A 4-Inch (102mm) Refractor Can Be An Excellent Deep-Sky Telescope: Finally Sirius B, Barnard’s Galaxy, and Much More….

All Observer’s Challenge Reports to-date:

https://rogerivester.com/category/observers-challenge-reports-complete/ 147 consecutive months as of April 2021.

      Walter Scott Houston, most often used his 4-inch Clark refractor for his observations of deep-sky objects while writing the monthly “Deep-Sky Wonder’s” column in “Sky & Telescope Magazine” for 46 years until his death in December, 1993.  

     When Sue French picked up DSW’s where Houston left off, she seemed to favor the use of her 105mm refractor for so many observations over her twenty years writing the column.  

      I purchased my 102mm f/9.8 refractor in 1997, and have enjoyed using this scope over the years.  It provides for a nice velvety black background with excellent contrast of faint deep-sky objects within its reach.  

      On nights of good seeing, it will easily exceed Dawes Limit:  https://www.astronomics.com/info-library/astronomical-terms/dawes-limit/  

       One thing I especially like about this scope:  It’s compact and portable enough to take out for those short observing sessions, when time is limited. 

      Double and multiple stars have always been of interest to me, and I’ve observed hundreds of close double and multiple stars over the years with this telescope.  At current, I’m working my way through another double star list with the refractor, taking my time to sketch each double, noting the colors, checking the position angle and also drawing a few field stars. 


The value of a correct image diagonal:

I’m now using a correct image 90º diagonal.  The view through a standard 90º diagonal, whether using a refractor, Schmidt-Cassegrain or Maksutov-Cassegrain makes it impossible to correctly draw “scientifically” a deep-sky object.  

I like to make my sketches as they are truly oriented in the sky, with north at the top and west to the right on my sketch card.  (See some sketches using my 10-inch reflector below) 

From Orion Telescope and Binoculars: 


I finally purchased an Orion 1.25-inch correct-Image diagonal for my Orion/Vixen 102mm Refractor. The precision 90º diagonal provides a right-side-up, non-reversed image. 

I have really enjoyed observing with my refractor, but didn’t like the reversed mirror image, due to the 90º standard diagonal. On many occasions I would choose my Newtonian, as it’s so easy to make a correctly oriented pencil sketch. For many years, I’ve wanted to try a correct image 90º diagonal, but thought the views might suffer.  I’d been using a 96% enhanced reflectivity mirror diagonal for many years.  

A correct image prism diagonal, also known as an Amici:

Within a few days after making my purchase, the diagonal arrived, and on March 5th, 2014, I set up my 102mm refractor for the big test. I started with a very high magnification of 200x, to examine the Trapezium stars and see how the view would compare to my current enhanced standard 90º mirror diagonal.

The stars were beautiful in both, and even the “E” star could be glimpsed intermittently in both diagonals.  

I then went to my favorite galaxy pair, M81 and M82 at 57x, and immediately loved the non-reversed and correct image view of these two beautiful galaxies.  I really couldn’t see any difference between the quality of the two diagonals. The next test would be Jupiter, and again both diagonals presented excellent views. The cloud bands appeared very sharp with an incredible amount of detail visible in both diagonals. 

It is my opinion, the correct-image diagonal, seemingly passed all tests with flying colors.  I plan on using this diagonal for all of my observations and pencil sketches in the future.  

 An example of my correctly oriented sketches as following, “mostly” via my 10-inch reflector:  



Rogers M-081 Inverted

Rogers NGC-2300 Inverted

Scanned Image 160920001

Roger IC 1805

M13 And The Elusive Propeller

Pacman Nebula - NGC 281

I wanted to include a picture of my (1992) Meade model DS-10A f/4.5 reflector.  This telescope was manufactured entirely in the old Costa Mesa plant, from all American parts, including the mirror, but with the exception of the focuser (Japan).  I did have to add a finder, and would later change to a 90º Antares correct image amici.    

The original mount, not shown, was also manufactured in the California operation.  In the following photo, the scope is mounted on a Celestron CGE-Pro mount.  However, due to the weight and size of this mount, I most often use the original, smaller, but much lighter Meade equatorial mount.  

Five years later in 1997, I purchased the 102mm Orion/Vixen f/9.8 achromatic refractor.  


Seeing Sirius B: 

“Finally….after more than 35 years, I was able to see Sirius B, better known as the “Pup.”  Date of observation:  March 14th 2012

Telescope:  4-inch (102mm) Orion/Vixen f/9.8 achromatic refractor.  Conditions:  Excellent seeing and transparency    

How did I become interested in this famous star and its faint companion?  

I purchased my first serious telescope in 1977, which was a 4 1/4-inch f/10, Edmund Scientific reflector.  Even though this was not my first choice for a telescope, it was the best my budget would allow at the time.  My first choice would have been the 6-inch Edmund f/8 EQ (Super Space Conquerer) reflector.  

I started reading anything and everything about astronomy, and was fortunate to find “The Edmund Sky Guide” by Terence Dickinson and Sam Brown.  In this book was a paragraph concerning Sirius and its companion which caught my attention.  Double stars were something new to me at that time.    

