APM Triplet Achromat

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Brand and Model:	APM Triplet Achromat
Price ($USD):	$295.00
Type:	Achromatic Refractor
Attributes:	Go-To PEC
Aperture:	102mm
f Ratio:	5.9
Focal Length:	600mm
Finder:	10x50
Electric Power:	n/a
Mount:	OTA only
Tripod:	none
Weight (lbs):	13.1
Dimensions (w/h/d):	5x23"
Description:	We are proud to announce our new APM Triplet Achromatic Refractor, made in China. They are an excellent economical telescope with a great performance and contrast. Our customers have found these Triplet Achromatic Refractors to be excellent for viewing and very easy to mount. If you are looking for a telescope that will perform, but do not want to break the bank, this is the one for you! Technical Information D= 102mm F=600 mm Fully coated optics 10 x 50 Finder PlÃ¶ssl 26 mm 1.25" PlÃ¶ssl 16 mm 1.25" 2â€ Rack and Pinion Focuser 2â€ Diagonal Adapter 2â€/1.25â€ Set of tube rings Weight of tube 5.95 kg = 13.1 pound Tube length 59 cm = 23.2 inch

Vote Highlights

APM Triplet Achromat

My comments were included with the original description and moved to the comments area by the webmaster.

Overall Rating: 9
Optics:9 Ease of Use:9 Value:10
Weight: 1 (Unreliable Vote)
Date: 08/02/2003 09:09:49 am PST
By: Anonymous (xxx.xxx.208.137)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=278477

Reply Replies: 0

APM Triplet Achromat

[Note: Vote moved from description by scopedreamer2032]

INITIAL REVIEW OF THE APM 102MM TRIPLET ACHROMATIC REFRACTOR

Overall Assessment: A pleasure to use. Good to very good optics. Heavy.
Compact. Very wide field. Good near focus. Excellent value for the price.

System Evaluated: -102mm triplet achromatic refractor; -Supplied accessories; -On hand components

The optical tube assembly (OTA) is sold by APM and is manufactured in China. The objective is an achromatic triplet, meaning that probably only two types of glass are used (crown and flint). This is not an apochromat. It has a stated aperture of 102mm and a focal length of 600mm (F 5.9). All surfaces appear coated with magnesium fluoride. One baffle is visible from the objective end. The focuser is a rack and pinion. The scope is compact and heavy. The objective cell is large, 5 to 6 inches across. The OTA is shiny black. The objective cell, OTA interior and dew cap interior are dull black. The focuser assembly has a mottled grayish appearance. The focusing tube is shiny aluminum. All in all, it appears attractive and well made. It is substantial (13 to 15 pounds) and robust.
Supplied with OTA are two felt line tube rings to hold the OTA to a mount, a 10X50mm finder with a single-piece two-ring three-screw dovetailed finder holder which fits into the dovetail holder on the OTA, a two inch diagonal, a 2/1.25 inch adapter, two plossl eyepieces (16mm and 26mm) with plastic tubes, two dust caps for the OTA and a dew cap.
The 10X50mm finder was sold. It has been replaced with an Orion 6X30mm right angle correct image finder and and Orion red dot pointer. The two OTA felt lined rings are attached to the modified top of an Orion mini EQ1 tabletop mount. This mount is attached to a CG4 tripod. An additional 5 pound weight has been added, providing 10 pounds of counterweight but another 5 is needed. The EQ1 has slow motion controls and allows the use of an RA tracking motor driven by 4 D cell batteries. Also used with this scope are a 2 inch 32mm Edmund Erfle, a 1.25 Celestron mirror star diagonal, plossls (32mm (Omcon) and 26mm (supplied)), orthoscopics (18mm, 12.5mm and 7mm by University Optics), a Barlow (2.8 Klee by University Optics), a cannibalized Shorty 2x Barlow tube (lens removed) to be used as a magnification enhancer by placing it between the Barlow and the eyepiece used), eyepiece filters (orange-red, green, light blue, deep yellow, yellow-green and lunar), and a homemade full aperture Baader solar filter.

