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New APM 100 90° Semi-Apo w/ Fork Mount Unboxing

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#301 GamesForOne

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Posted 22 May 2019 - 08:08 AM

...

Following up on a prior comment I posted regarding a yellow halo around the moon, based on what I've read from the link that Garrett posted as well as other preliminary reading, is this a phenomenon that can be "cured" if I were to buy an "ED" bino instead of a "Semi-APO"?  I believe they both have two lenses but the ED version is "higher" quality so that it has less CA?  That yellow halo is so distracting that it really takes away from the viewing experience.  It's a hard but bright yellow circle.  I can also see some bluishness on brighter stars.

 

...

James

The ED is better but it is not the equal of a top quality APO either. The 82mm and 120mm binos in the APM APO series have even better SD (i.e. "Super-low Dispersion) glass.

 

I believe it was posted here recently that APM is now offering the 100mm version with the SD glass, although I'm not seeing it on the APM website. The website is confusing in that some binos are marked "ED" that have SD glass, and others clearly say SD. SD glass would be the way to go for the best image quality. Yes, it makes a difference if yellow and blue fringing bothers you. The better focused image also goes marginally deeper revealing some fainter detail -- a very subtle but visible improvement.

 

However, a 100mm bino has only so much effective magnification range. For me personally, approaching and below 1mm exit pupil gets too dim and starts amplifying the problems in my old eyes. If you have young eyes, enjoy!

 

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#302 rockethead26

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Posted 22 May 2019 - 08:39 AM

Thank you Barry and everyone else.

 

Following up on a prior comment I posted regarding a yellow halo around the moon, based on what I've read from the link that Garrett posted as well as other preliminary reading, is this a phenomenon that can be "cured" if I were to buy an "ED" bino instead of a "Semi-APO"?  I believe they both have two lenses but the ED version is "higher" quality so that it has less CA?  That yellow halo is so distracting that it really takes away from the viewing experience.  It's a hard edged distinct bright yellow circle.  I can also see some bluishness on brighter stars.

 

I also compared the included 18mm APMs to a 17.3 Delos and 24mm Panoptic.  I think, but correct me if I am wrong, one gets what one pays for.  The Delos was night and day "better" than the stock EP.  Night and day better.  Stars were far easier to get close to pinpoint on the 17.3 and the entire FOV looked so much "cleaner" to me.  The 18 felt like a toy.  The 17.3 felt like I was using a piece of professional gear.  

 

James

Yes, the color on the Moon is bothersome, but I do not do Lunar viewing with my BT, I use telescopes that are a better choice. The BT was purchased for sweeping the Milky Way and looking at star clusters. Interesting about the EPs that you tried. I only have Delos for monoviewing, but I have the Pan 24s and the AMP UFF 18s for my Semi-APO and the 18s, by far are my go to eyepieces, sharp to the edge and extremely comfortable. We do each use our equipment differently and see different things with our eyes.


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#303 Rich V.

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Posted 22 May 2019 - 10:57 AM

Until not that many years ago "semi-apo" was as good as it gets for BTs.  Relatively short focal lengths for the sake of wide fields and compactness gave us little choice.  Some CA fringing and purple halos on the brightest objects was expected, as it has always been with standard binoculars.  Higher magnifications enlarge the effects of CA proportionally to the enlargement of the object itself.

 

The best views with BTs, IMO, are the sweeping vistas of the Milky Way at relatively low magnification, the dark nebulae embedded in it, and open clusters and globs at higher mags.  With summer nearly here, I look forward to sweeping up from Sco/Sag through Aql and Cyg into Cas; the MW river of stars.  Wonderful sights to behold.  CA is little problem when viewing the MW starfields and clusters and a "semi-apo" or achro bino generally does a fine job.

 

It's only on the Moon, planets and the brightest stars that CA becomes an issue and for those objects a telescope is still the best answer.  My high quality 80mm triplet refractor actually shows more detail on the Moon and planets than my 100mm BT despite its smaller size.  Many of us go both ways; binos and scopes.  The current ED "apos" cross into both worlds as they hold up to higher mags but they still are limited compared to the optical simplicity of a quality telescope.

 

Rich


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#304 astrofan007

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Posted 24 May 2019 - 07:27 AM

Anyone try/compare TV Plossls vs. "others" (in their 100/90s) and, if so, care to report what were your impressions (on any given target)?

 

Last night I compared pairs of DeLites (7mm & 18.2mm), Delos (17.3), and Type 6 (13mm) but I'd consider Plossls if there seems to be a consensus that they perform well on select targets.

 

James



#305 astrofan007

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Posted 24 May 2019 - 07:34 AM

What I am trying to do is get a sense for the spread in mm EPs that I will ultimately want as well as which models simply feel "right" to me when looking down the barrels.



