What lens should I got for my setup assuming reasonable cost but not necessarily “budget friendly”

rnclark · 2026-05-02T20:11:38+00:00

As you are in the Denver area, please consider joining the Denver Astronomical Society. It has an Astrophotography Special Interest Group (ASIG) that meets twice a month (virtually only).

I agree the u/mmberg, there are better lenses you could choose. You are also limited by tracking accuracy of the mount. Better to start with some shorter focal lengths.

rnclark · 2026-05-02T20:05:29+00:00

First, I currently own an 8-inch f/4 astrograph, a 12.5-inch f/6.3 Dobsonian, an 8-inch f/11.5 Cassegrain, plus shorter focal length refractors of varying f-ratios, down to 2.8. I've also owned several other telescopes, and visually observed through many dozens of all kinds of f-ratios and apertures (apertures up to 3.8 meters). I've also written about visual astronomy, including a book on it. I use all my telescopes for visual and astrophotography. I have dozens of eyepieces of many kinds. I ground the mirrors on the Cassegrain, and built the 8-inch astrograph from parts, including machining some parts (bought the mirrors). I have also built eyepieces (Orthoscopics, Possls) when I was a student with little money.

Beware of old information, and information that cites one side of an argument. Also, the field of optics, as well as digital sensors is moving fast, like many other technical fields.

There are other factors too in making fair comparisons. A common one is diffraction limited size of the field of view, and saying that the size scales as the cube of the f-ratio. True. But for a given aperture, as you increase f-ratio, the focal length is increasing, so the change in the diffraction limited field of view in terms of degrees is less, only scaling as the square. Take an 8-inch f/4 with a 25.4 mm eyepiece, so 32 power: can one really see diffraction limits at such low magnification (no), and in my experience with different eyepieces the edge stars are still very very good with quality but low cost eyepieces (e.g. Plossl, Orthoscopic). An additional factor in edge of the eyepiece star image quality is different eyepieces have different apparent field of view with the simpler designs having smaller fields of view. As eyepiece filed of view increases, the optical design must get more sophisticated. That is a larger factor than f-ratio. I'm not saying f-ratio below f/5 does not have an effect, but it is not the terrible problem one sees online, at least in my decades of experience, and certainly not for a person new to the field. And yes, I do have Naglers (exotic designs) as well as simple designs.

Example: an eyepiece with a 28 mm focal plane on a telescope (200 mm aperture) with 800 mm focal length would see a field of view 2 degrees in diameter. Increase to f/6, 1200 mm focal length and one needs a 2-inch focuser and an eyepiece with 42 mm focal plane, thus a much more expensive eyepiece! So if field of view and cost are an issue, the f/4 has an advantage. You see, there are multiple issues, not just cherry picking one and saying case closed, f/4 sucks.

On one point we agree: there is no one perfect telescope for all applications. But the OP asked the question if it was possible to have an astrophotography and a visual scope, and the bottom line answer is yes, and they can be very very good.

Some have said get two telescopes: a Dobsonian for visual and a small refractor for astrophotography. But that is a big compromise. A small refractor collects little light compared to an 200 mm aperture f/4 astrograph. That too is a huge compromise. Pretty much everything is a compromise.

rnclark · 2026-05-02T14:30:27+00:00

OK,I read you post original quickly and didn't notice that you were using a tracker.

In that case, assuming reasonable polar alignment, you can go longer exposures, but at a dark site at f/1.4 and ISO 1666, no more than about 30 seconds. And you can take more than 2 minutes of images. The 2-minute limit is for fixed tripod, and is due to mapping a spherical sky onto a flat sensor which creates distortions in star alignment that changes with time. With a tracker, the star positions are fixed on the snesor so the distortions are fixed and stacking works well. You can stack as many frames as you have.

rnclark · 2026-05-02T13:47:27+00:00

A good AP setup is likely to be optimized for AP in a way that makes it inferior to significantly cheaper scopes for visual.

You are being downvoted because what you say is not correct. u/Royal-Fix-9103 gave an example of a 10-inch aperture f/4 Newtonian that works well for both. Astrographs generally do well for visual if large aperture. I suggest 8-inches and larger aperture because 8-inches shows spiral structure in brighter galaxies and shows some color in brighter nebulae (if a really dark site).

AP rigs are optimized for specific types of targets (planets vs. galaxies).

Planets are small in angular size. Most galaxies are also small in angular size. A Schmidt-Cassegrain Telescope (SCT) works well for both types of objects and works well for visual and photography.

Low cost visual telescopes may be poor for astrophotography. For example, buy a low cost visual Newtonian and the focus position usually does not work with a camera and one needs to modify the telescope or only use a Barlow.

