Mel Bartels' Amateur Telescope Making

My telescopes...

My articles...

What's New - Making is the Key to Knowing

Three years in the making, I have completed a 30x25 degree mosaic of sketches of the Orion-Eridanus Superbubble and the area straddling the border between Eridanus and Orion that I call the 'Interlude'. I use a technique that I've developed that I call 'many-field' sketching. The brighter portions of the superbubble are surprisingly easy to see being just fainter than Barnard's Loop.

January 31, 2018 lunar eclipse sketch. Thrilling to see the sky darken to reveal the Beehive Cluster next to the Moon.

My 25 inch F2.6 mirror is back from the coaters. What a beautiful coating - not a single scratch or pit! See how I made this unique mirror.

My sketch of SH2-240, the Spaghetti Nebula (Simeis 147). My impression through my 10.5 inch [27cm] F2/7 2.5 degree field telescope is first, one of many bright stars with faint broad nebulosity that upon closer inspection shows brighter knots and upon lengthy investigation reveals filaments, particularly the double filament on the SE side. Also visible are several dark splotches.

A sketch of the newly identified H-alpha bubble, WD-1, and some thoughts on sketching and imaging.

Two more sketches of IFN in Aries: a wandering stream of IFN that is fairly bright that is fun to trace and a bright area next to Beta Arietis. Finally a detailed sketch of the M74 IFN with the 13 inch F3 including UGC 1167. My catalog of IFN is up to 64 sketches.

Two sketches IFN: an interesting mix of stars, M74 galaxy and IFN next to Eta Piscium and a broad cloud looking arc next to Eta Ceti.

I finished the 25.1 inch [0.64m] F2.60 mirror that is but half an inch [13mm] thick. I wrote a page describing my effort.

A wonderfully bright and shaped Integrated Flux Nebula (IFN) extending from the star CO Cam.

An IFN dagger pointing to Barnard's Galaxy.

IFN detail near Serpens Caput.

Largest crowd ever for innovative and throwback scopes: 2017 Oregon Star Party Eclipse Edition Telescope Walkabout.

My 2017 Oregon solar eclipse experience.

I shared my Sketchup model of my grinding machine and created a webpage with images and notes.

I added a 'W' stroke to my pitch lap calculator.

A faint and pretty field of IFN (Integrated Flux Nebula) sketch stretching from the orange star Theta Herculis to another orange star Kappa Lyrae with my 6 inch [15cm] RFT. My IFN catalog can be found here.

A faint IFN Integrated Flux Nebula (IFN) sketch centered on Leo's backbone, encompasing a 10 degree field using my 6 inch [15cm] F2.8 Richest Field Telescope with 4.3 degree field of view. My IFN catalog can be found here.

My latest Integrated Flux Nebula (IFN) sketch of Hercules Keystone's western side, encompasing a 10 degree field centered on M13 using my 6 inch [15cm] F2.8 Richest Field Telescope with 4.3 degree field of view under spectacular SQM 21.6 skies. The transparency was so clear that I could hold NGC 6207 steady at 24X. I completed the sketch over a two night period. My IFN catalog can be found here.

I created a pitch lap calculator to help me shape my full sized lap for my 25.1 inch [638cm] F2.6 ultrathin meniscus mirror. My process uses standard strokes on a parabolizing lap to meet the challenge of 62 waves of correction.

40 inch [1 meter] F3.75 Dob dedicated at Reynolds-Mitchell Observatory, Chiricacua Astronomy Complex. Mirror by Lockwood and OTA by Star Structures. Here's my list of largest amateur scopes.

Two recent confirmations of my IFN sketches. First, check out Rogelio Bernai Andreo's incredible image of the M64 area. Compare to my M64 sketch. And check out a deep image of M13 showing the nearby IFN. Then compare to my M13 IFN sketch.

Check out my article in the April issue of Sky and Telescope Magazine, "Herschel's Ghosts". I share my visual discovery of Integrated Flux Nebulae and my investigation into little known observations of earlier visual observers extending all the way back to William Herschel. See my catalog of IFN sketches.

Two unknown optimizations that I employ to improve my telescopes: optimizing for size and weight and optimizing for light throughput.

