Louis D

@Don Pensack in another recent thread about SCT RCs recommended finding a vintage made in Japan Celestron unit to hit that sweet point between price and quality.

Have you ever picked up a fully laden EQ mount including scope and counterweights?  Once setup, they're very hard to move around.  Can you see the entire sky from a single, convenient location?  I can't, so I have to be able to pick-up my scope/mount combo and move it about.  Make sure to consider this in your decision making.

28 minutes ago, iapa said:

I’d say that there people who can do the design work, and manufacturing facilities that can be adapted.

All we are talking about is precise optics and mechanics.

The general reputation of the UK failing engineering projects is mostly because we were innovating, so others benefitted from our experimentation. Let’s ignore car manufacture which was driven by designed obsolescent practices in the 1960s/70s

Only seems viable at the highest end of the consumer market and in governmental/industrial contracting for either the UK or US.

I think pressure washing might get the job done as well:

In Google English:

The new expensive little ones arrived to enrich my binocular setup in the turret. Two pairs of Takahashi MC LE 18 and 7.5 mm. I hope to try them as soon as possible (today it rains of course, until yesterday good weather) hoping that they do not suffer from parallax. So I will be able to give away all the UFF, FF, and WWF and company. At the moment I can say that they are beautiful and compact, of great quality. Excellent transparency, excellent treatments, excellent internal and barrel blackening.

This is the only 102mm ED objective in cell that I've found:

TS-Optics 102 mm f/7 FPL53 / Lanthanum Glass Objective in Cell

Yes, it's not in the UK.

1 hour ago, amaury said:

I am looking for something between 30 and 36mm. 

If you want perfection and are willing to live with a 70 degrees AFOV at 30mm, you can't really go wrong with the 30mm APM UFF for about $250.  It's basically flawless edge to edge and light and compact (relatively speaking).  It's also sold as the Altair Ultraflat, Meade UHD, and Celestron Ultima Edge.  It's the topmost image in the ~30mm group I posted above.

23 minutes ago, amaury said:

That's is good to know. 

I think I'd be happy with 68°. A wider field of view means more coma and a more expensive eyepiece too. 

Is there any other eyepiece option of the quality/price ratio of the already mentioned Explore Scientific / Meade 5000 / MaxVision?

The Aero ED looks ok but the ES is noticeable better. William Optics SWAN apparently don't perform nearly as good the ones above either. 

 

I also got the 40mm Pentax XW for Christmas which is almost as good as the 40mm Meade SWA, but considerable lighter.  It's also a bit easier to hold the view in it.  They were just reintroduced, albeit at a price probably above your budget.

58 minutes ago, JeremyS said:

That wonder fluidic stuff is pretty pricey, though. What about making your own?
 

Oh sorry, I think we’ve done this one before 🤐

Not difficult if you have access to a chemical supply house.  Just some combination of alcohols, ammonia, distilled water, and detergent.  There are a few exotics ingredients in some like Methylchoroisothiazolinon, Methylthiazolinon, and Ethylene glycol hexyl ether; but these can probably be left out.

On 28/03/2021 at 08:54, Marc1964 said:

I would like to have a higher power lens, say 8-10mm range, and wondering if sticking with the Omni plossls is a good idea, or if I should look at alternative options.

I would go with an 8mm BST Starguider for the comfortable eye relief and larger apparent field of view.  A Plossl at 8mm has fairly tight eye relief.

Yep, beetle-juice is how I've always heard it pronounced in US English.  Don't, don't say it three times in a row.

1 hour ago, Deadlake said:

They are basically barlowed so the FOV changes as you zoom (move the barlow).

This is true and false for varifocal zooms like the Speers Waler 5-8mm.  They literally have a moving Barlow or Smyth lens that changes the focal length, so that much is true.  However, they are far from parfocal, but have a constant field of view, so that part is false.

True zooms have three sections.  The upper section forms the image and never moves, the lowest section acts like a moving Barlow as in a varifocal, while the middle section moves opposite the Barlow as you increase power and maintains some semblance of parfocality.  Because that middle section moves to maintain parfocality, the field of view changes drastically from one end to the other.

Note that coma grows linearly with angular field of view, so it's twice as large at 100 degrees as at 50 degrees.  I really notice it in my ES-92 eyepieces without a coma corrector even at f/6.

Budget makes a huge impact on recommendations, so state yours.

Also, by portable do you mean slipping out the backdoor with it, putting it in the car and driving, putting it in a van and driving, putting it in a backpack, or airline carry-on compatible?

How heavy of a part are you willing to lift when it comes to breaking it down into sections for transport?

5 hours ago, amaury said:

@Louis D maybe it's a silly question, what's the implication of using a f/6 refractor compared to my 8" f/6 reflector? Should I expect similar relative performance?  Does it change the analysis in any way? 