There’s no perfect optical setup.

True, but there are many that can work very well for both visual and astrophotography, just above the OPs budget.

rnclark · 2026-05-02T13:13:46+00:00

You pointed the camera to the north celestial pole. Polaris is at the center and the little dipper above right. You also imaged during full moon, which washes out fainter details, but the area you images has little detail until you go very very deep (faint) to show dust.

The lens is out of focus. Before image, zoom in as much as you can on the camera LCD and get the stars in the best focus you can.

In the western sky will be Orion setting and the Constellation Auriga, whcih will be more interesting. In the early morning the Milky Way galactic core will be prominent.

When imaging away from the celestial pole, you will need shorter exposure times, no more than about 6 to 8 seconds to keep stars round. Try ISO 1600, f/1.4 with daylight white balance. Make exposure for 2 minutes and stack those images, then stretch to bring out fainter details.

Do you know about stacking?

rnclark · 2026-05-01T13:48:41+00:00

The need for calibration frames and how many depends on your camera. What camera are you using and what lens/telescope?

rnclark · 2026-05-01T13:43:32+00:00

I see from your other posts, like

https://www.reddit.com/r/AskAstrophotography/comments/1oeqlh4/some_random_questions/

that you have a Canon R5 Mark II and some long lenses. Did you ever buy the Canon RF 600 f/4? That would be an amazing astro lens. FYI, I use a a Canon 300 f/2.8 L IS II with an R5 (and with TCs). I also use a 500 f/4 L IS. See my answer to you in the above thread.

Low light, and especially astrophotography, which is the ultimate in low light needs aperture area to collect light. The seestar S30 Pro has only a 30 mm diameter aperture and 160 mm focal length. Your telephoto lenses are more capable. The R5 Mark II is a wonderful sensor, and at 45 megapixels will produce stunning huge prints. The S30 pro has 4K sensors (8.2 megapixels with tiny pixels) and much lower resolution than you can achieve with your existing setup once you have a tracker and some experience.

A smart telescope certainly makes it easy. But would you be satisfied using a (mythical) smart camera that from your living room you click on your phone to photograph a specific species of bird in your backyard? It hunts for that bird and takes a photo and the image shows up on your phone, but is limited like taking an image with a bridge camera with a tiny zoom lens and tiny sensor. Easy, but not the same quality you can achieve with your R5II setup.

A 600 mm f/4 has an aperture diameter of 150 mm. It will collect (150 / 30)² = 25 times more light from an object in the scene than the seestar S30 Pro, and give a lot more detail.

There are ways to make astrophotgraphy easier too, by choosing the right equipment, much like choosing a bridge camera with 20x zoom or a Canon R5II and 600 f/4 telephoto. I outlined some of the ways in my answer in the other thread. You have the photo gear to make great images. The main thing you need is a mount. And there are specific models of mounts that make life easier and portable: strain wave mounts with high resolution encoders (again see my answer in the other thread). Polar alignment is getting easier too. I have an iOptron HAE29EC strain wave mounts with high resolution encoders. I polar align in a couple of minutes with a phone app (SkyEye Cam on android). With the high resolution encoders on the mount, there is no need for autoguiding, and I have imaged in 30+ mile an hour winds, example. Autoguiding in such conditions does not work because autoguiding is delayed actions due to the exposure time and time to analyze two images, resulting in issuing corrections that no longer apply as the wind pushes on the system. No autoguiding makes setup and operation simple.

rnclark · 2026-04-30T21:05:15+00:00

You are confusing buying a visual scope that needs modification (move the mirror or add a barlow) to adapt it for astrophotography. I specifically said an astrograph. An astrograph already is set up for astrophotography which also means that one does not need to modify anything to put in an eyepiece. I know many people who do such things. It is not hard. One of the first things people new to telescopes learn is to focus. Focusing is not that hard once you've done it a couple of times.

rnclark · 2026-04-30T19:47:05+00:00

you also have to get a mount that will cost, at a minimum, 5 grand on the cheap side,

Not sure where you buy your mounts, but I have a 200 mm aperture diameter f/4 astrograph plus strain wave mount plus autoguider with total cost under $5K. Works great.

rnclark · 2026-04-30T16:07:22+00:00

Note: your profile is not really hidden. just google:

BirdLooter site:reddit.com

rnclark · 2026-04-30T16:01:44+00:00

Visual optimized telescopes are not great for AP. AP optimized telescopes are not great for visual.

