10 Controversial Opinions

Over my years dabbling in astrophotography I’ve formed a few opinions that are a little outside mainstream thinking. To my mind, some nuggets of conventionally accepted wisdom have been superseded by new technology and techniques, or are applicable to veteran astroimagers rather than the beginners who are often seeking advice. So, here are 10 controversial opinions, hopefully helpful to new astrophotographers in particular.

01. OSC cameras are fine to use from cities

Conventional wisdom: The light pollution in cities is so bad that you should only use Mono cameras. These allow you to use narrowband filters, which largely bypass light pollution.

This first controversial opinion shouldn’t be entirely unexpected given the theme of this site! The conventional wisdom was sound until quite recently when dual-band filters came onto the scene. Coupled with modern CMOS cameras, they mean that it’s possible to take great astrophotos using OSC even from a city. To be fair, more imagers are now starting to use OSC cameras from light polluted cities, so maybe a shift in thinking is happening.

Find out more in OSC vs Mono from a City, and see lots of examples in my gallery.

02. Small telescopes are the best for beginners

Conventional wisdom: Bigger telescopes are better, because they have larger apertures and so collect more light.

I think that the notion of needing a big telescope (i.e. one with a large aperture) is more applicable to gear that will be used for visual astronomy, rather than astrophotography. There are indeed benefits to big telescopes, but they tend to be heavy, bulky, and generally unwieldy. This means they’re more difficult to set up and consequently get used less. If you’re a beginner, you may well actually get more use — and so gather more light and therefore produce better images, in addition to having more fun — using a small telescope. Until recently I used an Askar FRA400 (review here), which only has an aperture of 72mm, but is very beginner friendly and capable of producing great images.

I recommend thinking in terms of focal length, which is a bit like how “zoomed” into the sky you are. In general, the longer the focal length, the harder the telescope is to use. So if you’re a beginner, consider starting with something wide-field, perhaps up to 400mm (like the Askar FRA400). Once you get good then maybe buy a telescope with a longer focal length. I’m currently using an Askar 130PHQ (review here), which has a focal length of 1000mm.

If you’re interested in dipping your toe into astrophotography but don’t want to spend a fortune, consider a ZWO Seestar S50 smart telescope (review here).

03. Don’t spend lots on a mount that’s overkill for your kit

Conventional wisdom: Spend as much as you can afford on a hefty mount as it’s the most important part of an imaging rig.

It’s absolutely true that a mount is the foundation of your imaging rig, so I’m not saying that you should buy something under-specced. But the conventional wisdom can be taken to extremes, and sometimes beginners are convinced that they need a high-end mount for even small telescopes. The main factor to consider is the weight of your telescope and all its accessories. You don’t want to use a mount that can’t handle the weight, but equally there’s not much to be gained by having a mount that’s over-specced for your kit. If the total load you’ll be putting on it is under 75% of what the manufacturers say it can handle, everything should be fine. If you’re using a modern CMOS camera, you can shoot short subs anyway, which reduces the pressure on your mount to perform. (More info in point four of this article).

A classic example would be buying something like an EQ6-class mount for a small telescope. It’s overkill, and — very important point here! — is so heavy that you’re less likely to actually set it up and use it. An HEQ5 with upgrade or similar is a-ok for most set-ups. You’ll save money too, which could be spent on a useful upgrade.

Just to go against my advice for a moment though, a benefit to buying a mount with a really large carrying capacity is that it does give you some future-proofing in case you want a heavier telescope in the future!

04. Be sceptical of light pollution filters

Conventional wisdom: If you’re in a city, use a light pollution filter to get better images.

I’ve written about this at length in my Light Pollution Filter Shootout, so I won’t repeat all that here. The executive summary is that the effectiveness of broadband light pollution filters is very dependent on your local sources of light pollution, as well as the kit you’re using. Light pollution filter reviews are largely pointless. You need to try them for yourself. Some may actually do you more harm than good.

Note that narrowband filters, like the Optolong L-eXtreme, are a bit different. They allow only specific wavelengths of light to pass, and they’re great for imaging certain targets from a city like many nebulae.

