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Lucky Imaging Gear

The  most important bits of kit for lucky imaging is the telescope. If your scope isn’t sharp enough then there is not point in lucky imaging. That’s because of the way optics works. Basically whatever is causing most blurriness in your system dominates all other sources of blurriness. So your telescope’s optics are making stars blur by about 4 arc seconds and if you are shooting on a night when the atmosphere wobbling around is causing each star to blur by 2 arc seconds then your resulting stars are going to have a blurriness of not 6 but 4.4arc seconds [ sqr(42+22)]. And if you do lucky imaging with this telescope and halve the amount of blurriness caused by the atmosphere (which would be very impressive) your resulting blurriness will be 4.1 arc seconds. All the effort of Lucky imaging has made almost no difference to the sharpness of your image and whats worse it will have cost you a huge amount in terms of your images noiseyness. In The BAT we only encourage folks to try lucky imaging when their scopes create less than 3 arc seconds of blurriness.

Find out about lucky imaging theory

The Sharpest Scopes

So when buying a telescope for lucky imaging the prime concern is that it is sharp.  Although telescope Companies don’t tell you how sharp their scopes are WE CAN! In The BAT we ask our members to test their scope by sending our team pictures which we can use to measure the Full Width Half Maximum (aka blurriness!) of the stars.  We now have a database of hundreds of scopes (which can be seen here). The blurriness of the stars depends on the seeing conditions  as well as the optics of the telescope itself, so this is not a perfect test BUT if the seeing conditions are good you would expect a very sharp scope to produce stars that have 2 arc seconds of blurriness or less.

All the  scopes to thebelowhave been tested by The BAT and are able to resolve stars with a FWHM of less than 2 arcseconds

GSO Newtonian 10″ f4 £599

The stand out budget lucky imaging scope is the GSO Newtonian. GSO are a Tiawanese optics company who clearly make beautiful mirrors. I now recommend GSO mirrors and optics. The GSO Newtonians are rebranded by different companies in different countries. Same scope different stickers. 

The simple Newtonian design is actually sharper that on axis than both the SCTs and Dall Kirkams AND its LOADS cheaper. The quality of the mirror and the smallness of the secondary obstruction are important factors but the diameter of the mirror is single most important consideration. The fatter the mirror the higher your potential resolution. Our tests show a good 8inch is fat newtonian is sharp enough to lucky image with but unless you have great seeing you really need a 10″aperture to be successfull. 

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You don’t have to buy a GSO newtonian. OLD Newtonians are also very good. My little 6 inch 50 years young ‘red devil’ by Edmund scientific has broken the 3arc second barrier and is one of the sharpest 6 inch newts in The BAT. TBH though I think 6 inches is really too small to lucky image with. 8 inches is really the minimum. Big Bertha my 40 years young 10inch f6 newt manages an impressive 1.6 arcseconds of blurriness but because I’m shootin 1/2 or 1/4 second exposures I plan on getting an even fatter newt which will catch more photons per second.

Celestron or Meade SCT £2000

The C9.25 (a schmidt cassegrain design -aka SCT) is in my opinion the best all round scope because its so versatile and relatively cheap.  Whilst the C9.25 is great I think that for lucky imaging the C11 and C14 are better still if you can afford them.

Orion Optics ODK12 £5,800

Not really suprising that this scope is sharp but at least we c an confirm it is.

Planewave CDK 12.5: £9,180

Not really suprising that this scope is sharp but at least we c an confirm it is.

Best Cameras for Lucky Imaging

Sensitivity (mono or colour?)

Lucky imaging relies on taking very short exposures. To gather enough photons in that short amount of time your camera needs to be sensitive (or your telescope needs to be very fast). Colour cameras have a problem here because they collect 1/3rd as many photons per second as a mono camera when the mono camera is shooting luminance frames. That’s why I’m not recommending colour cameras or dslr cameras for lucky imaging. Note this isn’t a hard and fast rule. Please try it if you have one.

