John

30 minutes ago, globular said:

In the copy of Suiter's book that I have the 'wobbly stack' items are listed without numbers or an order of importance - rather they are roughly stacked in the order that light from the object travels through the 'system'.  Read your list above with that in mind and you might agree that the same applies to Roger Vine's reproduction of the stack too.

That makes sense apart from 1 and 2 which could arguably be reversed perhaps ?

It's interesting to note that the diagonal is further up the "wobbly stack" of issues which impact the quality of the view than eyepieces. This is from a comparison of planetary eyepieces from Roger Vine's excellent "Scopeviews" website:

"The Wobbly Stack

What you see is a pretty subjective thing anyhow, but let’s look at some of the theory behind it.

In Star Testing Astronomical Telescopes, Richard Suiter describes the telescope system as like a wobbly stack of filters which at each level takes away a bit more contrast; tip it too far and the whole thing falls over. Items on the stack include:

1 Aperture

2 Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment)

3 Quality of the primary optics

4 Central obstruction size

5 Alignment of the optics

6 The diagonal (mirrors scatter much more than lenses)

7 The ability of the focuser to deliver critical fine focus

8 The eyepiece

9 The skill and fatigue level of the observer and their eyes"

If you add the weight of a 2 inch diagonal to that of a low power / wide angle 2 inch eyepiece you have 2lbs plus hanging off the back of the scope so the focuser needs to be reasonably robust and scope balance might need to be adjusted.

19 minutes ago, bosun21 said:

The ring is quite small in the WO diagonal and the open aperture is larger than the largest field stop in my WF eyepieces which is the SL 30mm UFF. This of course should be taken into consideration when buying a diagonal and making sure that it can accommodate all your eyepieces.

The 30mm UFF field stop (which I believe is 36.9mm in diameter or thereabouts) does not max out the 2 inch barrel so no issue with that one 🙂

The Nagler 31 has a 42mm field stop so that might be an issue.

The William Optics diagonals (and clones under other brandings) use quite a thick internal ring to attach the eyepiece holder to the diagonal body. This ring might slightly vignette the field of view of 2 inch eyepieces which max out the field stop diameter. I think this is the point that @Mr Spock makes in his earlier post ?

My own 2 inch diagonals are Tele Vue Everbright and Astro Physics but carry a substantial cost premium so I won't push those on you !

I have used the Revelation / GSO 2 inch diagonals in the past (and a number of others) and found the former pretty good performers. 

Galaxy A54 5G is an odd name for a cat ? 

30 minutes ago, RT65CB-SWL said:

The first viewing of Saturn is like a first date… unforgettable!

I can't recall much about my 1st date but my 1st view of Saturn (also around 45 years ago) is etched on my memory 😁

That looks about right.

I have a 31mm Nagler and that compared with a 32mm plossl looks like this:

So a little bit more again. 

Is that extra view worth the investment ?

Well that is a question that is often asked but virtually impossible to answer. I suppose it depends on your observing preferences. If you like to see as much of the larger deep sky objects as possible or to see well known pairings / groups of objects in the same field of view then you will welcome the wider view. If you are happy to stay with a quite wide view, which, lets face it, most deep sky objects will fit easily into, then there are probably better ways to spend the money.

Lots of droolworthy instruments together at the Giovale Public Observing Deck at the Lowell Observatory. This was just being completed when we visited the observatory back in 2019. I think the smallest scope there is a TEC 140 triplet and the largest a 32 inch dobsonian:

I wonder what the largest aperture apo refractor in private hands in the UK is ?

@stuy's must be right up there - it's magnificent 😁

6 hours ago, Don Pensack said:

One Zoom that gives sharp images, excellent contrast, and adequate eye relief PLUS a constant 66-67° over its range is the APM 7.7-15.4mm "Super Zoom".

You can run into in-focus issues if it's used as a 1.25" eyepiece, but used as a 2" one shouldn't have focus issues.

I liked the optics a bit better than the Baader over the same range (8-16mm on the Baader).

Maybe it doesn't qualify as cheap, though.

Yes, I felt the same when I compared those two recently. 

Very briefly, Europa's (rather small) shadow transiting Jupiter's southern hemisphere, with my 100mm refractor.

This is from the Sky & Telescope Jupiter's moon's app:

I've just been observing tonights Europa shadow transit. With my 100mm refractor the shadow was quite small and low on Jupiter's disk. Not as easy to see as some transit shadow's I agree. I found 150x showed the sharpest view tonight. The shadow did appear black but that is with more aperture.

Your Vixen SD81S (and your eye) are doing a good job 🙂

28 minutes ago, Jim L said:

The difference between Ernest’s reviews and most everyone else’s is the difference between objective and subjective analysis. Ernest bench tests eyepiece optics; to my knowledge that makes his analyses quite rare in the amateur astronomy community, if not unique.

Quantitative analyses takes no prisoners, makes no allowances for the name on the eyepiece or its price, and feelings be damned. It doesn’t replace the expert subjective analysis of extraordinarily experienced and astute reviewers such as our own Don Pensack and Bill Paolini, but it is an extraordinarily powerful approach and one well worth paying close attention to. 

