Equipment Reviews - Page 4

1) TMB 175mm f/8 Refractor

2) Starmaster 14.5" f/4.3 Reflector

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1) TMB 175mm f/8 Refractor

Side view of the TMB Optical 175mm f/8 apochromatic refractor showing the 3.5" Feather Touch Focuser, the CNC mounting rings, and dew cap.

Overview

I May 2004 I took delivery of a TMB Optical 175mm (7") f/8 refractor. This is the first telescope I have purchased from TMB Optical. To provide some background information on these telescopes Thomas M. Back designed the Air Spaced SD Triplet lenses, which are then manufactured, multicoated and tested using an interferometer by LZOS, a Zeiss subcontractor, in Russia. The lenses are and shipped to APM Markus Ludes in Germany. Markus tests the lenses, and has the lens cells, optical tube assembly (OTA), CNC focuser's, and CNC mounting rings manufactured. Customers may purchase telescopes from Markus Ludes or Thomas Back.

Note there are two versions of the 175mm f/8 available, a light weight (LW) versions that weighs in at 42 lbs., and a heavier CNC version that weighs around 5 lbs. more. In general there are LW versions available for most of the other refractor telescopes in the TMB line. If the customer orders a CNC version of the OTA Markus Ludes ships the CNC focuser to Thomas Back. If the customer orders a LW version Thomas Back purchases the Feather Touch Focuser from Starlight Instruments.

Once Thomas Back receives all of the telescope components he assembles the telescope, and performs final optical and mechanical testing and quality assurance. This includes testing the telescope in the shop using an autocollimator and star testing under the night sky, which must pass his high requirements before he ships it to the customer.

Telescope

The 175mm I received is one of the newer LW versions. It came with a 3.5" Feather Touch Focuser, CNC mounting rings, 8x50mm finder bracket, Intes focuser extension and 2"-1.25" eyepiece adapter, sliding dew cap with dust cap, and an inner dust cap. An owner's manual is provided as well.

The telescope arrived well packed in the shipping box with plenty of Styrofoam peanuts to protect the telescope during shipment and wrapped in a plastic bag. As I took the OTA out of the box I was impressed by the fine quality of the workmanship. Everything on it has a nice solid feel to it. The mounting rings come pre-drilled as well for mounting cameras, guidescopes, or other accessories.

The length of the telescope with the dew cap retracted is 48" long. With the dew cap fully extended the telescope is 58" long. In the above photograph the dew cap was almost fully extended and for a comparison the home made wooden box the telescope is shown sitting on is 27" long. The outside diameter of the OTA is 8.5", while the outside diameter of the dew cap is 10".

I noted when looking inside the OTA that there are five baffles spaced by three aluminum bars. Another baffle is located near the front of the dew cap. In addition the inside of the OTA and the dew cap is lined with black flocking or velveteen paper which helps to reduce light scattered and increase contrast.

I used flocking paper in a telescope I made many years ago for the same reason after reading an article by Richard Berry in the Winter 1983 issue of Deep Sky Magazine. The article was entitled "Of Stellafane, Optics, and the Art of Deep-Sky Observing", and in it he recommended ways to reduce light scatter and increase contrast a telescope so they would perform better when observing deep-sky objects.

This included smooth, high quality optics, the telescope having efficient baffles, a roughened tube interior (in this case flocking paper), and an extra long dew cap that extends beyond the objective. In the TMB 175mm the dew cap extends 11" beyond the objective, which in addition to helps reduce the likelihood of dew forming on the objective. The smoothness of the optical surface is important because any surface roughness or micro ripple left over from when the objective is being figured, which by its nature leaves "texture" on the glass, results in more scattered light and reduced contrast.

After observing with the telescope I noted that it seemed to have very low light scatter and high image contrast, more so than I have noted in other telescopes. I surmised that the baffles, flocking paper, and longer dew cap contributed to this, but wondered if there might be other factors as well. So I corresponded with Thomas Back to see what other factors may play a role. He indicated that the figuring process used for the lenses were very smooth, which helped to reduce scattered light, and increase contrast.

