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Going retro vintage Japanese glass


F15Rules

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Recently I've been concentrating on 3 main eyepieces in a drive to spend less time swapping eyepieces and more time actually observing. So I've been using a Pentax SMC 8-24mm zoom as my workhorse unit, with an excellent Pentax 10.5mm XL ( and until recently a fine XL7), and the Vixen LVW 22, probably my favourite fixed length eyepiece.

For finder work and dark sky sweeping I've also got a nice TS 40mm 2" Paracor ( Aero/TMB clone), which I will use more in the summer skies.

I've found this simplification quite satisfying, and recently concluded that for much of my viewing I don't need more than the LVW22 and the Pentax zoom: along with a WO 1.6x barlow nosepiece (which converts the zoom to a 5-15mm zoom unit).

So being a long time long refractor fan and also a fan of older Japanese orthoscopics and other older eps, I decided to look for a few good quality Japanese units with a view to maybe acquiring a small set.

To my surprise, a lovely set of Parks Gold plossls came up in one of my searches and I went for them - having ensured first that I could raise funds by first selling a couple of items. So, a pair of Pentax items were sold selling quickly, and I went for the Parks Gold set of 6 clones of the Celestron Ultima, Orion Ultrascopic, Antares Elite and Tak LE ranges.

These are, I believe, very early (early - mid 1980s) examples of the Parks Gold series, in very good original condition with boxes and similar, but not identical cosmetics to the later range of Parks GS's.

Here are some pictures: they all look great, but in particular the 25mm and 30mm ones look wonderful. And they all have smooth barrels, so no snagging in diagonals with these?.

Interestingly, only the 20mm has a "Japan" stamped barrel, but all 6 also carry a "Japan" sticker.

I have also secured a new-old-stock 3.8mm high power version, so I will have 7 out of the 9 sizes (I always liked "seven of nine " in Star Trek)!.

I'm really looking forward to trying these out with my FS128 when the skies clear..I'll post up my thoughts post - First Light.

Dave

 

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Very nice Dave. The 30 and 25 do look lovely!!

One of my biggest regrets is having sold a lovely set of Celestron Ultima Plossls with the barlow and a nice case. At the time I just didn't know enough to realize they were actually pretty good, sold them for way less than they were worth. Somebody got a good deal!

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3 hours ago, Stu said:

Very nice Dave. The 30 and 25 do look lovely!!

One of my biggest regrets is having sold a lovely set of Celestron Ultima Plossls with the barlow and a nice case. At the time I just didn't know enough to realize they were actually pretty good, sold them for way less than they were worth. Somebody got a good deal!

Cheers Stu☺. How often have we sold on items and regretted it? Usually years ago when we didn't realise their true worth (and "worth" is of course not only defined by financial value).

I am very pleased to have got a set of 7 Parks Gold (a 3.8mm is en route from the USA?) for about the cost of a new Pentax XW.

I will try to hold on to these..

BTW, I think the AFOV of the 30mm is significantly wider than the quoted 52 degrees. In daytime comparison vs a 32mm plossl of a known 50 degrees, the Parks GS 30mm showed  much the same details at the edge of the FOV as the 32mm plossl, but the "image circle/scale" was much larger than the plossl, maybe as much as 58 degrees? It really didn't seem much smaller than I recall my XF 12mm, which was a 60deg AFOV eyepiece..how does that work? Or am I imagining it? Whatever it is, I am going to love that 30mm!

Dave

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31 minutes ago, F15Rules said:

BTW, I think the AFOV of the 30mm is significantly wider than the quoted 52degrees.

Try the light projection method I've described elsewhere and measure the circle.  In fact, if you just swap eyepieces and keep all else the same, it should be quite apparent if the circle size is larger than a known 50/52 degree eyepiece without even measuring anything.  Just keep the distance from the eye relief point to the projected circle the same.

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17 minutes ago, Louis D said:

Try the light projection method I've described elsewhere and measure the circle.  In fact, if you just swap eyepieces and keep all else the same, it should be quite apparent if the circle size is larger than a known 50/52 degree eyepiece without even measuring anything.  Just keep the distance from the eye relief point to the projected circle the same.

Do you have a link that that method Louis D?

Thanks :icon_biggrin:

Dave

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4 minutes ago, F15Rules said:

Do you have a link that that method Louis D?

Thanks :icon_biggrin:

Dave

I rig up a miter box with wood blocks to hold an eyepiece in a 2" extension tube (possibly with 1.25" adapter) with a bright flashlight shining into the open end of the tube.  I then measure the eye relief point distance, the distance to the projected circle, and the diameter of the projected circle.  The longer the projection, the less measurement error.  Using trig, it's pretty simple to calculate the AFOV from these three measurements.

The eye relief point is where the projected circle is smallest, nearly a pinpoint.  Measure it and the distance to the projected circle from the top of the eyepiece with the eyecup at its lowest, flipped down position.

