Maximium useful mag 102 SLT

[huwbellamy]

Evening all, I have been getting your advice on eyepieces and barlows but maybe I'm expecting too much. The maximum useful mag quoted in my spec sheet is 240x (4" x 60). I have reasonably comfortable eye relief and good views of Saturn, venus and the moon with a standard 2x barlow and a celestron 9mm plossl (152x) and once got something approaching clarity with the barlow and a 6mm plossl (220x). I am upgrading my barlow to a meade apo 2x which will reach nearly 3x if put into the focuser. I was considering then getting a meade 5000 5.5mm to get 240x and good eye relief. Should I set my mag sights lower and perhaps consider a baader ortho for better detail and reasonable eye relief. What is my scope capable of?! Cheers, Huw.

[GordonCopestake]

The general rule of thumb is 50x your aperture in inches or 2x your aperture in mm. This means that your 102mm aperture can sustain a magnification of about 200x

You can of course go over this but you wont see any more detail just a larger image and lower contrast

[geppetto]

Hmmmmmmm

Perhaps your over estimating mate.

The seeing is rarely (hardly ever) good enough to mag up to the

maximum your scope can reach.

I think x150 would be a more sensible range to aim for and to get

the most comfortable eyepieces etc to suit that expectation.

Better a sharp small image than a large fuzzy image

[Macavity]

And there is also, another limiting factor with an Achromatic refractor - That of the dreaded "purple haze" - Especially around bright objects. This due to inherent(!) incomplete colour correction. It may intrude more, as you go up in magnificatation, but tolerance of this is very subjective! But you can remove some of the colouration with esp. the Baader "Fringe Killer" filter, designed for use with achromats. (Sometimes termed a "Minus Violet Filter" etc.) Also perhaps useful is the somewhat stronger effect of the Baader "Contrast filter". Both relatively cheap in 1.25" format, so not a bad thing to at least TRY out! The image, munus the "purple haze" will be a bit dimmer, and a slightly different coliur, but hopefully clearer. Of course, you may (or may not) LIKE the effect. You may be able to squeeze a little more magnification out of the scope though...

[robindurant]

And there is also, another limiting factor with an Achromatic refractor - That of the dreaded "purple haze" - Especially around bright objects. This due to inherent(!) incomplete colour correction. It may intrude more, as you go up in magnificatation, but tolerance of this is very subjective! But you can remove some of the colouration with esp. the Baader "Fringe Killer" filter, designed for use with achromats. (Sometimes termed a "Minus Violet Filter" etc.) Also perhaps useful is the somewhat stronger effect of the Baader "Contrast filter". Both relatively cheap in 1.25" format, so not a bad thing to at least TRY out! The image, munus the "purple haze" will be a bit dimmer, and a slightly different coliur, but hopefully clearer. Of course, you may (or may not) LIKE the effect. You may be able to squeeze a little more magnification out of the scope though...

[robindurant]

I have a 102SLT and the best I can get out of it in my Brighton area is 150x that is using a Fringe Filter

[russ]

I agree, mine manages 150x for the best view.

Russ