what eyepieces to use c6n

[colinger]

hi there ! i used to have a 3inch newt when i was about 16 yrs old just messed about saw rings of saturn moons of jupiter bits and bobs ! wasn't serious about astronomy ' now at 52 yrs i have just got myself a celestron c6n cos i just like gazing in to the night sky (i think it is brill also i want to learn a little ! the c6n states a highest magnification of 150x (useful) but i am confused about magnification as i have read that to calculate magnification is about 50x inch apperture so mine should be about 300x also can anyone give me a rough idea to different magnification's for planets nebulae ' galaxies ' if and when i find them . eyepieces i have are celestron 4mm 20mm and omni 2x barlow is this a good range or do i need more i hope someone can guide me in the right direction as i am only a learner cheer's

[Ambermile]

hi there

your c6 has an fl of 750mm. Maximum mag is a misnomer really as you will rarely have seeing (clear enough skies) to tkae advantage of it. To calculate the magnification you simply divide the fl by the size of the eyepiece. The c6 comes with a 20mm eyepiec so 750/20=37.5x. So, to get the maximum quoted magnification (354x) you are going to need a perfect night (once every couple of years) and a 2mm eyepiece. Or a 4mm and a 2x barlow (amplifying adapter). Or an 8mm and a 4x barlow.

Max mag is not what you are after anyway, rather you need as much light-gathering capability as possible - so the more inches the better.

Arthur

[moondog]

Hi there and welcome to the SGL forum.

Your 6 ins Celestron reflector should give you a great start in the hobby.

Arthur has given you the formula for working out the magnification.

So what magnifications for the different objects in the sky ?

For the moon you would get the whole moon easily in the 20mm EP. Depending on the EP you may get the whole moon with the 20mm and the Barlow. The 4mm EP should give you good close ups of the moon' craters.

Planets - there are not many about at the moment. You can see Saturn in the early morning , but it's a bit twinkly as it's low in the sky. Your 4mm may be OK but you might get a better view with the 20mm with the Barlow at the moment. With your scope when Saturn is higher in the sky you should get a fine view of the rings of Saturn with the 4mm.

Always you should try for the clearest image, which often means you are better going for a lower magnification.

For Deep Sky Objects ( DSO's), nebulae, globular clusters etc the magnification would vary depending what you look at.

Some are better at a lower magnification, and others such as Globular Clusters can take a higher mag.

Look at the sword hanging on Orion's belt with your 20mm EP, it should be a splendid sight. Or turn the scope with the 20mm on to the Pleiades. On a clear night you won't be disappointed !

8)

MD

[The Warthog]

I have a C6N. The eyepieces I use primarily are a 32mm plossl for searching and for large DSOs and the Moon. I also have a 20mm Wide Angle that I can also use as a search ep. I also have 12, 8 and 5mm X-Cels. I use the 8 the most out of those, but for planets I often put in the 5, and Barlow that on a very good night. I reckon the Barlowed 5mm gives the maximum 2x per mm of objective diameter. I do have several other eps, but the ones I use almost every time out are the 32 and the 8, with the 5 getting the next most use. If I had to take this scope and only three eps, those are the ones I would take.

[FLO]

Here are some FOV charts

[The Warthog]

As well as those three eps, I would take the barlow. Those FOV charts look about right. What's the AFOV of a SP4000?

[FLO]

SP4000?

[The Warthog]

SP4000?

As noted on the FOV charts. Is it 52 degrees?

[FLO]

Ah yes, sorry :oops:

It is 52 degrees.