#306 MB_PL

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Posted 25 May 2019 - 03:09 AM

Here's my two cents regarding EPs and their focal lengths (but I have the 120mm/90deg APM BT).
First off, Baader Genuine Orthos do not come to focus, if you were wondering ;)
I have the following pairs of TV Plossles: 8, 11, 15, 20, 32mms (I acquired these pairs over an extended period of time specifically for binoviewing with my 8" SCT and refractors I've had over the years).
My experience confirms the old adage that for critical, in-depth observation where you want to tweak out the smallest detail possible - the fewer elements an EP has the better. I do all my planetary and lunar observation exclusively using plossles and orthos. Good quality plossles and orthos simply have better transmission and on-axis sharpness than EPs with 8 or 9 elements. This has been the case among others when I've compared  12.5mm BP orthos with 13mm Vixen LVWs and 13mm Naglers; 8mm TV plossles with 7mm Naglers and 9mm Morpheuses. BUT plossles and orthos have a small to very small apparent FOV, very short eye relief in the shorter focal lengths and a tiny top lens, which translates into extremely easy fogging in the field and generally mediocre ergonomics (especially with no tracking).
For observing DSOs, I much prefer a larger apparent FOV (even at the expense of some loss of transmission) to view objects in a 'wider context' and for such type of observations (especially in the APM BT) I only use my LVWs, Morpheuses and Naglers, with one exception - the TV 32mm plossles. I use this pair when I want to have a large exit pupil under dark skies to observe very faint, extended objects, particularly with filters. The 32mm TV plossles however can be a pain to use - their excessively long eye relief causes problems with eye placement and results in blackouts. Generally, I prefer the 22mm Vixen LVWs, which offer the same true FOV but at a smaller exit pupil.
My three most used pairs are the 22 and 13mm Vixen LVWs and 9mm Morpheuses. The 6mm Morpheuses come next in terms of frequency of use. The 32mm TV plossles and 4.5mm Morpheuses get some but not that much use. 3.5mm Naglers are my least used pair – I bought them second-hand for binoviewing with a short focal length triplet refractor. I would not buy these for the APM BTs.
So to sum up, my take is you need three pairs of EPs – 22-24mm; 12-13mm; 6-9mm. Then get a pair of UHC or OIII filters and you’re set.
Clear skies


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#307 garret

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Posted 25 May 2019 - 05:02 AM

I sold my pair of Televue 32 mm Plössl, 50 degree of apparent field is like a viewing true a tunnel comparing LVW, Delos and Morpheus. 

But transmission was noticeable better.



#308 astrofan007

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Posted 25 May 2019 - 09:35 AM

Thank you MB_PL and Garret.  Excellent advice. 

 

I'm moving very quickly; closing in on precisely how I'll use this BT.  I can see now that my primary interest is going to be observing double stars and occasionally planets and moon.  I am going to try to qualify for the Astronomical League's Double Star certificate.  I have a neighbor with a large reflector who let's me view DSOs.

 

So with regard to EPs, after last night's session, I've ruled out the DeLite 18mm and 7mm.  They sometimes produced double images -- sometimes.  I'm guessing that DeLites simply don't agree with my IPD/face structure. 

 

I'm also ruling out the Delos 17.3.  It's very cool to view the expansive image but it's almost too wide a view.  IOW, the supplied APM 18mm offers close to the same field width so the Delos 17.3 seem redundant.  Other than that, the doubles that I'd be going after are way inside an 18mm field.

 

The most comfortable-to-me-easy-to-use-with-excellent-images EP was the Nagler 13mm Type 6.  I don't want to assume that the Nagler 9-7-5mm will perform as well so I'll just have to bring them in to try.

 

Before anyone replied to my prior post, I decided I should try out a Plossl just to see.  So I bought a pair of TeleVue 8mm and a pair of Takahashi 9mm.  I'm looking forward to comparing the short eye relief and narrow FOV of those EPs with the Nagler.

 

James


Edited by astrofan007, 25 May 2019 - 11:44 AM.


#309 Vondragonnoggin

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Posted 26 May 2019 - 01:41 AM

APM new prices on Fork Mount with Nexus DSC and encoders

 

https://www.cloudyni...rge-binoculars/


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#310 Mark9473

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Posted 26 May 2019 - 09:37 AM

For double stars, planets and the Moon, a telescope would be a far more logical choice than a BT. If you then want two-eyed viewing, get a binoviewer.

#311 astrofan007

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Posted 28 May 2019 - 10:16 AM

For double stars, planets and the Moon, a telescope would be a far more logical choice than a BT. If you then want two-eyed viewing, get a binoviewer.

Mark, I'm embarrassed to say that I didn't know that.  Yes, I would only want two-eyed viewing. I just wanted something that is grab-and-go.  I was under the impression that two scopes are "better" than one in terms of resolution and I was also under the impression that using a binoviewer would dilute the contrast/brightness of targets but I am learning that maybe that's not the case.



#312 Vondragonnoggin

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Posted 28 May 2019 - 10:46 AM

High powers required for planetary viewing usually translate better to telescope use where aperture gains are most desirable. To get equivalent binoviewer performance to a 100mm BT or binoscope, the aperture does not need to be doubled exactly. The binoviewer will split the signal delivering 50% of the light to each eye, then binocular summation can add an additional 1.41x is the general accepted philosophy.