Also, the baffle assembly was designed so that any stray light that entered the OTA does not reach the focal plane and reduce contrast. The combination of reduced scattered light and increased contrast puts more energy into the airy disk and produces a brighter image. This is important not just for deep-sky observing but when observing the Moon and planets as well, as it will make it easier to see fine detail. For all of these reasons the telescope provides, for lack of a better term, the most "natural" view of the Moon and planets I have ever had through telescopes I have owned or used since I bought my first telescope back in 1972. Based on this I ordered a TMB 130mm f/9.25 and 105mm f/6.2 from Thomas.

The 3.5" Feather Touch Focuser, with the 8x50mm-finder bracket mounted on top.

As noted my 175mm LW came with the 3.5" Feather Touch Focuser. While I considered this to be more useful for those who do imaging in practice I found it very useful for visual observing as well. It has very smooth focusing, and the fine focus adjustment made it very easy to focus the telescope at high power, even when wearing gloves. Also the entire focuser assembly can be easily rotated while observing. I found this particularly useful when observing the Jupiter and the Moon, as I find it easier to concentrate on the fine detail when their orientation is correct, such as Jupiter's belts and zones being parallel to the line of sight. Also as the focuser is rotated the finder scope is rotated also, keeping it at a convenient angle.

In addition the focuser has a gradated scale on the focuser barrel which makes it easy to note where my eyepieces reach focus and will be useful for future observing sessions. The Feather Touch Focuser doesn't use a set screw to hold a star diagonal or binocular viewer but rather a compression ring that is tightened by hand which works much better than a set screw.

I spent a couple hours testing the 175mm the first night, and six hours the second night. This gave me the opportunity to try it out on a variety of objects, including the Moon, Jupiter, stars, and deep-sky objects, using both a homemade Dobsonian-style mount and a German equatorial mount. Since then I have observed with the telescope on other nights and have added links below to these observations.

The 175mm f/8 lens with the dew cap retracted.

Optical Performance

Moon

One of the first things I noted when observing the Moon was how well controlled the light scattering was in the telescope. For example the sky next to the lunar limb was jet black. In addition the high contrast and sharpness of the lens made it easy to see subtle lunar detail such as the ray systems extending from craters including Copernicus across Mare Imbrium, as well as the wrinkle ridges and different shades of the lava flows across the various Mares at 60x. Isolated peaks in the northern portion of Mare Imbrium such as Montes Recti, Montes Teneriffe, and Mons Pico appeared to be 3-D. The eroded wall of Clavius was prominent also.

I noted too that the telescope was able to hold detail in lunar features far away from the terminator and under high sun angle at magnifications of 80x and 100x. For example I could see small craters in Palus Somni (which is next to Mare Crisium near the eastern limb of the Moon) when the Moon was just a few days from being full and the terminator was near the western limb. By the way for those observers who don't have a copy of Rukl's lunar atlas I found that a lunar map produced by Rukl and sold by S&T was very handy in identifying lunar features at the eyepiece.

Jupiter

The seeing was only fair when I observed Jupiter and it was only around 35 degrees in elevation but I noted that it all four Jovian satellites were defined as disks and had noticeable differences in color even when using magnifications of 60x. For example Ganymede appeared to be the largest and brightest, while Callisto the dimmest. Also Jupiter was near eastern quadrature so its 99% phase was noticeable, as was limb darkening on the side of the globe. Higher magnifications helped to bring out subtle detail in its belts and zones, including festoons along the North Equatorial Belt south (NEBs), as well as ovals within the NEB.

Deep Sky Objects, Double Stars, and Bright Stars

To round out my testing I observed a variety of deep-sky objects including M4, M8, M11, M13, M17, M27, M31 and M32, and M57, as well as Alberio and Altair. While the transparency was very good during these tests, the limiting magnitude was only around 4.5 due to interference from bright moonlight as the Moon a few days from full phase. For M8, M17, and M27 I used an OIII filter to help bring out fainter detail that was being washed out by the bright moonlight.

