viewing help, do i need a focal reducer ?

[gsketch]

I have recently bought a Celestron nexstar 8se, so far i have had great fun learning how to use it and viewing certain areas of the sky such as clusters and the moon. However whenever i try to view galaxies or nebula i just cant see any detail or colour what so ever. At this point in time astrophotography is not an option for me due to the cost of getting into it as i have absolutely 0 kit, other than the telescope obviously. I have read online that a focal reducer may help my problem but most of the information around focal reducers seems focused on astrophotography. Is the problem as simple as light pollution or is there an easy fix to this problem.

Any help would be appreciated, thanks. 

[laudropb]

Hello and a warm welcome to the SGL. A focal reducer will be of no help. What you are seeing is the normal views of these objects through an eye piece. To see some detail in galaxies you have to be at a dark sky site. Even then the detail will be limited for most. The images you see on this site are not possible with normal visual observing.

You can see some detail in some nebula, but again this is dependant on the skies under which you view. Some colour is also possible in some of the brighter nebulae. Using a nebula filter such as a UHC or OIII does help, but colour can be a very subjective thing. Some people are more receptive to seeing it than others.

[Stu]

As John says, dark skies are the best thing you can use to see a little more detail, but you won't see colour, or even that much detail in galaxies.

There is not much astro darkness left at this time of year, and it is rapidly disappearing until the late summer.

Some objects do show colour. The Blue Snowball and Blinking Planetary nebulae for instance, and I often see a greenish tint to M42, but these are exceptions rather than the rule.

[Ricochet]

17 minutes ago, gsketch said:

However whenever i try to view galaxies or nebula i just cant see any detail or colour what so ever.

Aside from the Orion nebula, which can appear a bit green, galaxies and nebulae will appear as shades of grey. These objects are simply not bright enough to activate the colour sensing cones in your eye. They are also all extended objects, which means that the contrast between them and the background sky is constant at all magnifications (rather than improving with magnification for star clusters that are resolved into individual point sources). This means that there are two things that you can do to improve viewing:

1. Darken the background sky more than the object to improve contrast
2. Observe at an exit pupil where your eye is most effective
3. Make sure you are properly dark adapted

Let's start with 1, darkening the background sky. The only way to darken the sky more than the object is to remove light pollution from your views. There are two sources of light pollution: man made lighting and moonlight. Moonlight is the easiest to remove, you simply choose to observe galaxies and nebulae when the phase of the moon is very small, or even sometimes before or after the moon has risen or set. During a full moon, limit yourself to bright targets.

To remove man made light pollution the best option is to observe from a location with less light pollution. In an ideal world, we could all do this easily, in the real world your time, energy and finances will limit how often this is a possibility.

The last way to darken the sky background more than the object is with the use of appropriate filters. For galaxies, most people say that there is no filter that can help but in my experience an Astronomik CLS filter can improve the views of some galaxies under certain conditions. It isn't going to be as good as observing from a dark site and, as it is designed for old sodium lighting, will become less effective as LED lights become more common. For galaxies there are two filters that can help, the UHC filter and the OIII filter. The OIII filter is designed to allow a small area of the spectrum around two OIII emission lines through. The UHC is slightly wider and allows the two OIII lines and the H-beta line. Which filter is most useful will vary from nebula to nebula so I would suggest getting both and testing on each object. According to a well known test, the UHC is better on a larger proportion of nebulae, but this test was from what I would consider a dark site. I think that the more light pollution you have, the more likely you are to find a narrower OIII of more use. The following resource is quite useful for comparing the different brands of filters that are available: https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8 

Moving on to 2, the exit pupil. The exit pupil of any given eyepiece-telescope combination can be found by dividing the focal length of the eyepiece by the focal ratio of the telescope. If you know the exit pupil you want you can multiply if by the focal ratio to find the eyepiece you should buy. In your case your telescope has a focal ratio of 10 which makes things quite easy.

For an unfiltered view your eye is going to be best on extended objects at an exit pupil in the region of 2 - 2.5mm. This translates to using an eyepiece in the 20mm - 25mm range. This is is quite an easy eyepiece to get with a reasonable FoV so there is definitely no need for a focal reducer here.

For filtered views you will need to increase the exit pupil to make up for the fact that you are dimming the object by using the filter. To avoid the apparent field of view becoming very narrow you will either have to invest in 2" eyepieces (and a diagonal/visual back) or you could try a focal reducer. However, the maximum field of view that your telescope can support is going to be limited by the baffle through the primary mirror at the rear of the telescope. I will leave it to other forum members with hands on experience with your scope (or similar) to advise on the limits on eyepiece size that effectively apply to your telescope.

Finally, you need to make sure that you are properly dark adapted. Aside from your pupil expanding to the size required for larger exit pupils, it also takes at least 20-30 minutes to get properly dark adapted. If you look at any bright lights then this dark adaption is instantly lost. Make sure that you keep out of direct line of sight with any local lights and if you're sitting at the telescope a hood or towel over your head will help as will a patch over the non-observing eye. Dim red light will not destroy your dark adaption so a red light torch rather than a normal one is a good idea, and any screens you sue should be dimmed and set to red light mode.

[gsketch]

thank you very much for the help guys that was really useful, just shows how naive i was as a beginner astronomer thinking i could see galaxies and nebula perfectly. I think from this information i will do some more research on filters and consider the UHC, OIII and CLS filters. Once again thanks so much i really appreciate the replies.