Astrophotography with Canon Powershot A560,Nikon D3100 DSLR and ETX-80
I want to share my experience how to do astrophotography with ETX-80.This is more hardware oriented with some examples. The ETX-80 is not the perfect telescope for doing astrophotography because of short focal distance, but that I have and I managed it to work. IsnÕt a easy job. For long time I used Canon PowerShot A560 point-and-shot camera with CHDK operating system loaded, that work pretty well. You have bracketing, intervalometer, a lots of scripts-lua and basic, fun menu, calendar, games, text reader, etc, etcÉFor doing astro I donÕt find much of usefull things inside, long exposure going only to 24 sec, even not 32,for short shutter I donÕt even thing he is able to do 1/10000 sec. Another nice future is the parameters menu on the screen when you half-press shutter button. For long astro exposure I rarely use CHDK options, just battery indicator, temp sensors, timers and parameters on the screen. Picture of CHDK:
To put my A560 on the eyepiece port I needed one eyepiece with low magnification and some sort of link between them, evidently they have the same diameter. So I buy one short plastic tube 1 ½, cut it en half and connected one 17mm KELNER eyepiece with A560.Super cheap solution for 1.50$ instead of 30-40$ for more complicated ones. Here is the picture:
And here connected to the telescope:
ItÕs a very light and have no need for balance. Generally I do solar ,lunar and planetary astrophotography. For planetary astro the CCD is not enough sensible, need more than 5000 frames to stack for good results. Also the resolution is 640x480 pixels, not so hi. Here some of my pictures:
And a lot more galaxies, nebulaÕs, star clusters. You probably remarque that I push very hard my scope at the limits of magnifications, the values of 1000x-1500x isnÕt unusual . Two stacked barlow, 17mm eyepiece and 4x-16x digital zoom from A560.For 80 mm (3.15ÕÕ) aperture and heavy light polluted Montreal the results isnÕt so bad, right?
Now for Nikon DSLR setup, that creates me a big headache. Due to easiness of my A560 setup before I wasnÕt prepared for this. That short telescope focal distance kills me. Impossible to achieve focus in normal way. The only one place where it was ok is on the back port at the end of focus knob, need very thin adapter, may be the Meade #64ST is the right one, but you telescope should be limited to 50 degree altitude because of camera hit, impractical for astrophotography, for terrestrial only. I decided to put my camera at eyepiece port. I get one adapter here plus T-ring for Nikon:
You can put small PLOSSL and KELNER inside for more magnification, generally 17mm and less. When I stacked my adaptor ,t-ring and camera without eyepiece inside:
and put it on the telescope:
two big surprise emerge-the camera cannot come to focus without Barlow lens and with Barlow engaged one white spot come at the centre: I tested many variants and finally concluded – this is internal reflection of my new adapter. I removed only the eyepiece tube and composed a short adapter:
Put this on my camera:
And all the gear on the telescope:
Additional weight is something like 0.810 kg (1.78 lb) and need to be balanced.
Finally with internal Barlow engaged I got this:
The Barlow reduce FOV, from 4 degree initially to maximum 2 degree now. I wanted more, but with this telescope for astro photo (not terrestrial) is impossible. I have also this very good Barlow lens:
She have slightly better FOV compare to internal and is slightly shorter to achieve focus on ETX-80.Bad newsÉNeed to unroll 2-3 turns –the lens from the eyepiece base, they have tread between. Even like that the focus is on the limit. I use it like second Barlow lens stacked behind the internal, but not for primary one with DSRL. Now you understand why ETX series have internal Barlow. I asked myself why for long time É
Some results for that setup:
Nikon D3100 with original 18-55mm lens adjusted to 55 mm:
And here with ETX-80, barlow and eyepiece 9.7mm:
This is single night shot from 1km(1.6mile) away at 3200 ISO, 30 sec. Simply 34 x magnifications compare to 55mm lens and 102x compare to 18mm, this is equivalent to 1870mm telephoto lens!
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Ask me on English, French, Russian or Bulgarian I should be happy to answer you!
Thank you and happy stargazing!
George - LZ3GT, VE2BUA