Highest Practical Power

[twelly27]

Hi All

I am wondering how to get my telescope to its highest practical power of x254, as i am new to all this im also wondering is it worth it?

my telescope is a Skywatcher 127, (http://www.rothervalleyoptics.co.uk/skymax-127-synscan-az-goto-telescope_d3193.html) theres the link to exactly what im using.

Any help a equipment tips would be helpful i dont really understand what i would get if i got it to its highest practical power

Regards

Chris

[Double Kick Drum]

254x magnification is quite a lot for a scope of that size. Although the general rule of thumb is 2x for every millimetre of aperture, this is a best case scenario only.

I have a 127mm refractor and the most I generally use is 127x (with a 5mm Celestron X-Cel LX eyepiece). To use more, you need a combination of a very steady sky and a reliable mount that doesn't wobble when ever you move or adjust the scope.

In addition, most deep sky objects do not need that level of magnification.

You can calculate magnification by dividing the focal length of your scope by the focal length of the eyepiece you are using. Eg a 1000mm FL scope with a 25mm eyepiece will give 1000 / 25 or 40x magnification.

[twelly27]

Ahh i see, i think ill leave it as it is then, i was just wondering if i can get a closer view of jupiter and saturn etc

Thanks for the information

Regards

Chris

[nephilim]

Seeing conditions play a big part aswell, its rare for me to be able to push my 200p much past 150x/180x (and I live in a pretty dark part of the country with hardly any lp) even tho it has the potential for 400x, in this country the seeing is naff to say the least.

Steve

Btw, I rarely feel the need to go past 100x unless for lunar or planetary & then i will push it, but as iv said usually no more than 180x

[RichieP]

Well it will depend on seeing conditions but your scope, being a maksutov cassegrain, will take higher magnifications quite well. You should have no problem at 200x if the skies are steady enough.

[Stu]

I would have thought you could use somewhere in the x150 to x180 range to get decent views with your scope. It's a mak so is never going to be widefield like a refractor but should give good planetary views. Maybe a decent quality 8 or 9mm ep would improve the views and give you a little more magnification. The standard 10mm ep is not brilliant as I understand it.

Stu

[John]

Hi Chris,

I've used a scope like yours at magnifications of 180x - 200x and, if the seeing conditions are good and the scope is well cooled (that can take an hour on a cold night of the scope has come from a warm place), the views of the Moon, Saturn, Jupiter Mars and binary stars can be very good. To get to around the 170x -180x mark you need a 9mm or 8mm eyepiece.

With the caveats above (cooled scope / good seeing) it's a worthwhile investment I reckon

Edit: Stu beat me to it !

[twelly27]

ahhh, think ill pop to the shop i use then see what they have to say, but if its worth in vesting as you say then i might give it ago, the webisite of the shop are charging a great deal, i just dont want to waste money really buying things i wont use is just pointless.

I also have another question which is off topic, but when i look at say jupiter through my DSLR its further away then when i have the eye piece in, is that because the ep gives abit more magnification or to do with the camera? and also ive just ordered a webcam, will i see things as close as i do when looking in the ep or just the same as the DSLR?

Regards

Chris

[John]

ahhh, think ill pop to the shop i use then see what they have to say, but if its worth in vesting as you say then i might give it ago, the webisite of the shop are charging a great deal, i just dont want to waste money really buying things i wont use is just pointless.....

Out of interest what are the shop offering and what are they charging ?

You should not need to spend a great deal to get a decent quality eyepiece for your scope - £30-£50 per eyepiece should do fine.

It's worth remembering that the advice here is unbiased - we are not trying to sell you anything

[twelly27]

they have a 9mm ultrawide ep for £34.50

[twelly27]

and it was ment to say arnt chagring a great deal, i have a dodgy letter T on my laptop haha!

[nephilim]

ahhh, think ill pop to the shop i use then see what they have to say, but if its worth in vesting as you say then i might give it ago, the webisite of the shop are charging a great deal, i just dont want to waste money really buying things i wont use is just pointless.

I also have another question which is off topic, but when i look at say jupiter through my DSLR its further away then when i have the eye piece in, is that because the ep gives abit more magnification or to do with the camera? and also ive just ordered a webcam, will i see things as close as i do when looking in the ep or just the same as the DSLR?

Regards

Chris

With a webcam the image will be quite a bit bigger than with a DSLR, the Moon for example is that big only part of it will be visible on the screen. To give u an idea I took this with an XBox cam & 2x Barlow with my old Skywatcher 130m/EQ2

[twelly27]

oh right, thats giving me hope then, thanks for that

Regards

Chris

[nephilim]

oh right, thats giving me hope then, thanks for that

Regards

Chris

Theres no reason at all why u couldnt achieve the same, if not better as your scope will be better on the planets than my 130m is plus i'm fairly new to this to & that was my first attempt.