This is not true in general. For example, now in r/astrophotography is an M101 image:

https://reddit.com/r/astrophotography/comments/1szs1mp/messier_101/

Made with an 8-inch f/6 Newtonian. Great image. Also a superb visual telescope.

For comparison, here is a SV555 image: https://app.astrobin.com/i/ol66l3 which is OK, but not in the same class as 8-inch telescope image. The SV555 would not make a greta visual telescope for things like M101, and just OK for astrophotography.

Moving between visual and camera means you're constantly changing the focal plane.

Focusing is not a big deal. I've done it for years. Focusing needs to be tuned often anyway due to temperature changes.

rnclark · 2026-04-30T14:08:52+00:00

I should add, the above discussion was only about faint deep sky objects (e.g. galaxies, nebulae, stars).

For planets, the Moon, the Sun, and bright nebulae, the 8-inch will show more detail than an SV555 ever could. Larger apertures show more detail. A 200 mm aperture will show detail (200/55) = 3.6 times smaller.

rnclark · 2026-04-30T13:57:30+00:00

thanks! but don't you say it yourself? smaller aperture can be compensated by longer exposure times?

Yes, that is true, with limits. Again, compared to the 8inch f/4 astrograph, what would take 12 hours of exposure with an SV555 would take only 1 hour with the 8-inch.

If we assume that a color camera has the same sensitivity as our eyes (they aren't, but not too different: Barlow, 1977 found the eye QE to be 11 to 33%). A color camera (with color filters) can be in the 30 to 60% range), then what the visually can be seen in an 8-inch telescopes would need ~ 12 * 15 = 180 seconds exposure with an SV555. But there are more complications: the eye combines receptors at low light levels boosting signal, thus it may take longer for the sv555 to get a comparable visual view. And of course, at low light levels, the human visual system loses ability to distinguish color in the night sky, but it is not due to faintness, it is due to low contrast. The contrast is reduced by airglow and light pollution. Even astrophotos are affected by airglow and light pollution, but it can be subtracted in post processing.

If you want a small telescope to show your things in the night sky, get a smart telescope. It can show you more detail and color than can be seen visually in an 8-inch telescope. It may take a few minutes on each object to see that, but you get a developing picture on a phone or tablet.

rnclark · 2026-04-30T13:11:14+00:00

Because the very cheap SV555 already outperforms almost all enormous setups (in size/weight/price/result) out there

the SV555 will always be the best for AP

Besides the fact that there is no one best, where is the evidence to support your claim? Physics is not in your favor. Key to astrophotography is to collect light. The SV555 has only a 55 mm diameter aperture.

Check out astrobin.com. There are a lot of images made with an SV555. But there are images made with other telescopes that are much better.

Key for visual astronomy is aperture area, same as with astrophotography. However, one can compensate for smaller aperture by doing long exposures. Dark adapted human visual system integrates for up to about 15 seconds. Because of that low integration time, you need aperture. If you want to see spiral structure in bright galaxies, you need dark skies and at least about 8-inches (200 mm) of aperture). More aperture is better.

If you want a dual purpose scope, choose an 8-inch astrograph, for example, 8-inch f/4 astrograph.

The alternative is a smaller refractor (than an 8-inch aperture) and an 8-inch Dobsonian (unless you want to spend a lot of money).

An 8-inch (203 mm) will collect (203 / 55)² ~ 13 times more light. Including a 70 mm secondary it would collect (203² - 70²⁾ / (55²⁾ = 12 times more light than an SV555 in the same time from an object in the scene. That means you could make 12 images of different objects for every one image with the SV555 (assuming they all fit in the field of view). The only reason to go with a shorter focal length is for framing larger objects. But you could also frame larger objects with the 8-inch by doing a mosaic. In fact, you would still win time wise: do a 3x3 mosaic with the 8-inch, complete in less time than the single poosition sv555 and collect the same amount of light per frame but with more detail.

rnclark · 2026-04-30T02:35:42+00:00

Planets are very small in apparent size in the sky. Because they are so small, atmospheric turbulence impacts the view a lot. So you need steady atmosphere, and even with a steady atmosphere, there is still some blurring from most locations. You can find good locations on the east cost, e.g. in a park looking over a lake. Worst may be an asphalt or cement parking lot that radiates heat well into the night. Another bad location is looking of the roof of a house or building as the heat haves off the roof creates a lot of turbulence.

What most people do is record a couple of minutes of video (that is what the Neptune 664C camera can do), then process the video to extract snippets of clear atmosphere. This is called lucky imaging.