 

 An unobstructed telescope of 140mm with a binoviewer would theoretically give the same performance as the Binocular telescope of 100mm, but generally the 140mm telescope like TEC 140 or APM 140 is also a longer focal length and better at handling higher powers with less aberrations.

 

Provided the binoviewer was high quality and capable of clear aperture large enough to handle the eyepieces you wish to use with it, the higher power in the telescope/binoviewer configuration should be easier to obtain without pushing optical limits. If a theoretical limit of 50x per inch as maximum is used, you are at a higher theoretical maximum with a 140mm objective than with a 100mm objective.

 

If Jupiter at 200x is a goal, the BT with 100mm objectives is now at that 50x per inch limit (4” objective at 50x per inch) but the 140mm telescope with BV will be at 275x for 50x per inch limit.



#313 Rich V.

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Posted 28 May 2019 - 11:52 AM

Mark, I'm embarrassed to say that I didn't know that.  Yes, I would only want two-eyed viewing. I just wanted something that is grab-and-go.  I was under the impression that two scopes are "better" than one in terms of resolution and I was also under the impression that using a binoviewer would dilute the contrast/brightness of targets but I am learning that maybe that's not the case.

Binos and scopes/BVs each have their strengths and weaknesses as pointed out in posts above.

 

Binos are optimized for lower mags/wider fields and scope/BVs for higher mags.  As an example, using your 100mm f5.5 bino, it has approx. the same light gathering surface area for each eye as a 140mm scope/BV (100² per eye vs 140²/2 per eye).

 

The advantage of the bino's two tubes is that for a given f ratio you have a shorter focal length than the 1.4x larger single tube scope.  Generally, as aperture is increased, so must focal ratio to keep the color correction at the same level.

 

Your 100mm bino has a short 550mm focal length so with a 24mm 68° eyepiece you'll get 23x and a 2.8° FOV.  The hypothetical "equivalent" 140mm refractor/BV would likely be at least F7, 980mm, and the same eyepiece would provide 41x @ 1.66° FOV.  While the scope/BV can't produce the wide fields of the bino, it still has the resolution advantage of its 140mm aperture since resolution scales with aperture.  Many refractors won't focus with a BV unless is has an OCA (barlow) in the light path, even further increasing mag. and decreasing FOV.

 

Which would you prefer for wide field MW views?  Which would you prefer for Lunar/planetary views?

 

Rich



#314 astrofan007

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Posted 28 May 2019 - 12:30 PM

Binos and scopes/BVs each have their strengths and weaknesses as pointed out in posts above.

 

Binos are optimized for lower mags/wider fields and scope/BVs for higher mags.  As an example, using your 100mm f5.5 bino, it has approx. the same light gathering surface area for each eye as a 140mm scope/BV (100² per eye vs 140²/2 per eye).

 

The advantage of the bino's two tubes is that for a given f ratio you have a shorter focal length than the 1.4x larger single tube scope.  Generally, as aperture is increased, so must focal ratio to keep the color correction at the same level.

 

Your 100mm bino has a short 550mm focal length so with a 24mm 68° eyepiece you'll get 23x and a 2.8° FOV.  The hypothetical "equivalent" 140mm refractor/BV would likely be at least F7, 980mm, and the same eyepiece would provide 41x @ 1.66° FOV.  While the scope/BV can't produce the wide fields of the bino, it still has the resolution advantage of its 140mm aperture since resolution scales with aperture.  Many refractors won't focus with a BV unless is has an OCA (barlow) in the light path, even further increasing mag. and decreasing FOV.

 

Which would you prefer for wide field MW views?  Which would you prefer for Lunar/planetary views?

 

Rich

Thank you Rich.    

 

I would prefer lunar/planetary/double star views.  And so, because of that preference, people with my observing interests would be better served going the scope/BV way, if I read your explanation correctly?  

 

Does resolution have anything to do with overall contrast and/or object brightness?  I am going to have to think this one through, but for the sake of clipping through time, if I increase the focal ratio to f/7 - f/11 on a pair of 100 mm telescopes, wouldn't that increase resolution/contrast too? Or is it only as you stated, that resolution/contrast scales with aperture?

 

James



#315 Beg

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Posted 28 May 2019 - 01:59 PM

Thank you Rich.    

 

I would prefer lunar/planetary/double star views.  And so, because of that preference, people with my observing interests would be better served going the scope/BV way, if I read your explanation correctly?  

 

Does resolution have anything to do with overall contrast and/or object brightness?  I am going to have to think this one through, but for the sake of clipping through time, if I increase the focal ratio to f/7 - f/11 on a pair of 100 mm telescopes, wouldn't that increase resolution/contrast too? Or is it only as you stated, that resolution/contrast scales with aperture?

 

James

I think you are a candidate for a nice 8" SCT with an inexpensive WO binoviewer. Plug in and go simplicity and it hits your interests. 


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