The math is as follows:

1. Subtract the distance to the eye relief point from the distance to the projected circle.  This becomes the adjacent (A) leg of the right triangle

2. Divide the measured diameter of the projected circle by 2 to get the opposite (O) leg of the right triangle.

3. Divide the opposite length by the adjacent length and take the arctan (inv-tan) of it.  That is, arctan(O/A).  I'll allow the use of a scientific calculator in degree mode for this calculation rather than using trig tables. :wink:

4. Multiply the resulting value by 2 since what you just calculated is the half-angle from the axis to the edge.

5. Summarizing: AFOV = 2 * arctan([circle diameter / 2] / [circle distance - eye relief distance])

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2 hours ago, Dave1 said:

Looks like a very nice set of glass. :)

Would you say the Pentax zoom is better than the Baader mk3 zoom optically? 

 

Dave

Hi Dave,

Some nice long focus scopes you have there! :hello2: 

Honestly, I couldn't say the difference is huge - I've owned 3 Baader zooms and I liked them.

I would say that contrast on the Pentax is slightly better. The FOV is very similar, if anything the Baader is slightly wider at the 24mm setting (is it 40 something degrees?). The Pentax is 38deg at 24mm, but never feels tunnel like. I remember having a few weeks ago a view of M42 at the 24mm setting in my FS128, it was just like a photograph, so sharp and "etched" into the view. Up at the 8-10mm setting, the zoom is, to my eyes, every bit as my XL7 (just sold, as the zoom got close enough at 8mm) and my XL10.5mm, which I am keeping.

But my main preference for the Pentax is the build quality. It is far, far superior in solidity to the Baader (and so it should be at over £300 (it was RRP at £400 when I got mine originally in a sale for c£300). The machining is lovely, if anything even better than XW Pentax', and it's JIS Level 4 water and dust resistant. This does make it slightly stiffer when new, due to the O ring seal inside, but it does free up and I use mine with a Baader clicklock adapter which grips it like a vice, and so allows the zoom mechanism to work ok.

Hope that helps, I really love mine.

Dave

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1 hour ago, laudropb said:

Lovely looking set Dave. Glad you got them. I have fallen in love with your old XL 7 already.

Thanks John, you might find the XLs (or XWs of course) to be addictive, and one day find you have several of them!

cheers,
Dave

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1 hour ago, F15Rules said:

I've never been any good at maths or trigonometry, so I will just bask in the belief that the 30mm eyepiece has a very nice AFOV!

Understood.  I was never much at sports.

You could still just grab a flashlight (UK torch) and shine it through two eyepieces and compare the projected image circles to verify that one is bigger than the other.

I've always wondered if Brits call a flashlight a torch, what do they call a stick with a flaming end to it (i.e., a US torch)?  I'd hate for someone to take an open flame to an eyepiece because of a US/UK English mixup. :wacko:

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1 hour ago, F15Rules said:

Hi Dave,

Some nice long focus scopes you have there! :hello2: 

Honestly, I couldn't say the difference is huge - I've owned 3 Baader zooms and I liked them.

I would say that contrast on the Pentax is slightly better. The FOV is very similar, if anything the Baader is slightly wider at the 24mm setting (is it 40 something degrees?). The Pentax is 38deg at 24mm, but never feels tunnel like. I remember having a few weeks ago a view of M42 at the 24mm setting in my FS128, it was just like a photograph, so sharp and "etched" into the view. Up at the 8-10mm setting, the zoom is, to my eyes, every bit as my XL7 (just sold, as the zoom got close enough at 8mm) and my XL10.5mm, which I am keeping.

But my main preference for the Pentax is the build quality. It is far, far superior in solidity to the Baader (and so it should be at over £300 (it was RRP at £400 when I got mine originally in a sale for c£300). The machining is lovely, if anything even better than XW Pentax', and it's JIS Level 4 water and dust resistant. This does make it slightly stiffer when new, due to the O ring seal inside, but it does free up and I use mine with a Baader clicklock adapter which grips it like a vice, and so allows the zoom mechanism to work ok.

Hope that helps, I really love mine.

Dave

Thanks for the insight there. Yes I don't have problem with tunnel vision, with any of my eyepieces. Can't remember the exact figure for the FOV at 24mm. That is impressive in regards to the build quality of the Pentax, the Baader is no shrinking violet, the build is generally very good on the Baaders too. 

If somebody brings a Pentax zoom to the SGL mini star party, I will try it out and compare to my Baader zoom, been thinking about the Pentax for a while now. 

Thanks for the complement of my telescopes. The Vixen has a modern Crayford focuser on it, that wont bring a normal eyepiece to focus, but will bring a Zoom eyepiece to focus. I will probably invest in a focus tube extender or extend to OTA, so that I can use normal eyepieces, want to build up a collection of Brandon's.

My Towa might be going up for sale soon.

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I started out with a Vixen 32mm Erfle, unbranded 20mm Erfle and a 2x unbranded Barlow, later adding a 13mm T1 Nagler. They covered most magnifications. There was not much choice then.

Later Vixen LV lanthanum and a TV Barlow. Only ep I miss is the 32mm. I like my 30mm Eudiascopic (equivalent to your Parks). Prefer it to TV 32mm Plossl. 

 

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22 hours ago, Louis D said:

've always wondered if Brits call a flashlight a torch, what do they call a stick with a flaming end to it (i.e., a US torch)?  I'd hate for someone to take an open flame to an eyepiece because of a US/UK English mixup. 

Yes, we do call a flashlight a torch, and we also call the "stick with a flaming end to it" either a torch, or "dynamite"!:grin::grin:

Dave

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