I added an equatorial table optimizer to my telescope criteria calculator. This optimizer lays out a four corner table.

I've discovered more Integrated Flux Nebulae encompassing the head of Pisces and the eastern side of the Pegasus Square.

I created a Strehl to RMS to Peak-Valley optic rating converter.

I added a diopter calculator.

Check out Fabio Marioni's 40 inch [1 meter] scope that saw first light a few nights ago. He ground the 24mm thick meniscus F5 mirror himself.

New super wide angle sketch of the Andromeda Galaxy. This shows the IFN extensions to the south up to 10 degrees away along with a better view of the shelf below M110 and how the shelf curves up to touch the extreme sides of the galaxy. I was also able to spy the 'hook', an extension of the IFN that curves in to the south of the galaxy, almost surrounding the galaxy in a shell of gas and dust. I also believe that I saw the deflected arm of the galaxy that extends to the northeast into the IFN, making me suspect that the deflected arm is actually an arm of the IFN. The glow of the galaxy nicely encompassed M32.

I have finished nine more Integrated Flux Nebulae sketches covering Capricornus through Aquarius to Pegasus. This region is full of faint streamers, often running in parallel, with the occasional beautiful scene. The astonishingly bright orange of Beta Aquarii contrasts with streams of IFN flowing through the field; M2, bright and resolved, resides in a field of IFN; Beta Pegasi sports a 'V' shaped cloud hugging a chain of stars; Rho Capricorni is part of a rich star field with a band of IFN off to the side; a complex of IFN is to be found in the beautiful star field of Alpha Capricorni; M75 sports four parallel bands of IFN crossing the field; parallel IFN streams make for an interesting view of Alpha Aquarii; IFN in the Mu Pegasi form a complex 'hat' shape and more bands of IFN are to be found next to Alpha Pegasi.
My IFN catalog is up to 48 entries.
I was able to trace IFN across 40 degrees of sky from Beta Pegasi (the northwest corner of Pegasus' square) down through Alpha Pegasi (southwest corner of Pegasus) then curving westward past Aquarius' propeller to Alpha Aquarii and finally into M2. Also not sketched is the continuation of the parallel streams in the region of M75 that continue both north for a short distance and southward for a much longer distance, eventually curving south of Sagittarius into Corona Australis for a total of perhaps 40 degrees. Clearly I need a telescope of modest aperture than can cover dozens of degrees of sky in a single view!
I am also experimenting with process and medium, discovering that pen or pencil, one drawing or multiple, makes a difference to the finished drawing. Process affects what I notice: the extent of the IFN, the brightness levels and the boundaries. I also tried observing with my other eye. While it has a bit less yellow coloring due to age so the blue stars and overall field brightness seem a tad brighter, I found the IFN invisible at first, then only the brighter portions visible after a number of minutes. One of my major challenges is that I've trained myself to notice the field to the lower right of my left eye, my main observing eye. Using my right eye I had to constantly repoint my eye to the upper right to place the subtle IFN in the more sensitive lower left area.
Then there's transparency. I had two superb nights and a good night to start the three night effort. I was able to see more IFN on the superb nights. I shudder to think how invisible the IFN would be on a poor night or in less than idea skies, like with some light pollution.

I am adding a flex rocker optimizer to my telescope criteria calculator. This gives you the ability to adjust the telescope design to optimizer the flex rocker dimensions.

I take a deeper dive into diagonal offsets, discovering that the edges of the field are not equally illuminated when the diagonal is offset.

The 2016 Oregon Star Party Telescope Walkabout is history. Check out the interesting telescopes and their builders.

Four more Integrated Flux Nebulae sketched at the Oregon Star Party: a surprising cocoon surrounding M13 of all objects, a large IFN in Corona Australis and two nice IFN in the foreground of faint NGC galaxies: NGC 7497 and NGC 918.

Three more IFNs: the Iris nebula with IFN/ISM (Integrated Stellar Medium) to the south of the nebula proper, a galaxy/IFN pairing: NGC 6951 and an unusual pairing of a planetary nebula and the IFN. The latter two are small in angular size so likely will look more detailed and dramatic in a larger wide angle telescope.