I’m really glad that I purchased the Edmund books, so many years ago. 

Back to Sirius B: 

Due to the extreme and overwhelming brightness of Sirius as compared to the much fainter companion, it can be extremely difficult to see the dimmer star.  

I tried for at least a couple of years (mid-70’s) in a feeble attempt to see the companion (a.k.a the “Pup” or Sirius B) with my humble 4 1/4-inch Edmund reflector, but without success.   

During the fall of 2011, double star expert and astronomy author, James Mullaney, informed me that he had heard of an amateur being able to see the companion to Sirius using a 4-inch refractor. 

I had pretty much given up on seeing Sirius B in 2012, thinking it was not possible with an amateur scope.  However, after hearing that an another amateur had been successful at seeing the companion gave me the idea that I should try again.   

The 102mm refractor has allowed me to separate many close and difficult doubles over the years, often achieving or exceeding “Dawes Limit”  on nights of excellent seeing. 

When Sirius B was at a relatively wide separation during the 70’s, again, I was using a spherical mirror, 4 1/4-inch f/10 reflector, not exactly the preferred telescope for accomplishing this feat.  

March 14th 2012, and using the 102mm refractor:

I made preparations to observe Sirius.  After letting the telescope cool down for at least an hour and making a few visual test…the seeing appeared excellent!   

Afteadjusted my astro-chair and removing the diagonal, I started with a magnification of 83x, but to no avail.  I increased the magnification to 232x, all the while keeping my eye perfectly still.  

Sirius was fairly sharp, not the large bloated star that I was so used to seeing. 

I looked very carefully for at least an hour, when a very faint star appeared so very close to Sirius.  

That was it, but probably knowing the position-angle made it possible.  However, I could not hold the companion, or Sirius B constantly.  It was extremely difficult.  But after 40 years, I had finally seen the companion to Sirius.  

I had glimpsed Sirius B (or so I thought) the previous month (February 2012) but seeing was not that good, and just had to have another observation to confirm my sighting.  

Seeing the companion with another 4-inch refractor:   A Takahashi FC-100H, f/8 fluorite doublet during the winter of 2016:

Another sighting of the companion of Sirius using a 4-inch Takahashi FC-100H, f/8 doublet fluorite.  Sirius B was “actually very easy” with this scope.  It was much easier with this “premium” telescope as compared to the view through my 102mm f/10 achromat…as one would expect.  

Winter of 2016: 

A group of at six or more amateurs took the test using the Takahashi refractor, and what did they see?   

Using the face of a clock, and all without sharing their perceived position of the companion until everyone had the opportunity to observe.  When the last person completed their observation, all correctly identified the position of Sirius B.  

Some were very skilled observers, but a couple or more were not, however, all could “fairly easily” locate and see the companion.  

I was not surprised, as when I observed the companion earlier, it was easy (yes…easy) and was so precise and pinpoint in this telescope. 

Completing a list of deep-sky objects: 

One of my first reference books was “The Finest Deep-Sky Objects” by James Mullaney and Wallace McCall.  I had observed all 105 objects many times, accumulating over 600 or more, 3 x 5 note cards, complete with notes and sketches.  

However, one of the objects on this list was missing…the companion to Sirius.  After my visual sighting of Sirius B, I now have notes and sketches of all objects listed in that great list of deep-sky objects.  

I couldn’t have selected a better reference book to start with: 

The 105 objects featured in the FDSO’s is comprised of many famous and popular double/multiple stars, but also galaxies, star clusters, red stars and nebulae.  

This book was the perfect primer for a new and budding amateur like myself, as It gave me an introduction to all types of deep-sky objects.           

Back to Sirius B: 

After seeing Sirius B, I went to bed smiling, as another observing goal had been accomplished.  

Have you seen Sirius B, better known as the Pup?  Why not give it a try?  

Sirius. “A dazzling blue-white sapphire with famed white-dwarf companion!  Orbital period 51 years.  Now widening but still not an easy split most nights.  Mags -1.5/8.5  Sep.  7”  “The Cambridge Double Star Atlas”  by James Mullaney and Wil Tirion

Why not consider a small refractor for some visual observing of other deep-sky objects?    

I have always been interested in the possibilities of using a small telescope, especially a good quality refractor.  A refractor can present pin-point star images and a velvety black background which can improve the contrast of most deep-sky objects.  The superior contrast of a refractor can often times allow views of deep-sky objects to rival or even exceed larger telescopes of more complex designs.  

NGC 6822 (Barnard’s galaxy) in Sagittarius:

It should also be noted that a very low surface brightness object, can often times be better observed at low magnification with a small refractor.  A good example of this would be NGC 6822 (Barnard’s Galaxy) in Sagittarius. 

“A weak glow but definite glow in 6 cm, where it appears elongated N-S and shows a very slight central concentration.  In 25 cm motion of the field helps in showing the low surface brightness galaxy, but it is difficult and ill-defined at best.”  Observing Handbook and Catalog Of Deep-Sky Objects by Christian B. Luginbuhl and Brian A. Skiff.  