The french magazine "Ciel et Espace" used to include optical bench tests in their eyepiece group tests. They stopped a while back but while they were doing it, they were the most comprehensive equipment reports I've seen in any publication. 

Here are a couple of examples (in french): 

https://web.archive.org/web/20110622011950/http://cieletespace.fr/files/InstrumentTest/201102_test_oculaires.pdf

https://web.archive.org/web/20130829052725/http://www.cieletespace.fr:80/files/InstrumentTest/201306__6_oculaires_10mm.pdf

2 minutes ago, Mark2022 said:

I'd find it interesting to compare the Baader with the SVBony just for the heck of it. Vlad of AVT Astro on youtube has and I tend to respect his opinion while even he has suggested, while the Baader wins, it's by a hair or two. I just didn't wish to spend 10x more for a hair and now, having the zoom, I realise I don't need to. People go  on about FOV differences of one eyepiece against another and  debate till the cows come home. I say, you use the kit you have and the kit you have is the 'norm' for you and, if it does the job, who cares about an extra degree or two at the highest mag?

The margins of performance gain between eyepieces (and other optical systems for that matter) are usually quite fine these days. The "other" brands have been continually pressing closer and closer to the "premium" branded products for the past few years so the value for money equation for the top performers is looking very marginal these days.

It's good news really - you don't need to spend big for good performance today and for those who value those extra "hairs" and who don't worry so much about the cost, there are options there as well 🙂

I have the Mk IV Baader 8-24 zoom and feel that it's pretty good. It compares quite well with my Pentax XW's in the 16mm-10mm part of it's range. Not too keen on the narrow AFoV at 24mm and there is quite a bit of re-focusing needed through the focal length range though. 

The only Svbony zoom that I've used is the 8mm-3mm one but that I guess is quite a different design to the mid-range Svbony zooms mentioned on here ?

Congratulations on 10 years of your excellent web site Matthew 👍

I own a few of the items that you have reviewed and agree 100% with your opinions of them.

Thanks for all the effort you put in to your site and for your input to SGL as well. Much appreciated.

To @JAC51, as Matthew says, I use a T-Rex with my 130mm F/9.2  but I think the currently available equivalent would be the Rowan AZ100.

I have used the scope on a Skytee II and an Ercole and it works but vibrations when observing at 200x and above (which is often with such a scope) don't do the views any favours.

Hi,

I'm at Portishead so not far from Bristol. I'm a member of Bristol Astro Society.

I've been using newtonians for many years now so might be able to help. Send me a PM (Private Message) if you like 🙂

21 minutes ago, Roy Challen said:

Agree with this, I don't even like removing eyepieces or diagonals...so I need to buy at least one more!😁

It seems like 3 or 4 scopes is the right number of scopes needed.😉

Agreed here as well - which is why I own 5 diagonals and 7 finders 😁

I have a 3 scope agreement with my other half. So I'm on very thin ice currently with 7 😬

With car suspension springs you can uprate them for towing by fitting rubber inserts into the springs. I wonder if something similar but on a much smaller scale could be used for newtonian primary springs to make the upgrade easier ?

7 hours ago, JeremyS said:

I thought you wouldn’t be without a Dob for long, John. Which did you go for?

I found an practically unused Skywatcher 200P "Classic" (a lockdown purchase I reckon) for a snip so could not resist. It will be a good, robust, alternative to my fracs and a good outreach scope as well. Hoping to do quite a bit of the latter with Bristol AS this Autumn. Had fun last night using my Ethos eyepieces in a scope that cost a fraction of the price of each of the eyepieces !

I have stuck a 9x50 RACI finder that I already had on it to replace the straight though stock one one plus some collimation tweaking but otherwise it's as it came out of the box. The scope still has that "new scope" smell about it 🙂 

Just now, Mr Spock said:

It's not difficult, but it is critical to good image quality 

And the manufacturer must know this and especially so at F/4. And yet .........

4 hours ago, Mr Spock said:

So, new springs fitted 👍It's surprising how weak the supplied springs are. Why have they never sorted this? 

 

GSO made scope ? - weak springs have been reported for around 15 years as I recall.

Why indeed on otherwise good telescopes 🙄

Judging by the comments on here, the one issue that folks are concerned about with newtonians is collimation !

Glad you have got it sorted 🙂

Here are a few refractors that I've owned / still own. 1st photo shows a Synta 150mm F/8 achromat, a Bresser 127L F/9.4 achromat and my Vixen ED102SS F/6.5. 2nd photo compares my TMB/LZOS 130 F/9.2 triplet, Skywatcher ED120 F/7.5, Takahashi FC100 F/9 and the Vixen ED102SS again. 3rd photo shows the Vixen 102, the Skywatcher 120 and the rather monstrous Istar 150 F/12. The latter is physically the largest and heaviest refractor that I've owned.

I managed a quick first light with a Skywatcher 200mm dob that I've recently acquired (today in fact). Much cloud cover restricted observing options but I was pleased with the views of M57 and Saturn plus moons.

The scope was pretty much straight out of the box but delivered surprisingly nice views. It's been a long time since I had one of these but I can see why they are so popular 🙂