Initial Mechanical Performance:
The focuser is smooth. There is a screw on the top of the focuser assembly to
increase or decrease tension on the rack and pinion motion. The use of the right angle correct image finder makes it easier on the neck to find objects in the sky. The use of this finder in conjunction with the red dot pointer is very convenient. The dew cap slides on and off, held snuggly in place by two pieces of felt (a third may have been present but was no longer attached when received). With the dew cap in place, on a night of severe humidity and dewing, the objective remained free of moisture for six hours of observing.
The EQ1 mount is severely taxed by this scope. The scope with counterweights (25 to 30 pounds) weighs 300% above the recommended specifications for this mount (c. 10 pounds). However, having tightened various screws and glued various components, the EQ1 seems to hold its own. Dampening time is under three seconds when viewing near the zenith and under two when viewing closer to the horizon. On the down side, the slow motion cables and the RA drive are not well placed with the use of this scope. One needs to switch the RA slow motion cable to the opposite side of the mount depending on what part of the sky one is observing. Also, sometimes the OTA is in physical contact with the RA drive assembly.

Initial Optical Performance:
At best focus there is violet (reddish, not bluish) fringing. The degree of fringing depends on the object. On Mars there is extensive fringing. On first and second magnitude stars, there is some fringing. On the moon there is a slight amount. In no case does this fringing distract me from the viewing experience. Nor does the fringing seem to impede contrast. No violet fringing is apparent on bright stars when low powered eyepieces are used (32mm, 26mm, 18mm) (magnifications of 19X to 33X). At best focus, the moon reveals a little fringing and often no fringing at all regardless of magnification.
Focus is sharp. Best focus â€œsnapsâ€ into view. All views of all objects are crisp up to 33X per inch (134X), 60X per inch (240X) is a bit mushy on Mars but not on the moon and this may be of atmospheric origins. Absurd magnifications in the 100X to 200X per inch range show no increase in detail on the moon, but no loss of detail either nor any noticeable violet fringing. 20X to 33X per inch is very crisp and very pleasing.
All 1.25 inch oculars have completely flat fields (plossls at 32mm and 26mm; orthos at 18mm, 12.5mm and 7mm). In the two inch mode, the 32mm Erfle reveals spherical aberrations in the outside 25%, but this is hardly noticeable as one is usually looking down the middle of the view.
The 1.25 inch diagonal seems to be better corrected than the 2 inch diagonal when high powered (short focal length) eyepieces are used.
The wide field of view is very pleasing; 2.6 degrees for the 1.25 inch 32mm plossl and 3.6 degrees for the 2 inch 32mm plossl. Even the 18mm orthoscopic has a 1 degree-plus field of view and the 12.5 ortho has nearly a 1 degree field of view.
On bright objects such as planets, 1st magnitude stars, the moon or terrestrial objects at night next to a bright street light, there seems to be little or no stray light filtering into the view.
On the infocus, extra and intra focal star images there is no indication of astigmatism in the scope when the orthoscopics are used. There seems to be tiny amount of astigmatism when the 32mm Omcon plossl is used. Also, the brightest of stars appear to have many little spikes through the 32mm plossl. All stars fainter than 1st magnitude are pinpoints. However, when an infocus bright star is observed at 60 to 100X per inch, there appears to be no astigmatism most of the time, and only little â€œflitsâ€ of astigmatism at odd moments. Though it is hard to quantify a result that is near zero, I would say that the amount of astigmatism is half of what is present in a diffraction limited Astro-Rubinar and identical to that present in a 1/6 wave-front error MK67. In focus star images show the classic large airy disk (for an unobstructed system) and a number of faint nearly concentric diffraction rings. The optics appear to be well collimated, but there is a slight emphasis to the number of diffraction rings to one side compared to the opposite side of the in focus image of a first magnitude star. This may be due to some type of focusing tube tilt as it does not seem to be always apparent. I am not able to assess the extra/intra focal star images, other than to say they are reddish one side and bluish on the other; distinct on one side and mushy on the other (reddish side); completely circular, similar darker outer diffraction ring in both images. Though this may be very wrong, the images appear similar to an achromat doublet measured as better than diffraction limited on Corâ€™s Aberrator site.
In the field performance reveals this scope to out-perform a certified 106mm diffraction limited Astro-Rubinar. In terms of contrast, it appears to lie halfway between the Rubinar (4inch, 34% central obstruction) and the MK67 (6 inch, 34% central obstruction). On terrestrial viewing of brick walls and leaves, the detail seen by through the triplet was a â€œnotchâ€ better than the admirably performing rubinar. Similarly, the four components of the double-double epsilon Lyrae, though distinguishable in the Rubinar, were clearly and definitively so in the triplet. Through the triplet, the four components were revealed to be separate at 48X. At 86X, 134X and 240X they appeared to be beautifully distinct and separate with clear black spaces between and of a slight bluish tint. M13 revealed a couple outliers to direct vision at 240X and a number of stars with indirect vision at lower magnitudes (steady 4.0 magnitude ZULM city sky). Saturn, in a very muggy sky and at under 25 degrees above the horizon was clearly seen to be ringed at 33X, and gave the slightest hint of the cassini. This test awaits later in the season when the planet is better placed in the sky. Uranus is a beautiful aquamarine but the disk was barely noticeable. Mars (at 24 seconds of an arc) clearly shows the south polar cap and reveals the presence of the surface features of Syrtis Major, Mare Cimmerium, Mare Tyrrhenum and Mare Sirenum. At magnifications of 19X and 33X, sunspots appear crisp and clear with well delineated umbral and penumbral regions. At these magnifications, rice grain is detectable. With fairly steady views, the sunspot views retain their contrast up to 48X (12X per inch).