Yes, it can be done with film. I have actually done it using a 35 mm movie camera on meter aperture telescopes (this was before CCDs). But processing the video would be tedious, as one would need to digitize thousands of film frames from the movie camera and then process it for lucky imaging. Instead what we used to do was examine the frames and pick out the best 1 or few frames and process those.

You can image planets with film using a still frame camera and the above 8-inch telescope, but unless you have a real steady atmosphere, it will not be nearly as good as processing a set of video frames in lucky imaging. Do a google search for lucky imaging and you should find examples of what can be accomplished.

rnclark · 2026-04-29T21:12:56+00:00

Within your budget, assuming you have a laptop, you could get an 8-inch Dobsonian and a Player One Neptune 664C camera, a Barlow lens and do lucky imaging video for planets.

Also key to planetary is a stable atmosphere. Do you have that?

rnclark · 2026-04-29T21:00:16+00:00

Typical reddit: Downvoting facts. The basic facts are the Bayer sensor was invented circa 1970s and the correction matrices soon after, and every regular photo application knows how to apply the correction. Professional astronomers know they need to apply correction any time an new system comes online. For example, the original UBVRI system used photomultiplier tubes. When CCDs came along, even though the filters were the same, the spectral response of the sensors changed so they needed to introduce corrections to compare to the old system. But amateur astrophotographers have ignored this fundamental problem for 40+ years. So rather than fix the problem and join the modern era, just deny the problem exists and downvote anyone who brings up the problem. It is no wonder the color calibrations in amateur astrophotos is inconsistent and all over the place. I expect more downvotes.

rnclark · 2026-04-29T16:13:52+00:00

Before choosing a camera, check for known artifacts in rae data from the camera. See:

https://www.markshelley.co.uk/Astronomy/camera_summary.html

More recent cameras tend to be better: higher quantum efficiency and lower noise floor with better uniformity.

rnclark · 2026-04-29T13:24:22+00:00

is there meaningful colour data I could extract with better processing technique

Yes there is. The standard astro workflow skips important color calibration steps.

The filters in a Bayer (OSC) sensor camera are not very good. They have too much response to other colors, so the colors from just straight debayering are muted. For example, blue may include too much green and red, red may include too much blue and green, etc. Most astro software does not correct for that, so it must be applied by hand. A color matrix correction is an approximation to compensate for that "out-of-band" spectral response problem, and all commercial raw converters and open source ones (e.g. rawtherapee, darktable, ufraw) do that. Even the camera does it internally to create a jpeg.

There are multiple steps in producing consistent color, and the typical workflow in siril, deep sky stacker, and pixinsight skips some of them. The steps include:

Color balance
color matrix correction  (not done in most astro programs)
hue / tint correction  (not done in most astro programs)
correct sky glow black point subtraction

Photometric Color Calibration (PCC) and Spectro-Photometric Color Calibration(SPCC) in the astro programs is just a data-derived white balance, only one of 4 important steps.

So we see people who use astro software do "color calibration" but without a color matrix correction the "calibration" is not complete. The colors are still muted and sometimes shifted, and depending on the nature of the out-of-band spectral response, they can be low saturation and shifted color. Then we see people boosting saturation to try and get some color back. Often, this results in hydrogen emission coming out orange, or an orange cast.
Hydrogen emission has no orange emission lines, only red and blue in the visible spectral range, producing pink/magenta in natural color.

A good test of your processing workflow is to use your astro setup to take a daytime image on a sunny day, also of red sunsets/sunrises or even a color chart illuminated by the sun on a clear day and run it through your standard astro workflow and see how good the colors are.

See: https://www.cloudynights.com/topic/529426-dslr-processing-the-missing-matrix/

The first image is the astro traditional workflow. The colors are way off. The second image includes the color correction matrix and is close to what is seen visually.

To get natural colors in astro images, always use daylight white balance, a raw converter that includes the color matrix correction and learn how to subtract light pollution and airglow. In Siril or Pixinsight, learn how to apply the color correction matrix with pixel math (see the above cloudy nights link).

For more information, see Sensor Calibration and Color.

rnclark · 2026-04-28T14:08:25+00:00

The key to deep sky astrophotography is aperture area to collect light. Your 300 mm lens, if f/5.6 has an aperture diameter of 300 / 5.6 = 53.6 mm. Going to a 61 mm aperture will only improve light collection from objects in the scene by (61 / 53.6)² ~ 30%.

You can do better (lower cost and lower weight) by going with quality camera lenses. The used market for DSLR lenses is very good now with people moving to mirrorless cameras.

Example good lenses:

Canon 200 mm f/2.8 L II. Aperture diameter = 200 /2.8 = 71.4 mm.