Five more IFNs: the beautiful gossamer Barnard's Galaxy region, the bright Epsilon Lyrae area, the the Alcor and Mizar area, the Alpha Herculis region and the M92 area.

I'm creating a catalog of visual IFN that includes sketches and descriptions - everything you need to see the IFN for yourself except dark skies!

Five more IFNs including one of the most remarkable objects of any type I've observed: a narrow arrow straight IFN extending from Serpens Caput past Libra to Virgo - 40 degrees long. The Vega IFN is surprisingly bright in crowded fields of stars. The Big Dipper's IFN starts as an easily seen arc next to Megrez. The star Arcturus sports several IFN: two to the west and one to the east. Finally, the IFN above the star Nekkar at the northern tip of Bootes may form a larger arc that includes the M51 to M63 IFN.

Two more IFNs: first is west of Draco's Head and the second is near Eta Draconis. These two have interesting shapes.

The Draco Dwarf Galaxy proved very difficult and fairly confusing: difficult because it was so faint and confusing because of the brighter nearby IFN! In the end though a rewarding view. The galaxy, comprised of old stars, is thought to be one of the most dark matter dominated known.

My first attempt at sketching a long IFN streamer. This streamer of galactic cirrus is maybe 20 degrees long, stretching from SE Hercules to Serpens Caput.

The Blue horsehead nebula, IC4592 and IC 4601.

Two new Integrated Flux Nebulae near Denebola, Leo's tail.

A new Integrated Flux Nebula discovery in the wide angle field of M51 and M63, the Whirlpool and Sunflower Galaxies under excellent transparency of SQM 21.63.

A new Integrated Flux Nebula immediately south and east of M64, the Blackeye Galaxy. My first sketch shows the dim glow under SQM 21.1 skies; the last sketch shows how much more can be seen in better skies of SQM 21.4. I also include the matching area from the Plank Thermal Map. My second sketch shows a glow adjacent to the east that's missing from the infrared map. This must be blue light reflected from dust that comprises the IFN.

Herschel's Ghosts, discovering the Intergrated Flux Nebula and uncovering the lost story of the original discoverers.

The Virgo Cluster Markarian's Chain Integrated Flux Nebula is surprising, both for its distance from the galactic plane and for its relative brightness. Though sparse in detail, the juxtaposition of the nearest galaxy cluster with our own Milky Way's galactic cirrus makes for a busy field.

The Volcano Integrated Flux Nebula MW3 is the brightest IFN and very easy to find. Lots of detail awaits those who spend a great deal of time here.

The Polaris Integrated Flux Nebula MW1 is centered on Polaris and begins a very long chain of IFN. It's not the brightest IFN.

Angel - Integrated Flux Nebula. My first IFN that is not associated with another deep sky object. I am really thrilled to see it; and you know, it's relatively easy. In fact, a couple of times I got lost, so instead of star hopping from M81/82, I followed the IFN from the galaxy pair to the chain of stars to the Angel's side. The star denoted the Angel's eye, HD 90696, is a nice star hop from M81/82. A Nebustar filter helped, but was certainly not required. In fact, after using the filter, I found the nebula harder to trace, a curious 'post-filter' effect. It does not take much aperture to see the Angel - just a wide field and very dark skies.

Leo Triplet (M65, M66, NGC 3628) with IFN. This is a simply beautiful view, the large galaxies with their dusky gray to nearly white hues with the IFN encircling the galaxy trio. For decades I've enjoyed the trio, yet simply failed to notice subtle changes in the foreground glow. I also managed to glimpse portions of NGC 3628's tidal extension that reaches to the IFN. A Skyglow filter helped with the IFN, but dimmed the galaxies.

I've made a great deal of progress on my reflecting telescope optimizer. Currently I have the telescope, eyepiece, diagonal and off-axis mask, baffle, lowrider, center of gravity and friction of movement optimizers built. I just added etendue and radiance calculations to the telescope optimizer that shows the total light throughput of the telescope design.

M44 with the Integrated Flux Nebula. I swung my scope over to the Beehive Cluster after an hour and a half of intense observing, intending to enjoy a relaxing super-wide angle view of a bright popular object. To my astonishment I saw broad nebulosity - the IFN. I used my 10.5 inch [27cm] F2.7 reflector at 40x with a 2.5 deg FOV and a NPB filter.

