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ST120 only in retro black and white.. do not adjust your sets !


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Hi all , I have a skywatcher st120 .. it’s a fine scope and has let me see many dso’s but I was looking at stars the other night and of course there was some CA visible on the brighter ones .. ie Vega . I also viewed Antares which was a lovely pale orange . Then I switched to doubles and looked at Albeiro and it’s companion .. but , there was no colour on either star . I have a very cheap refractor that I also used and it showed distinct yellow and blue colours of the stars ! My friend also has the same scope St120 and has exactly the same experience.. question to you guys is … why can we not see these stars in colour ? 

Edited by Stu1smartcookie
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Strangely I was using my Celestron Omni XLT 120 the other night and thought the star colours on Albireo were quite strong. Not sure what difference the focal ratio (f8.8 vs f5) would make, so I’m a little confused by what you are seeing.

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12 minutes ago, Stu said:

Strangely I was using my Celestron Omni XLT 120 the other night and thought the star colours on Albireo were quite strong. Not sure what difference the focal ratio (f8.8 vs f5) would make, so I’m a little confused by what you are seeing.

Yes , my 70/700 bresser F10 picks up the colour very well ….. but it is weird that both my mate and I have the same anomaly with the ST120 , especially as I see colour in other stars 

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The F/8.3 that @Stu is using will produce less CA than the F/5 version. It's possible that the additional CA might mask certain star colours, to some extent ?

 

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41 minutes ago, John said:

The F/8.3 that @Stu is using will produce less CA than the F/5 version. It's possible that the additional CA might mask certain star colours, to some extent ?

 

I was wondering something similar. Could it be the CA causes the colour to somehow get cancelled out a little? 

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11 minutes ago, badhex said:

I was wondering something similar. Could it be the CA causes the colour to somehow get cancelled out a little? 

That does seem logical...

BdP4bbq.jpg

Then, short, "fast" achromats are primarily if not exclusively for observing the dimmer, deep-sky denizens of the night, and which are colourless, for the most part.

Indeed, here, have we stumbled upon yet another reason to own a long-focus achromat?

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With my ST80 I felt that it scattered away the blues leaving all stars white or orange. I also find dark adaptation weakens color sensitivity. A quick glance at my neighboring streetlight makes the colors pop.

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So , thanks to all of you for commenting… I really do love my ST120 … but I also know it has limitations . It’s up for sale on here but I am hooked on its portability . And it’s large aperture ( for a frac) means it gathers a fair amount of light . And scanning the night sky is where it thrives of course . 
it’s strange that the orange comes through when viewing Antares . 

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