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dave cooke

Testing, testing, testing

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Hello all,

I have had to send a recently purchased 4" APO back as I was unhappy with its performance. I wish to be a bit coy about the make at this stage except to say that it was towards the expensive end off the market, I will also add that the shop is willingly replacing the scope and I have no criticism whatsoever of the retailer.

My question is what should I be able to see with such an instrument. I believe the following should be possible.

1 Detect 5 stars in the trapezium

2 Split epsilon Aries

3 Detect the craterlets in Plato

I would welcome opinions on wether my expectations are too high given my approx mag 4 skies. It seems to me that is difficult to remain objective(sorry) when testing telescopes unless it is taken to an optical laboratory or similar. On receipt of the second scope I need to give the retailer a decision on the scope fairly quickly as he has been fair with me.

Regards

Dave Cooke

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Dave,

You won't be able to see more than 4 stars in the Trapezium with a 4 inch under normal conditions - I managed 2 more (the E and F componants) with a 10 inch scope - and that was very challenging in ideal conditions.

I can just make out one or two craterlets in Plato with my 4 inch Vixen ED on an excellent night - again these are very challenging targets.

Epsilon Arietis is right at the edge of a 4 inch scopes capability on a very good night of seeing.

With objects which are right at the edge of the possible performance of a scope, sky conditions and experience of the observer come into play - frankly under Mag 4 skies you might be asking to much of any 4 inch scope IMHO.

John

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Dave, I'd have to agree with John. In mag 5.5 skies using a precisely collimated 10" reflector and very good eyepieces I can sometimes see the E star in the Trapezium. I've yet to see the F star.

Usually seeing conditions cause problems and its fairly rare in the UK to be able to push any telescope to its theoretical limits and light pollution is another problem...

James

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Craterlets on Plato anyone ? :D

I must try that with my 10"

Matt

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I would welcome opinions on wether my expectations are too high given my approx mag 4 skies

To be honest i do think your expectations are on the optomistic side :D. I would be surprised if your replacement fairs any better.

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Craterlets on Plato anyone ? :lol:

I must try that with my 10"

Matt

I think I'm probably kidding myself that I can make them out TBH :D

Trouble is, once you have read somewhere that something should be visable in a scope like yours it's darned hard to look dispassionately :D

I'd still rather blame the seeing conditions or my observing skills than the scope - I suspect they are much more variable than optical quality is these days !.

John

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Many thanks for your replies, not what I was hoping to hear but at least I will not be looking for the unobtainable.

MEMO TO SELF Stop reading Cloudy Nights' road tests.

Regards

Dave Cooke

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Many thanks for your replies, not what I was hoping to hear but at least I will not be looking for the unobtainable.

MEMO TO SELF Stop reading Cloudy Nights' road tests.

Regards

Dave Cooke

Don't worry Dave - I think we've all been there at some time or other :D

At least you have found yourself a good dealer and hopefully a scope you will enjoy :D

Look forward to hearing about your observing on SGL - clouds allowing that is !.

Johhn

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