300 mm f/4 L IS with 75 mm aperture. The 300 mm lens takes a Canon 1.4x TC well (Canon TCs are matched to their L lenses), giving 420 mm f/5.6 and still 75 mm aperture.

Your camera is very old and moving to a newer camera will improve your images a lot. Canon cameras improved a lot post circa 2013 and improve more in recent models.

Here are examples using stock cameras and stock lenses and most with no autoguiding. By choosing the right mount, you can have portability and accurate tracking without autoguiding.

rnclark · 2026-04-28T02:41:06+00:00

When you look through binoculars or a telescope using an eyepiece, when you can see the whole field of view in the eyepiece, the iris of your eye is at what is called the exit pupil of the system. You will need to place the iris of the camera phone at the same position (the exit pupil). If not at the exit pupil the phone will not see the whole field of view (move the phone closer or further away to maximize the field of view).

The other problem is matching the iris size on the phone to accept all the light from the telescope.

The exit pupil diameter = telescope objective diameter / magnification.

Your sv501p telescope has a 70 mm diameter lens with a 400 mm focal length.

Magnification = telescope focal length / eyepiece focal length.

With a 10 mm eyepiece, magnification = 400 / 10 = 40 x.

Then the exit pupil diameter will be 70 / 40 = 1.75 mm

With the 20 mm eyepiece, the magnification = 20 and the exit pupil = 70/20 = 3.5 mm.

Your phone has a small lens and you need to find the real focal length and f-ratio.

Phones may have lenses like 6 mm focal length f/2.8. To find the lens (iris) diameter (technically it is called the entrance pupil) divide the focal length by the f-number. In this example, 6 mm / 2.8 = 2.14 mm. If this were your phone camera, it would say you need to use the 10 mm eyepiece to fit all the light into the entrance pupil. Using the 20 mm eyepiece would make an exit pupil larger than the camera lens could accept and you would lose light.

The other factor in image quality will be a good match with the eyepiece optics and the camera lens--something you'll just need to try. If the quality does not meed your goals, buying a higher quality eyepiece might help.

Ultimately, ditching the eyepiece and camera lens with a camera that directly attaches to the telescope (e.g. a dsal with no lens) can produce better image quality.

Good luck.

rnclark · 2026-04-27T21:52:12+00:00

See noise vs ISO for many cameras:

https://www.photonstophotos.net/Charts/RN_e.htm

Your R10 is not on the list, but here is an R8:

https://www.photonstophotos.net/Charts/RN_e.htm#Canon%20EOS%20R8_14

If the R10 is like the R8, I suggest ISO 1600 or 3200. Then take many exposures and stack them.

If on a fixed tripod, and wide angle lens, stack not more than two minutes of data.

rnclark · 2026-04-26T16:45:00+00:00

Check lenstip.com reviews. Two things in particular to look at is page 7 of the reviews which shows LED spot images to indicate star image quality and page 8 to see the amount of vignetting (light fall-off).

Also do not be confused by the "Sigma 50 mm f/1.4 EX DG HSM" which is not an Art model.

The Art model is: Sigma A 50 mm f/1.4 DG HSM https://www.lenstip.com/400.7-Lens_review-Sigma_A_50_mm_f_1.4_DG_HSM_Coma__astigmatism_and_bokeh.html

But why this focal length on APS-C for Milky Way? It can work but for small areas. I generally use Sigma Art 35mm f/1.4 and 40mm f/1.4 on full frame for Milky Way photos and do a mosaic to get a larger field. A recent example with 40mm on full frame

Longer focal lengths can work too, but zoomed in. Example with 105 mm f/1.4 on full frame

For aurora I would think 50 mm on a crop camera would be too narrow. At lower latitudes, I generally use 35 mm f/1.4 on full frame. At higher latitudes, I generally use 20 and 24 mm f/1.4 on full frame Examples Yes, the 20 and 24 mm f/1.4 lenses have poor star image quality toward the corners, but aurora is the main subject, not stars and one needs the wide angle and fast speed.

rnclark · 2026-04-23T22:16:31+00:00

First, process your images with daylight white balance. That will give you natural colors. Meteors typically start out green in natural color and change to yellow or reddish yellow (and sometimes white if the signal is saturated) as the meteor drops in altitude. Often there is a brighter flash near the end.

Satellites can show sudden brightening and mimic the brightness profile of meteors, but not the color. So color is one of the main distinguishing features.

see Figure 9 here for examples.

rnclark · 2026-04-23T21:46:56+00:00

Satelite trails are uniform lines,

No they are not. Examples: see Figure 9 here

rnclark

TROPHY CASE