Complete beginner looking for advice: Entry setup for galaxy imaging

The question that has to be asked, given that you want to image at focal lengths longer than 1500mm. What’s your budget? Nothing about what you want to do is easy so knowing how much money you have to throw at the problem is key to pointing you in the right direction.

Saving up for 4 or 5 months and buying something like an EQ-6 mount would be a very wise course of action. The mount is the foundation of any astrophotography rig and is the last place you want to skimp. For shooting long focal lengths you’re going to be dealing with weight and you’ll need fairly precise guiding. The mount will need to be able to handle it and there’s no way to do that cheaply.

I’ve found that the smaller the thing you want to image the greater the expense; and it is not a linear relationship… more like exponential.

The problem isn’t usually the glass, camera, or filters, but instead holding the whole imaging system steady against the sky.

You’re really fighting two problems:

1.) The air is “boiling” to some degree or another: Your stars are going to be blurring out over time similar to looking at something at the bottom of a pool of water while you throw pebbles in. This is called “seeing”

2.) The mount holding the telescope is “jiggling” to some degree or another as the motor turns it to track the stars across the sky as the Earth rotates. This is called RMS error.

The unit of measure for these issues is “arc-second”. There are 360° in a circle; now for each degree divide it up into 60 slices. Each “slice” is called an arc-minute (there are 360 × 60 = 21,600’ in a circle); the ‘ character denotes arc-minute). Now take each arc-minute and divide it by 60 again. This is a called an arc-second (there are 360 × 60 × 60 = 1,296,000” in a circle). the “ character denotes an arc-second.

To give you an idea of how small of an angle this is; it’s the width of a dime viewed from 2 miles away.

We typically talk about the width of size of the star half-way between complete black and it’s most intense peak after the atmosphere has gotten through blurring it out. This is called FWHM (Full Width Half Max) and is measured in arc-seconds (“). What you’ll get depends on where you live; the weather patterns at the time; etc. It will vary a lot but the typical value is about 2”. This sets a bound on how small the things you can “see” in the sky. Things smaller than this are just smeared into a blurry blob by the air.

Now let’s talk about your camera and telescope. You’ve got the air smearing infinitely small points of star-light into a 2” blob of light in the sky. In order for this to look like a star in your pictures (instead of some random white speckles) you need to arrange things for this 2” blob of starlight to cover between 3-4 pixels across it’s FWHM (diameter).

Today, in the modern era of Russ Croman post processing tools; (BlurXterminator, StarXTerminator; NoiseXTerminator) you want to favor the larger end of that range. I shoot for 4 pixels across the average star’s FWHM for my shots because BlurX likes it “better” that way.

This means you need to pick a telescope/camera combination such that each pixel on the sensor “sees” 2”/4 = 0.5” square patch in the sky.

You really don’t have a lot of choices in good astronomy cameras today: It’s pretty much down to those with 3.76u (letter u means microns) pixels (larger sensors) and one with 2.9u pixels (tiny sensor). I strongly recommend you go with a 3.76u camera.

So where does that leave us: What focal length of telescope combined with 3.76u pixel camera gets a patch of sky about 0.5” in size on each camera pixel? https://astronomy.tools/calculators/ccd_suitability answers that question for you: ~1550mm focal length telescope gets you there. There’s no “beginner friendly” scope in that focal length where beginner means plop it outside and let it rip with no (or minimal setup) required. The closest I can think of would be something like an EdgeHD 8” w/ F7 reducer (1487mm or 0.52” per pixel) or the EdgeHD 9.25” w/ F7 reducer (1645mm or 0.47” per pixel); or the new SkyWatcher SkyMax 200DX with F7 reducer (1400mm or 0.55” per pixel). Of these 3, I’d recommend the SkyMax which is a gamble since it hasn’t been released yet, but it is advertised to be designed to overcome the typical issues in using a EdgeHD (of which there are many).

So now you have a telescope and a camera designed for small target (galaxy) hunting. Now here comes the hard part:

You’ve got to have a mount that can hold that telescope system still against the sky to less than 3/4 (preferably 1/2 or better) the pixel scale (above we calculated that to be 0.5” per pixel) which means you need a mount capable of guiding at 0.35” RMS (root-mean square error) or better. If the mount can’t do this then all you’re doing is smearing that star image around on your camera sensor. (what’s the point of having all those small pixels if you’re doing that?)

Here’s a chart showing you the size of the blurry star spot in FWHM with different air (seeing; down) and mount (RMS; across) smearing.

📷 image.png
Let’s look at your 2” seeing case: If the mount can guide perfectly (no errors) then you get a star 2” in size in your pictures. If it has about 0.35” RMS error then the 2” star is 2.08” in your picture (8% larger in area); if it can only guide with 0.5” RMS error (the same as your pixel size) then the star is 2.17” in your pictures (17% larger in area); and it goes up quickly from there.

So we get to the most famous quote in astrophotography by Roland Christen the founder of Astro-Physics; the builder of the (arguably) finest refractor telescopes in the world:

The 3 most important things in astrophotography are:
1.) The mount
2.) The mount
3.) The mount

Now if you want to image tiny things (galaxies) then you need the most precise mechanics you can buy which can hold the telescope steady against the sky as the earth rotates. This means premium; which means $$$.

The good news is that if you buy premium first then you’ll never have to do it again for the rest of your life.

Here are my recommendations in my preferred order:

1.) 10Micron 1000 HPS
2.) Astro-Physics Mach2
3.) Software Bisque MyT (with encoders)

These guys are about the cost of a used car; but I’ve seen them go second hand for a little less than $10k many times.

There are somewhat cheaper alternatives that (sometimes) may perform to 0.35” (if you get lucky and get a good one); but it is not a guarantee and what you buy probably won’t last a lifetime. When I started I tried these cheaper alternatives and spent a lot of time, sleepless nights, trying to “tweak” things just so to get this performance until Ed Thomas at Deep Sky Products pulled me aside and told me what I’m telling you right here. I wish someone had done it when I was at the beginning and saved myself a lot of $ and time.

The last thing is now that you’ve got this expensive galaxy imaging system you’re not going to want to run it from your light polluted back yard. You’re just wasting your money and time trying to see incredibly dim things through the light pollution. You need to budget to send it to a remote observatory like Starfront. You can get a galaxy system on a pier out there for $199/mo.

This is an expensive hobby, but if it’s your passion then the expense is worth it and the personal satisfaction in the images you create with your equipment can be very rewarding.

Feel free to PM me with any further questions. I’m glad to help.

Dave Stirling · Jun 4, 2026, 07:27 PM

an EQ6 is going to get you up and going sooner

I wanted to reply about my personal experience going this route. An EQ6-R will typically guide ~[0.5” - 0.7”] RMS. (I’ve owned 3 and they’ve all performed in this range.) Remember when I said I regret all those sleepless nights spent trying to “tweak” things to perform better … those were with my EQ6-Rs.

When I finally got a 10Micron those numbers went down to 0.25” - 0.3” RMS (about ½ the error for 5x the price)

The EQ6-R are great mounts and with that guiding error you’d want your image scale to be about 0.7” - 1.0” per pixel which is about 1100mm - 775mm focal length but that’s a little under-sampled (less then 3 pixels across the star’s FWHM at 2” seeing).

You’ll get great pictures with a petzval refractor (just pop on a camera, focus and go) with a scope in this focal length but you’re giving up some resolution.

This what I was talking about: The smaller the thing you want to see (i.e. the sharper the resolution), the more exponentially expensive the equipment is.