Equatorial mounts, Newtonian reflectors, refractors, registax, counterweights, polar alignment, autostakkert, wavelets, webcams, tracking motors, collimation, Saturn, Venus, avi’s, sharpcap… Astro photography, it’s enough to put you off just thinking about the bewildering array of stuff to learn. What the hell are those things, where are they, what do they do, how do I use them? Well, with a little perseverance it DOES get a bit easier.
Take the telescope and mount to start with. When I first got it I had no idea what I was doing, Even now the EQ5 mount seems more like an instrument of mental torture than something to mount a telescope on but I am getting used to how it works. I’ve never attempted an accurate polar alignment yet mainly due to how late it is in summer until I can see Polaris but even a rough alignment is enough to get you moving. Simply set your latitude on the mount, 55 degrees for Edinburgh point the North leg funnily enough North and make sure the mount is level. It’s not perfect but it’ll allow you a go at some planetary imaging at least.
Just doing the above steps I’ve found that it’s adequate enough to keep a planet in the field of view for ages with the tracking motors engaged. It wouldn’t be any use at all for imaging deep space objects but for now, for planets and moon its working ok.
The tracking motors too came with the vaguest of instructions, now though I’m confident enough to find my target, lock the clutches and start the tracking and it works fine.
So, as I’d got hold of a Philips SPC900 webcam, all ready to be used with the scope and the skies had cleared it was time to give this planetary imaging a shot.
There’s not a lot of targets at this time of year, Venus is rapidly heading for its appointment with the Sun in June and Jupiter is long gone is the twilight sky. Saturn is getting higher and Mars to be honest has never been my favourite subject so Venus and Saturn were to be the targets.
When I setup, only Venus was visible in a still twilight sky. I can’t wait till dark as it’ll be lost behind the neighbourhood roofs. It’s so easy to locate in a twilight sky and the crescent shape is very visible in the scope and it’s quite a thin crescent now too. After centering Venus in the eyepiece I slipped in the 2x Barlow and made sure it was centered and then switched to the webcam.
Luckily for me, Venus was still there with the webcam and using the free capture software, SharpCap I was able to get it centered on the camera and adjust the settings till I got a clear view. I got a couple of short captures with the webcam until Venus was lost to the shed roof. I then ran the avi file through another free bit of software, Autostakkert which stacked the best frames from the movie.
The resulting image was saved as a TIFF and then opened in Registax 6 where you can adjust the wavelets. I have no idea what a wavelet is but it certainly works and greatly brings out the image detail and sharpness. I then finally opened the image in Photoshop CS5 for some final tweaks and this was the end result.
A million times better than I’ve managed with the DSLR, the webcams much smaller sensor gives a much bigger final image which in turn lets you get more detail. Using a webcam also lets you capture those microseconds of clarity through the atmosphere where the viewing is at its clearest and the stacking software puts all these together to get your final image. It takes a bit of getting your head around but it does work!
Saturn was next up and this was the AVI file I processed to get to the final image:
It’s probably way too long but after processing this in the same way as the Venus image I got to this final shot.
Which is a vast improvement on my best with the D90 attached to the telescope:
As you can see, there’s a lot more detail in the stacked image, some colour too.
For a first shot with this style of imaging I’m pretty pleased especially as the seeing was pretty bad. There’s a lot of room for improving especially with the software end all of which I’ve hardly even scratched the surface of yet. I also need to get hold of a quality 5x Barlow lens to get a larger image. Lots to do, I just a few more clear nights!
One thing about Astro-photography, you’re totally at the mercy of the weather. No matter what’s going on in the night sky, you can only see it if the clouds let you see it. There’s nothing you can do about it other than cross your fingers and hope that as darkness falls the skies clear. Which predictably they don’t 9 times out of 10. The conjunction of Venus and Jupiter last month being a perfect example. The night the 2 planets were at their closest in the sky thick cloud hung about all night over Edinburgh spoiling the celestial display.
With the weather rollercoaster central Scotland was experiencing yesterday I held out little hope of even seeing, let along photographing 2 meetings of night sky objects last night. All afternoon the weather swung from heavy snow/hail showers to broken cloud and back again. As the twilight approached this was still the case so getting anything was going to take timing and a hefty dose of luck.
With this in mind, I set up the camera and tripod in the garden shed. This is the kit I’ve been using until I finally get my telescope. It’s a Nikon D7000, fitted with a Sigma 70-200mm f2.8 EX HSM and 2x tele converter which gives me a 400 f5.6 lens, 600mm on the Nikon crop sensor. The D7000 is fitted with a Hahnel Giga T Pro remote receiver so I can use the powerful IR remote to trigger the camera. Exposure delay mode is on the try and minimise any shake. At 400mm the slightest movement will be obvious, more so when the subject is many thousands of light years away.
The first object to try for was the conjunction of the planet Venus and the Pleiades open star cluster, also known as M45 or the Seven Sisters. Venus has been steadily getting closer this month and on April 3rd it was sat right on the edge of the cluster to our view. 400mm fills the frame nicely and even though M45 wasn’t visible in the twilight sky, the camera could see it. There was just the small issue of the passing torrential hail shower to wait out first. As the dirty ominous clouds passed I got my first few shots at the target which was made difficult with a biting strong wind. 18″ long lens setups and strong winds don’t go too well together.
So, high ISO of 1600 and 1s exposure to try and keep the stars as dots rather than oblongs and the full 400mm was the order of the day. The wind affected a lot of shots but this was the pick of the bunch. Venus is of course very bright and the star cluster much dimmer, so I exposed for the stars and let Venus appear as an attractive starburst. Exposing for Venus would leave the stars not visible at all.
This shot was taken later on in the night with a darker sky and the 2x teleconverter removed to try and combat some of the “wind wobble”. ISO1600, 200mm and f5.6, 0.8s exposure time.
The 2nd object of the night was the close proximity of the Moon to Mars and the star Regulus forming a celestial triangle in the constellation of Leo. The clouds hadn’t parted at all over this part of the sky and it took a while to get any hope of photographing it. With the 2x tele removed due to the distance between the objects around 9.45pm the clouds moved and I got my first shot at the Moon. The final shot had to be a blend of 2 shots, one for the Moon and one for the planet and star. To expose for the very bright Moon left Mars and Regulus nearly invisible, to expose for Mars and Regulus burned out the moon totally and worse still caused huge lens flares.
As the clouds rolled over again the final shot of the night was a closer shot of the moon with the clouds looking all atmospheric. ISO800 at 400mm, f5.6 and 1/25th exposure time done the damage. It’s hard to get decent focus with clouds moving over the moon so I consider this a fairly lucky shot.
An enjoyable, if cold, night but hammers home the need for a telescope again, even just for tracking purposes it would be invaluable. I’ve pretty much decided on a Skywatcher Explorer 150p Newtonian on an EQ3-2 mount which I’ll fit with the optional motor drives. Hopefully I’ll have it soon when the real fun and steep learning curve will start.