EP advice

[Dan148]

ive got a skywatcher Astrolux 76mm (3") Newtonian Reflector f=700. it came withe a 25mm wide view and a 10mm super but was wondering if i could go lower than 10mm like 6mm or 5mm or will the results just be not worth it?

[hemihaggis]

probably not .... the max usable mag you could get from your scope is x 75

your telescope if F700 divided by 10mm ep = x 70 mag

therefore if you used a 5mm ep the mag would be 140

im sure some people will tell you up to twice your appeture in mag is usable, possibly from a dark site on a moonless night with fantastic seeing , but in general whatever you appeture is that will be your useable mag

[Dan148]

@hemihaggis

Yeh i know all about the mags etc. and some of the best views ive had have been through the 25mm. i did come with a 2x barlow which ive attempted to use on the 10mm and the views have been pretty **** TBH, maybe down to poor conditions. just woundered if the scope could go more than its x140 (practical power) or will it just not cope (work)

[John]

140x would be too much for much of the time. The theoretical max of a scope (usually expressed as twice it's aperture in mm) is rarely the practical maximum that will be of any use due to the seeing conditions. I'd stick to 100x as a max - it's better to have smaller, sharper views than larger, mushy ones.

[Mr Spock]

76mm isn't a lot of aperture and you'll probably struggle with magnifications as high as x140.

[hemihaggis]

@hemihaggis

Yeh i know all about the mags etc. and some of the best views ive had have been through the 25mm. i did come with a 2x barlow which ive attempted to use on the 10mm and the views have been pretty **** TBH, maybe down to poor conditions. just woundered if the scope could go more than its x140 (practical power) or will it just not cope (work)

hi dan , i think we have some kind of comunication breakdown somewhere , my self and the other posters on here have all said the maximum usable mag you could achive with your scope is around x70 - x100 .

you said you "know all about mags ect" then you would already know all about how to calculate what mag each individual ep will give ion your scope , you also said you tried the x 2 barlow with the 10mm ep ..... you said it gave poor results ... meaning it was too much mag for your scope ...so i think you have actually answerd your own question ? lol

ps a 10mm ep and a x2 barlow will give you how much magnification on your scope ?? please tell us ......

[Dan148]

x140 dont think i need to tell u that lol. just wanted to know if a could get a good image if i was gunna buy a smaller ep. thanks for your replys.

[hemihaggis]

x140 dont think i need to tell u that lol. just wanted to know if a could get a good image if i was gunna buy a smaller ep. thanks for your replys.

but you have already tried that much mag and the image was poor you said .......

a 10mm ep + x2 barlow is the same as a 5mm ep

so you answerd your own question lol

:icon_scratch:

[Dan148]

Yehhhh........didnt really look at it like that lol. still newbie Like i said before some of my best views have been through a 25mm so i might go for a 15mm. thanks for replys