Last summer at a regional star party, a 14-year-old with a beat-up 70mm achromatic refractor he'd scored at a garage sale for $20 asked me a question I've heard a hundred times: "Everyone says I need a huge Dobsonian to see variable stars, right? This thing can't pick up anything that faint."
I handed him my eyepiece, pointed his scope at T Tauri, a faint, irregular variable in Taurus that hovers around 9th magnitude at its brightest, and watched his jaw drop when he saw the faint, fuzzy smudge of the star's surrounding nebula next to it. By the end of the night, he'd logged three variable star observations to submit to the AAVSO (American Association of Variable Star Observers) database.
Here's the thing no one tells new amateur astronomers: small refractors (60mm to 100mm aperture) are actually ideal for variable star work. Their lack of a central obstruction (the secondary mirror that blocks light in reflectors) gives them far higher contrast than similarly priced reflectors, making it way easier to pick out faint, low-contrast variable stars against busy background star fields. Their wide natural field of view lets you see the full patch of sky around a variable, so you can easily match it to comparison stars to confirm its brightness. And they're lightweight enough to toss in the back of a car for dark site trips, or even use from a light-polluted backyard for brighter variable targets.
If you've been writing off variable star observing because you don't have a giant scope, these techniques will have you logging your first observations in a single night.
Prep Work That Cuts Your Search Time By 90%
The biggest barrier to finding faint variables with a small scope isn't aperture---it's wasting time scanning the wrong part of the sky. Skip the generic star maps you use for constellation hunting, and do this prep first:
- Ditch generic maps for free AAVSO finder charts. Every registered variable star has a custom chart with pre-plotted comparison stars of exact, verified magnitudes, plus a clear marker for the variable's location. You don't have to guess which faint star is your target, because the chart will show you exactly what the star field looks like through a small scope.
- Pre-load your exact scope and eyepiece combo into an app like Stellarium or SkySafari. Set the app to show the exact field of view you'll see through your eyepiece, so you can practice matching the star pattern on your phone screen to the real sky before you even step outside. This eliminates the endless scanning for the right patch of sky that trips up most new observers.
- Pick starter targets that match your scope's limits. A 60mm to 80mm refractor under moderately dark (Bortle 4-5) skies will easily pick up stars down to 10th magnitude, so start with variables that hit that brightness at their peaks. Great first targets include T Tauri (Taurus, ~9.5th mag at peak, with a visible surrounding nebula for extra context), SS Cygni (a dwarf nova that brightens from 12th to 8th mag every 6-7 weeks, perfect for regular observing), and R Coronae Borealis (a carbon star that drops from 6th to 14th mag during dimming events, so you can catch it when it's bright enough for small scopes).
- You don't need a dark sky preserve for your first tries. Even from a light-polluted backyard, you can confirm bright variable peaks (8th to 9th magnitude) as long as you know the exact star field to look for.
Small Refractor Hacks That Make Faint Variables Pop
You don't need to upgrade your eyepieces or buy a fancy filter kit to get the most out of your small scope. These tweaks cost $0 to $30, and will make faint stars way easier to spot:
- Use the right eyepiece order. Start with a low-power, wide-field eyepiece (25mm to 30mm for an 80mm refractor) to get the full context of the star field first, so you can match the pattern of stars to your AAVSO chart. Once you've confirmed you're in the right patch, switch to a mid-power eyepiece (10mm to 15mm) to boost contrast and make the faint variable stand out against the background.
- Stop down your achromat (yes, really). If you have a budget achromatic refractor (the kind with purple fringing around bright stars), stop down your aperture by 10-15% with a neutral density filter or a low-power Barlow lens. The tiny loss of light is nothing compared to the massive gain in contrast: chromatic aberration disappears, and faint, low-magnitude stars that blend into the background will suddenly pop. This is the single biggest hack I've found for small refractors, and it costs $0 if you already have a Barlow lens lying around.
- Collimate your scope before every session. Even a slightly out-of-collimation refractor will kill contrast for faint objects. Pick up a $20 laser collimator and spend 2 minutes adjusting your scope before you head out---you'll be shocked at how much sharper faint stars look.
- Skip the fancy filters. Unlike nebulae, variable stars are point sources, so most nebula filters won't help. If you're observing from a light-polluted area, a mild broadband light pollution filter can cut through sky glow just enough to make 9th-10th magnitude stars easier to pick out, but don't waste money on narrowband filters for this work.
How to Confirm You're Actually Looking at the Variable (Not a Random Faint Star)
The biggest mistake new variable star observers make is mistaking a random faint background star, a distant galaxy, or even a smudge of light pollution for their target. Use these checks to be sure:
- The comparison star check is non-negotiable. Your AAVSO chart will have two or three comparison stars with known magnitudes: one slightly brighter than the variable's expected current brightness, one slightly dimmer. Once you spot a faint star that matches the variable's expected brightness, compare it directly to those reference stars: if it's the same brightness as the brighter comparison star and dimmer than the next one, you've almost certainly found your target.
- Use averted vision the right way. Small refractors don't have a central obstruction, so you can use slightly off-center averted vision without losing sharpness. Look just to the side of the faint star---if it brightens when you don't look directly at it, that's a sign it's a real point source (the variable) rather than a faint smudge of background light.
- Do a quick 30-minute time check if you're unsure. If you think you found the variable, look at it again 30 minutes later. True variables will shift in brightness slightly even over that short window (even slow variables have a detectable 0.2 magnitude change with practice), while fixed background stars will stay exactly the same brightness.
- Snap a quick eyepiece projection photo if you're still unsure. Hold your phone up to the eyepiece and take a 10-second exposure, then compare the photo to your pre-loaded chart later to confirm you have the right star. This is a game-changer for beginners who aren't confident in their visual magnitude estimates.
Common Mistakes That Will Make You Miss Faint Targets
- Don't start with high magnification. High power narrows your field of view to a tiny patch of sky, so you'll spend hours scanning empty space if you start with a 5mm eyepiece. Always start wide, then zoom in once you're in the right star field.
- Don't observe when the variable is low on the horizon. Atmospheric extinction (the thickening layer of air you're looking through) can make a star look 1-2 magnitudes dimmer when it's less than 30 degrees above the horizon, so you might miss it entirely. Plan your session so the variable is at least 45 degrees high in the sky.
- Don't ruin your dark adaptation. Even 5 minutes of looking at your phone or a bright flashlight will make 10th magnitude stars invisible. Use a red light flashlight, and keep your phone screen brightness as low as possible if you need to check your chart.
- Don't get discouraged if you miss the first time. Even experienced variable star observers miss targets on the first try, especially if the seeing is poor or the variable is at the low end of its brightness range. Keep a log of your attempts, and you'll get faster and more accurate with every session.
Your Small Refractor Is Enough
Last February, I used my beat-up 80mm achromat refractor (the same one I've had since I was 15) from my Bortle 5 suburban backyard to catch R Coronae Borealis during its 2024 dimming event, when it dropped to magnitude 10. I submitted my observation to the AAVSO database, where it's now part of the public record used by astronomers studying these strange, fading stars.
No giant Dobsonian, no $10,000 astro camera, no hours-long drive to a dark sky preserve. Just a small scope, a little prep, and the techniques above.
Variable star observing is one of the most accessible, rewarding citizen science projects on the planet. You don't need to upgrade your gear to contribute---your small refractor is exactly the tool you need to start making real astronomical observations tonight. Grab your eyepiece, download a finder chart, and go find a star that changes.