Can I use a 5mm EP

[NotSoSuperNova]

Hi all,

I think I've done my maths right but preferring DSO's I'm not overly comfortable in this range of magnification. I thought I'd double check with you helpful lot just to put my mind at ease. I have a Celestron C10 as below with a 254mm (10") aperture and a 1200mm focal length. I know I'm within my max magnification but I was hoping that someone that has a bit more experience than me could either say "that's fine, go for it" or "you're an idiot"   Hopefully a little less blunt than that though. Anyway, thanks in advance. 

Ryan

[Kropster]

What are you intending to look at?

[NotSoSuperNova]

Mars when it comes into opposition next year. I'm a serial planner 

[Schorhr]

240x is nice for planets and smaller DSO - If the seeing is good!

What eyepieces do you have so far? Did you use them with your barlow?

[NotSoSuperNova]

I’ve got a 12 18 and stock 25mm in my collection currently. I've used them with my Barlow but I'm looking for more clarity with these smaller EP’s and my first thought is that I need less glass between me and it.

[alan potts]

A magnification of 240 has its uses, Moon, Planets and Globulars hold up well to this power especially tight ones like M15. The only real trouble it the seeing conditions caused by the atmosphere will only permit this amount on a good night. Recently I have had nights where X120 was a bind, I packed up and went in and warmed up.

Alan

[John]

It's good to have the option for a really high magnification to use when conditions are good and the subject benefits from it. If things look a bit ill defined then you also want something to back off a bit to so a 7mm would also be a good idea. 240x isn't that high really when it comes to a really small target such as Mars.

[Northern Soul man]

Hi Ryan, Mars will take the extra mag, may even take a little more, but Mars is a very hard target to observe, depending on how high it gets in the sky and how close to us it gets, it can be a nice target which allows slightly more mag than the fine contrast Jupiter and Saturn give, when I mean "fine" contrast - I should say subtle contrast as the gas giants need a lot more than just a quick peek at - but Mars gives nice contrast between the maria, highlands and larger land forms, but you really have to look for these - the large aperture will help, but when Mars gets close, certain apparitions give a disk below 20 arc seconds in actual size, so your getting a very small disk that looks really bright in the sky, pushing the mag a little more gives you a larger image - and because of the brightness - this allows for more mag, but you still have to view it for long periods of time, as with the gas giants, there's nothing better than just observing each for a good session, as the minutes tick by and the atmosphere steadies, you get maybe a second or two of real steady air - then you can build a picture of all the detail, from the really bright polar caps to the more subtle areas, maybe near the limb, then I tend to drop a lower power ep in and hunt the same detail down, trust me this becomes ADDICTIVE !!!!   Paul.

Oh forgot to mention I use a Variable Polarising filter on Mars a lot - alot of Astronomers use no filters at all, but the actual "glare" I find, the filter can be adjusted - I place 1 filter in the back of the star diagonal (this sits inside closest to the main mirror), then depending which size ep I use i can screw the other "side" of the filter into the base of the ep, then its a matter of just rotating the ep to vary the transmission you get - nothing too harsh - just a little turn to increase the contrast and "dim" the overall image.

[ronin]

A 5mm should work, just how often is the question, will agree that 240x for Mars will be useful even necessary.

I would however suggest the idea of a 6mm or 7mm at hand for when the 5mm is a little too much.

In which case the 5mm BST to match what you have would be OK for the 5mm but they do not do a 6mm or 7mm.

[NotSoSuperNova]

Thanks for that team SGL. Most helpful, as always.

[Reeny]

I am in a similar boat Ryan.

I ordered an 11mm Explore Scientific to Barlow up to 230x.

But I may need a 6mm intermediate to go inbetween 160x and 230x.

Baader Hyperions have had some mixed reviews on the 10" dobs (mine is an 8")

The 8mm version can be adjusted to 6mm with the fine tuning rings.

Quality 6mm eyepieces are very hard to find.

My next option up would be a 6mm TV Delos / or a second hand Radian.

In the meantime I have some 52 degree Plossls to fill the gap at 200x magnification.

I was warned that it could get expensive.

[faulksy]

as said 240x isnt crazy high certainly achievable quiet often, what ep was you thinking of ? 

[andrew63]

A 6mm ortho would be great for mars - if you can handle the tight eye relief.  A 6mm BCO for £50 or similar would be hard to beat.

andrew

[rwilkey]

I am in a similar boat Ryan.

I ordered an 11mm Explore Scientific to Barlow up to 230x.

But I may need a 6mm intermediate to go inbetween 160x and 230x.

Baader Hyperions have had some mixed reviews on the 10" dobs (mine is an 8")

The 8mm version can be adjusted to 6mm with the fine tuning rings.

Quality 6mm eyepieces are very hard to find.

My next option up would be a 6mm TV Delos / or a second hand Radian.

In the meantime I have some 52 degree Plossls to fill the gap at 200x magnification.

I was warned that it could get expensive.

Hi Reeny, the 6mm William Optics SPL is a good option to consider, a very fine planetary ep in my opinion.

[Kropster]

Is 230x manageable in a Dob?

Won't the nudges zip the planet out of view at that magnification?

[RikM]

I have a Skywatcher 250PX which is optically the same the C10-N I believe. 5mm is about the max for me. Very occasionally I will use higher, but 5mm is generally the best high power. I also use a 7mm and this is almost always good to use but a difference of just a mm or two at this end of the scale is quite significant so it is good to have options.

[Mr Spock]

With my former 250mm I used a 4mm on Mars. Those were some of the best views I've ever had.

[Peter Drew]

I've found that for Mars, the highest magnification the seeing will allow is often best. I've had better views in the past at 600X than 400X on suitable nights. I think Mars is going to be relatively small this apparition, I was observing it with a C8 on Tenerife a couple of weeks ago and 250X was not nearly enough. Glare is the enemy of Martian detail, it needs to be addressed either by ND filtration, high magnification or in a light sky. One of the best views I've had of Mars was at Kelling with my 16" LX200 having followed it into broad daylight. 

[Moonshane]

Is 230x manageable in a Dob?

Won't the nudges zip the planet out of view at that magnification?

if bearings are smooth yes. I regularly use 250-300x and have even used 450-600x in my 16" dob with which I have the best ever views of Mars

[Pig]

Very interesting, I didn't know Mars could take such high magnification   I will have to give it a go.