M4 - The linear shape to the central portion of this globular cluster was well resolved even at 45x, as were the stars around the outer edge.

M8 - The shape of the Lagoon Nebula was well resolved at 54x as were brighter areas within the nebula and stars embedded in it.

M11 - This open cluster, also known as The Wild Duck Cluster (although it reminds me of the shape of the Music Television or MTV symbol so I always think of it as the MTV Cluster), was well resolved at 45x, and the color of bright nearby yellow star was very pronounced.

M13 - The stars across the core and near the edge of this globular cluster were well resolved at 88x.

M17 - The shape of the Swan or Omega Nebula was very pronounced as the nebula appeared bisected by dark rifts with lighter areas. Also several stars appeared embedded within the nebulosity at 70x and 88x.

M27 - The Dumbbell Nebula showed many variations in brightness and tone at 100x, as well as a couple of stars embedded within it. The football shape extension to the nebula was visible as well.

M31 and M32 - Even though the Andromeda Galaxy and M32 were only 25 degrees in elevation when I observed it at 25x they both looked nice and showed some detail.

M57 - At 34x the Ring Nebula was resolved including the lighter inner portion of this planetary nebula. At 100x the nebula appeared elongated at both ends and bright.

Alberio - At 34x the colors of this double star were very pronounced and the stars well resolved.

Altair - Light scatter was very well controlled around Altair even at magnifications of 200x.

An observing report of deep-sky objects and the Moon using the TMB 175mm was added in August 2004, and an observing report of deep-sky objects, Venus and Saturn using the TMB 175mm was added in October 2004.

Also a sketch of Comet Machholz, as well as an observing observing report of the comet using the TMB 175mm was added on January 3rd, 2005.

An observing report of deep-sky objects, Moon, Saturn, and Jupiter was added on April 4th, 2005, as were sketches of Mars on September 25th, 2005 and October 22nd, 2005 showing a dust storm.

A sketch of Comet Pojmanski March 5th, 2006.

A sketch of Comet 17P Holmes October 31st, 2007.

An observing report of Jupiter, Vesta, Uranus, Mars, the Moon and deep-sky observations September 2nd - 3rd, 2007.

A sketch of Comet 17P Holmes October 26th, 2007.

A sketch of Comet 17P Holmes October 29th, 2007.

A sketch of Comet 17P Holmes November 12th, 2007.

A sketch of Saturn November 22nd, 2009.

An observing report of the planets and deep-sky objects August 2010.

An observing report of the Venus, Mars, and Saturn April 13th, 2012

Summary

Overall I have been very impressed by the performance of this telescope. Mechanical features such as the Feather Touch Focuser makes it very convenient to observe with and aids in obtaining sharp focus at high power.

Also the very fine quality of the lens, coupled with very low light scatter, high image contrast and brightness, has shown me detail on the Moon I have not seen before in over 30 years of observing, as well as the promise of fine detail on the planets and in deep-sky objects under more favorable viewing conditions.

All of this leads to the telescope delivering more performance than I expected for its 7" aperture. Highly recommended.


2) Starmaster 14.5" f/4.3 Reflector

Side view of the Starmaster 14.5" f/4.3 reflector. The Star Bound observing chair next to the SM gives an idea of how tall the 14.5" is when pointed at the zenith.

Overview

I April 2004 I took delivery of a Starmaster (SM) 14.5" f/4.3 reflector. I have owned large reflectors in the past, including a 12.5" f/6 reflector on a German equatorial mount, and a 20" f/5 reflector on a Dobsonian-style mount. However the 12.5" was quite large and bulky making it difficult to set up, and the 20" required a ladder to reach the eyepiece. While it provided stunning views when the transparency and seeing conditions permitted, I found that after a while I did not look forward to climbing a ladder to observe. Then by chance I saw a Starmaster at a star party and was impressed by its features. The shorter focal ratio of the telescope meant that the eyepiece would not be as high off the ground. Also the Sky Tracker GOTO-Then-Track drive system made it easy to locate objects, something that was not available when I owned my 12.5" and 20" reflectors.

