How Can I See Deep Space Objects Better?

How Can I See Deep Space Objects Better?


M101 - Pinwheel Galaxy

Your telescope computer has a database of 4,000 objects to see, but you don’t know where they are in the sky or how dim they might be. The deep space objects are some of the most fascinating and awe-inspiring objects to see in amateur astronomy but they can be very elusive to observe. These “grey fuzzies” barely stand out from the background blackness of the night sky, and if there is any light pollution in your location it can make things much harder still. So how do you ensure the best chance of seeing the deep space wonders? Read on for tips on how to improve your chances.

 

Adapt your eyes to the dark

 

Probably one of the most important things to do is increase the sensitivity of your eyesight in the dark. This happens naturally and takes 20 to 30 minutes to occur. The eye contains light receptors on the retina. There are two different kinds, the rods and the cones. The cones are better at colour viewing and are dominant through the day. The rods are better in the dark and take some time to sensitise to the darkness. Once you have obtained your dark vision you must protect it at all costs. The best way to do this is to cover your viewing eye with a patch. Any momentary bright light can ‘reset’ the vision back to daytime viewing, meaning you would need to wait 20 minutes again for it to adapt. So make sure you protect it and use red coloured lighting when outside in the dark.

 

Averted Vision

 

Averted vision is a technique for viewing dim objects where you try to look at an object using your peripheral vision. Look at where you expect to see the deep space object and then move your focus a small way from it. It takes practice but by doing this you increase the sensitivity of your vision to dim objects.

 

This is because where you focus your vision on the retina of your eye is called the fovea and it is packed full of cone light receptors which, as you’ll remember, are excellent at colour vision. Around the fovea is a higher concentration of rods over cones. The rods are much better at black and white vision and more sensitive in the dark. So, by trying to observe an object in the field of view to the side of your most focussed area you can increase the sensitivity of your eyesight to seeing the dimmer objects.

 

Low Magnification, Big Aperture

SkyWatcher 200P EQ5

 

Your telescope is a light bucket, it collects a cylinder of light equal to its aperture size. The larger the aperture the more light the telescope can collect and hence, the dimmer the object you can see. So the biggest aperture telescope you can afford will definitely help. Find some low cost recommended 8 inch telescopes here.


 

At higher magnification you are reducing the amount of light coming into the eye. You have probably noticed that at high magnification the background looks darker and at lower magnification the night sky has a brighter appearance. So use a low power eyepiece when looking for deep space objects. In the constellation guide the pictures of the deep space objects are framed in a 30 arcminute circle, which is the approximate size of a full moon. This helps you to gauge the actual size the deep space object will be in your field of view.

 

Limit Light Pollution

 

If you can, try to go to a dark sky location away from the light pollution of the city or town. Planning a trip is well worth the effort for the unbelievable experience you will have under a truly dark sky. Make sure you choose a moonless night sky as the light from the moon is a very potent source of “light pollution”.

 

If you can’t get away from the city you can still limit local light pollution. Turn off the lights in the house and ask the neighbours to switch off any external lighting. Most neighbours are happy to oblige if you offer them a chance to have a look down the telescope too. Put a hooded top on or use a towel over your head to cut out any local light sources.

 

Filters

Light Pollution Filter

 

Filters can’t increase the brightness of a deep space object but some filters can improve the contrast between the background night sky and the deep space object making it easier to spot. There are many filters available but this is a good low cost light pollution filter.


 

Choose the Right Deep Space Objects

 

M13 - Great Globular Cluster

M13 found in Hercules is an easy an wonderful deep space object to see.

M13 - Great Globular Cluster of Hercules

All of the tips above help to improve your chances of seeing a deep space object. However, there is a limit to how dim an object can be before you can see it. There are many objects out there that no matter what you do you won’t be able to see them, as they are too dim for your location and gear. It’s important to find your limiting magnitude so that you don’t become frustrated trying to observe objects that you have no chance of seeing. The limiting magnitude is a number that corresponds to the brightness of the dimmest object you could see in perfect conditions. There is a guide here on how to determine your limiting magnitude.


 

Once you know how dim you can go, consult the constellation guide and see which deep space objects you should be able to see in and around a constellation. No more wasted time and frustration trying to see these fascinating wonders of the night sky.


Related Posts: Observing


Back to Beginners guide to Astronomy

Or next:

Part 1. Getting Started in Amateur Astronomy

Part 2. Binoculars or a telescope, which should I buy first?

Part 3. 5 Things you Need to Know Before Buying a Beginner's Astronomy Telescope

Part 4. Goto or Not Goto? That is the Question

Part 5. How to Set-up an Astronomy Telescope

Part 6. 8 Tips for Making Your Goto Telescope More Accurate

Part 7. 10 Easy Astronomical Objects to see From the City

Part 8. 5 Things to do on a Cloudy Night

Part 9. Which Eyepieces Do I Need?

Part 10. 10 Useful Astronomy Accessories

Part 11: How Can I See Deep Space Objects Better?

Part 12: How Can I See More Detail On Planets?

Part 13: How to Dress for Astronomical Success

Extras: Beginner Astronomy Telescopes

Or Start reading the Learn Astronomy Blog

Or Start Finding Deep Space Objects with the Constellation and DSO Guide.


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