Can my Sky Watcher Infinity 76P "make the sky bright" & do I want it to?

Question

I've seen quite a few time-laps films where the Milky Way is seen as bright and filling the sky, as some fantastic glowing cloud full of glittering stars.

I wonder if it is possible to see this (or something a little similar) through a telescope using my eyes (not a camera)?

It seems to me that you would want as little magnification as possible to see the sky like this, and it would be all about gathering as much light as possible? This answer describes this scenario as "Low Brightness" (and low resolution) objects.

I have a Sky Watcher Infinity 76P telescope. At the moment, it has a 30x erecting lens that tends to wobble in its helical mount, and doesn't give a good image. I've read claims that with a non erecting lens and a bit of care, this telescope can give good images.

• Are non magnifying lenses available for the Sky Watcher? Or would I be better off taking a different approach completely, such as buying binoculars?

• I'd like to be able to share this with my children, and they find the existing Sky Watcher lens hard to use – as well as its wobble, I think this is because it has a narrow "exit pupil" (?), so that you need to get your eye in just the right place. Can I get a low magnification lens that is more forgiving for the user?

• Can I expect to be able to see something from my backyard in a small UK town? Some of the shots in that film I link to seem to show clear bright sky pictures when there are other sources of light on the ground, or even the setting sun.

Many thanks.

Answer 1

To make the images in the time-lapse (and similar Milky Way photos), the photographer uses time exposures with wide angle lenses, may stitch together multiple images from longer lenses, and uses extensive post-processing to balance contrast and include foreground or bright objects in the scene.

The closest you can get to the same thing visually is to go someplace with very dark skies (middle of the ocean, or a wilderness with no nearby towns) and use the naked eye or wide-angle binoculars. In dark skies, the Milky Way overhead is obvious and impressive, but it still won't match the color or vividness of the photos.

Your telescope isn't really useful for looking at the Milky Way as a whole, but it can probably give a satisfying view of the many star clusters that dot the Milky Way--the Pleiades and the Beehive are naked eye objects and so shouldn't be too hard to find with your telescope. When these clusters are "resolved" into their individual stars, they are impacted less by the light-pollution you probably have in your backyard location. I can't tell if the 76p eyepiece is one of the standard sizes that can be replaced (1.25", 0.965" OD). If it is, an inexpensive eyepiece of about 25mm focal length might improve your views of astronomical objects.

Answer 2

The answer provided by @antlersoft is very much on point. Just adding to it:

The SW76 is a fun little scope mainly concerned with ease of use. It's a lot simpler to handle than refractors of similar aperture, and it's very robust. If there ever was a child-friendly scope (in a good way), this would be it - but adults can have fun with it too.

There might be several different models available? Not sure. I'm seeing reviews saying that it actually comes with two eyepieces, a 15x and a 30x. The 15x would provide a wider view, closer to binoculars.

Unfortunately, it uses a proprietary format for the eyepieces, so you can't just buy some commonly available eyepiece and use it. This is my main criticism for an otherwise well-designed instrument. If you're missing the 15x lens, maybe you could find it cheap on eBay?

I am the author of the answer you're quoting. Let me rephrase it. DSOs (deep sky objects) or "low brightness" objects are very sensitive to light pollution. If you live in the city, no matter what telescope you use, DSOs will not look that great. They just drown in the ambient light, reflected back down to Earth by the atmosphere.

You will see most of the Messier objects (the ones that begin with the letter M, followed by a number) with your instrument, they just don't look super-impressive. E.g. the Orion Nebula (M42) is visible now in the winter months and you'll see it as a little smudge or "cloud" - just google "how to find the orion nebula".

You will never see the sky full of stars unless you go far away from the city. In my trips to the Death Valley I've carried binoculars with me, and it's amazing - while in the desert, point the lens in any direction and it's like a river of stars. But a very dark sky is mandatory to see it like this. This might be a little tricky to find in the Old World. There are many light pollution maps online that could help you find good spots. But as a rule of thumb - far away from people and industrial facilities is good.

If you could find the 15x lens, your scope would be more or less equivalent to a pair of powerful binoculars, a 15x76 effectively, very similar to what I have (15x70). The 30x would work also, but the field of view would be 2x smaller (you're zooming in with the stronger lens).

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Re: the usability issues

I'm not sure what to say about the wobble. Hopefully nothing is broken.

What you're experiencing is not the narrow exit pupil. At 30x with a 76mm aperture the exit pupil is 2.5mm, which is plenty. Things get difficult below 0.5mm. It's probably a combination of small eye relief and narrow apparent field of view.

Eye relief is the optimal distance between the lens and your eye. High end eyepieces have generous amounts of it, e.g. 20mm. Cheaper eyepieces tend to vary, some are fine, others pull the eye relief as close as only a few mm. That's not very comfortable to use, and it's tricky to find the sweet spot.

The apparent field of view is the size of the "hole" you're looking through. Not the lens diameter, which has nothing to do with it, but the apparent diameter of the image you see in the lens, from dark edge to dark edge. Some lenses are like looking through a keyhole. Other lenses are like looking through a big porthole on an ocean liner.

These two together determine how comfortable an eyepiece is to use. The good news is, once you learn the trick, you can find the sweet spot every time afterwards.

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Your eyes will never compete with a digital camera sensor. That's just a fact of life. There are spectacular views to be seen in a telescope with your eyes, just understand that a camera can simply sit there and collect light patiently for minutes or even hours, and it will outperform your human "hardware" eventually.

It's a matter of taste, but for me that still doesn't eliminate the thrill of seeing things with my own eyes in a telescope.

Your scope should be just fine for watching the Moon. It will show you craters and mountains.

Saturn, when it's up in the evening sky again in a few months, will have its ring visible in your scope. It will be pretty small, but should be there in the image.

The moons of Jupiter, again later this year, will be visible in your scope like anywhere between 1 and 4 little "stars" that keep following the planet around. The configuration changes from one day to the next, demonstrating that these are not stars, but objects bound to the planet.