05. Don’t necessarily travel to darker skies

Conventional wisdom: If you live in a city, you should take your astro kit on the road and travel to darker skies whenever you can. You’ll get better pictures as a result.

Ok, bear with me on this one because it takes some explaining! It’s absolutely true to say that darker skies give your images much better signal-to-noise ratio, so your pictures will have greatly superior quality compared to those taken from a city. There’s no getting around that: countryside astrophotographers have a huge advantage. So why am I saying don’t travel to darker skies..? Let me tell you a story.

Back when I started out as a city astrophotographer, I had the same idea as many in my situation: put together an imaging rig that I’d use on my balcony or in my garden, and occasionally take the opportunity to travel to properly dark skies to get really high quality data. So I bought kit that was at least relatively portable, and used a tripod that could be moved around. So far, so standard. But I found that I didn’t actually have as many chances to travel to dark skies as I’d hoped, and setting up what designed to be a portable set-up at home was a hassle; lugging the tripod and mount out from the shed, running through the polar alignment routine in the cold… Ugh, no fun. As a result, I wasn’t using the kit as much as I should.

So, I decided to ditch the idea of travelling to dark skies. I’d double-down on being a city astrophotographer! I had a DIY pier built in my garden, and set up all the necessary electrics in a waterproof box. More info here. This took my set-up / pack-down time to literally five minutes, and hey presto I started getting data every time the skies were clear. Even though the image quality from occasional trips to a dark sky site would be better, from my city location I was getting really long integration times that more than made up for it.

That’s why I say don’t necessarily travel to darker skies. If you settle on one imaging location, it makes things easier. Note that if you actually are able to travel to dark skies a lot, then the gains in image quality during those trips could well be worth having fewer imaging sessions at home!

06. Image even when the Moon is full

Conventional wisdom: The Moon is a huge source of light pollution. Don’t bother imaging when it’s up, and especially not when it’s full.

It actually seems like common sense that you shouldn’t image when the Moon is out. It’s so bright, like having a giant street light next to whatever you want to image. But I find that it’s still worth gathering data even when the Moon is full. There’s signal to be had in among all that noise, and processing software — particular shout-out for PixInsight’s NormalizeScaleGradient function here — can be very good at removing light gradients caused by a bright Moon.

I think that sometimes we astrophotographers can be quite good at thinking of reasons to not go out imaging, and the Moon being up is one of these. Personally, I don’t even consider the Moon’s phase or position; if the skies are clear, I’ll be gathering photons. If the data really is junk, that’ll be flagged by PixInsight’s SubframeSelector process, which graphs subframe quality. Normally it’s a-ok.

07. Image during short Summer nights

Conventional wisdom: The skies don’t get properly dark during the Summer (in the UK at least!) so it’s not worth going out imaging.

This is actually rather similar to the point made above about imaging when the Moon is out. Even if the nights are short, don’t use that as an excuse to not image! A few hours each night adds up. I think one of my best images is the Elephant’s Trunk Nebula, shown below. It was taken over the course of about six weeks, May to June. Hardly any properly dark skies at all.

08. Image quality < Fun

Conventional wisdom: High image quality is the ultimate aim.

Saying that having fun is important seems obvious, but I’m surprised how often it seems to be forgotten in discussions about astronomy kit. To be fair, I’m guilty of this too. Whenever there’s talk about which new camera or telescope to buy, the focus inevitably goes to technical specifications and detailed comparisons. That info is useful, for sure, but what would you find most fun to use? That’s the number one factor. You could produce a wonderful, high quality image, but what if you have a torrid time taking it? I think that for most people, and beginners in particular, having a set-up that’s a bit simpler is more fun. And if it’s more fun, you’ll use it more, and then improve your skills and produce better images. Hooray!

09. Don’t aim for perfection

Similar-ish to the point above, but I think it deserves a section of its own. For beginners, aiming for perfection can actually hinder progress. You see amazing photos online and it’s demoralising when you don’t produce something as good. Just aim for each picture to be a little better than the last one. And don’t forget to have fun!

10. TBC

I don’t actually have a number 10, but I couldn’t exactly call this article “9 Controversial Opinions”. Consider this a placeholder for the future!

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Nothing will motivate me to create more content quite like money!