Magnification

[Corkeyno2]

I know it's not all about magnification with telescopes, so does anyone know what eyepiece would be the best for viewing deep sky objects and a good eyepiece for viewing the moon and planets? I have a Celestron Nexstar 4SE, which has an aperture of 4 inches. Any suggestions or advice would be greatly appreciated.

Thanks,

Corkey

[John]

Deep sky objects vary immensely in size in the sky so a range of magnifications can be useful. With your scope I would suggest something like a 32mm plossl would be a good place to start. This will show a low power relatively wide angle (for the scope) field of view which will be good for finding deep sky objects and viewing the larger ones or those that are in small groups.

Something like a 15mm would also be useful for viewing smaller deep sky objects (eg: the Ring Nebula M57) once you have found it with the lower power eyepiece.

The brighter galaxies, nebulae and clusters will be quite clear with your scope as "not stars" but don't expect anything like the photos you see !

[Corkeyno2]

Just now, John said:

Deep sky objects vary immensely in size in the sky so a range of magnifications can be useful. With your scope I would suggest something like a 32mm plossl would be a good place to start. This will show a low power relatively wide angle (for the scope) field of view which will be good for finding deep sky objects and viewing the larger ones or those that are in small groups.

Something like a 15mm would also be useful for viewing smaller deep sky objects (eg: the Ring Nebula M57) once you have found it with the lower power eyepiece.

The brighter galaxies, nebulae and clusters will be quite clear with your scope as "not stars" but don't expect anything like the photos you see !

Do you think a 12mm eyepiece would be useful for some DSOs?

[ronin]

The 4SE is f/13 and about 1300mm focal length, not going to be exact.

The moon is half a degree, so allowing for framing you need about a degree field of vie for a full moon. On a 60 degree eyepiece that is 06x mag and 60x mag on your scope is about a 20mm eyepiece. So for a full moon all in one view yopu are looking at something like the BST 18mm Staguider. but really a 25mm is easier.

For a non-full moon you are likely lokking at segments of the moon so really from 18mm to however much mag the scope can dekliver reasonably, so the 12mm BST and MAYBE the 8mm BST.

Planets: Saturn needs about 120x and Jupiter 80x as a minimum, that is Saturn = 10mm eyepiece, maybe the 12mm, Jupiter = 15mm. Obviously if the 12mm is good then use the 12mm on Jupiter as well as Saturn.

I use the BST's as my standard set and reference, but for planets they do not have the range, 5mm, 8mm, 12mm so to "fill" in Ibought the Altair lightwave 6mm. So I have 5mm, 6mm, 8mm, 12mm. If I could find a 10mm of the right specification I would get one of those also. For planets you can easily end up with eyepieces in 1mm increments. At present the planets are so low that I have not really bothered to try and observe them,

DSO's, you need a wide low power one to find them. Find may be get some small dim faint smudge in the centre. You initially are looking for a "patch" not an "object". Thinking M1 here. Yo centre this patch and increase the magnification until either it is too dim to examine or it becomes what you expect. Again no rule M1 is a DSO so is M31. But with reference to the BST's I suspect the 25mm to locate the the 18mm and 15mm to see more.

Do not askwhat makes a good planetary or DSO eyepiece as the answer to either/both is clarity, sharpness and contrast and whatever the object, DSO or planet, you want that.

My suggestion is that you find someone try try a BST from and see how they perform. If good then buy one a month or every other month and collect the set, that is more or less what I did. Maybe omit the 5mm.

Do you drive - I will try to read any reply as I cannot recall where I asked this earlier.

[laudropb]

You can work out the magnification an eye piece will  give with your scope by dividing the focal length of your scope by the focal length of the eyepiece ( both in mm ). As has been pointed out, different DSOs require different magnifications. For nebula like the Ring a UHC or OIII filter are also useful.

[John]

51 minutes ago, Corkeyno2 said:

Do you think a 12mm eyepiece would be useful for some DSOs?

For the smaller ones, yes. Using a lower power eyepiece will make finding them in the 1st place a lot easier though !.

Many DSO's will look no more than a faint patch of hazy light - you may well not even realise that you are looking at one !. The brightest ones will be more noticable though.

 

 

[Corkeyno2]

19 minutes ago, John said:

For the smaller ones, yes. Using a lower power eyepiece will make finding them in the 1st place a lot easier though !.

Many DSO's will look no more than a faint patch of hazy light - you may well not even realise that you are looking at one !. The brightest ones will be more noticable though.

 

 

I also have a 25mm which I  could use for locating DSOs, and then switch to 12mm to observe them. Is this a good idea?

[John]

13 minutes ago, Corkeyno2 said:

I also have a 25mm which I  could use for locating DSOs, and then switch to 12mm to observe them. Is this a good idea?

Yes, that would work. Don't be in a hurry to crowd on the magnification though. Pick your early targets to give you some "easy wins" such as Messier 13 (globular cluster), Messier 81 & 82 (galaxy pair), Messier 57 (the Ring Nebula) and Messier 27 (the Dumbell Nebula) etc.

 

[ronin]

It would be a good idea if it works, but if the 12mm is not up to it and the magnification is too much or the eyepiece is poor then no. it's not a good idea.

It really comes down to if the 12mm you have works fine, but if it doesn't and the 15mm I have does then you have to make a decision. I have mentioned at other times that with a scope you can realistically expect to end up purchasing eyepieces that in total more or less match the cost of the scope. Not sure why but it seems to work that way. The 4SE is about £400, the longer 5 BST's are £250, 5 X-Cel LX's are £350 area, if you add in a good 32mm or 40mm plossl you are looking at £300+ easily, so getting close to the scope cost. If you bought a couple of ES82's for the additional width in place of a BST or 2 then you will pass the scope cost. And the terrible aspect is that you have little option as you need a selection of eyepieces to use the scope. 5 is about the number, people may say 3 or 4 but 5 is the realistic number for not finding out you are missing one.

My  half set is 5mm, 8mm, 25mm BST  and a 6mm Altair, that is £200 worth of eyepieces on what I acknowledge to be a half set of eyepieces. A "full" set to head out with is all the BST's, the Altair and a 32mm and/or 40mm TV plossl. So around £450 worth of eyepieces and the scope cost me £450 when I bought it.