The Beast: My Humungous Newtonian Telescope
The Beast is easily the biggest scope I have ever owned. I bought her 1980’s giant red forked mount second hand for £850(bargain) and her 2000’s (i think) aluminium skeleton frame which was built specially for this mount for £450 (not a bargain!) from the website uk astro buy and sell. I estimate her total weight to be 300kg. So the beast doesn’t fall through the roof onto my daughter beneath I’ve mounted her on reinforced concrete beams which spread the beast’s weight to the roof’s walls.
The skeleton frame is designed to carry a 16 inch, 1800mm focal length parabolic mirror. I bought the mirror new (see below). The 13kg mirror flexes the skeleton frame as it points to different parts of the sky and therefore the beast holds collimation quite poorly. I have to recollimate whenever I point to a new target.
The skeleton frame is held by giant red and quite sexy looking equatorial forks which are mounted on a super heavy steel wedge. The wedge allows me to line the forks up with the rotation of the earth making this an equatorial mount. In theory an equatorial mount allows me to do long exposure deep space astrophotography without having to worry about field rotation but in practice the beast’s tracking is too poor to attempt long exposures. Still being as I use 1/100th second exposures on solar system targets like the planets and the sun and the moon and the ISS to negate the atmospheric wobble then I don’t mind too much… and its something that hopefully can be fixed. Be sure to check out the video above to see what the beast can do or you can look at my blog.
Probably worth mentioning that you would be able to get the same results I got with the beast on the planets with a 16inch goto dob like this one: Unlike the Beast these scopes work straight out of the box🤣. My supporters can watch a 30min video about how I overcame the Beast's problems on YouTube here or on Patreon here. It costs £3 to become a supporter, there are currently two other supporter video tutorials and if you join Patreon its easy to message me anytime.
For planetary imaging I use a dedicated camera (its the red thing in the picture), below the camera is a filter wheel, below that an atmospheric dispersion corrector , below that a Barlow lens (sometimes I use two Barlows!), and the other red thing to the left is my electronic focuser. More details below...
Camera
The ZWO asi585mc is a fantastically sensitive colour camera which remains sensitive in the infra red. In fact beyond 800nm the camera effectively becomes a mono infrared camera as the green and blue pixels absorb as much light as the red pixels. I have a 650nm long pass ir filter which is very useful for reducing the atmospheric wobble. I can reduce the wobble even more if after filming I throw away the red signal (with the help of free software like PIPP) and combine the remaining green and blue channels into a single monochromatic image. This effectively turns my 650nm long pass filter into an 800nm long pass ir filter. This is very useful when shooting targets like Venus.
ZWO ASI 585mc
This a great cheap camera for live views and planetary.
Top Pick
- Very Good Value
- 2.9um pixels
- Very low read noise 0.8e per pixel
- 13mm diagonal sensor
- hi infra red sensitivity
- Colour
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But to get the very best shots I would recommend using Player One Saturn M camera. Mono cameras have more resolution than colour cameras because they don’t have a bayer matrix. However they are more complicated to use because you need to shoot red, green and blue channels separately and then line up separate channels (accounting for the planet’s rotation in free software called winjupos) before you can finally see a colour image. As I’m showing people live views in my videos I use the colour camera more often but if my only goal was to get the best image possible I’d be using this camera. A big advantage of Player One cameras is that they will shoot more frames per second than the zwo equivalent and that will result in images with less noise.
Player One Saturn M SQR
This a one of the best mono cameras for planetary on the market.
- highest fps on the market
- 3.76um pixels
- low read noise 1e per pixel
- large 1" square sensor
- great for solar and lunar imaging
- great for deep space lucky imaging
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Atmospheric Dispersion Corrector (ADC)
To cancel out the variable refraction of red, green and blue light as it passes through the earth’s atmosphere (what I would call “rainbowing”) you need an atmospheric dispersion corrector (adc) which when correctly set refracts the light passing through it's prisms in exactly the opposite direction to the atmospheric refraction thereby cancelling out the problem. This is an essential bit of kit especially when the planets aren’t directly overhead. I asked Damien Peach if you needed one of these if you were using a mono camera and he said yes as it will improve your blue channel. NOTE the adc does not reduce the wobble in the atmosphere – the wobble is a different and more persistent source of blurryness.
