Astroimaging on a budget

With the starting price of decent CCDs at over 1000, apo refractors, mounts the price of a small car, not to mention a micosoft office block's worth of software it is easy to think Astroimaging is for the wealthy, the reckless or quite probably both. Well it isn't!!! The expensive kit is definitely pushing the boundaries of what can be achieved by amateurs but excellent results can be achieved with very reasonably priced kit.

The trouble is that imaging is hard, there's just no getting away from it. It's one thing placing a camera at the eyepiece, focussing and producing an image of M42 (great fun though that is), quite another to produce detailed images with good signal to noise ratio. This requires an understanding of the target, the equipment, capturing techniques and processing. The fact is that very few people reach the limit of what their existing equipment is capable of. Have a look at Roger Warner's Atik 2HS images. Admittedly these were taken on a very nice Nexstar GPS scope but similar results can be achieved with a small refractor on a relatively light motorised mount. Roger worked and worked on capturing and processing these images, learning to squeeze out every last photon from that camera. If you have a scope which can be brought to a focal length of 600mm or less and a motorised mount with enough weight to carry it you are laughing.

You then need either a DSLR or a modded webcam such as an SC3/atik 2HS etc. Afocal imaging (through the EP) is always going to be fraught with problems and adds a whole lot of extra difficulty. OK for 1st images but not recommended long term A laptop is necessary for a web cam and desirable for DSLR - but they certainly don't need to be state of the art. A cheap second hand model will do. Goto is a luxury you can manage without.

Here is a cheap set up which will provide great results on a budget. An achromat short focal length 80mm refractor (around F6 say - 50 second hand). To avoid chromatic aberration you need a green filter - this will remove light pollution as well but does increase exposure time slightly (but you have a fast scope). You can pay more of course and get a second hand ED80 which will deliver some improvements (200 second hand). A motorised EQ3 will do, again second hand but better still would be a second hand CG5 or even better, one of the Vixen Polaris mounts. At the lower end of the range you should be able to find something for around 150. If you have a DSLR you are away. Although there must be a lovely sense of freedom with a DSLR being freed from the need to link up with a laptop, my impression is that ultimately a laptop and some capture sofware will make the whole process easier. There is some excellent software available at around 100 but that might be out of budget at the mo.

ED80 ZS66

A second hand ED 80 (200) on a second hand Vixen Super Polaris (200). This SP doesn't have goto but note the Telrad finder on the dew shield of the ED80. With planetarium software such as Starry Night and a Telrad you will be soon be finding your targets quickly enough and learning the sky as well. The little orange scope is a William Optics ZS66 a great little imaging scope as well, side by side one scope can be used to guide the other but that's probably best left until later. This Super Polaris mount is old and a bit tatty but tracks very accurately and is a superb imaging platform for small refractors

The alternative to a DSLR is a modded web cam. These have a much smaller chip and need a laptop. However they work with some great free software called K3CCDtools, the chip is very sensitive and has small pixels providing excellent resolution. You can use focal reducers without introducing vignetting which can give you 2 or 3 scopes in one. For around 25 you can pick up a 0.5 reducer designed specially for web cams. You can often find a second hand Atik 2HS for around 200 and are highly recommended.

The beauty of a light, short focal length refractor with a modded web cam is that you have a wide field view which is great for a small chip, there is little weight on the mount, it is very forgiving of tracking and other errors allowing long, unguided exposures.

Leo Triplet 29th April 2006

This image above was taken with the the ED80 scope and Super Polaris mount shown above along with a second had Atik 2HS. The total cost of this set up was around 600. I was only into my 3rd month of imaging so there is plenty of room for improvement.

K3CCDTools will stack your images or DSLR users can use Deep Sky Stacker which is also free. Registax also does a good job. You don't need to pay a fortune for processing software. Many of the budget packages will do a good job for you. Ideally you should have something with the "curves" tool to allow proper stretching of the histogram. A number of budget image processing software packages have this too. Photoshop Elements has never had it but now there is a plug in which will finally provide Elements users with curves -

You will then need the usual extras - a red dot finder gets you in the right area and a nice wide field EP will often work better than a finder scope with a small refractor. Later on you can build your system as finances permit - you might want to collect some RGB filters and maybe a narrow band Ha filter for emission nebulae.

Do your homework - get slicker with your set up esp a good polar alignment routine, make sure your mount is performing at it's best - strip down and regrease if necessary. Understand the characteristics of you mount and how long it can go without tracking errors appearing. Work hard on your focussing skills - you might want to make a hartmann mask. If you want to be serious about imaging you have to be serious about exposure times. 7x30 seconds = grainy images without much detail. You should be aiming for at least an hour on most targets. With the above set up you should be able to track unguided for 1 minute so 60 sub exposures should give you something to be proud of. If you buy wisely second hand you can be up and running for under 500. You also have a modest visual set up for grab and go.

Like I said, it's not easy but it doesn't have to be that expensive. Be warned though, you can get hooked very easily. Then your idea of how much spending is justified changes quickly, welcome to the club!!