Wednesday, July 25, 2012

Digital Astrophotography Advice for Beginners


The Cincinnati Astronomical Society was recently contacted via our website asking for some beginner's advice on digital astrophotography. This person has a Meade LX50 telescope, with a Meade DSI (deep sky imager) and a Canon Rebel DSLR. They were curious about the idea of going to a CCD camera. CAS members Pat Freeman and Eric Africa have tag teamed on some excellent advice:

Pat said:
My bias is towards DSLRs for beginners as the learning curve gets real steep once the jump to a CCD camera is made.  Additional factors:

The DSI would probably be a satisfactory guide camera, although it’d probably require a GPUSB to use for the guide pulses.  Under $100.
The Rebel is probably already useable for galaxies and star clusters, and bright nebulae.
The guiding software can be had for free (PHD Guiding) and it’ll work fine with the DSI and GPUSB…I have used it with two DSI II Pro cameras and a DSI III Pro camera.
The imaging software can be had for relatively low – or no – cost (Nebulosity or ImagesPlus).
Image processing software can be had for no cost (Irfanview).
Flats?  Darks?  Flat-Darks?  Bias shots?  Even basic deepsky astrophotography can get complicated quickly.

My advice would be to take the low-cost route as above, at least until one is certain they want to be a serious imager.  They could probably leap to the next level of maturity in their imaging with their current hardware and an out-of-pocket expense of under $100, particularly if they had some mentoring.  They would be completely amazed at how much they could do with no cost, but the right software and the right techniques.  Only once they are completely in the pool with both feet would I recommend leaping to a CCD camera.  As an example, I’ve been shooting some decent DSLR photos for more than 6 years and I’ve had a modest CCD camera with color filter wheel for 2 years now, and yet I still tend to reach for the DSLR first, since my time is limited and I can get full-color shots in less time and with less complications.

Eric said:
What are your imaging goals?

If imaging planets, almost any webcam can work as a start. Celestron’s original Neximage is a good starter camera. Although for best sensitivity, monochrome webcams work far better at capturing subtle details over color webcams. A good example (and much pricier than the Neximage Solar System imager) is the line of CCD-based monochrome cameras from Imaging Source.

If you want to see more details of dimmer deep sky objects (DSO) without squinting at an eyepiece, consider sensitive video-stacking cameras such as the Mallincam.

If you do want to capture nice images of mostly DSO’s, then we start to creep into the realm of CCD imagers. However, you may already have a nice imaging camera on hand right now!

What are your existing cameras?
You could be pleasantly surprised at what can be achieved using the cameras you already have. Brighter deep sky objects (all the Messiers, for instance) can be captured with today’s DSLR’s with impressive results.

Is your scope mounted on a wedge? For longer exposure imaging, all telescopes must be polar aligned on an equatorial mount to prevent the effects of field rotation from creeping in. Equatorial mounts are either German Equatorial mounts or wedge-mounted forks.

Specifically for any fork-mounted Schmidt-Cassegrain telescope (SCT) owners, one challenge you are facing is that you are imaging with a Schmidt-Cassegrain. Nothing inherently wrong with the design, but more than anything, you are starting off imaging at about 2500mm focal length. This is considered high resolution imaging. Look at it this way: if you gaze with a hand-held pair of low-power binoculars (let’s say 5X magnification), views will be less magnified but also less shaky than they would be with a pair of 12X binoculars. The same can be said of long-focal length (roughly translated in imaging terms to magnification) imaging: the least tremors or vibrations will be picked up by your optics, which will translated to smeared or trailed images. You are not out of luck, though; you can alleviate this somewhat by installing a focal reducer (the standard f/6.3 SCT reducer/corrector is perfect) on your SCT. Even better, you can start off with wide-field imaging by (budget allowing) piggybacking a small refractor on your SCT and using that to start off with. The lower magnification (by virtue of its shorter focal length) of the refractor will provide pleasing wide-field views of bigger targets, and will also be more forgiving of tracking errors.
Are there any clubs nearby?
It will be very helpful to meet experienced imagers in your area who can mentor you and guide you through your astro-imaging journey. Short of that, the Internet is a wonderful resource as well. Sites such as Cloudy Nights or imaging-related discussion groups at Yahoo and elsewhere can also prove invaluable. But having someone to chat with, or just hang out with so you can see their workflow can also prove to be valuable.

Check out Pat's website (www.astro-pat.com) and Eric's website (www.skiesbyafrica.com) for examples of their amazing astrophotography!

Thanks for contacting the Cincinnati Astronomical Society! We hope this was helpful!

Monday, October 31, 2011

The CAS website gets a facelift!

If it's been a while since you've checked out the Cincinnati Astronomical Society website, give it a look at www.cinastro.org.  It has been migrated over to the Google Apps platform so we could leverage all of the great functionality that they make available so we can better reach the astronomy enthusiasts in the Cincinnati, Ohio area and around the world.

Bookmark our site and check back often.  We have many new ideas in the works!  Also add our blog to your news reader of choice, and add our event calendar to your own so you don't miss a thing!

Thanks and enjoy!