Close up side view of the Starmaster 14.5" f/4.3 reflector without the light shroud.

Telescope

One of the first things I needed to decide when ordering the SM was what size to get. An 18" f/4.3 would be shorter than my old 20", but it would still require a ladder to observe with. At the time I was considering ordering the SM they had stopped producing the 16" (although they recently began making them again) so that left the 14.5". While at first I thought I would want a larger aperture telescope for deep-sky observing, I have noted over the years that I find it much easier to concentrate and see more detail when I am comfortably seated rather than standing. When pointed at the zenith the eyepiece of the 14.5" is approximately 65" high, which is just eye level for me when sitting in the Star Bound observing chair. In addition I have found that the more portable a telescope is the more likely I am likely to set it up and observe. So I decided to go with the 14.5".

Close up side view of the Starmaster 14.5" f/4.3 reflector with the light shroud.

The 14.5" SM comes with the following standard features: a custom built, all steel, open design, quick-detach mirror cell; a 1.6" thick Pyrex mirror manufactured by Zambuto Optics with mirror coatings utilize Ion-Assisted Deposition (IAD) and quartz overcoat; a lightweight oak transport case for the mirror; secondary mirror with 96-97% enhanced coatings and dust cover; a Crayford 2" focuser with 1 1/4" adapter; Telrad finder with dew shield; aluminum truss poles with black, rubberized armor coating with carrying case; light shroud for trusses; oak construction with polyurethane finish.

After deciding to order the 14.5" my next choice was what options to order with the telescope. I ordered Feathertouch 2-speed focuser upgrade, the Tectron Collimation Tools, the Transport Handles, and the Sky Commander digital setting circles, the Sky Tracker GOTO-then-track drive system. I have been a star hopper since I first began observing back in the early 1970's, but decided to buy the Sky Tracker as with my family and work life I don't get to observe too often. I felt it would help me track down some of the fainter deep-sky objects I have not seen before. In addition I ordered a TV visual Parracorr that I use mostly at low and medium powers. The visual Parracorr is tunable, as it is possible to adjust it to work best with the eyepieces you are using, and stars appear sharper across the field of view. I use mostly TV Naglers and Panoptics for my low and medium power observing, and TMB Super Monocentric eyepieces for high power observing.

Close up view of the upper cage assembly showing the Feather Touch Focuser, Telrad finder, and Sky Commander hand controller.

The 14.5" is a so-called Hybrid as it was designed to be as portable and easy to set up as possible. For example the trusses and secondary cage can be left assembled together and attached to the rocker box using four hand knobs. In addition the telescope comes with a mirror transport box so that the primary mirror can be carried safely when removed from the mirror cell. The mirror and cell together weigh 33 lbs., the mirror box 25 lbs., while rocker box and ground board weigh 25 lbs. (the Sky Tracker drive system with battery adds an additional 11 lbs.), and the secondary cage weighs 8 lbs.

Close up view of the rocker box with the Sky Commander, tangent arm, altitude encoder, altitude motor, altitude clutch, cables, and faceplate where the cables are plugged in.

The SM arrived well packed in seven shipping boxes with plenty of Styrofoam peanuts and packing material to protect the telescope and accessories during shipment. I was impressed by the fine quality of the workmanship, and the instruction manuals for the telescope and Sky Commander digital setting circles were well illustrated and easy to read. The instructions for collimating the mirror with the Tectron Collimation Tools were straightforward and Rick Singmaster is available to help answer any questions via phone or email.

Optical Performance

Close up view of the upper cage assembly showing the four-vane spider, secondary mirror holder, and primary mirror. The cover for the secondary and primary mirror are visible in the lower left hand side of the photograph.