Not really as long as you're using a coma corrector in the Newt.  Even at f/6, I see noticeable improvement in wide field eyepieces when using a coma corrector.  It doesn't even have to be expensive.  I use a GSO/Revelation/TPO coma corrector with a 25mm spacer ring between the eyepiece holder and the optics section and don't even both with parfocalizing most eyepieces.  The lone exception is my 12mm Nagler T4 which focuses 20mm below its shoulder.  I put five 4mm O-rings around the 2" skirt along with a 20mm extension on that skirt to give the focuser something to tighten onto as seen below.

Pretty much, focal ratios behave much the same across design types as far as eyepiece edge correction.  Differences arise due to other aberrations like coma, chromatic aberration, and field curvature.

4 hours ago, amaury said:

My question is, how bad edge performance would I have with an affordable low power wide AFOV like the one below (30mm 68 AFOV)

Well, I've taken lots of images through my eyepiece collection at f/6 (albeit a field flattened 72ED refractor).  Here's the ~30mm group and the 32mm and up group.  You can judge for yourself how much edge falloff there is for simpler designs.

The 35mm Aero ED is in the second group.  It's pretty decent out to 75% of the way to the edge.  The 40mm Meade 5000 SWA is optically identical to the 40mm ES-68.

Once you know you have the Orion nebula centered, shine a light on a white card for a few seconds and stare at it to activate the cones in your fovea and then quickly look back in the eyepiece to see if you can detect color.  I've seen hints of green in an 8" scope using this technique.  Of course, this totally obliterates any dark adaptation you might have had, but you make your choices.

And by the way, look down the front of the scope and see if there is a metal restriction plate with a hole in the middle just behind the objective.  If so, you really have a 35mm or so objective instead of a 70mm objective.  I disassembled mine and pushed that plate out the front with a small board and then reblackened the interior and reassembled the scope.  Correction isn't as good now, but the image is brighter which is what I was going after.

Check that your scope doesn't take 0.965 inch instead of 1.25 inch eyepieces first.  I picked up one of those 70x300 scopes last spring for parts to make a super finder and tossed everything but the lens, lens cell, and metal tube.  Mine came with a 0.965" focuser and eyepieces.

In case you don't know where to measure, it's the outer diameter of the eyepiece insertion barrel (the lower part that is generally unpainted).  If it is 0.965", you'd have to get a 0.965" to 1.25" diagonal or an adapter that might not reach focus.

On 25/03/2021 at 10:25, Space Hopper said:

Just seen the new prices on Celestron Edge HD scopes.

Open mouthed...........the 8" has gone up by a over third !!  

It was always priced very temptingly compared to its bigger 9.25 brother.

I can't see the economic sense by such a large price rise. Its certainly put me off considering one.

 

That, and their current scarcity, might explain why I see used EdgeHD scopes going for close to the old list prices on CN classifieds recently.

On 28/03/2021 at 02:22, Steve Clay said:

Start solar observing. Can't beat doing astronomy in shorts and t-shirt. 

Steve

Although I can't stand the heat for longer than 20 to 30 minutes during Texas summers.  I start sweating all over my equipment as well.  I don't know how hot it gets in the UK during July, for instance, but we average 98 degrees F (37 C) for highs here.  I sometimes run a box fan across me to draw off some heat.

On 01/03/2021 at 03:23, Frank the Troll said:

Makes no difference what mode camera is in, cant be the camera, as a teleconverter works just fine

Was it a manual teleconverter with no electrical connections like the T-ring?  Some cameras won't fire if they can't electrically talk to a lens.  Try firing the camera with no lens attached as a test of this theory.

On 03/03/2021 at 11:54, Louis D said:

OMG! 😲 32mm of in-focus will be required???  I've only got about 15mm of in-focus left on my Dob with a CC in place.  It would be fine in my fracs and Maks, though.

Upon reexamining the diagram, that's 32mm of in-focus in 1.25" mode and 8mm in 2" mode, which is workable for me.

However, notice that the prototype and design diagrams don't match up very well:

So, who know where the focus point will end up?

4 minutes ago, Deadlake said:

I think they have stopped this now, now they make their own scopes. However nice they are, no dealer network in the EU any more. 

It's my understanding that they take Chinese scopes and refigure, respace, and recoat the lenses for optimal performance.  At least that's what I read somewhere once.  They don't do everything from scratch like A-P.

9 minutes ago, Deadlake said:

They do not sell Stellarvue cases or EP's.

Well, the 55 degree planetaries have been sold over the years under numerous other labels, their UWAs are the same as the 4mm, 7mm, and 16mm UWAs sold under other labels, and their Optimus eyepieces are the same as the APM XWA HDCs.  I'm not as familiar with other suppliers for soft cases, though.