Good luck

Steve

[twelly27]

Theres no reason at all why u couldnt achieve the same, if not better as your scope will be better on the planets than my 130m is plus i'm fairly new to this to & that was my first attempt.

Good luck

Steve

thanks very much, and ye ive noticed that when its come to jupiter and saturn its been pretty spectacular thanks for the info its much appreciated

Regards

Chris

[nephilim]

thanks very much, and ye ive noticed that when its come to jupiter and saturn its been pretty spectacular thanks for the info its much appreciated

Regards

Chris

No problem mate

Steve

[Moonshane]

I use a rule of thumb of 1.5x aperture in mm as the maximum magnification you can regularly use with a scope. this can be better or worse depending upon seeing and target.

the other night I was using my 6" dob on the moon, Jupiter and some double stars. Jupiter was good to about 180x, I could use 350x-400x on the moon and even higher on double stars. the moon takes magnification well but you don't in truth see much more detail at 400x than say 150x, it's just fun and feels a bit like you are on the lunar lander - well, as close as you'll get anyway

double stars take magnification well quite often as you are not looking for detail, just a clean split. I have used 600x on doubles with my big dob and quite effectively when at the zenith.

my point in many ways is that whilst there's a maximum theoretical limit you can have some fun either side of it. don't worry about it, just enjoy the challenge.

[John]

they have a 9mm ultrawide ep for £34.50

The 9mm is the best one of that series although "ultra wide" is a bit of an exaggeration - "wide angle" would be more accurate

It should work pretty well with your scope and they are quite comfortable to look through as they have a decent size eye lens and reasonable eye relief (the distance your eye needs to be from the top lens) for a 9mm.

[twelly27]

Great ill wait til I've been paid and ill invest in the 9mm then, I'm going to start saving for an EQ mount as well so thanks for the help people! Much appreciated

Regards

Chris

[Stargazer_00]

Just chiming on on what 'highest practical power' actually means. It means the magnification at which the exit pupil will be 0.5mm.

It's very difficult to see much of anything at an exit pupil of 0.5mm.

The reason I say this is it can be confusing. For instance 254x in a 127 mak would look, quite frankly, awful - in my opnion. however in an 12" SCT 254x would look much better- the reason being an 12" SCT would show the same magnification with a 1.2mm exit pupil.

aperture(mm)/magnification = exit pupil (mm)

My point here is that the magnification quality scope to scope isn't constant. If you looked at someones scope at a star party and they had a large aperture and you saw 250x magnification you should not expect that brightness on a smaller aperture scope because as the aperture shrinks the exit pupil does as well (if the magnficiation remains constant). It gets to a point that the light exiting the eyepiece is so small that it's too dim to actually see anything and that is anything less than 0.5mm diameter

Large aperture isnt just to get more light but also to make the exit pupils larger at higher magnfiicaitons

[Moonshane]

I take your point but don't necessarily agree with ,0.5m exit pupil being unusuable. I regularly use smaller exit pupils on double stars and the moon with my 6" f11 dob. granted not often on Jupiter or other objects though.

[Peter Drew]

It also depends on the object being viewed. The Moon certainly looks bright enough in my 220mm refractor at 650X (.34mm exit pupil) but Jupiter at 300X is getting dim.

[Stargazer_00]

it's just what is seen as practical I guess. I've pushed my scopes to the very limit and quite far beyond in terms of magnification and it can show you something, sure. I think it's reasonable to set the practical limit at 0.5 but you can of course push past this if you choose - it wont stop working it'll just degrade more the smaller it gets.

I think double stars are a good example, if you are trying to split a tight double then getting extremely high magnfication is useful and potentially the dimming effect of a smaller exit pupil may even make it a tiny fraction easier to discern a double. For planetary viewing I personally wouldnt bother going that low. Sure you see a bigger disc but it's dimmer and grainy and ultimately seems to give less detail for it. better to back it off a few notches and get a brighter more condensed image. Moon can tolerate extreme magnficiations and still show detail, albeit dimmer views

[P_Monty]

Just wondering why nobody really talks about eye-piece projection when it comes to photography (I'm new too, so I may have missed something critical) - use the eyepiece in a holder on the T mount and you get the magnification back.

[Mr Spock]

I usually find x1 per mm is about right for most nights. Above that you don't really see any more detail, things just get bigger and dimmer. For my scope x235 is perfect, though I do push it to x294 on the moon sometimes. When you get one of those very rare still nights, I can get up to x392 on the moon and doubles.