My first impression when observing with the 14.5" is how well designed and thought out the entire telescope is. It is easy to assemble and use. It is evident also that Rick spent a lot of time figuring out how to make his telescopes work well with the Sky Commander digital setting circles (DSC) with the Sky Tracker GOTO-then-track drive system. It is easy to locate DSO's by doing a simple two star alignment, engaging the altitude and azimuth clutches, then selecting the object you wish to observe on the DSC computer, and pressing the GOTO button on the hand controller of the Sky Commander. The hand controller conveniently attaches to the secondary cage via Velcro just to the right of the Feather Touch focuser, with the Telrad located just above the focuser. If you prefer not to buy the Sky Tracker systems but do invest in Sky Commander it is still relatively easy to locate DSO's. This is done by entering the object you wish to observe in the Sky Commander, and as you push the telescope by hand it will display how far away you are from the object.

Solar System Objects

Saturn

When I received the SM the major planets were well passed opposition so I could only run a few tests to see how well the telescope performs on them. At 198x Saturn looked nice with the colors appearing a bit more pronounced than in smaller aperture telescopes. Four moons were visible nearby including Titan, which appeared as a disk with an orange-red color to it.

Venus

Showed it gibbous phase well and the dusky appearance along the terminator was prominent.

Jupiter

Jupiter's North and South Equatorial Belts (NEB and SEB) appeared somewhat pink-brown in color at 198x. There were bays and festoons along the belts, as well as a nice shadow transit in progress from one of the moons. The moons themselves appeared as disks and were identifiable by their size and differences in color.

Uranus

Uranus was low in the sky when I observed it but its disk was clearly resolved. There were times when I thought I could make out some variations in its cloud structure but I wasn't 100% sure.

Moon

The Moon showed fine detail even at low power in craters and mare and the Earthlit portion of the Moon was easily visible.

Deep Sky Objects

Since I received the 14.5" I have observed a variety of deep-sky objects with it, including the Blue Snowball Nebula, The Veil Nebula, The North American Nebula, M4, M13, M15, M33, M51, M101, and M106. The transparency varied from 5.3 to 4.5 depending upon observing conditions and whether the Moon was up or not.

NGC 7662 - The Blue Snowball Nebula, this planetary nebula is located in Andromeda. It appeared light blue in the eyepiece, and reminded me M57, but it is not as large or circular as it appeared more elongated than M57. Its outer portion appeared brighter than its inner portion, which showed some darker structure or variation in tone. At 396x there was a fainter elongated outer portion running SW-NE, and the central portion appeared more concentric in shape.

NGC 6992 & NGC 6995 - The Veil Nebula showed a remarkable amount of detail, with portions of nebula appearing like a claw. Best view was at 51x with an OIII filter.

NGC 7000 - The North American Nebula showed very fine detail, with portions of nebula in the Gulf of Mexico and Central America appearing feathered. Best view was at 51x with an OIII filter.

M4 - Large and well resolved at 132x, this cluster has a central linear shape that is very pronounced. Around the center there were a number of star chains that formed concentric rings, with the stars appearing more dense on the left side than the right side.

M13 - Large a very pretty with the central region resolved and many, many, many star chains extending out from the center.

M15 - Gorgeous, the best I have seen this cluster. Strong central condensation in the center, with the star chains radiating out from the center well resolved.

M33 - At low to medium power appeared as a large, light green colored multi-armed galaxy with bright central area with several HII regions visible.

M51 - Beautiful, one of the best views I have had of this spiral galaxy. At 132x the spiral arms and dust lanes were clearly visible, as was the connecting arm between M51 and NGC 5195.

M101 - At 132x showed a bright central region with four spiral arms and dust lanes, with HII regions visible at the ends of some of the dust lanes.

M106 - This galaxy appeared elongated with kind of a spindle shape to it and showed a brighter inner portion and core. A dust lane was faintly visible.

Summary

Overall I have been very impressed by the performance of this telescope. It is one of the best designed telescopes I have ever had the pleasure of observing with, offering large aperture with very fine optics in a highly portable package that is easy to set up and use. In addition with the ability to add tracking and GOTO it is makes it easy to locate deep-sky objects even under less than ideal observing conditions. Highly recommended.

This telescope was sold in 2004.


Articles 2000 - 2015, Eric Jamison, All rights reserved.

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