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Observing with Small Apertures: 130mm and Below

Discussion in 'Telescopes and Mounts' started by Ray of Light, Jul 26, 2016.

Observing with Small Apertures: 130mm and Below

Started by Ray of Light on Jul 26, 2016 at 5:34 AM

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  1. Mak the Night

    Mak the Night Well-Known Member

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    Yeah, but will it run on the Moon lol?
     
  2. Ray of Light

    Ray of Light Well-Known Member

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    Good question Mak !
     
  3. Mak the Night

    Mak the Night Well-Known Member

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    Another good question is why can't I acquire a decent 7mm eyepiece? lol!

    I've decided to invest in a 7mm Kokusai Kohki Fujiyama orthoscopic. This should give me an exit pupil of about 1mm with a magnification of 128.5x on the Bazooka. Ideal for splitting binaries and observing many MO's as well as planetary. It will Barlow to 257x with a 2x. I believe they are the same as the UO ortho's.

    Kokusai Kohki Fujiyama.jpg

    Not a large EP though:

    Eye relief: 6.1 mm
    Field stop diameter: 4.8 mm
    Eye lens diameter: 6.5 mm
     
    Last edited: Aug 6, 2016
  4. Ray of Light

    Ray of Light Well-Known Member

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    What happened to the Pentax? No good? How about price diffrence. I wouldn't mind getting a 7mm, I guess not an X-Cel after what you went through.
     
  5. Ray of Light

    Ray of Light Well-Known Member

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    Oh, I could Barlow a 7mm up to 171x. Not bad. Glad I got the Starguider 3.2mm for 187x without a Barlow though.
     
  6. Mak the Night

    Mak the Night Well-Known Member

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    I haven't got any 7mm EP's, but it can be a useful size for the Bazooka. I haven't ruled the Pentax out, but it's huge, like my 10mm Delos. I wanted something lighter with a similar FOV to the X-Cel. I had to return two defective 7mm TeleVue DeLites as well. If the DeLites had been OK it would have been perfect. Unfortunately TV's quality control isn't what it should be. I considered a 7mm Nagler until they went up to around the equivalent of $400 US at Telescope House. If I hadn't have hesitated I could have got the Nagler for a hundred dollars less. They still seem reasonably priced at TS Optics though. Everyone in the UK is banging the prices up possibly because of the Brexit result, but more likely they're just using that as an excuse.

    SW7mm UWA.jpg

    So, I decided on a 7mm Sky-Watcher UWA and the 7mm Fujiyama. The Fujiyama was 99 euros and the SW UWA was under 40 quid, so I'm 'quids in' really lol. The SW is Barsta (BST) made and I've heard every bit as good as an X-Cel and then some. I'll see. If the Fujiyama is as good as the Astro Hutech ortho's it should be superb. You really can't beat an ortho' for sharpness and clarity. The undercut on the SW looks a bit vicious but I think I'll cope. The Fujiyama is a smoothie.


    *'quids in' is a British colloquialism meaning to gain something monetarily.
     
    Last edited: Aug 6, 2016
  7. Ray of Light

    Ray of Light Well-Known Member

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    What prices are we talking? I may be interested in a 7mm. Probably be a good eyepiece for my scope.
     
  8. Mak the Night

    Mak the Night Well-Known Member

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    These look good:

    http://agenaastro.com/kokusai-kohki-fujiyama-hd-orthoscopic-eyepiece-7mm.html

    http://agenaastro.com/bst-1-25-uwa-planetary-eyepiece-7mm.html

    These are basically what I've ordered.

    A 7mm will give you around an 88x magnification I think. A 6mm might be more useful and would give you about the 1mm exit pupil a 7mm gives me on the Bazooka (900mm f/l, f/6.9).

    See this thread: http://astronomyconnect.com/forums/threads/sky-watcher-uwa-planetary-eyepieces.2944/#post-5145
     
    Last edited: Aug 6, 2016
  9. Ray of Light

    Ray of Light Well-Known Member

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    It looks like the Fujiyama has a 6mm version but the eye relief doesn't seem to be good for an eyeglass wearer, it is also 95 US. The BST 6mm has like a 16mm ER and is 55 US from Agena. I read your link and it does look suspiciously like the pants TMB clone I bought and hated but I realize the outer casing is where the similarity ends? Am I close to the mark here? I guess I would consider the 6mm BST UWA.
     
  10. Mak the Night

    Mak the Night Well-Known Member

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    I have an Astro Hutech 6mm which is more or less identical to the Fujiyama. I'm pretty sure they're actually manufactured in the same factory.

