RigTonight12 beginner astrophotography mistakes, and how to avoid them
Almost everyone makes the same handful of mistakes in their first year of astrophotography. Some cost a night; some cost a few thousand dollars. Here they are, roughly from most to least expensive.
1. Buying a telescope before a mount
The mount decides whether every exposure is usable. A great telescope on a weak mount gives trailed, wobbly stars; a modest telescope on a solid mount gives good images. Budget for the mount first, and buy one size up.
2. Starting with too much focal length
A 2000 mm Schmidt-Cassegrain is a wonderful telescope that magnifies every tracking error, every gust of wind and every bit of bad seeing by a factor of five compared with a 400 mm refractor. Start at 135–450 mm. See the best telescope for beginners.
3. Loading the mount to its rated payload
The rating on the box is what the mount can hold, not what it can image with. For worm-gear mounts, plan on about half to two-thirds of it. See How much can your mount really carry?.
4. Buying a visual telescope for imaging
Dobsonians and many visual reflectors can't track the sky the right way, or can't bring a camera to focus at all. Imaging telescopes are designed differently: short, flat-field and with strong focusers.
5. Ignoring back focus
Most flatteners and reducers need the sensor at an exact distance, often 55 mm, to within about a millimetre. Get it wrong and stars stretch into lines or seagulls in the corners. Add a filter wheel or an off-axis guider and there may be no room left at all. See back focus explained.
6. Buying parts that don't work together
A camera brand your controller doesn't support. Filters too small for your sensor. A sensor bigger than the scope's corrected field. A guide scope too short for your telescope. Each one is easy to miss on a product page, and the rig builder checks all of them before you buy.
7. Too little total exposure
Twenty minutes on a faint nebula gives a noisy picture whatever the gear. Total time matters more than almost anything else: an hour for bright targets, several for faint ones, and more nights stacked together if you can.
8. Chasing the wrong targets for the season, sky or moon
Galaxies need dark, moonless skies. Emission nebulae can cope with the moon and city light through a dual-band filter. Every target has a season when it's high in the dark hours. Planning around all three is most of the battle. See moon phase and astrophotography and what to image each season.
9. Skipping calibration frames
Without flats, every dust speck becomes a donut and the corners stay dark. Without darks, hot pixels and amp glow stay in. They take a few minutes to take, and make processing far easier. See your first night of astrophotography.
10. Rushing polar alignment and focus
Ten extra minutes on polar alignment and focus can save a whole night of trailed or soft frames. Use a Bahtinov mask, refocus as the temperature drops, and use a plate-solving polar alignment routine if you have a computer on the mount.
11. Forgetting dew and power
A lens that's fogged by midnight, or a battery that's empty at 2 AM, ends a night that the forecast said was perfect. Fit dew heaters before you start, and work out your power budget before you leave. See dew prevention and field power.
12. Over-processing
Stretching too hard, pushing saturation, and heavy noise reduction make images look grey, blotchy or painted. A gentle stretch on more data always looks better. See stacking and processing for beginners.
The cheapest way to avoid most of these
Mistakes 1 to 6 all happen before you take a single picture, which means they're all avoidable on paper. Put the rig you're thinking of buying into the rig builder: it adds up payload, back focus, sampling, guiding, filter size, controller support and power, and tells you what to change. If a part isn't listed, add it as your own with the numbers from its manual.
New to all of this? Start with How to get into astrophotography.