NGC 459, igen

[Hakann]

Ang NGC 459 jag missade på LaPalma i December på SQM 21.5-6 i 20” i medium himmel.

Nu på Ölands träffen var ju den i hyffsad himmel fast SQM 21.3 och med troligtvis mycket fukt i för det borde ha varit 21.6-7 där och mera klart.

Men med 30” var ju galaxen lätt att se ( tolka mig rätt ) så apertur behövdes men fick lite info nu från en kompis i USA om apertur och mörker.

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Ah yes, our favorite NGC 459!
-Glad you saw the little fuzzy! It’s a little galaxy so the aperture makes it bigger which makes it easier to see.

Also, aperture increases contrast and makes objects more visible. Less than perfect skies need more aperture for sure. And poor skies need a ton of aperture. I wrote up my analysis:
going from Bortle 1 to Bortle 4 calls for a doubling of aperture.

Dividing object visibility into six categories: very easy, easy, moderate, difficult, very difficult, and impossible, I investigated how much the aperture needs to be increased when comparing Bortle level 1 to level 4 skies.

We see that a scope of size ‘x’ in dark skies (Bortle 1) performs roughly as a scope of size ‘2x’ in modestly light polluted skies (Bortle 4). This is true in a coarse sense for all object types. Put another way, increases in aperture make more of a difference in object detection in darker skies compared to light polluted skies. In heavily light polluted skies, aperture must be dramatically increased to make a practical difference not to mention that low magnification / high etendue views are precluded. Generally speaking, darker skies are more important than aperture. Each person will have to answer the question of how far to drive with what size of scope. One approach that this suggests then, is to make most observations in suburban skies, occasionally traveling to dark skies to finalize the observations.

 

[Hakann]

Bild bifogad.

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