M81, M82 and the Integrated Flux Nebula. An incredible observing experience, seeing the Integrated Flux Nebula with my 10.5 inch [27cm] F2.7 reflector at 40x with a 2.5 deg FOV and a NPB filter.

Cone Nebula, Christmas Tree cluster. Best view was with the 13mm Ethos and UHC filter at 1.1 deg FOV and 90x. The view at lower power with the 21mm Ethos and 1.8 deg FOV at 55x showed more of the surrounding nebulosity but made the Cone too small and indistinct. At the lower power, the NPB filter worked best. Without a filter, the Cone was hardly there.

SH2-308, a Wolf-Rayet shell.

I am figuring the 25 inch [635cm] F2.6 meniscus mirror that's half inch thick and weighs 25 pounds [11kg]. The mirror shows no astigmatism after polishing out on my mirror making machine, a major milestone. Finally, the precision refractory molds for slumping the 42 inch mirrors in the kiln are proving too thin. Not to despair - I have a plan. See my updated notes and pictures.

IC443, the Jellyfish Nebula with my 13' and various filters.

My new grinding machine, polishing a 25 inch [635cm] diameter mirror.

The extended HorseHead Nebula area (IC434).

Abell 12, a faint planetary almost touching Mu Orionis.

The telescope criteria calculator. I explain the master telescope relationship comprising the five telescope criteria and offer a telescope design calculator where the criteria can be compared against each other.

The Flying Bat and Giant Squid nebulae. The Flying Bat is the huge arc to the left of the field and the Giant Squid is the bipolar nebula in the middle of the field. They are known as SH2-129 and OU4. The red carbon star is V419 Cephei.

The 'Ring' of Betelgeuse is broken into clumpy dark nebulae with B36 the dominant feature on the western side as a long diagonal streak. There are offshoots to the northwest, one leading to B35. The arced bell to the north of Betelgeuse is clumpy and splotchy. The long curved section to the south of Betelgeuse is beautiful - subtle, mottled, striated.

I added some thoughts on 'How to know that you are finished' with a mirror making project.

I'm busy updating my meniscus mirror thinking; adding to my star testing article a comment about the optimum star testing elevation, a realization that when a zone's location becomes difficult to locate using the star test, it's a sign that the mirror is diffraction limited; adding to my polishing a mirror article how to fix astigmatism with a local lap; and links to Kai Kretzschmar's 47 inch project: slumping and grinding, on my precision mold making for slumping mirrors webpage.

Drawing of the river of dark nebulae that leads north of the North American Nebula.

Drawing of M15 with surprising nebulosity nearby. What is the nebula - emission, Milky Way or ?

What an amateur astronomer needs to know about the Airy disk.

Understanding telescope magnification is the key to using a telescope.

The Bartels' equation for telescope value.

Another astronomical truth: when aperture differences matter.

Some thoughts on telescope requirements.

Preparing for a night's observations.

Why observe? Three amateurs speak.

My latest drawings. First, the Cave Nebula or Caldwell 9. Next, a dynamic complex of dark nebulae, stars and Milky Way next to Albireo. A cure for Albireo Myopia?

The Oregon Star Party Telescope Walkabout for 2015 featured eight telescopes: Don Peckham's new Tenesegrity telescopes, Rob Brown's white light sun bucket solar scope, Hitoshi Yokoyama's binocular telescope from Japan, Frank Szczepanski's unequal large aperture binocular, Bill Fates beautiful 5 inch binoculars, Scott Lee's 14 inch novel Newtonian, Greg Rohde's well-built computerized digital drive system and Jerry Oltion's equatorial table adaptation.

Some thoughts on how to become a better mirror maker.

I dug out my old notes on my secondary size study from the 1970's using my wonderful 14 inch telescope.

Progressive sketches of supernova remnant G65.3 5.7 north of Albireo.

I'm adding Howard Royster's 1 meter alt-alt to my largest amateur telescopes page.

I've ported Mauritz Andersson's ground-breaking mirror test ( to JavaScript so that it runs entirely in the browser. Mauritz's made the source code open source under the MIT License (

The toolmaker, the thinker and the telescope. More astronomical truths...

