TheSkySearchers

On this subject, I know that filters are good for viewing nebulae. What type or power of scope would be a minimum to use filters in order to enhance nebulae?
This is a great thread, by the way. It's why I subscribed to it.

I’ll take another look at some plossls too.
I don’t wear glasses so don’t need the additional eye relief and although a wider field is nice, it’s not everything!
Thanks for all the help, it’s been greatly appreciated!

ChrisP90 wrote: ↑Wed Sep 02, 2020 6:04 pm While the 0.5 exit pupil may theoretically be the better EP, the 1mm exit pupil will be more useful on a regular basis?

The 1mm exit pupil will be much more useful as nFA has stated, 0.5mm is going to require excellent skies and good optics to get the most from it.
A wider FOV is helpful if locating dimmer DSOs but for normal bright targets a Plossl of 52° AFOV will show you 85% of targets we as amateurs can see.
The other use of wider FOV is framing a larger object in the view. (how much area you see around the object)

The Celestron eyepieces are good, just make sure if buying used that they are the X-Cel LX version. The original X-Cel (no LX) version was a poor eyepiece.
The Meade HD-60 nay as well be the same eyepiece so purchase which ever is cheapest.

Buckethead 2.0 wrote: ↑Wed Sep 02, 2020 7:07 pm What type or power of scope would be a minimum to use filters in order to enhance nebulae?

Exit pupil is more important than magnification with viewing nebula with filters.
A 5mm is a very good place to start with slight increases of magnification (smaller exit pupil) as you go.

Buckethead 2.0 wrote: ↑Wed Sep 02, 2020 7:07 pm On this subject, I know that filters are good for viewing nebulae. What type or power of scope would be a minimum to use filters in order to enhance nebulae?
This is a great thread, by the way. It's why I subscribed to it.

[mention]j.gardavsky[/mention] has successfully used filters with binoculars. You need a pair that accepts filter threads though. Mainly you want to choose an exit pupil that makes the maximum use of your dark adapted pupil size. For me that's something in the 5-6mm range.

While many folks like the broad band light pollution filters, they don't do much for me. I prefer the narrow band filters like an H-beta or an OIII (for planetary nebulae). I detected the Horsehead Nebula with an H-beta filter and a 35mm Panoptic in my SV ED 80mm scope on a very transparent night. A lot of folks claim an H-beta filter is no good short of 8-10" aperture. Nope! It's all about the exit pupil....

thank you

To add a little bit to the discussion:
A few philosophies:

1) constant jumps. Take your low power eyepiece. Let's say it's 50x. The eyepieces up the ladder might be at 100x, 150x, 200x, 250x, etc.

You might favor a jump of 40x instead of 50x, but you get the idea. This works well in most scopes.


2) constant % jumps. Take the lowest magnification and multiply by 1.4 for a 40% increase. Keep going until you have as high a power as you need.

The main flaw with this idea is that the low powers are too close together, and the highest powers too far apart. You end up with a pile of low power eyepieces

that seldom get used, and you find yourself needing a high power eyepiece in between two because one is too high for the seeing conditions and the next lower one is too low to see the details.


3) The exit pupil jumps. This is where the focal lengths are chosen so each eyepiece is a set amount darker than the previous. Let's say you start with an eyepiece that yields

a 5mm exit pupil. A 50% dimmer view is had with a 3.5mm exit pupil. 50% dimmer than that is a 2.5mm exit pupil. And so on. The % drop would be by personal preference,

but the flaw here is that it results in too many low power eyepieces.


4) the field size decrease jump. This is where the next eyepiece up has, say, a field size 3/4 as wide as the next lower power, so field sizes of perhaps 1°, 45', 34', 25', 19'.

This works OK if all your eyepieces have the same apparent field, though it results in odd jumps when they don't. A subset of this idea would be constant differences, like 1°, 45', 30', 15'.

The flaw with constant differences is the higher powers are farther apart. In that example, the difference is 25%>33%>50% by width, and even larger by area.


5) the "U" shaped curve. This is where you have a most-used medium power eyepiece and you make the magnification change on either side a small one, and then increase the magnification

changes with distance from the center, i.e. +/- 30x, then +/- 40x, then +/- 50x, etc. This works when most of your viewing is in a range in the middle. For example, say almost 100% of your

observing is in the 100-300x range. Having closer gaps in that range with larger gaps above and below that makes sense. When you want high power, you want HIGH power. When you want

low power, you want LOW power. But most of your observing is choosing the right magnification and framing of the object, so a choice around the most used magnifications makes sense.

The flaw here is you can end up with a lot of eyepieces.


6) the 1X, 2X, 3X protocol. This is an idea aimed at the beginner who wants a basic set to start and then fill in later as personal preferences dictate.

The idea is that X represents a particular magnification and the basic set has 3 multiples of that. So, an 8" scope might use x=50 for a starter set of 50x, 100x, and 150x.

A 12" scope might use x=60 for a 60x, 120x, 180x set. A 4" might use 35x, for a set of 35x, 70x, and 105x. The goal here is to have some anchor points around which to build a set.

And a 2 power Barlow can be added to yield 4X and 6X. Time will likely dictate you want a magnification in between one of the X powers, but it's not a bad place to start.



So those are some different ways people have chosen their sets of eyepieces. And none of the protocols is wrong because people have different approaches to observing.

Currently, I'm using #5 above, but I have eyepieces I really like but seldom use. I think we all run into that from time to time. But selling one is like "Sophie's Choice"--which one do I sell?

Maybe it's best to keep all of them. LOL.

I use combination of increase by factor (i.e. by 1.4x), exit pupil and U curve.

I star with 2mm exit pupil, where most of my galaxy hunting is done and populate close to 2mm exit pupil using 1.2x increments and father away using 1.4x increments.

An excellent thread. I would welcome comments on my own small eyepiece collection. My 11mm is used almost exclusively for white light solar incidentally. The scopes fl is 8.6.

Thanks in advance.

Your 11 mm eyepiece will give exit pupil of 1.28 mm, TFOV of 0.625° and a power of 20x per inch of aperture.
Well within the limits of the telescope.
Using a 6 mm dark adapted pupil the lowest power would be 17x with a 52 mm eyepiece.