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Diascope 85 & Astro eyepieces (1 Viewer)

Lou H

Well-known member
I tried a number of my astronomical eyepieces on my Diascope 85 after purchasing the Zeiss adapter, which comprises a sleeve that converts the 1.25” eyepiece to the inside diameter of the ocular end of the scope and a threaded ring the holds the adapter in place. The eyepiece is retained in the sleeve with a set screw which if used, necessitates removing the whole thing to switch eyepieces.

First off, the focal plane of the body is inside the end of the body so the eyepieces must be inserted as far as they will go in order to focus at infinity. All the 1.25” eyepieces I have will come to focus, including a 9mm Nagler which yields 56x with an 82 degree apparent FOV and a 1.45 degree 78’@1000yds actual FOV compared to 1.15 degree 60’@1000yds of the Zeiss Vario zoom eyepiece. The longest 1.25” eyepiece I have is 24.5mm which yields about 20x. This eyepiece has a 67 degree apparent FOV and yields a whopping 3.35 degree 175’@1000yds actual FOV compared to the 2.5 degree 129’@1000yds of the Vario.

So, at each end of the magnification, the high-end astro eyepiece provide significantly wider fields of view compared to the Zeiss zoom, which is pretty much expected considering the compromises inherent in a zoom eyepiece. At high power the image quality was pretty much the same with the two eyepieces. What was interesting was that at 20x, the flatness of the image and edge sharpness were way better even with the wider FOV of the astro eyepiece. Evidently edge sharpness at low power is another compromise in the Zeiss zoom.

Unfortunately, with the position of the focal plane, it’s not really possible to use a Barlow so observing at powers great than 60 will require either very short focal length eyepieces or afocal coupling with another telescope.
 
Diascope 85 @ 107x

I now have a Meade 5000 4.7mm eyepiece that I've been using with a Diascope 85 yielding 107x. At this power, brightness is certainly suffering but the views remain sharp and detailed across the field with little sign of chromatic abberation.

The eyepiece has an expansive 82 degree effective field of view. The moon is totally amazing as it occupies a 50 degree of that view and is covered with detail. The Trapezium in Orion is stunning. Saturn is lovely.

It'll take a steadier night and probably even higher power to do a proper star test but from what I could see, there might be a slight bit of spherical abberation starting to show itself.

Lou
 
just a word of thanks for your post, Lou. Following your information, I bought the 4.7mm Meade eyepiece - truly awesome! I've put some details in another thread.

Pete
 
Lou,
I too would like to add my thanks for the interesting post, which I somehow missed earlier.
I tried out an 11mm Televue Plössl on my Diascope 65 (about 35x) having read of the superiority of contrast of Plössl and Ortho eyepieces as against complex WA designs. It was a fairly inexpensive experiment but I can't say I notice any gain in contrast vs. the 16,7mm (23x) Zeiss eyepiece and fov and eye relief are, of course, miserable in comparison.
I also use the Zeiss adapter but were you aware that Baader Planetarium sell a cheap bayonet adapter for 1 1/4" astronomical eyepieces for the Diascopes? However, there may be problems with some eyepieces reaching focus at infinity.

John
 
Hi Lou

A very interesting thread

A couple of questions if i may ask?

Regarding the astro eyepeice 1.25 inches / 24.5 mm that gives around 20X mag on a diascope 85, i would like to see if this astro eyepeice is suitable for digiscoping,

what is the eye relief on this eyepiece?

Can you give me a link to a website where i can look at the adapter and eyepiece please?

Can you give an estimated magnification of this eyepiece if it were attached to a Diascope 65?

Lastly, in your opinion how does this lens perform optically, brightness, colour, edge to edge etc, against the Zeiss WA eyepeice 30X/23X?

Any help would be greatly appreciated

Best Regards

Paul
 
Hi!
More on astro eyepieces on Diascope: How long (in mm please) can the barrel be on an 1,25" astro eyepiece and still fit the Diascope 85mm, with a) Zeiss astroadapter b) Baader astroadapter?
Is there a way without practical testing, to caluculate if a certain astro eyepiece will reach focus at infinity on a Diascope?
My purpose is to get an eyepiece thet can give me circa 20x and about 60m/1000m on a Diascope 85, like the 20x on the big Swarovski's and Leica's. What brand are you using Lou H? Other suggestions? Preferably an eyepiece of good quality, but not necessary.
Best regards, Mikael
 
Hi Mikael,
I use a TeleVue Radian 5mm in a Dyascope 85. For my first impressions, see the previous post in the forum. With the Zeiss adapter there's no problem neither watching birds nor Jupiter. So, I suposse is possible to use all range of focusing. Closest focusing distance is fairly higher, compared with the Zeiss zoom. The Baader has a bayonet sistem, as the Swaroski, wich looks more reasonable for fast change.
I don't understand your question about how long...Imagine you take the eyepiece out the Dyascope. The body of the telescope is closed by one glass. Well, my TV astro eyepiece touches this glass. The distance between eyepiece and spotting scope body does't be fixed for the adapter. The sleeve of the Zeiss adapter is only a cilindric emptied piece whose external diameter is 2" and in the inner side is 1 1/4" plus a screw to avoid the sliding.
I was also interested in something round 20X or a bit less, for nights. My first old Adlerscope 80 had, among others, an 15X eyepiece wich I enjoyed a lot. I remember several consecutive nights watching, and listening, wolves eating in a cow corpse. My binoculars, a pair of Zeiss 10X40 Classic were absolutely useless. I'd like to have had the Dyascope at low power then. My experience with astropiece is limited to one. The main disadvantage is the shallow deep of field. Which priority can be in the design, thinking in astronomy?
 
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