Richest Galaxy Observing. With my 10.5 inch [27cm] f2.7 scope with 2.5 degree field I'm able to see the Leo Triplet plus a fourth galaxy further away; I'm able to capture the Markarian Chain from M86 and M84 sweeping across to M88 and down to M87. Also I glimpsed a rarely seen dark nebula to the south. Field after field is littered with galaxies; often 5-20 galaxies in any field of view as I sweep through the Virgo / Coma Berenices region. I call this 'Richest Galaxy Observing'.

Amateur astronomy truths...

What is TTO and TEO?

Is aperture king? Let's compare the Sombrero Galaxy through side by side 6 inch and 13 inch telescopes across a range of magnifications.

I wrote a new calculator that shows altazimuth tracking errors when the motors are commanded to move at a constant rate. It illustrates how long altazimuth constant rate tracking can continue before the error becomes too great.

I built a new aperture calculator that determines aperture from exit pupil, the eyepiece field stop diameter and the desired field of view.

I've put my thoughts on star testing into its own webpage.

See my thoughts on the Earl of Crawford's tracking arm.

New sketches of the Horsehead area and the Pleiades.

Check out my awesome observations of the Orion-Eridanus Super Bubble, SH2-245, SH2-264 and the southern arc of Barnard's Loop.

See my sketch of Comet Lovejoy with my 13 inch [34cm] F3 telescope.

I extend the Morse transformer design to three axes and to a side mount.

I investigate the tilt tracking table and hexapod mount with a fellow tilter. Can they replace the equatorial table?

Can an equatorial table be designed to use simple Dobsonian motions? Continue reading about my turret table design...

I've added a provocative section to my re-designed Richest Field Telescope article. In it I make the case for 'telescope mode' observing. Continue reading my RFT article...

My links for weather forecasts and dark skies. Check out my links...

50 inch F3.5 amateur telescope, mirror by Fullum, appears in California. I've added it to my list of world's largest amateur telescopes.

Dynamic collimation, the Andrew Angle and the Seven Ways. Recently I was sitting on Jerry Oltion's couch, mulling over his collimating approach to his spectacular 12 inch binoscope. You really need to know your way around collimation if you own a binoscope. It occurred to me that there are seven ways to collimate a reflector. At the same time Andrew Bell was finding collimation issues with his telescope: the collimation would change as he tipped the scope up and down. What is the best angle to aim the scope to minimize collimation changes? Andrew devised a mathematical approach to calculating the optimum angle. Get the lowdown...

I am observing features in my small super fast reflectors like the Pleiades Bubble and the Andromeda Shelf that apparently have not been observed; at least there are no records that I can find. Why? Read my thoughts...

My latest telescope, a 10.5 inch f2.7. It resolves globular clusters yet provides a two and a half degree field view. Just spectacular and a joyful scope to operate. See my scope...

The small scope, a 6 inch f2.8, that stunned me on the very first object I observed, the Pleiades, revealing a bubble surrounding the cluster that can only be seen on deep digital images. This scope cries out to be looked through. See my scope...

Improved folded Newtonian calculator: the tertiary mirror can be moved. Play with the calculator...

I follow an explicit plan for telescope innovation. Using this plan I've designed innovative scopes such as the ZipDob, the TriDob, super fast meniscus Scope.exe and computerized telescopes. Read how I innovate...

I am now making slumping molds up to 42 inches in diameter to curve large glass into a meniscus shape that survive through multiple kiln cycles. See the molds...

A review of the rare George McHardie's 'Preparation of Mirrors for Astronomical Telescopes'. A wonderful little instructional pamphlet that emphasizes the practical. Turns out little has changed, plus some forgotten tips. Read my review...

The 2014 Oregon Star Party Telescope Walkabout. Three bino-scopes, two scopes faster than F3, plus a lot more. See the scopes...

The night of 6000x power; when we ran out of doubly stacked barlows. Read about that astonishing night...

An electrophonic meteor and the Leonids..

I've made observing dark nebulae my specialty the past several years. Some thoughts on dark nebulae, observing them, and lots and lots of sketches. Read how I observe and see my sketches...

