though.

2 minutes ago, johnturley said:

The Masuyama UltraWideField 32mm looks promising on paper with a quoted APFOV of 85 degrees, and about half the price and weight of the 31 mm Nagler, but wonder what the edge performance of the 5 element modified Plossl design of the Masuyama would be compared to the latter. 

John 

https://www.cloudynights.com/topic/562496-masuyama-32mm-85-deg/

https://www.cloudynights.com/topic/585719-31mm-nagler-type-5-vs-32mm-masuyama-85-degree-at-f7/

The Aero ED 35mm is a better corrected eyepiece than either the Superview or the Baader Aspherics IMHO. From the reports, the Superviews are performing as I expected. The Baader Aspheric (I had the 36mm for a while) was a disappointment - I had hoped that it would be better.

The Aero ED's are the best of the lower cost super wide eyepieces that I've used. For around £50 pre-owned they are great buys.

If the scope has foil spacers these can cause indentations of sorts around the edge of a de-focussed star image.

29 minutes ago, Saganite said:

So close to getting E&F with the bino, but I think it is going to need better seeing than I have at the moment. Definitely think it is doable.

I've found that they are within the grasp of a 4 inch but conditions are key with that aperture. 4.7 inches makes them more routine.

E is seen more readily than F.

I had about 15 minutes of clearish sky earlier this evening. The views of Mars were very mediocre. The Moon was rather nice though. That was it though. Cloudy since then.

Great stuff Steve

I got about 15 minutes cloud free here - just enough for a quick look and Mars and the moon, then that was it.

Just as well there was the SGL zoom cast to watch !

Very interesting - I enjoyed that

Famous US mailbox

19 minutes ago, Saganite said:

Thanks John, this my first ever Vixen !

First light with this scope is showing glorious views of the Moon, very sharp and steady at 159X.  The sky looks very promising for tonight. Hope it is the same where you are.

Not so good here Steve but it's been a bit like that lately

Vixen do know how to make a good objective lens I reckon. Not just the glass types used but the figuring and polishing as well

It is either a Skywatcher Explorer 200 or 250PX optical tube on what looks like an EQ5 mount head on what looks like a Bresser tripod. It's not the standard Skywatcher tripod but it should work OK. The 250PX would a bit undermounted on the EQ5 mount though. Might be OK for visual observing. There is a black label under the focuser which will have the specs of the scope printed on it - perhaps the owner could confirm for you ?

She might have measured the tube diameter rather than the main mirror diameter which is what defines the aperture.

The eyepiece position can be awkward at times when observing with this type of setup but you can, with some care, rotate the scope in the tube rings to help with that.

The mount does not look like it has motor drives so you use the manual slow motion controls to track with it.

The main thing to check is the condition of the mirror coatings. Ideally they should be very good, clean and bright but slight dust is not an issue.

I would have thought £200-£250 might be a fair price if all is in good order ?

Lovely scope Steve

A longer version of my Vixen ED102SS.

I enjoyed reading that - thanks for posting it

Vixen made a lot of stuff for Celestron in the past. Scopes, eyepieces and mounts.

Way back I owned and used the Celestron 1.25" 32mm Erfle (also circle V).

There was a short bodied version of the 2 inch Erfle as well:

Many of todays low cost super wide eyepieces are derived from the erfle design.

The 1.25 inch or 2 inch barrel internal diameter restricts the max AFoV regardless of what the specs state. There used to be a 1.25 inch format 32mm Erfle eyepiece under various brandings that claimed a 60 degree AFoV. Once I got my eager hands on one I soon realised that the AFoV was no larger than a 32mm plossl because the field stop could not be any larger. I'd been a little naive to believe the specs

If a manufacturer is using a smaller field stop it's likely that is because the optical design would show unacceptable distortion if a wider field stop / AFoV was used. There are examples around where a manufacturer has "pushed" an optical design beyond it's capabilities eg: the Meade 5000 super plossls where they pushed the AFoV out to 60 degrees and the results were not pretty.

1 hour ago, Alan White said:

Wow, what a small watch! Makes the 17mm look big 😉

Action mans watch !

I've reported a 2nd one as well.

There will be others though. From past patterns I'd expect this to crop up frequently for a while as the scammers work through their list of hacked e.bay accounts.

This, by the way is a genuine advert from APM Telescopes in Germany who are actually offering this scope for sale on their website and on e.bay:

https://www.ebay.co.uk/itm/Nikon-100-MM-For-1200-MM-Ed-Apochromatic-Lens-Refractor-Telescoping/131977350869?hash=item1eba768ed5:g:AVcAAOSwCNJfLg6Z