    6mmahortho.jpg

    I don't need glasses to observe so I'm OK with the small eye lens and short eye relief. They're a bit specialist in the fact that the small FOV tends to limit them to planetary, binaries and some DSO's. A Barlow does help though and an 18mm Fujiyama (I have the 18mm AH version) with your TV x3 Barlow effectively turns it into a 6mm. The views I recently had of the Moon with a 6mm ortho'/TV 2x Barlow combination for 300x were outstanding. I reckon I could have got more but 300x is basically the resolution limit for a 130mm scope on the Moon (60x per inch).

    18mm 20mm.jpg

    You can see the 18mm AH compared to a TV 20mm Plossl above. The eye lens is a bit smaller than the Plossl's, but if you can deal with a 20mm Plossl, the 18mm ortho' should be similar.

    AH 18mm Ortho.jpg

    The Barlow would improve the eye relief as well. About a 1mm exit pupil is good for splitting binaries but also works well for some Messier Objects.

    I remember the pants 'TMB clone'. AFAIK these eyepieces aren't actually TMB clones but the Pacific Rim manufacturer just utilises the same external body (possibly outsourced). The Sky-Watcher UWA is almost certainly the same Barsta (BST) made eyepiece as the TS Optics and Agena equivalent with different bodies. What did you dislike about it Ray? I've heard that these EP's are decent for the money. Barsta make some very high quality gear. The Omegon 2x Short Barlow below is Barsta, apparently the glass is Japanese, it's the only Barlow I've ever owned I thought was as good as a TeleVue.

    Omegon Barsta.jpg

    I suppose I'll find out tomorrow when my Sky-Watcher 7mm UWA is delivered lol. Hopefully the Fujiyama will arrive sometime next week as well.

    ts7mm.jpg
     
  11. Mak the Night

    Mak the Night Well-Known Member

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  12. Dave In Vermont

    Dave In Vermont Well-Known Member

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    I have a few orthoscopics, all from different places. And all work beautifully. I figure there's really not too much that can go wrong when you're dealing with only 4 elements of glass. As long as you start with top-quality lenses to begin with.

    When I first got a telescope of my own choosing - a 3" F/15 refractor - the orthoscopic eyepiece was the Holy Grail of the day, This being before Nagler got loose and TeleVue® appeared on the stage. And the ortho's are still an ideal choice for getting close-in with excellent contrast on smaller objects such as planets and globular clusters. As long as you don't need to wear glasses at the scope.

    If I get another eyepiece, it will be an orthoscopic.

    Thanks for the data, MTN!

    Dave
     
    Last edited: Aug 7, 2016
  13. Mak the Night

    Mak the Night Well-Known Member

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    You're welcome Dave. I'm a great fan of ortho's myself, as you know. You can't really go wrong with an ortho', as long as you can handle the small size of some of the smaller focal lengths. For sharpness and contrast I'd put a good ortho' up against anything. They can't be beaten for the money IMO.
     
    Last edited: Aug 7, 2016
  14. Ray of Light

    Ray of Light Well-Known Member

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    As eyeglass wearer the're out for me. The TMB gave me lousey views and I have my doubts that is the same LER, WA eyepiece that Agena is selling. They said, I believe, that whilr the body might be the same as the TMB clone, that is where the similarity ends. That is good news for me if I decide to get a 6mm. I will read the Agena blerb again in case I've lost the few remaining marbles I have left!
     
  15. Ray of Light

    Ray of Light Well-Known Member

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    Just FYI, see the "Please note" section under the description on the Agena website for the eyepiece in question.
     
  16. Mak the Night

    Mak the Night Well-Known Member

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    It's a possibility that you could use an 18mm ortho' with a Barlow Ray.

    7mm Sky-Watcher UWA.jpg

    Well, it came! It seems fairly well made for something under 40 quid. The flip-up rubber eyeguard actually threads off plus there is additionally a mechanism not unlike the DeLite or some Vixens to raise the entire eyeguard assembly. It came with a microfibre cloth, so, one up on the 7mm TeleVue DeLites and Celestron X-Cels which just came with a defect. At least the X-Cel came with its own bolt case though. The chromed brass draw tube undercut is quite manageable and plays well with TeleVue Barlows and the Baader helical focuser. In a cursory daylight test it appears as bright and sharp as the X-Cel with good overall contrast and definition. It does seem to have a tendency to kidney bean, although that can be negated somewhat with attention to eye placement. I don't think it would be comfortable for glasses wearers however. I have a feeling there is some form of Barlow or Smyth lens in the draw tube which may be detachable. Surprisingly, it Barlows well (tested with a TV 2x and a Celestron achromatic 2x). It isn't a DeLite, but it does seem quite usable. The 7mm Fujiyama should arrive tomorrow, all being well.
     