[colinger]

I have a C6N. The eyepieces I use primarily are a 32mm plossl for searching and for large DSOs and the Moon. I also have a 20mm Wide Angle that I can also use as a search ep. I also have 12, 8 and 5mm X-Cels. I use the 8 the most out of those, but for planets I often put in the 5, and Barlow that on a very good night. I reckon the Barlowed 5mm gives the maximum 2x per mm of objective diameter. I do have several other eps, but the ones I use almost every time out are the 32 and the 8, with the 5 getting the next most use. If I had to take this scope and only three eps, those are the ones I would take.

hi there ! thank's for the info ' i managed to view saturn the other morning 5am i showed the wife before she went to work but she was more interested in her toast! ha ! anyway

i used my 20mm barlowed ' the image was clear and crisp ! then i put a 4mm celestron ( dont know what model ep it was but it was hard to keep in view as it kept dissapearing if i didn't have my eye positioned correctly in the ep ? i am thinking of getting a celestron 5mm x cel for high power that will give 150x

am i not pushing it a bit if i use a barlow as well 300x? or would you reccomend the 8mm x cel .also i have no filter's yet as i dont know what to get 'say for saturn ect i would be glad for any advice cheer's

[FLO]

300x is pushing it - it is also very rare that our seeing conditions here in the UK will permit such a high mag'.

The 5mm Celestron Excel is a good choice, particularly if you wear glasses (I can also offer a second-hand 5mm Lanthanum). Some motors for the mount would be good too.

[The Warthog]

I have Barlowed the 5mm only once or twice. I occasionally Barlow the 8mm for a magnification of 188, which is pretty good. As Steve says, you don't often get the kind of seeing that rewards a very high magnification, and things tend to race out of the FOV pretty quickly when you do.

[colinger]

300x is pushing it - it is also very rare that our seeing conditions here in the UK will permit such a high mag'.

The 5mm Celestron Excel is a good choice, particularly if you wear glasses (I can also offer a second-hand 5mm Lanthanum). Some motors for the mount would be good too.

thanks for the advice ! the 8mm x cel sound's like a good choice 'barlowed to get me up to about max mag 188x i have read that most amateur astronomers usually only use up to about 200x like you say condition's don't allow very high mag also i may consider motor's in the future as i am only in the early learning stages yet cheer's and thank's again

[colinger]

I have Barlowed the 5mm only once or twice. I occasionally Barlow the 8mm for a magnification of 188, which is pretty good. As Steve says, you don't often get the kind of seeing that rewards a very high magnification, and things tend to race out of the FOV pretty quickly when you do.

hi like i said to steve with what you say i think my best option would be to get the 8mm x cel with a barlow 188x would be ample can you reccomend any decent filter's for planets as i haven't got a clue cheer's.

[GordonCopestake]

I had a set of x-cels and sold them rapidly, didnt like them at all due to black outs and kidney beaning. They are clones of the Vixen LV's and if you plan on using the eyepiece as a "main" eyepiece then it's worth paying the extra and getting the LV's (or the radians which are better IMO)

[ZOG]

If I may add a question to this thread, if I focus a star in my 25mm kelner EP I have to re focus when I drop the 10mm kelner into the focuser. However, if I focus with the 32mm plossl and then drop in the 10mm kelner the focus stays sharp. Is there an obvious reason for this ?

[FLO]

Certain 'families' of eyepieces (Meade Series 5000, for example) are designed to be parfocal - little or no re-focusing is required when changing eyepieces for others from the same family.

If eyepieces from different families/types are parfocal - that is simply coincidence.

[The Warthog]

If I may add a question to this thread, if I focus a star in my 25mm kelner EP I have to re focus when I drop the 10mm kelner into the focuser. However, if I focus with the 32mm plossl and then drop in the 10mm kelner the focus stays sharp. Is there an obvious reason for this ?

My X-Cels are roughly parfocal, usually only requiring a twitch to get them back in absolute focus. Coincidentally, as Steve says, my 32mm Celestron Plossl is roughly parfocal with them, and I often dont' bother refocusing when I go from the shorter X-Cel to the 32mm Plossl as it's close enough for a search, but going the other way I do have to nudge the focuser a little. Using any of my other eps, I have to refocus considerably from the X-Cells or the 32mm.

I have a 'parfocalising ring' which I have yet to use. It is a slim ring with a set screw that you can put on the part of the ep that goes into the tube, to stop it at the point where it is focused when the tube has been focused for another ep. Naturally, this only works if the parfocalising ring is on the ep that requires the ep to be farther out. I may get around to trying it out, yet.