ZWO Atmospheric Dispersion Corrector (ADC)
Does the job at a good price
- essential for the best planetary results
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Barlow lens
A good barlow (which increases your telescope’s magnification) makes a big difference when filming the planets. Tele Vue’s powermates are considered some of the best ‘Barlow’ lenses on the market. In fact they are slightly better than regular Barlow lenses when filming big targets like the sun or the moon because they keep the objects sharp to the edge of frame. I chose the 2inch x 4 Powermate bringing the Beast’s focal ratio up to 18. On bright targets like Jupiter and Mars I also added a Baader VIP modular Barlow which brough my focal ratio up to about F25. On dim targets like Uranus or when filming Venus through a very dark and narrow UV filter I removed the VIP Barlow to allow more photons to pass through.
Tele Vue Powermate
Probably the best 'barlow' on the market (even though its actually a telecentric lens). They come in many different strengths x2, x4, x5 and both 2" and 1.25" diameters. All flavours are good, what is important for the planets is that you get your focal ratio up to around F20 (maybe even higher (F28) for the brighter planets).
- proper quality
- not cheap
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Baader VIP modular barlow
Extremely high quality modular barlow designed to offer varying magnifications depending on the distance between the barlow and the camera.
- High quality
- Versatile
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Electronic focuser
With a big scope like the Beast you can't reach the focuser so an electronic focuser is essential. This offering from ZWO did the job although my basic moonlight Crayford focuser is a bit ‘slippy’ and this makes the electronic focuser imprecise. Me thinks a new focuser is needed! I really like the Baader Diamond Steeltrack focuser that I currently have on my smaller scope Betty.
ZWO Electronic Focuser
Does the job at a good price
- pretty much essential with a big telescope
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Betty’s secondary Mirror holder
As the beast needs to be continually recollimated I added a ‘Betty’s Secondary Mirror holder’ which makes secondary collimation very quick. All my Newtonian’s now have a betty’s secondary mirror holders in one form or another which is not really surprising being as me and Ceri designed them with the view of selling them around the world and becoming millionaires.... It hasn't quite worked out like I'd hoped. I love the design but there have been quality control issues in the past so I now have to check each unit individually before posting it out and once sent I fear getting hit with a customs charge ( I was charged £70 for one shipment to Slovakia) and of course customer care takes time and if anyone isn't happy I offer a full refund and pay for return postage which ends up costing me money… so it turns out selling these small and fiddly to produce items is not a good use of my time. I will be offering these units again soon and I’ll probably be hoping only folks in the UK buy them so I don't have to worry about customs or returns. These secondary mirror holders are extremely useful for nerds like me as they make collimation easy and quick but if you bash them they can slip out so they are not perfect however the more expensive Betty's full front end is fully bash proof and is pretty close to perfect...
Betty's Secondary Mirror Holder
Easy to collimate secondary mirror holder for your Newtonian telescope. Find out more
Primary Mirror
I opted for a GSO 16inch F4,5 mirror made from BK7 glass. This is an upsized version of the mirror I used successfully with Betty. I suspect GSO mirror’s are beautifully smooth and very accurate being as they helped me produce my best ever picture however the bk7 glass is like jelly and unless the mirror is held very lightly it will bend producing odd shaped stars. As with Betty I cushioned the Beast's mirror with padded 3M double sided sticky tape at the back to reduce stress on the mirror and to negate the need for clamping the mirror down from the front.
GSO 16inch F4.5 Mirror
This is a 'cheaper' option made with BK7 glass
- extremely smooth surface
- accurate figure
- BK7 glass is easy to flex leading to astigmatism if not careful
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