Astronomy and Sky Website of Martin Lewis

Page last updated 15th July 2020


After many years of struggling with low-cost eyepieces I now own a wonderful set of premium TeleVue eyepieces. These eyepieces are all of the Nagler design, with an 82° field of view. The Naglers are great to use on all objects whether deep sky or planets, and have high contrast, comfortable eye position and wide field. The quality of these eyepieces is incredible.

From left to right, 3.5mm, 5mm, 7mm, 11mm all Type 6 Televue Naglers with 1.25″ barrels, then 16mm and 26mm Type 5 TV Naglers. The 26mm has a 2″ barrel. Missing from the photo is my more recently purchased 20mm Type 5 Nagler also with 3″ barrel

I did previously also have 9mm and 13mm Type 6 Naglers but sold these to fund some of the above eyepieces with other focal lengths. This ended up giving me a set of eyepieces with a more uniform stepwise increase in magnification. I previously also owned a 3-6mm Nagler zoom that I thought I would use regularly, especially on the moon. In reality I never really used it, however, mainly because of its much narrower field of view, and sold it to fund the purchase of the dedicated 3.5mm focal length Nagler. A 1.25″ barrel 24mm Panoptic was also sold and replaced with the 26mm Nagler which I am much happier with, despite its much greater weight and 2″ barrel.

My most recent addition to the set is a 20mm T5 Nagler which is a useful low power addition with a power between that of the 16mm and the 26mm. 


I have several different optical amplifiers to increase image scale for viewing or imaging purposes;

  • Meade 2x Barlow (4000 Series, #160 air-spaced triplet). This is used for visual work only as it is not of sufficient quality for imaging suffering massively from over-correction as you see in my star test webpage
  • 2.5x Televue Powermate which can if necessary be screwed to the bottom of my atmospheric dispersion corrector (ADC) for imaging using the PTR-1250 adaptor
  • Two 2.7x APM coma correcting Barlows. These can be used visually in the versatile 1.25″/2″/T-thread adaptor, or for imaging by unscrewing the M28.5 filter threaded business end and screwing it to an adaptor in front of the ADC. These form the heart of my current imaging configuration singly or in a pair as described in detail on my imaging cameras page. As a two-up configuration they make a 6.25x amplifier.
  • 3x Televue Barlow (BLW-3125). For visual work or imaging. The magnification increases significantly with increasing back-focus distance so that the 3x increases to 5x when used at an increased back focus of 105mm
  • 5x Televue Powermate which can also be screwed to the bottom of my atmospheric dispersion corrector (ADC) for imaging using the PTR-1250 adaptor. Again the magnification increases significantly with back-focus distance, increasing to 7.7x at a back-focus distance of 105mm.
Barlows and Powermates (L to R); 2x Meade barlow, 2.5x TV Powermate with PRT-1250 adaptor fitted and normal (1.25″) adaptor to its RHS; APM 2.7x coma-correcting barlow with optical end removed and in front of its multipurpose barrel; 3x TV barlow; 5x TV Powermate


For visual work on nebulae I have the following filters;

  • 1.25″ Lumicon OIII
  • 2″ Astronomiks OIII
  • 1.25″ Lumicon UHC
  • 1.25″ Astronomik HBeta

I also have a set of Orion colour filters that occasionally get used on the moon and planets.

For imaging work I use the following

  • For RGB planetary video imaging I use the Astronomiks Type IIC L, R, G & B filters.
  • For imaging in the infra-red and to steady the views I also have;
    • Baader 610nm (Red) longpass filter. This is the brightest of all the filters below and is useful for imaging of dim objects like Uranus and Neptune
    • Astronomik Planet Pro 642nm Bandpass filter (642nm-842nm). I particularly like this filter which does not darken the image too much but yields significantly more detail in images.
    • Baader 685nm longpass filter.
    • AstronomikPlanet Pro 742nm longpass filter. Too long a wavelength for the 222mm scope but great on Venus with the 444mm.
    • AstronomikPlanet Pro 807nm longpass filter. Too long a wavelength for the 222mm scope but great on Venus with the 444mm.
    • I also own a 850nm Trutek 1.25″ filter but this lets so little light through that it rarely get used. Another filter that gets regular use on Uranus is my Baader.
  • I also own the following specialist planetary imaging filters
    • Edmunds Optics 1000nm filter with 25nm bandpass (Edmund Optics part number #87-823)
    • ZWO methane filter for CH4 imaging of Jupiter and Saturn
    • Baader Venus filter (type 2 IR blocking)

These filters can be screwed into the threaded ends of eyepieces and 1.25″ adaptors but generally for imaging get used in my custom filter block which can be see on my imaging cameras page. To use them in here they are all mounted on individual paddles as shown in the photo below. Filter change is quick and easy and there is no limitation to which filter I can use at short notice.

Astronomiks RGB filter set mounted on custom holders for my custom filter block
Custom filter block in the middle of my standard imaging train. See Imaging Cameras page for more details

Atmospheric Dispersion Corrector

NOTE: A full description of the use and benefits of the Atmospheric Dispersion Corrector can be found on my dedicated page here, which is the most popular page on my whole website.

Late in 2011 I bought an atmospheric dispersion corrector (ADC) from Astro System in Holland, on the recommendation of Damian Peach. This easy-to-use device cancels the prismatic effects of the atmosphere at a given altitude by careful setting of a pair of adjustable orientation prisms. The device can significantly improve the image resolution, especially in the blue, even when planets are as high as 60°. The benefit increases the lower the altitude of the planet. Jupiter and Mars images in 2012 benefited significantly from the use of the ADC and I have been using one for my planetary imaging sessions every time since then.

In March 2013 I bought a UV transmitting version of the Pierro Astro ADC which is the one I currently use and which is built into my standard imaging train – see image above. This is available in the UK from Rupert Smith at Astrograph

When correctly set, the ADC allows one to image through just the luminance filter (filtering out just the UV and the IR) and still to get a nicely detailed image with minimal dispersion effects. This allows one to obtain a true L(RGB) image with the luminance information coming from the L alone and the R,G & B containing the colour information and no luminance information. This approach works well on low surface brightness planets like Saturn as the L channel, being minimally filtered, is much brighter than the image through R, G or B, allowing both shorter exposures and higher frame rates.

Observatory in a Box

As I don’t observe from an observatory, all my eyepieces and filters etc need to be carried to telescope. A few years back I made a custom box with drawers to fit everything in and this contains all the eyepieces, filters and Barlows I use and which are detailed above.  The box also contains my sketching equipment, maps, torches and other assorted useful bits. Barlows are held in various plumbing fittings as you see in the picture below.

The eyepiece box has a 12v heating panel in the base and this keep the eyepieces dew-free when things get damp. There is a red light in the lid which is microswitch controlled so it goes out when the lid closes, saving battery life.

Imaging Storage Box

I have a separate box for storing my cameras, filters and imaging train parts which is shown below. This keeps all the parts together that I need for planetary imaging. The box is a conductive tote WEZ box available in the UK from Teknis (part no. W4317000992) – be aware that lids are purchased separately. The box contains:

  • Cameras
  • Filters on paddles (see in yellow box below)
  • Various imaging trains (see my Imaging Cameras page)
  • USB3.0 lead
  • Electric focus controller
  • ADC extra prisms