The 2012 Waimea Hawaii AltAzInitiative conference and a trip to Mauna Kea. See pictures of the giant telescopes...

A mountain meditation. Observing in the rugged Oregon Cascades one summer evening. Continue reading...

Mel Bartels' homepage

BBAstroDesigns, Inc.


One of my most vivid memories as a child is resting in the back of my parents station wagon while driving back home to the city.

The stars were so bright and the sky so black as I peered out the window.

My telescopes...

My articles...

The past and the future

Who invented the reflecting telescope?

Remembering John Dobson

The Morse transformer mount

The Holcombe mount

Can the Dobsonian revolution happen again?

Telescope makers' future

Amateur astronomy's future

The largest amateur scopes

Largest amateur scopes (40 inches and larger)

Telescope Design

Reflecting telescope optimizer

Rich Field Scopes

Diagonal size

Secondary size study

Folding and sliding telescopes

Variations on the ballscope

Flex rockers

Two unknown optimizations

A smaller upper cage

Off-Axis masks

The Earl of Crawford's tracking arm

Omni latitude equatorial table

A turret equatorial table

The tilt tracking table

Three axis mounts

Ultra-Light Dobsonians

Telescope vibration

Telescope innovation

Natural telescope design

A new way to look at things

Some thoughts on telescope requirements


Amateur astronomy truths

Bartels' equation for telescope value

Tips to improve your telescope

Dynamic collimation

Collimating a f/3.0 telescope

Telescope slang

Mirror making

Joy of making mirrors...


rough grinding

fine grinding



star testing

Making a 25 inch [0.64m] F2.6 mirror

Grinding machine

Rating mirrors

Become a better mirror maker

Large thin mirror grinding

Polishing theory

Polish+pitch tips

Ronchi test

Artificial star testing distance

Holographic Foucault test

Waineo null test

Sagitta calculator

Precision molds for mirrors

Mirror slumping calculator

pitch lap calculator

McHardie's 'Preparation of Mirrors...'

16 inch mirror figuring class

Some calculators

All calculators...

Computerized telescopes

Computer operated telescopes

History of computerized telescopes

Telescope mounting's primary axis errors

Coordinate errors


Coordinate calculator + tracking

Equatorial tracking rates calculator

Astronomical time calculator

Sky to telescope position calculator

Motor calculator

Trajectory calculator

Initialization simulator

2 star initialization study


Herschel's Ghosts, observing Integrated Flux Nebulae

Is aperture king?

Why am I seeing more?

Telescope magnification is key


Preparing for a night's observations

Why observe? Three amateurs speak

Progressive sketches of supernova remnant G65.3 5.7 north of Albireo

Observing dark nebulae

Count the Pleiades

Drawings at the eyepiece

What is TTO and TEO?

The Airy disk

The contrast controversy

Seeing, atmospheric turbulence

Visual detection at the eyepiece

Visual detection calculator

An electrophonic meteor; the Leonids

The green flash (and blue flash)

A mountain meditation

Lunar graze occultation

Messier observations

Magnitude differences

SQM magnitude calculator

Air mass calculator

Refraction calculator

My weather forecasts and dark sky links

Star parties, conferences

2017 Oregon Star Party Eclipse Edition

2016 Oregon Star Party

2015 Oregon Star Party

2014 Oregon Star Party

2013 Oregon Star Party

2012 Oregon Star Party

2012 Waimea Hawaii AltAzInitiative

2011 Oregon Star Party

2010 Oregon Star Party

2010 RETA Spain

2009 Oregon Star Party

2008 Oregon Star Party

2007 Oregon Star Party

2006 Oregon Star Party

2005 Oregon Star Party

2004 Oregon Star Party

2003 Oregon Star Party

2002 Oregon Star Party

2002 Winter Star Party

2001 Oregon Star Party

1999 Oregon Star Party

1999 Okie-Tex Star Party

1998 Oregon Star Party


2017 Oregon solar eclipse

2009 Asian solar eclipse

2001 African solar eclipse

1999 Turkey solar eclipse

1998 Caribbean solar eclipse

1991 Mexican solar eclipse

1979 Oregon solar eclipse

Imaging old style


CCD Images