Finally, after more than 20 years using my 10-inch reflector) I’d never been successful.  In September 2014, I was able to sketch and make notes of this elusive galaxy, NGC 6822, using the 102mm refractor.  Much of my problem was/had been due to light glow from a pesky unshielded street light in close proximity to my backyard.  A dark sky is critical for locating and observing this faint and low surface galaxy.  

And so, with NGC 6822, another difficult object was checked off my list. 

The following sketch was made using the refractor with nothing more than a No. 2 pencil, a blank 5 x 8 notecard, with the colors inverted using a scanner.

Rogers NGC-6822

The following image by James Dire of Hawaii using a 190 mm Maksutov-Cassegrain telescope.


The complete Observer’s Challenge Report for NGC 6822:


“The Observing Handbook and Catalog of Deep-Sky Objects” By Christian B. Luginbuhl and Brian A. Skiff

This is the reference book that took me to a higher level as an amateur astronomer, and it remains the book that I use most often with all my observing sessions.  I like the descriptions by the authors describing the views with various telescopes, especially with a 60mm refractor.  This causes me to want to follow their observations and see what’s possible for me using a 60mm refractor, however, I don’t have one.  

No problem:  I have a home-made 60mm stop-down mask for use with my 102mm refractor.  This allows me the opportunity to observe the object with a 60 mm refractor, without having to add another telescope.  I can then make visual observing notes and sketches for two scopes.

Seeing the companion to Polaris using an effective aperture of 60mm’s:   

Polaris has a magnitude of 2.1 and the secondary or companion at a much fainter 9.0 magnitude with a wide separation of 19 arc seconds.  The extreme difference in magnitudes can make this double more difficult to separate than you might think, especially if seeing is less than good. 

April 19th 2018:  102mm f/9.8 achromatic refractor with an effective aperture of 60 mm’s.  

Seeing excellent: 12.5mm eyepiece plus a 2.8x Barlow for a magnification of 80x.  The companion was clearly visible as a tiny bluish dot.  



What is the smallest aperture that will allow me to see the companion to Polaris?  The following photo shows an effective aperture of 45 mm’s.  

However, as of current, I’ve been unable to see the companion with this aperture (45mm’s).  


Seeing the companion of Polaris using an 80 mm f/5 refractor:

My son surprised me with an 80 mm f/5 refractor for a birthday present…

In the spring of 2018, I received my present:  An 80 mm model f/5 achromatic refractor.  But how would it perform?

Seeing was very good, and using a 12.5mm eyepiece plus a 2.8x University Optics Klee Barlow for a magnification of 90x.  

The companion to polaris was visible as a tiny bluish dot.  Very similar to the view using the 102 mm reduced to 60 mm’s.  Beautiful in both telescopes.   



When observing with my 80mm or 102mm refractor, I always use my 1.25-inch correct image diagonal.  For me it’s essential when sketching a deep-sky object, to have the correct “scientific” orientation in the eyepiece field-of-view.  

April 20th 2018:  80mm f/5 achromatic refractor.  Similar conditions to my observation on the 19th. Using the same eyepiece combinations (90x) and was easily able to see the companion as a tiny bluish dot.  A great little scope which is very easy to take outside, including the mount…all in one trip.  If time is limited to an hour or less, this is the telescope I use. 

Beginning amateur astronomy in 1967 with a 60 mm refractor: 

My older brother purchased a 60mm f/15 EQ Jason Refractor in the mid-60’s, when I was only thirteen years old.  This was the telescope that got me interested in astronomy.  I would set it up in a weedy field beside of my house in a very rural area of the foothills of North Carolina.  I had difficulty finding anything other than the moon, Venus, Saturn and Jupiter, but eventually my observing skills did improve.  I’m really glad that I persevered and stuck with it. 

Maintenance of a refractor: 

I have always kept the lens capped on the 102mm refactor, when not in use and the OTA is always stored in a padded case.  In the eighteen years that I have owned this telescope, the objective lens has never required cleaning.   The objective lens is also permanently collimated, without any adjusters, and was in perfect collimation when I received it.  There has been no change after purchasing the scope in 1997, and with plenty of use.   

For most part, a refractor is much more durable and able to suffer less from mishandling and rough treatment than reflector’s and catadioptric telescope’s.   

A very high quality 4-inch refractor during the 50’s through the 70’s, had to be a Unitron, with the standard f/15 focal ratio.  The long focal length was necessary for an achromatic refractor telescope…to reduce false color.  

This telescope could be obtained with either of two mounts.  One being a field tripod with wooden legs, and the other…a massive bell-shaped pier with a mechanical weight-driven clock drive.  The latter was designed for a permanent location.  A 4-inch f/15 refractor with any type of equatorial mount for most part should not be considered a portable instrument.        

John Mallas who co-authorded “The Messier Album” with Evered Kreimer, used a 4-inch f/15 Unitron to examine all Messier objects between 1958 and 1962, from Covina, California.  This is a fabulous book and I still use it as a reference quite often, even to this day.    

The modern era of refractor telescope’s arrive:

However, with the advent of exotic glass, better anti-reflection coatings and short focal lengths… like the slide-rule, the day of the 4-inch and larger f/15 refractor was over.     Roger Ivester

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