Strengths:
-Compact and portable
-Wide field of view
-Flat field
-Better than acceptable fringing
-Diffraction limited or better optics
-Excellent on wide field star fields, fair on deep objects, good on planets and moon and sun
-Smooth focusing
-Excellent price ($300)

Weaknesses:
-Heavy (13 pounds OTA, with attachments closer to 15 pounds)
-Supplied plossls are average quality
-Supplied diagonal is of average quality
-Supplied finder is substantial but not convenient (hurts neck)

Comparison to a diffraction limited 106mm Astro-Rubinar and a 1/6 wavefront error 150mm MK67 (both 34% obstructions) :
-In terms of contrast, halfway between the two
-In terms of object brightness, closer to the Rubinar
-In terms of chromatic aberration, inferior to both
-In terms of flat field, similar to both
-In terms of wide field, greatly superior to both
-In terms of cost, superior to both

A note on the supplier: APM-US:
My dealings with APM-US were pleasant and mostly satisfying. The conversation over the phone was productive, helpful and pleasant. Delivery time was stated at a week. Actual delivery, after a request for a tracking number, took about two weeks. This is about average for the telescope industry. Though the office phone is not always answered, more often than not, when I called I was able to speak with the owner/manager. Having said this, it need be added that messages left on the phone and emails were almost never returned. Also, one piece (a bar connecting the two OTA rings) shown on the website but not listed on the manifest was not included in the order received. However, I did notice that the total charge for the scope, delivered, seemed to be less than what I would expect for a UPS delivered scope of 17 pounds by ground, plus the stated scope price; perhaps $5 less.

All in all, I found the interaction pleasant and productive. I found the purchase, delivery and payment experience to be nearly equal to ITE, Orion, Astronomics, Surplus Shed, University Optics and Eric's Telescopes (with whom I am very pleased). I found the quality and condition of the shipment to be above average for the industry.

Overall Rating: No Vote
Weight: 1 (Unreliable Vote)
Date: 08/02/2003 07:02:35 am PST
By: Anonymous (xxx.xxx.127.88)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=278476

Reply Replies: 0

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