  17. Ray of Light

    Ray of Light Well-Known Member

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    Do they sell that in the states or is that the same one as the UWA Agena sells? It says Sky Watcher. If the ER is long why would't it be good for an eyeglass wearer? Am I wrong but wouldn't it be better for me to be able to get over 170x with a 6mm Barlowed then an 18mm or am I thinking of the wrong eyepiece?
     
  18. Mak the Night

    Mak the Night Well-Known Member

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    I'm pretty sure it's the same as the TS Optics and Agena eyepieces but with a slightly different body. They are all made by Barsta (BST) and rebadged. The eye relief doesn't seem particularly long to me.

    If your scope has a 600mm focal length a 6mm eyepiece will give you 100x magnification. It will also give you an exit pupil of about a millimetre (1.03mm) which should be good for splitting doubles/binaries and viewing some DSO's that can handle a bit of magnification. You only really need 150x - 240x for planetary and lunar as it enables you to see more detail. At these magnifications you are getting around a 0.5mm exit pupil, which is around the limit the human eye is efficient I think. It's a good rule of thumb anyway. For really faint objects or for using a ultra high contrast filter it's probably better to use an eyepiece that will give you a 3mm exit pupil (or above). Having said that, I've used eyepieces giving me a 1mm exit pupil (or thereabouts) for some of the brighter Messier Objects successfully.

    The reason I recommended an orthoscopic eyepiece was that for the money you are getting views equal to the most expensive Pentax, TeleVue and Vixen eyepieces but for up to a third of the cost. Unfortunately, because of its design, the Abbe orthoscopic has certain limitations.

    or1.jpg

    It's quite a simple design consisting of a cemented triplet and a fourth lens. As a consequence the smaller focal lengths tend to have small field stops, eye and field lenses, and shorter eye relief than most Plossl equivalents.

    However, an 18mm orthoscopic would be quite similar to using an 18 or 20mm standard Plossl. So, if you felt comfortable with that size, by combining it with your TeleVue 3x Barlow you can make it a 6mm orthoscopic in a way.

    If the Fujiyama are as good as the Astro Hutech it would make a very high quality combination with a TeleVue Barlow. This would give you 100x and an exit pupil of around 1mm with very high quality eyepieces, but cheaper than actually buying a Delos, Pentax XW or Nagler. The downside is that orthoscopics only have around a 43° FOV. This isn’t neccesarily a disadvantage for many DSO’s though and is generally fine for separating double stars and splitting binaries.
     
  19. Mak the Night

    Mak the Night Well-Known Member

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    I got first light on the 7mm SW UWA (23:00 BST). Arcturus looked good at 128.5x and I looked at a couple of globulars.

    M3.jpg
    The conditions weren’t particularly good, although I could see the Milky Way, the transparency could have been better. Highlights include M81, M82, M3 and M52. I dropped down to 60x after a short while.

    M81.jpg

    As I was trying to locate M31 and wrestling with the EQ mount the mount head shifted on the tripod altering the latitude setting so I decided to call it a night. Eyepieces used were the 7mm Sky-Watcher UWA and a 15mm Antares Plossl M.C. A 15mm Celestron Kellner was used as a finder. A Baader UHC-S was deployed on M81 and M82.

    M81 82.jpg
     
  20. Mak the Night

    Mak the Night Well-Known Member

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    Well, I fixed the borked mount and swapped the Orion RACI for its Sky-Watcher equivalent. I bought the Orion over a year ago (mainly for my 102mm Mak) but it's been acting weird recently and I think the O-ring has skewed or something. Plus I tried to clean it after it dewed up badly the other night, and I don't think it was successful, so I took it to pieces.

    Sky-Watcher RACI 2.jpg

    I'm pretty sure it can be salvaged but I needed a basic RACI for the Bazooka (the Celestron illuminated RACI for the Big Cat doesn't fit Synta mounts) and the SW is £20 cheaper than the Orion! It's exactly the same except the body is a sparkly Sky-Watcher black, the mounting bracket is white and it doesn't have 'Orion' written on it (there is no writing at all). I'm pretty sure they're all made by the same manufacturer, possibly Synta, as I don't think they're GSO.

    Sky-Watcher RACI 1.jpg

    I think it looks OK.
     
    Last edited: Aug 9, 2016

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