Pixel scale…

As we’re hoping to use lucky imaging techniques to resolve details around 1arc second wide I’d say as a rule of thumb we want our pixel scale (that is the amount of sky each pixel ‘sees’) to be around 0.5arc seconds per pixel. So my recommended choice of camera relies on matching the size of the camera’s pixels to the focal length of the camera.

 Cooled  or uncooled?

Dark current  can be reduced by cooling you camera. However very short exposures are dominated by read noise not dark current. So cooling your camera is far less important when lucky imaging.

Sensor Size

Small sensors are actually quite useful for lucky imaging. Each sub doesn’t take up much space on your hard drive – and when you’ve got 10,000 subs that becomes important. I actually only shoot cropped with my qhy268m to save hard drive space. Also we’re generally looking at the fine detail when lucky imaging and small sensors are naturally looking at a smaller area of the sky.

Please note I have tested the read noise from all the below cameras myself using sharpcap sensor tester software which is why my values may differ from those released by the cmanufacturers.

QHY533m

With its extremely low read noise and low price tag this is a brilliant camera for lucky imaging. Its basically a mini version on the qhy268m Review here

TOP PICK

 

    • Very Low read noise 1.09e per pixel

    • 15.97mm diagonal sensor

    • High sensitivity

    • Great Value for Money

ZWO ASI 178MM

This a great cheap camera for planetary imaging too

TOP PICK

  • Very Good Value

  • 2.4um pixels

  • Low read noise 1.4e per pixel

  • 14mm  diagonal sensor

  • Versatil

  • mono

ZWO ASI 585mc

Great for planetary and deep space

TOP PICK

ZWO winter sale just $359

  • Very Good Value

  • 2.9um pixels

  • Very low read noise 0.8e per pixel

  • 13mm  diagonal sensor

  • Colour

QHY268m

With its extremely low read noise (better than ZWO’S ASI2600MM at a certain setting) and large sensor this camera is brilliant for lucky imaging and regular long exposure astrophotography.

TOP PICK

  • 3.76um pixels

  • VERY Low read noise 1.08e per pixel

  • 28.3mm diagonal sensor sensor

  • High sensitivity

  • Low Dark Current

  • Great Value when compare with ZWO’s  asi2600m

ZWO ASI294mm

Very sensative camera with a fairly high dark current so if you plan on taking long exposures you do need the cooled version.

    • 2.3um pixels in Bin 1 mode

    • Low read noise 1.2e per pixel

    • 33mm diagonal sensor

    • High sensitivity

ZWO asi2600mm

This is an amazing camera. I bought this camera with money donated to me from very lovely biscuit fans… then I discovered that the read noise on the QHY268m was lower, so I sold it and bought the 268. 

    • 3.76um pixels

    •  Low read noise 1.3e per pixel

    • 28.3mm diagonal sensor sensor

    • High sensitivity

    • Low Dark Current

My mount recommendations for lucky imaging

For years astrophotographers have said you must spend more money on your mount than anything else. The reason is that traditional long exposures are extremely susceptible to mount wobble. Lucky Imaging utilises much shorter exposures. Over a short period of time you may find that your mounts wobble is negligible. Or that your mount wobble is sporadic in which case you just throw away exposures during  the unlucky moments of mount wobble. Its a bit like double lucky imaging where you only keep the frames where both the atmosphere and the mount aren’t wobbling. The flip side of the coin is that hi resolution imaging is imaging at sub arc second scales and it is therefore critical to minimise all sources of blurriness as much as possible. 

I have discovered that my 10 inch newt on an Avalon linear which is similar to an EQ6 doesn’t work even for 1/2 second exposure lucky imaging when there is a breeze. So I would recommend using a sturdy mount for lucky imaging. I intend to test motorised dobsonians at some point because these big boys could potentially be fantastic and relatively cheap lucky imaging monsters.